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or osmotic diuresis&#44; characterized by a urine osmolarity &#40;Osm<span class="elsevierStyleInf">u</span>&#41; of greater than 300&#160;mOsm&#47;kg&#46;</p></li><li class="elsevierStyleListItem" id="lsti0010"><span class="elsevierStyleLabel">&#8226;</span><p id="par0020" class="elsevierStylePara elsevierViewall">An excessive elimination of water&#44; or water diuresis&#44; characterized by an Osm<span class="elsevierStyleInf">u</span> of less than 150&#160;mOsm&#47;kg&#46;</p></li></ul></p><p id="par0025" class="elsevierStylePara elsevierViewall">If both mechanisms are present&#44; the Osm<span class="elsevierStyleInf">u</span> will be between 150 and 300&#160;mOsm&#47;kg&#44; which indicates a condition called mixed polyuria<a class="elsevierStyleCrossRef" href="#bib0025"><span class="elsevierStyleSup">5</span></a>&#46;</p><p id="par0030" class="elsevierStylePara elsevierViewall">Urine volume is directly related to the total number of osmoles excreted per day&#46; The solutes involved in water excretion can be electrolytes &#40;Na<span class="elsevierStyleSup">&#43;</span>&#44; K<span class="elsevierStyleSup">&#43;</span>&#44; Cl<span class="elsevierStyleSup">&#8722;</span>&#44; and Ca<span class="elsevierStyleSup">&#43;&#43;</span>&#41; and nonelectrolytes such as urea&#44; glucose&#44; or others &#40;mannitol&#41;<a class="elsevierStyleCrossRef" href="#bib0030"><span class="elsevierStyleSup">6</span></a>&#46; The daily excretion of osmoles is estimated to be 10&#160;mOsm&#47;kg per day and they must be excreted in water&#46; This volume of free water can increase significantly when the intake of solutes is greater than 900&#160;mOsm&#47;day<a class="elsevierStyleCrossRef" href="#bib0035"><span class="elsevierStyleSup">7</span></a> or decrease if the excretion of solutes decreases significantly&#46;<a class="elsevierStyleCrossRef" href="#bib0040"><span class="elsevierStyleSup">8</span></a></p><p id="par0035" class="elsevierStylePara elsevierViewall">Polyuria can be incapacitating and severely affect quality of life&#44; altering the sleep cycle and daily activities&#44; and can even cause volume depletion and fluctuations in serum sodium levels&#46; Therefore&#44; polyuria is a challenge for clinicians&#44; given that because it can be generated due to multiple causes&#44; a diagnosis requires knowledge of the homeostasis of water balance&#44; sodium&#44; urine concentration mechanisms&#44; and a quantitative analysis of urine losses through electrolyte-free water clearance&#46; These concepts will help us understand the cause of the polyuria and identify appropriate treatment&#46;</p><p id="par0040" class="elsevierStylePara elsevierViewall">We will briefly explain some aspects of the physiology of urine concentration&#44; the determination of urine osmolarity&#44; and the concept of free water loss in order to facilitate comprehension of the differential diagnosis of polyuria&#46;</p><span id="sec0010" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0030">Physiology of urine concentration</span><p id="par0045" class="elsevierStylePara elsevierViewall">Plasma osmolarity &#40;Osm<span class="elsevierStyleInf">p</span>&#41; is monitored by osmoreceptors located in the hypothalamus&#44; which detect subtle changes in it&#46; In response to an increase in Osm<span class="elsevierStyleInf">p</span>&#44; vasopressin&#44; or antidiuretic hormone &#40;ADH&#41;&#44; is released&#46; Vasopressin is produced in the hypothalamus and is released through the neurohypophysis to act on V2 receptors in the basal membrane of the principle cells of the collecting duct tubules&#46; Its mechanism of action consists of increasing water reabsorption through transmembrane channels called aquaporins &#40;specifically aquaporin 2&#41;<a class="elsevierStyleCrossRef" href="#bib0020"><span class="elsevierStyleSup">4</span></a>&#46; If there is a decrease in vasopressin production or the kidney is not sensitive to it&#44; diabetes insipidus occurs&#46; In this case&#44; the Osm<span class="elsevierStyleInf">u</span> will be very low in relation to the Osm<span class="elsevierStyleInf">p</span>&#44; which will be elevated&#46;</p><p id="par0050" class="elsevierStylePara elsevierViewall">It is important to remember that the osmotic gradient for the movement of water through aquaporins depends on the concentration of solutes in the cells&#44; interstitium&#44; tubules&#44; and vessels of the medulla&#46; The osmotic gradient promotes the passage of water from the collecting duct tubules towards a more concentrated interstitium&#44; provoking an increase in interstitial osmolality<a class="elsevierStyleCrossRef" href="#bib0045"><span class="elsevierStyleSup">9</span></a>&#46; The main solutes involved in the osmotic gradient are sodium and urea&#46; However&#44; a precise mathematical model that evaluates the urea gradient has not been able to be developed&#46;</p><p id="par0055" class="elsevierStylePara elsevierViewall">The clinical importance of this physiological knowledge lies in the fact that urinary concentration defects have been observed due to abnormalities in the transporters of urea and other small solutes &#40;aquaglyceroporins&#41;&#46; Both are overexpressed as a response to the increase in ADH<a class="elsevierStyleCrossRef" href="#bib0050"><span class="elsevierStyleSup">10</span></a>&#46; This limits the interpretation of the water deprivation test for differentiating between diabetes insipidus and psychogenic polyuria &#40;a psychiatric disorder induced by excessive water intake&#41;&#46;</p><p id="par0060" class="elsevierStylePara elsevierViewall">On the other hand&#44; polyuria that continues over time can generate a renal medulla concentration gradient washout&#44; triggering a decrease in the maximum capacity for concentrating urine regardless of the polyuria&#8217;s primary cause and generating a relative resistance to ADH&#46; Therefore&#44; an absolute distinction between primary polydipsia and central diabetes insipidus or nephrogenic diabetes insipidus is often not able to be made&#46;</p></span><span id="sec0015" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0035">Determination of urine osmolarity</span><p id="par0065" class="elsevierStylePara elsevierViewall">Urine osmolarity is a measurement which expresses the total concentration of solutes and is defined as the number of osmoles &#40;Osm&#41; per liter of solute&#46; Urine osmolarity &#40;Osm<span class="elsevierStyleInf">u</span>&#41; can be measured using an osmometer or calculated using two formulas&#58;<ul class="elsevierStyleList" id="lis0010"><li class="elsevierStyleListItem" id="lsti0015"><span class="elsevierStyleLabel">1</span><p id="par0070" class="elsevierStylePara elsevierViewall">In the first formula&#44; Osm<span class="elsevierStyleInf">u</span> can be obtained by multiplying the last two urine density &#40;UD&#41; values by 35&#46; It is important to correct for glycosuria &#40;decrease UD by 0&#46;004 for every g&#47;dL&#41; and for proteinuria &#40;decrease UD by 0&#46;003 for every g&#47;dL&#41;<a class="elsevierStyleCrossRef" href="#bib0055"><span class="elsevierStyleSup">11</span></a></p><p id="par0071" class="elsevierStylePara elsevierViewall">Osm<span class="elsevierStyleInf">u</span> &#40;mOsm&#47;kg&#41;&#160;&#61;&#160;&#91;urine density&#160;&#8211;&#160;1000&#93;&#160;&#215;&#160;35</p></li></ul></p><p id="par0075" class="elsevierStylePara elsevierViewall">This formula is not valid if the patient is administered mannitol&#44; piperacillin&#44; carbenicillin&#44; or carbapenems&#46;<ul class="elsevierStyleList" id="lis0015"><li class="elsevierStyleListItem" id="lsti0020"><span class="elsevierStyleLabel">2</span><p id="par0080" class="elsevierStylePara elsevierViewall">The second formula is based on the determination of urine electrolytes and urea without considering glycosuria<a class="elsevierStyleCrossRef" href="#bib0055"><span class="elsevierStyleSup">11</span></a>&#58;</p><p id="par0081" class="elsevierStylePara elsevierViewall">Osm<span class="elsevierStyleInf">u</span> &#40;mOsm&#47;kg&#41;&#160;&#61;&#160;&#91;Na<span class="elsevierStyleInf">u</span>&#160;&#43;&#160;K<span class="elsevierStyleInf">u</span>&#93;&#160;&#215;&#160;2&#160;&#43;&#160;&#91;urea<span class="elsevierStyleInf">u</span>&#47;5&#46;6&#93;</p></li></ul></p><p id="par0085" class="elsevierStylePara elsevierViewall">The use of these formulas is limited because urine is a complex mixture of organic and inorganic compounds that can cause variation in the results obtained by the different UD measurement methods&#46; The Osm<span class="elsevierStyleInf">u</span> formula calculated for UD has very disperse correction values &#40;0&#46;73&#8211;0&#46;86&#41; and is better in &#8220;clean samples&#44;&#8221; that is&#44; those without proteinuria or glycosuria<a class="elsevierStyleCrossRef" href="#bib0060"><span class="elsevierStyleSup">12</span></a>&#46;</p><p id="par0090" class="elsevierStylePara elsevierViewall">What&#8217;s more&#44; when the urine pH measured by a reactive strip is high&#44; the UD will be falsely decreased and vice-versa&#46; For this reason&#44; this test is more reliable with a pH between 7 and 7&#46;5<a class="elsevierStyleCrossRef" href="#bib0065"><span class="elsevierStyleSup">13</span></a>&#46; Reactive strips indirectly measure specific gravity&#44; assuming that the ionic and nonionic constituents of urine are at a constant proportion&#46; This does not always happen in practice&#44; given that ionic constituents can be disproportionately elevated in children &#40;lower urea concentration&#41; and with conditions such as proteinuria&#44; hyperparathyroidism&#44; and hypercalciuria<a class="elsevierStyleCrossRef" href="#bib0070"><span class="elsevierStyleSup">14</span></a>&#46; In conclusion&#44; these formulas are useful as an initial approach if we know their limitations and interpret them cautiously&#46;</p></span><span id="sec0020" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0040">Determination of free water losses</span><p id="par0095" class="elsevierStylePara elsevierViewall">Free water clearance is the volume of water that must be removed or added to urine to make it isosmotic&#46; When urine is hypotonic&#44; free water clearance is positive&#44; that is&#44; the kidney is eliminating water from the organism&#46; In this case&#44; this would be the quantity of water that would have to be removed from the urine to make it isotonic&#46;</p><p id="par0100" class="elsevierStylePara elsevierViewall">Urine free water losses can occur in the diluted urine of patients with concentration abnormalities or also in relatively concentrated urines&#44; as occurs with the use of osmotic diuretics during recovery from acute kidney failure or due to excretion of highly osmolar content &#40;elevated protein intake&#44; administration of total parenteral nutrition&#44; or hypercatabolic states&#41;&#46; These latter conditions allow for explaining the onset and persistence of the hypernatremia these patients can present with<a class="elsevierStyleCrossRef" href="#bib0075"><span class="elsevierStyleSup">15</span></a>&#46;</p><p id="par0105" class="elsevierStylePara elsevierViewall">To understand free water clearance&#44; the total volume of urine &#40;V&#41; is conceptually separated into two components&#58; one consisting of isosmotic urine that contains all the solutes &#40;C<span class="elsevierStyleInf">osm</span>&#41; and another that only contains water &#40;C<span class="elsevierStyleInf">water</span>&#41; &#40;<a class="elsevierStyleCrossRef" href="#fig0005">Fig&#46; 1</a>&#41;&#46; The increase or decrease of this last component allows us to predict the plasma sodium concentration<a class="elsevierStyleCrossRef" href="#bib0080"><span class="elsevierStyleSup">16</span></a>&#46; Mathematically&#44; it is expressed in the following formula&#58;<elsevierMultimedia ident="eq0015"></elsevierMultimedia></p><elsevierMultimedia ident="fig0005"></elsevierMultimedia><p id="par0110" class="elsevierStylePara elsevierViewall">Osmolar clearance can be calculated using the general clearance formula&#58;<elsevierMultimedia ident="eq0020"></elsevierMultimedia></p><p id="par0115" class="elsevierStylePara elsevierViewall">Simplifying these equations&#44; we obtain the free water clearance formula&#58;<elsevierMultimedia ident="eq0025"></elsevierMultimedia></p><p id="par0120" class="elsevierStylePara elsevierViewall">By definition&#44; C<span class="elsevierStyleInf">osm</span> includes all osmoles&#46; However&#44; urea is not relevant to the generation of osmotic gradients because it is distributed in the intra- and extracellular space in equal concentrations&#59; it easily crosses cell membranes and moves through specific transporters in the collector duct tubules&#46; Therefore&#44; the original formula was modified<a class="elsevierStyleCrossRef" href="#bib0085"><span class="elsevierStyleSup">17</span></a> to only include urine osmoles that affect plasma sodium concentration &#40;Na<span class="elsevierStyleInf">p</span>&#41;&#44; called electrolyte-free water clearance or C<span class="elsevierStyleInf">water</span>&#40;e&#41;&#46;</p><p id="par0125" class="elsevierStylePara elsevierViewall">The equation can be modified by replacing Osm<span class="elsevierStyleInf">p</span> with Na<span class="elsevierStyleInf">p</span> and Osm<span class="elsevierStyleInf">u</span> with urine sodium and potassium &#40;Na<span class="elsevierStyleInf">u</span>&#160;&#43;&#160;K<span class="elsevierStyleInf">u</span>&#41;&#58;<elsevierMultimedia ident="eq0030"></elsevierMultimedia></p><p id="par0130" class="elsevierStylePara elsevierViewall">In conclusion&#44; if Na<span class="elsevierStyleInf">u</span>&#160;&#43;&#160;K<span class="elsevierStyleInf">u</span> is less than Na<span class="elsevierStyleInf">p</span>&#44; then the C<span class="elsevierStyleInf">water</span>&#40;e&#41; formula will have a positive result&#44; reflecting a loss of free water with a consequent hypernatremia with hypotonic urine&#46; On the contrary&#44; if Na<span class="elsevierStyleInf">u</span>&#160;&#43;&#160;K<span class="elsevierStyleInf">u</span> is greater than Na<span class="elsevierStyleInf">p</span>&#44; then C<span class="elsevierStyleInf">water</span>&#40;e&#41; will be negative&#44; reflecting an increase in free water with a consequent hyponatremia with hypertonic urine&#46;</p><p id="par0135" class="elsevierStylePara elsevierViewall">This formula also allows for understanding that in mixed or osmolar polyurias&#44; hypernatremia is generated by &#8220;diluted&#8221; urine&#46; For example&#44; in a patient with a high amount of urea excretion&#44; the original equation would predict a negative water excretion and a decrease in Na<span class="elsevierStyleInf">p</span>&#44; but in fact in these cases&#44; Na<span class="elsevierStyleInf">p</span> increases&#44; which can be predicted precisely by the latter equation&#46;</p></span><span id="sec0025" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0045">Polyuria due to water diuresis</span><p id="par0140" class="elsevierStylePara elsevierViewall">The causes of polyuria in outpatients are most frequently classified as polyurias due to water diuresis&#46; The three main causes are central diabetes insipidus&#44; nephrogenic diabetes insipidus&#44; and psychogenic polydipsia or primary polydipsia &#40;<a class="elsevierStyleCrossRef" href="#tbl0005">Table 1</a>&#41;&#46;</p><elsevierMultimedia ident="tbl0005"></elsevierMultimedia><p id="par0145" class="elsevierStylePara elsevierViewall">The incidence of diabetes insipidus in the general population is three cases out of every 100&#44;000 inhabitants&#44; with a slightly higher incidence in men &#40;60&#37;&#41; than women&#46; Congenital nephrogenic diabetes insipidus is a very rare disease with an incidence of four cases out of every 1&#44;000&#44;000 males<a class="elsevierStyleCrossRef" href="#bib0090"><span class="elsevierStyleSup">18</span></a>&#46;</p><p id="par0150" class="elsevierStylePara elsevierViewall">Psychogenic polydipsia is a defect in thirst control&#46; It is caused by a dysfunction in the production or release of ADH and is not always accompanied by a psychiatric disorder&#46; Psychogenic polydipsia is characterized by compulsive water consumption due to fear of dehydration or a belief that one&#8217;s health improves with excessive consumption&#46; It can also be observed in patients with hypothalamic sequelae of cranioencephalic trauma&#44; vascular diseases&#44; or infiltrative diseases of the hypothalamus such as sarcoidosis<a class="elsevierStyleCrossRef" href="#bib0095"><span class="elsevierStyleSup">19</span></a>&#46; Its incidence is not known&#44; but it seems to primary affect women &#40;80&#37; of cases&#41; and its onset occurs in the third decade of life&#46; Up to 40&#37; of patients with schizophrenia present with it<a class="elsevierStyleCrossRef" href="#bib0090"><span class="elsevierStyleSup">18</span></a>&#46; Nevertheless&#44; the prevalence of psychogenic polydipsia is increasing in the general population due to a belief in the beneficial health effects of high fluid consumption<a class="elsevierStyleCrossRef" href="#bib0100"><span class="elsevierStyleSup">20</span></a>&#46;</p><p id="par0155" class="elsevierStylePara elsevierViewall">When polyuria is due to water diuresis&#44; conducting a water deprivation test has classically been suggested in order to differentiate between diabetes insipidus and psychogenic polydipsia&#46; This test&#44; initially described by Miller et al&#46; in 1970<a class="elsevierStyleCrossRef" href="#bib0105"><span class="elsevierStyleSup">21</span></a>&#44; has demonstrated a limited diagnostic precision of 70&#37;&#46; It has even been found that just 41&#37; of patients with psychogenic polydipsia have the correct diagnosis<a class="elsevierStyleCrossRef" href="#bib0005"><span class="elsevierStyleSup">1</span></a>&#46; For this reasons&#44; other diagnostic methods such as magnetic resonance imaging of the hypophysis and copeptin measurements are used&#44; achieving sensitivities and specificities of greater than 90&#37; in differentiating between psychogenic polydipsia and partial central diabetes insipidus with each of these tests<a class="elsevierStyleCrossRef" href="#bib0005"><span class="elsevierStyleSup">1</span></a>&#46;</p><p id="par0160" class="elsevierStylePara elsevierViewall">Copeptin is a glycopeptide formed by a chain of 39 amino acids&#46; It is the terminal fraction of the provasopressin molecule &#40;precursor of vasopressin or antidiuretic hormone&#41;&#46; There is a high correlation between levels of copeptin and levels of vasopressin &#40;coefficient of correlation 0&#46;8&#41;&#46; Due to the difficulty of measuring vasopressin levels&#44; measurements of copeptin levels are used in clinical practice&#46; Their blood values in normal individuals range from 1 to 12&#160;pmol&#47;L<a class="elsevierStyleCrossRefs" href="#bib0110"><span class="elsevierStyleSup">22&#44;23</span></a>&#46;</p></span><span id="sec0030" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0050">Polyuria due to osmotic diuresis and&#47;or mixed polyuria</span><p id="par0165" class="elsevierStylePara elsevierViewall">The most frequent cause of polyuria due to osmotic diuresis in outpatients is hyperglycemia&#46; However&#44; there are also cases due to consumption of nutritional supplements that are high in protein&#44; mainly in athletes<a class="elsevierStyleCrossRef" href="#bib0120"><span class="elsevierStyleSup">24</span></a>&#46;</p><p id="par0170" class="elsevierStylePara elsevierViewall">In order to diagnose polyuria due to osmotic diuresis or mixed polyuria&#44; it is necessary to collect a 24-h urine sample and measure electrolytes&#44; glucose&#44; creatinine&#44; and urea nitrogen&#46; With these values&#44; it is possible to calculate the daily excretion of osmoles and measure Osm<span class="elsevierStyleInf">u</span> in order to detect solutes that generate intratubular water movement &#40;<a class="elsevierStyleCrossRef" href="#tbl0005">Table 1</a>&#41;&#46;</p><p id="par0175" class="elsevierStylePara elsevierViewall">Daily osmole excretion &#40;Osm<span class="elsevierStyleInf">u</span> multiplied by 24-h urine volume&#41; is the sum of the excretion of electrolyte and nonelectrolyte solutes&#44; all expressed as milliosmoles per day&#46; Then&#44; the next step in the study is to determine the type of solute responsible for the polyuria &#40;<a class="elsevierStyleCrossRef" href="#fig0010">Fig&#46; 2</a>&#41;&#46;</p><elsevierMultimedia ident="fig0010"></elsevierMultimedia><p id="par0180" class="elsevierStylePara elsevierViewall">The contribution of electrolytes to the polyuria can be estimated by multiplying the sum of Na<span class="elsevierStyleInf">u</span>&#160;&#43;&#160;K<span class="elsevierStyleInf">u</span> measured in a 24-h urine sample by 2&#44; assuming that there are no other quantitatively significant cations in the daily excretion of osmoles<a class="elsevierStyleCrossRef" href="#bib0125"><span class="elsevierStyleSup">25</span></a>&#46; Values greater than 600&#160;mOsm&#47;day suggest that electrolytes are the solutes that generate the polyuria whereas a value lower than 600&#160;mOsm&#47;day points toward the diuresis being due to a nonelectrolyte solute&#44; typically glucose or urea&#44; as we will explain later on&#46;</p><p id="par0185" class="elsevierStylePara elsevierViewall">This can be confirmed if an osmometer-measured Osm<span class="elsevierStyleInf">u</span> value is available&#59; if there is concordance with the osmometer-measured Osm<span class="elsevierStyleInf">u</span> value&#44; the polyuria is due to electrolytes&#46; On the contrary&#44; if the osmometer-measured Osm<span class="elsevierStyleInf">u</span> is greater than what is calculated using the formula&#44; it can be assumed that it is an osmotic diuresis not mediated by electrolytes<a class="elsevierStyleCrossRef" href="#bib0025"><span class="elsevierStyleSup">5</span></a>&#46;</p><p id="par0190" class="elsevierStylePara elsevierViewall">Polyuria due to electrolyte washout is usually measured by a sodium salt &#40;often chloride&#41; as a consequence of excessive administration of saline solution&#44; intravenous sodium bicarbonate administration&#44; excessive salt intake&#44; or use of loop diuretics&#46; However&#44; there may be other possibilities&#46; Measuring Na<span class="elsevierStyleInf">u</span>&#44; K<span class="elsevierStyleInf">u</span>&#44; and urinary chloride &#40;Cl<span class="elsevierStyleInf">u</span>&#41; values can be of help&#44; as these values are used to calculate the urine anion gap&#44; which allows for searching for an anion other than chloride which may be associated with the sodium&#46; The urine anion gap is calculated by adding sodium and potassium and subtracting chloride &#40;&#91;Na<span class="elsevierStyleInf">u</span>&#160;&#43;&#160;K<span class="elsevierStyleInf">u</span>&#93;&#160;&#8722;&#160;&#91;Cl<span class="elsevierStyleInf">u</span>&#93;&#41;&#46;</p><p id="par0195" class="elsevierStylePara elsevierViewall">A positive value indicates the presence of one or more anions apart from chloride in urine<a class="elsevierStyleCrossRef" href="#bib0130"><span class="elsevierStyleSup">26</span></a>&#46; This anion tends to be bicarbonate&#44; therefore a pH of around 7&#46;4 indicates large quantities of this anion in the urine<a class="elsevierStyleCrossRef" href="#bib0135"><span class="elsevierStyleSup">27</span></a>&#46; A urine pH value of less than 6&#46;4 rules out the bicarbonate anion as the cause and makes it necessary to search for others&#44; such as ketoacids and an excess of anions related to toxins or drugs such as salicylates<a class="elsevierStyleCrossRef" href="#bib0130"><span class="elsevierStyleSup">26</span></a>&#46;</p><p id="par0200" class="elsevierStylePara elsevierViewall">Osmotic diuresis not mediated by electrolytes can be observed in patients who are catabolizing a large quantity of protein&#44; whether due to enteral or parenteral nutrition&#44; hypercatabolic states&#44; or the resolution of obstructive uropathy&#46; In these patients&#44; the urea is dragged by the water&#46; When this occurs&#44; values of daily nonelectrolyte osmole excretion of less than 600&#160;mOsm can be abnormal and be enough to generate polyuria&#44; depending on patient&#39;s pathophysiological state&#46; Urea nitrogen values of 0&#46;7&#160;g&#47;dL or its equivalent of 1500&#160;mg&#47;dL of urine urea are able to generate solute diuresis<a class="elsevierStyleCrossRef" href="#bib0125"><span class="elsevierStyleSup">25</span></a>&#46;</p><p id="par0205" class="elsevierStylePara elsevierViewall">In daily practice&#44; particularly in critical care units&#44; it should be suspected that these patients lose hypotonic fluid in the urine due to urea-induced osmotic diuresis&#46; At the same time&#44; these losses are replaced with isotonic fluids that are in fact hypertonic compared to their urine&#44; resulting in an increase in sodium and secondary hypernatremia&#46; In this case&#44; it is again useful to calculate C<span class="elsevierStyleInf">water</span>&#40;e&#41; as it allows for guiding the quantity of free water necessary for maintaining natremia at a desired value&#46;</p><p id="par0210" class="elsevierStylePara elsevierViewall">Glucose becomes present in urine if there is a decrease in the capacity to reabsorb filtered glucose or when there are plasma glucose concentrations greater than 200&#8211;250&#160;mg&#47;dL &#40;exceeding the maximum transport capacity of SGLT-2 and SLGT-1 transporters in the proximal tubule&#41;<a class="elsevierStyleCrossRef" href="#bib0140"><span class="elsevierStyleSup">28</span></a>&#46; The glycosuria observed in diabetic ketoacidosis or hyperglycemic hyperosmolar syndrome can generate excretion of more than 833&#160;mmol&#44; corresponding to 150&#160;g of glucose per day&#44; which is able to produce an additional 1&#46;7&#8211;2&#46;8&#160;L of urine<a class="elsevierStyleCrossRef" href="#bib0025"><span class="elsevierStyleSup">5</span></a>&#46;</p><p id="par0215" class="elsevierStylePara elsevierViewall">In clinical studies&#44; pharmacological inhibition of SGLT-2 generated an increase in urine volume just a few days after initiating treatment&#44; leading to osmotic diuresis mediated by natriuresis with glycosuria&#44; achieving an increase of 1&#8211;1&#46;5 times the baseline level<a class="elsevierStyleCrossRef" href="#bib0145"><span class="elsevierStyleSup">29</span></a>&#46;</p><p id="par0220" class="elsevierStylePara elsevierViewall">In these cases&#44; the results of the urine study must be evaluated individually according to the clinical context<a class="elsevierStyleCrossRefs" href="#bib0130"><span class="elsevierStyleSup">26&#44;30</span></a>&#46; Likewise&#44; it should be remembered that an approach using the C<span class="elsevierStyleInf">water</span>&#40;e&#41; formula based on osmolarity &#40;influenced by urea concentration&#41; may not correctly evaluate the renal management of water<a class="elsevierStyleCrossRef" href="#bib0155"><span class="elsevierStyleSup">31</span></a>&#46;</p></span></span><span id="sec0035" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0055">Clinical case 1</span><p id="par0225" class="elsevierStylePara elsevierViewall">A 31-year-old male consulted for intense&#44; progressive thirst that had been ongoing for six months&#44; with consumption of 18&#160;L of water per day associated with nocturia and polyuria of 18&#160;L&#47;day&#46; He did not take protein supplements&#46; Upon physical examination&#44; he did not present with any relevant findings&#46;</p><p id="par0230" class="elsevierStylePara elsevierViewall">The study found an Na<span class="elsevierStyleInf">p</span> of 144&#160;mEq&#47;L&#44; Osm<span class="elsevierStyleInf">p</span> of 283&#160;mOsm&#47;kg&#44; 24-h urine volume of 11&#44;660&#160;mL&#44; and Osm<span class="elsevierStyleInf">u</span> of 79&#160;mOsm&#47;kg&#46; On the 24-h urine test&#44; an Na<span class="elsevierStyleInf">u</span> of 20&#160;mEq&#47;L and K<span class="elsevierStyleInf">u</span> of 6&#46;8&#160;mEq&#47;L were found&#46;</p><p id="par0235" class="elsevierStylePara elsevierViewall">As the Osm<span class="elsevierStyleInf">u</span> was hypotonic&#8212;less than 150&#160;mOsm&#47;kg&#8212;the polyuria was due to water diuresis&#46;</p><p id="par0240" class="elsevierStylePara elsevierViewall">Given that the patient had not increased water intake in association with a particular diet&#44; did not have a psychiatric disease&#44; and his levels of blood sodium were within the upper normal limits&#44; a diagnosis of diabetes insipidus was proposed&#46; A water deprivation test was performed to differentiate between central or nephrogenic diabetes insipidus or primary polydipsia &#40;<a class="elsevierStyleCrossRef" href="#fig0015">Fig&#46; 3</a>&#41;&#46; It was interpreted as polyuria due to water diuresis secondary to central diabetes insipidus&#46;</p><elsevierMultimedia ident="fig0015"></elsevierMultimedia><p id="par0245" class="elsevierStylePara elsevierViewall">In the case of our patient&#44; despite not having reached a concentration greater than 800&#160;mOsm&#47;kg&#44; perhaps due to the mechanisms of medullary concentration washout secondary to the polyuria&#44; an increase in the Osm<span class="elsevierStyleInf">u</span> of greater than 50&#37; was achieved&#44; which was enough to diagnose central diabetes insipidus&#46;</p><p id="par0250" class="elsevierStylePara elsevierViewall">When we calculated the electrolyte-free water clearance using the C<span class="elsevierStyleInf">water</span>&#40;e&#41; equation&#44; the result was positive&#58; 6&#46;6&#160;mL&#47;min&#46; In other words&#44; the patient had a loss of 9504 cc of free water in a total urine volume of 11&#44;660 cc&#44; concordant with the hypernatremia observed due to a large loss of free water&#46;</p><p id="par0255" class="elsevierStylePara elsevierViewall">For the central diabetes insipidus study &#40;<a class="elsevierStyleCrossRef" href="#tbl0005">Table 1</a>&#41;&#44; magnetic resonance imaging of the sella turcica with gadolinium was performed to search for a CNS tumor&#46; The results were suggestive of lymphocytic infundibular neurohypophysitis&#46; Treatment was started with intranasal desmopressin with a good response&#59; the natremia&#44; urinary frequency&#44; and thirst normalized&#46;</p></span><span id="sec0040" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0060">Clinical case 2</span><p id="par0260" class="elsevierStylePara elsevierViewall">An 85-year-old male with a medical history of benign prostatic hyperplasia&#46; Consulted due to anuria and abdominal pain&#46; Of note on the blood test were a plasma creatinine level of 8&#160;mg&#47;dL and a plasma urea level of 192&#46;6&#160;mg&#47;dL&#46; The kidney ultrasound showed bilateral hydroureteronephrosis&#46;</p><p id="par0265" class="elsevierStylePara elsevierViewall">A urinary catheter was placed&#44; which drained 5500&#160;mL of urine in 90&#160;min&#59; an improvement in renal function was observed in the following days&#46; Replacement was started with 0&#46;9&#37; saline solution at a ratio of 75&#37; of the diuresis&#46; However&#44; polyuria of 6000&#160;mL in 24&#160;h persisted&#46;</p><p id="par0270" class="elsevierStylePara elsevierViewall">The study found a Na<span class="elsevierStyleInf">p</span> of 148&#160;mEq&#47;L&#44; Osm<span class="elsevierStyleInf">p</span> of 285&#160;mOsm&#47;kg&#44; and Osm<span class="elsevierStyleInf">u</span> of 289&#160;mOsm&#47;kg&#46; The 24-h urine collection test showed a urine volume of 6000&#160;mL&#44; Na<span class="elsevierStyleInf">u</span> of 110&#160;mmol&#47;L&#44; K<span class="elsevierStyleInf">u</span> of 30&#160;mmol&#47;L&#44; Cl<span class="elsevierStyleInf">u</span> of 149&#160;mmol&#47;L&#44; and urea of 828&#46;9&#160;mg&#47;dL&#44; without glycosuria&#46; The urine anion gap &#40;&#91;Na<span class="elsevierStyleInf">u</span>&#160;&#43;&#160;K<span class="elsevierStyleInf">u</span>&#93;&#160;&#8722;&#160;&#91;Cl<span class="elsevierStyleInf">u</span>&#93;&#41; was negative&#46;</p><p id="par0275" class="elsevierStylePara elsevierViewall">Given that the Osm<span class="elsevierStyleInf">u</span> was 289&#160;mOsm&#47;kg&#44; it was considered to be mixed polyuria&#46; To define the type of solute that generated the polyuria &#40;electrolyte or nonelectrolyte&#41;&#44; the total quantity of urine solutes in 24&#160;h was estimated as electrolytes &#40;Ue&#41;&#58;<elsevierMultimedia ident="eq0035"></elsevierMultimedia><elsevierMultimedia ident="eq0040"></elsevierMultimedia></p><p id="par0280" class="elsevierStylePara elsevierViewall">Upon comparing this value to the urine solute load&#8212;Osm<span class="elsevierStyleInf">u</span>&#160;&#215;&#160;6&#160;L &#40;289&#160;&#215;&#160;6&#41;&#8212;the result was 1734&#160;mOsm&#46; Given the above&#44; it can be concluded that out of the total solute load &#40;1734&#160;mOsm&#41;&#44; 1680&#160;mOsm corresponded to electrolytes&#46; This indicates that it was polyuria due to electrolyte-dependent solutes&#46;</p><p id="par0285" class="elsevierStylePara elsevierViewall">The next step in this clinical case was to determine the predominant electrolyte in the urine&#46; This was obtained by calculating sodium and chloride excretion in the urine&#44; which is obtained by multiplying the concentration of each of these electrolytes by the urine volume &#40;in liters&#41;&#58;<elsevierMultimedia ident="eq0045"></elsevierMultimedia><elsevierMultimedia ident="eq0050"></elsevierMultimedia></p><p id="par0290" class="elsevierStylePara elsevierViewall">These values exceed the relatively normal figures for a patient who follows a typical American diet &#40;Na<span class="elsevierStyleInf">u</span> 150&#160;mmol&#44; Cl<span class="elsevierStyleInf">u</span> 120&#160;mmol&#41;<a class="elsevierStyleCrossRef" href="#bib0025"><span class="elsevierStyleSup">5</span></a>&#46; Therefore&#44; Na<span class="elsevierStyleInf">u</span> and Cl<span class="elsevierStyleInf">u</span> were the main solutes in the patient&#8217;s urine&#46; The above&#44; together with the negative urine anion gap value&#44; means that there was little excretion of nonchloride anions&#44; which indicates that the mechanism of the polyuria was secondary to the administration of saline solution as a fluid replacement solution&#44; which perpetuated the polyuria&#46; In this case&#44; there was no mechanism mediated by a nonelectrolyte solute &#40;urea&#41;&#44; as is expected in obstructive uropathy&#46;</p><p id="par0295" class="elsevierStylePara elsevierViewall">The electrolyte-free water clearance calculated using the C<span class="elsevierStyleInf">water</span>&#40;e&#41; equation was positive&#58; 0&#46;2&#160;mL&#47;min&#46; In other words&#44; there was a loss of 288&#160;mL of free water in a total urine volume of 6000&#160;mLc together with electrolyte-free water diuresis&#44; which was concordant with the mild hypernatremia observed&#46;</p></span><span id="sec0045" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0065">Conclusion</span><p id="par0300" class="elsevierStylePara elsevierViewall">The evaluation of polyuric states is a challenge in internal medicine due to a lack of familiarity with the formulas presented herein&#46; However&#44; their understanding and use allow us to organize the diagnostic study of polyurias and estimate free water losses with a very high degree of precision&#46;</p><p id="par0305" class="elsevierStylePara elsevierViewall">Therefore&#44; measured and calculated urine osmolarity&#44; the estimation of daily urine osmole excretion&#44; their nature&#44; the water deprivation test in water and mixed polyurias&#44; and electrolyte-free water clearance are essential diagnostic tests that must be included in the evaluation of polyuria-polydipsia syndrome&#46;</p></span><span id="sec0050" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0070">Funding</span><p id="par0310" class="elsevierStylePara elsevierViewall">The research has not received specific grants from agencies in the public&#44; commercial&#44; or non-profit sectors&#46;</p></span><span id="sec0055" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0075">Conflicts of interest</span><p id="par0315" class="elsevierStylePara elsevierViewall">The authors of this article have no conflicts of interest to declare&#46;</p></span></span>"
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          "titulo" => "Introduction"
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              "identificador" => "sec0010"
              "titulo" => "Physiology of urine concentration"
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            1 => array:2 [
              "identificador" => "sec0015"
              "titulo" => "Determination of urine osmolarity"
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              "identificador" => "sec0020"
              "titulo" => "Determination of free water losses"
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              "identificador" => "sec0025"
              "titulo" => "Polyuria due to water diuresis"
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            4 => array:2 [
              "identificador" => "sec0030"
              "titulo" => "Polyuria due to osmotic diuresis and&#47;or mixed polyuria"
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          "titulo" => "Clinical case 1"
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            1 => "Hypernatremia"
            2 => "Electrolyte free water clearance"
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          "clase" => "keyword"
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          "palabras" => array:3 [
            0 => "Poliuria"
            1 => "Hipernatremia"
            2 => "Aclaramiento de agua libre de electrolitos"
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        "titulo" => "Abstract"
        "resumen" => "<span id="abst0005" class="elsevierStyleSection elsevierViewall"><p id="spar0045" class="elsevierStyleSimplePara elsevierViewall">Polyuria is a common clinical condition characterized by a urine output that is inappropriately high &#40;more than 3&#160;L in 24&#160;h&#41; for the patient&#8217;s blood pressure and plasma sodium levels&#46; From a pathophysiological point of view&#44; it is classified into two types&#58; polyuria due to a greater excretion of solutes &#40;urine osmolality &#62;300&#160;mOsm&#47;L&#41; or due to an inability to increase solute concentration &#40;urine osmolality &#60;150&#160;mOsm&#47;L&#41;&#46; Sometimes both mechanisms can coexist &#40;urine osmolality 150&#8211;300&#160;mOsm&#47;L&#41;&#46; Polyuria is a diagnostic challenge and its proper treatment requires an evaluation of the medical record&#44; determination of urine osmolality&#44; estimation of free water clearance&#44; use of water deprivation tests in aqueous polyuria&#44; and measurement of electrolytes in blood and urine in the case of osmotic polyuria&#46;</p></span>"
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      "es" => array:2 [
        "titulo" => "Resumen"
        "resumen" => "<span id="abst0010" class="elsevierStyleSection elsevierViewall"><p id="spar0050" class="elsevierStyleSimplePara elsevierViewall">La poliuria es una condici&#243;n cl&#237;nica frecuente caracterizada por un volumen de orina inapropiadamente alto para los niveles de presi&#243;n arterial y sodio plasm&#225;tico del paciente &#40;volumen de orina &#62;3&#160;L&#47;24&#160;h&#41;&#46; Desde el punto de vista fisiopatol&#243;gico se clasifica en 2 tipos&#58; debido a una mayor excreci&#243;n de solutos &#40;osmolaridad urinaria &#62;300&#160;mOsm&#47;L&#41; o debido a una incapacidad de aumentar la concentraci&#243;n de solutos &#40;osmolaridad urinaria &#60;150&#160;mOsm&#47;L&#41;&#46; En ocasiones pueden coexistir ambos mecanismos &#40;osmolaridad urinaria 150&#8211;300&#160;mOsm&#47;L&#41;&#46; La poliuria supone un reto diagn&#243;stico y su tratamiento correcto exige una evaluaci&#243;n de la historia cl&#237;nica&#44; la determinaci&#243;n de la osmolaridad urinaria&#44; la estimaci&#243;n del aclaramiento de agua libre&#44; el uso de pruebas de deprivaci&#243;n h&#237;drica en la poliuria acuosa y la medici&#243;n de electr&#243;litos en sangre y orina en el caso de la poliuria osm&#243;tica&#46;</p></span>"
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        "nota" => "<p class="elsevierStyleNotepara" id="npar0005">Please cite this article as&#58; Ram&#237;rez-Guerrero G&#44; M&#252;ller-Ortiz H&#44; Pedreros-Rosales C&#46; Poliuria en el adulto&#46; Una aproximaci&#243;n diagn&#243;stica basada en la fisiopatolog&#237;a&#46; Rev Clin Esp&#46; 2022&#59;222&#58;301&#8211;308&#46;</p>"
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          "en" => "<p id="spar0005" class="elsevierStyleSimplePara elsevierViewall">Free water and electrolyte-free water clearance flowchart and formula&#46;</p> <p id="spar0010" class="elsevierStyleSimplePara elsevierViewall">C<span class="elsevierStyleInf">water</span>&#40;e&#41;&#58; electrolyte-free water clearance&#59; C<span class="elsevierStyleInf">osm</span>&#58; osmolar clearance&#59; K<span class="elsevierStyleInf">u</span>&#58; urine potassium&#59; Na<span class="elsevierStyleInf">p</span>&#58; plasma sodium&#59; Na<span class="elsevierStyleInf">U</span>&#58; urine sodium&#46;</p>"
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          "en" => "<p id="spar0015" class="elsevierStyleSimplePara elsevierViewall">Suggested flowchart for the differential diagnosis of polyuria&#46;</p> <p id="spar0020" class="elsevierStyleSimplePara elsevierViewall">UAG&#58; urine anion gap&#46; Difference in milliequivalents per liter between the sum of Na<span class="elsevierStyleInf">u</span>&#160;&#43;&#160;K<span class="elsevierStyleInf">u</span> and Cl<span class="elsevierStyleInf">u</span>&#59; Ue&#58; urine electrolytes&#46; 2&#215; &#40;Na<span class="elsevierStyleInf">u</span>&#160;&#43;&#160;K<span class="elsevierStyleInf">u</span>&#41;&#46;</p>"
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          "en" => "<p id="spar0025" class="elsevierStyleSimplePara elsevierViewall">Water deprivation test&#46;</p> <p id="spar0030" class="elsevierStyleSimplePara elsevierViewall">In the figure&#44; it can be observed that the patient started the deprivation test with a reduced Osm<span class="elsevierStyleInf">u</span> and continued with diluted urine despite 240&#160;min of water deprivation&#46; Following administration of desmopressin&#44; a urine concentration appropriate for the Osm<span class="elsevierStyleInf">p</span> was achieved&#46;</p>"
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          "leyenda" => "<p id="spar0040" class="elsevierStyleSimplePara elsevierViewall">DKA&#58; diabetic ketoacidosis&#59; iSGLT-2&#58; sodium&#47;glucose cotransporter 2 inhibitors&#59; ATN&#58; acute tubular necrosis&#59; HHS&#58; hyperglycemic hyperosmolar syndrome&#59; CNS&#58; central nervous system&#59; OU&#58; obstructive uropathy&#46;</p>"
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                  \t\t\t\t\ttable-head\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t" scope="col" style="border-bottom: 2px solid black">Osmotic&nbsp;\t\t\t\t\t\t\n
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                  \t\t\t\t\ttable-head\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t" scope="col" style="border-bottom: 2px solid black">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t\t\t</th><th class="td" title="\n
                  \t\t\t\t\ttable-head\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t" scope="col" style="border-bottom: 2px solid black">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t\t\t</th></tr></thead><tbody title="tbody"><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
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                  \t\t\t\t"><span class="elsevierStyleItalic">Electrolytes</span>&nbsp;\t\t\t\t\t\t\n
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                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
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                  \t\t\t\t">Sodium&nbsp;\t\t\t\t\t\t\n
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                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
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                  \t\t\t\t">Infusion of iso- or hypertonic sodium chloride&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
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                  \t\t\t\t">Renal sodium losses&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Anion&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
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                  \t\t\t\t">Chloride&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
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                  \t\t\t\t">Diuretics&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Bartter syndrome&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
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                  \t\t\t\t">Bicarbonate&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
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                  \t\t\t\t">Exogenous administration&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Acetazolamide&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Ketoanion&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">DKA&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " colspan="3" align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t"><span class="elsevierStyleVsp" style="height:0.5px"></span></td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t"><span class="elsevierStyleItalic">Nonelectrolyte</span>&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Glucose&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Exogenous loading&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">DKA-HHS&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">iSGLT-2&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Urea&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Exogenous loading&#44; protein or amino acids&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Hypercatabolism&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">ATN&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">After OU&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Mannitol&#47;sorbitol&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t"><span class="elsevierStyleBold">Water</span>&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t"><span class="elsevierStyleItalic">Excess intake</span>&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Psychogenic polydipsia&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Iatrogenic&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t"><span class="elsevierStyleItalic">Diabetes insipidus</span>&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Central&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Cranioencephalic trauma&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">CNS tumors&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">CNS infections&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Sheehan syndrome&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Subarachnoid hemorrhage&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">CNS lupus&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Sarcoidosis&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Nephrogenic&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Hypokalemia&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Hypercalciuria&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Lithium&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Sarcoidosis&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
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                  \t\t\t\t</td><td class="td" title="\n
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Review
Polyuria in adults. A diagnostic approach based on pathophysiology
Poliuria en el adulto. Una aproximación diagnóstica basada en la fisiopatología
G. Ramírez-Guerreroa,b,
Corresponding author
ramirezguerrero.g@gmail.com

Corresponding author.
, H. Müller-Ortizc,d,e, C. Pedreros-Rosalesc,d,e
a Unidad de Diálisis y Trasplante Renal, Hospital Carlos Van Buren, Valparaíso, Chile
b Departamento de Medicina Interna, Facultad de Medicina, Universidad de Valparaíso, Valparaíso, Chile
c Departamento de Medicina Interna, Facultad de Medicina, Universidad de Concepción, Concepción, Bío Bío, Chile
d Unidad de Nefrología, Diálisis y Trasplante, Hospital las Higueras de Talcahuano, Talcahuano, Bío Bío, Chile
e Instituto de Nefrología Concepción, Concepción, Bío Bío, Chile
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or osmotic diuresis&#44; characterized by a urine osmolarity &#40;Osm<span class="elsevierStyleInf">u</span>&#41; of greater than 300&#160;mOsm&#47;kg&#46;</p></li><li class="elsevierStyleListItem" id="lsti0010"><span class="elsevierStyleLabel">&#8226;</span><p id="par0020" class="elsevierStylePara elsevierViewall">An excessive elimination of water&#44; or water diuresis&#44; characterized by an Osm<span class="elsevierStyleInf">u</span> of less than 150&#160;mOsm&#47;kg&#46;</p></li></ul></p><p id="par0025" class="elsevierStylePara elsevierViewall">If both mechanisms are present&#44; the Osm<span class="elsevierStyleInf">u</span> will be between 150 and 300&#160;mOsm&#47;kg&#44; which indicates a condition called mixed polyuria<a class="elsevierStyleCrossRef" href="#bib0025"><span class="elsevierStyleSup">5</span></a>&#46;</p><p id="par0030" class="elsevierStylePara elsevierViewall">Urine volume is directly related to the total number of osmoles excreted per day&#46; The solutes involved in water excretion can be electrolytes &#40;Na<span class="elsevierStyleSup">&#43;</span>&#44; K<span class="elsevierStyleSup">&#43;</span>&#44; Cl<span class="elsevierStyleSup">&#8722;</span>&#44; and Ca<span class="elsevierStyleSup">&#43;&#43;</span>&#41; and nonelectrolytes such as urea&#44; glucose&#44; or others &#40;mannitol&#41;<a class="elsevierStyleCrossRef" href="#bib0030"><span class="elsevierStyleSup">6</span></a>&#46; The daily excretion of osmoles is estimated to be 10&#160;mOsm&#47;kg per day and they must be excreted in water&#46; This volume of free water can increase significantly when the intake of solutes is greater than 900&#160;mOsm&#47;day<a class="elsevierStyleCrossRef" href="#bib0035"><span class="elsevierStyleSup">7</span></a> or decrease if the excretion of solutes decreases significantly&#46;<a class="elsevierStyleCrossRef" href="#bib0040"><span class="elsevierStyleSup">8</span></a></p><p id="par0035" class="elsevierStylePara elsevierViewall">Polyuria can be incapacitating and severely affect quality of life&#44; altering the sleep cycle and daily activities&#44; and can even cause volume depletion and fluctuations in serum sodium levels&#46; Therefore&#44; polyuria is a challenge for clinicians&#44; given that because it can be generated due to multiple causes&#44; a diagnosis requires knowledge of the homeostasis of water balance&#44; sodium&#44; urine concentration mechanisms&#44; and a quantitative analysis of urine losses through electrolyte-free water clearance&#46; These concepts will help us understand the cause of the polyuria and identify appropriate treatment&#46;</p><p id="par0040" class="elsevierStylePara elsevierViewall">We will briefly explain some aspects of the physiology of urine concentration&#44; the determination of urine osmolarity&#44; and the concept of free water loss in order to facilitate comprehension of the differential diagnosis of polyuria&#46;</p><span id="sec0010" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0030">Physiology of urine concentration</span><p id="par0045" class="elsevierStylePara elsevierViewall">Plasma osmolarity &#40;Osm<span class="elsevierStyleInf">p</span>&#41; is monitored by osmoreceptors located in the hypothalamus&#44; which detect subtle changes in it&#46; In response to an increase in Osm<span class="elsevierStyleInf">p</span>&#44; vasopressin&#44; or antidiuretic hormone &#40;ADH&#41;&#44; is released&#46; Vasopressin is produced in the hypothalamus and is released through the neurohypophysis to act on V2 receptors in the basal membrane of the principle cells of the collecting duct tubules&#46; Its mechanism of action consists of increasing water reabsorption through transmembrane channels called aquaporins &#40;specifically aquaporin 2&#41;<a class="elsevierStyleCrossRef" href="#bib0020"><span class="elsevierStyleSup">4</span></a>&#46; If there is a decrease in vasopressin production or the kidney is not sensitive to it&#44; diabetes insipidus occurs&#46; In this case&#44; the Osm<span class="elsevierStyleInf">u</span> will be very low in relation to the Osm<span class="elsevierStyleInf">p</span>&#44; which will be elevated&#46;</p><p id="par0050" class="elsevierStylePara elsevierViewall">It is important to remember that the osmotic gradient for the movement of water through aquaporins depends on the concentration of solutes in the cells&#44; interstitium&#44; tubules&#44; and vessels of the medulla&#46; The osmotic gradient promotes the passage of water from the collecting duct tubules towards a more concentrated interstitium&#44; provoking an increase in interstitial osmolality<a class="elsevierStyleCrossRef" href="#bib0045"><span class="elsevierStyleSup">9</span></a>&#46; The main solutes involved in the osmotic gradient are sodium and urea&#46; However&#44; a precise mathematical model that evaluates the urea gradient has not been able to be developed&#46;</p><p id="par0055" class="elsevierStylePara elsevierViewall">The clinical importance of this physiological knowledge lies in the fact that urinary concentration defects have been observed due to abnormalities in the transporters of urea and other small solutes &#40;aquaglyceroporins&#41;&#46; Both are overexpressed as a response to the increase in ADH<a class="elsevierStyleCrossRef" href="#bib0050"><span class="elsevierStyleSup">10</span></a>&#46; This limits the interpretation of the water deprivation test for differentiating between diabetes insipidus and psychogenic polyuria &#40;a psychiatric disorder induced by excessive water intake&#41;&#46;</p><p id="par0060" class="elsevierStylePara elsevierViewall">On the other hand&#44; polyuria that continues over time can generate a renal medulla concentration gradient washout&#44; triggering a decrease in the maximum capacity for concentrating urine regardless of the polyuria&#8217;s primary cause and generating a relative resistance to ADH&#46; Therefore&#44; an absolute distinction between primary polydipsia and central diabetes insipidus or nephrogenic diabetes insipidus is often not able to be made&#46;</p></span><span id="sec0015" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0035">Determination of urine osmolarity</span><p id="par0065" class="elsevierStylePara elsevierViewall">Urine osmolarity is a measurement which expresses the total concentration of solutes and is defined as the number of osmoles &#40;Osm&#41; per liter of solute&#46; Urine osmolarity &#40;Osm<span class="elsevierStyleInf">u</span>&#41; can be measured using an osmometer or calculated using two formulas&#58;<ul class="elsevierStyleList" id="lis0010"><li class="elsevierStyleListItem" id="lsti0015"><span class="elsevierStyleLabel">1</span><p id="par0070" class="elsevierStylePara elsevierViewall">In the first formula&#44; Osm<span class="elsevierStyleInf">u</span> can be obtained by multiplying the last two urine density &#40;UD&#41; values by 35&#46; It is important to correct for glycosuria &#40;decrease UD by 0&#46;004 for every g&#47;dL&#41; and for proteinuria &#40;decrease UD by 0&#46;003 for every g&#47;dL&#41;<a class="elsevierStyleCrossRef" href="#bib0055"><span class="elsevierStyleSup">11</span></a></p><p id="par0071" class="elsevierStylePara elsevierViewall">Osm<span class="elsevierStyleInf">u</span> &#40;mOsm&#47;kg&#41;&#160;&#61;&#160;&#91;urine density&#160;&#8211;&#160;1000&#93;&#160;&#215;&#160;35</p></li></ul></p><p id="par0075" class="elsevierStylePara elsevierViewall">This formula is not valid if the patient is administered mannitol&#44; piperacillin&#44; carbenicillin&#44; or carbapenems&#46;<ul class="elsevierStyleList" id="lis0015"><li class="elsevierStyleListItem" id="lsti0020"><span class="elsevierStyleLabel">2</span><p id="par0080" class="elsevierStylePara elsevierViewall">The second formula is based on the determination of urine electrolytes and urea without considering glycosuria<a class="elsevierStyleCrossRef" href="#bib0055"><span class="elsevierStyleSup">11</span></a>&#58;</p><p id="par0081" class="elsevierStylePara elsevierViewall">Osm<span class="elsevierStyleInf">u</span> &#40;mOsm&#47;kg&#41;&#160;&#61;&#160;&#91;Na<span class="elsevierStyleInf">u</span>&#160;&#43;&#160;K<span class="elsevierStyleInf">u</span>&#93;&#160;&#215;&#160;2&#160;&#43;&#160;&#91;urea<span class="elsevierStyleInf">u</span>&#47;5&#46;6&#93;</p></li></ul></p><p id="par0085" class="elsevierStylePara elsevierViewall">The use of these formulas is limited because urine is a complex mixture of organic and inorganic compounds that can cause variation in the results obtained by the different UD measurement methods&#46; The Osm<span class="elsevierStyleInf">u</span> formula calculated for UD has very disperse correction values &#40;0&#46;73&#8211;0&#46;86&#41; and is better in &#8220;clean samples&#44;&#8221; that is&#44; those without proteinuria or glycosuria<a class="elsevierStyleCrossRef" href="#bib0060"><span class="elsevierStyleSup">12</span></a>&#46;</p><p id="par0090" class="elsevierStylePara elsevierViewall">What&#8217;s more&#44; when the urine pH measured by a reactive strip is high&#44; the UD will be falsely decreased and vice-versa&#46; For this reason&#44; this test is more reliable with a pH between 7 and 7&#46;5<a class="elsevierStyleCrossRef" href="#bib0065"><span class="elsevierStyleSup">13</span></a>&#46; Reactive strips indirectly measure specific gravity&#44; assuming that the ionic and nonionic constituents of urine are at a constant proportion&#46; This does not always happen in practice&#44; given that ionic constituents can be disproportionately elevated in children &#40;lower urea concentration&#41; and with conditions such as proteinuria&#44; hyperparathyroidism&#44; and hypercalciuria<a class="elsevierStyleCrossRef" href="#bib0070"><span class="elsevierStyleSup">14</span></a>&#46; In conclusion&#44; these formulas are useful as an initial approach if we know their limitations and interpret them cautiously&#46;</p></span><span id="sec0020" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0040">Determination of free water losses</span><p id="par0095" class="elsevierStylePara elsevierViewall">Free water clearance is the volume of water that must be removed or added to urine to make it isosmotic&#46; When urine is hypotonic&#44; free water clearance is positive&#44; that is&#44; the kidney is eliminating water from the organism&#46; In this case&#44; this would be the quantity of water that would have to be removed from the urine to make it isotonic&#46;</p><p id="par0100" class="elsevierStylePara elsevierViewall">Urine free water losses can occur in the diluted urine of patients with concentration abnormalities or also in relatively concentrated urines&#44; as occurs with the use of osmotic diuretics during recovery from acute kidney failure or due to excretion of highly osmolar content &#40;elevated protein intake&#44; administration of total parenteral nutrition&#44; or hypercatabolic states&#41;&#46; These latter conditions allow for explaining the onset and persistence of the hypernatremia these patients can present with<a class="elsevierStyleCrossRef" href="#bib0075"><span class="elsevierStyleSup">15</span></a>&#46;</p><p id="par0105" class="elsevierStylePara elsevierViewall">To understand free water clearance&#44; the total volume of urine &#40;V&#41; is conceptually separated into two components&#58; one consisting of isosmotic urine that contains all the solutes &#40;C<span class="elsevierStyleInf">osm</span>&#41; and another that only contains water &#40;C<span class="elsevierStyleInf">water</span>&#41; &#40;<a class="elsevierStyleCrossRef" href="#fig0005">Fig&#46; 1</a>&#41;&#46; The increase or decrease of this last component allows us to predict the plasma sodium concentration<a class="elsevierStyleCrossRef" href="#bib0080"><span class="elsevierStyleSup">16</span></a>&#46; Mathematically&#44; it is expressed in the following formula&#58;<elsevierMultimedia ident="eq0015"></elsevierMultimedia></p><elsevierMultimedia ident="fig0005"></elsevierMultimedia><p id="par0110" class="elsevierStylePara elsevierViewall">Osmolar clearance can be calculated using the general clearance formula&#58;<elsevierMultimedia ident="eq0020"></elsevierMultimedia></p><p id="par0115" class="elsevierStylePara elsevierViewall">Simplifying these equations&#44; we obtain the free water clearance formula&#58;<elsevierMultimedia ident="eq0025"></elsevierMultimedia></p><p id="par0120" class="elsevierStylePara elsevierViewall">By definition&#44; C<span class="elsevierStyleInf">osm</span> includes all osmoles&#46; However&#44; urea is not relevant to the generation of osmotic gradients because it is distributed in the intra- and extracellular space in equal concentrations&#59; it easily crosses cell membranes and moves through specific transporters in the collector duct tubules&#46; Therefore&#44; the original formula was modified<a class="elsevierStyleCrossRef" href="#bib0085"><span class="elsevierStyleSup">17</span></a> to only include urine osmoles that affect plasma sodium concentration &#40;Na<span class="elsevierStyleInf">p</span>&#41;&#44; called electrolyte-free water clearance or C<span class="elsevierStyleInf">water</span>&#40;e&#41;&#46;</p><p id="par0125" class="elsevierStylePara elsevierViewall">The equation can be modified by replacing Osm<span class="elsevierStyleInf">p</span> with Na<span class="elsevierStyleInf">p</span> and Osm<span class="elsevierStyleInf">u</span> with urine sodium and potassium &#40;Na<span class="elsevierStyleInf">u</span>&#160;&#43;&#160;K<span class="elsevierStyleInf">u</span>&#41;&#58;<elsevierMultimedia ident="eq0030"></elsevierMultimedia></p><p id="par0130" class="elsevierStylePara elsevierViewall">In conclusion&#44; if Na<span class="elsevierStyleInf">u</span>&#160;&#43;&#160;K<span class="elsevierStyleInf">u</span> is less than Na<span class="elsevierStyleInf">p</span>&#44; then the C<span class="elsevierStyleInf">water</span>&#40;e&#41; formula will have a positive result&#44; reflecting a loss of free water with a consequent hypernatremia with hypotonic urine&#46; On the contrary&#44; if Na<span class="elsevierStyleInf">u</span>&#160;&#43;&#160;K<span class="elsevierStyleInf">u</span> is greater than Na<span class="elsevierStyleInf">p</span>&#44; then C<span class="elsevierStyleInf">water</span>&#40;e&#41; will be negative&#44; reflecting an increase in free water with a consequent hyponatremia with hypertonic urine&#46;</p><p id="par0135" class="elsevierStylePara elsevierViewall">This formula also allows for understanding that in mixed or osmolar polyurias&#44; hypernatremia is generated by &#8220;diluted&#8221; urine&#46; For example&#44; in a patient with a high amount of urea excretion&#44; the original equation would predict a negative water excretion and a decrease in Na<span class="elsevierStyleInf">p</span>&#44; but in fact in these cases&#44; Na<span class="elsevierStyleInf">p</span> increases&#44; which can be predicted precisely by the latter equation&#46;</p></span><span id="sec0025" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0045">Polyuria due to water diuresis</span><p id="par0140" class="elsevierStylePara elsevierViewall">The causes of polyuria in outpatients are most frequently classified as polyurias due to water diuresis&#46; The three main causes are central diabetes insipidus&#44; nephrogenic diabetes insipidus&#44; and psychogenic polydipsia or primary polydipsia &#40;<a class="elsevierStyleCrossRef" href="#tbl0005">Table 1</a>&#41;&#46;</p><elsevierMultimedia ident="tbl0005"></elsevierMultimedia><p id="par0145" class="elsevierStylePara elsevierViewall">The incidence of diabetes insipidus in the general population is three cases out of every 100&#44;000 inhabitants&#44; with a slightly higher incidence in men &#40;60&#37;&#41; than women&#46; Congenital nephrogenic diabetes insipidus is a very rare disease with an incidence of four cases out of every 1&#44;000&#44;000 males<a class="elsevierStyleCrossRef" href="#bib0090"><span class="elsevierStyleSup">18</span></a>&#46;</p><p id="par0150" class="elsevierStylePara elsevierViewall">Psychogenic polydipsia is a defect in thirst control&#46; It is caused by a dysfunction in the production or release of ADH and is not always accompanied by a psychiatric disorder&#46; Psychogenic polydipsia is characterized by compulsive water consumption due to fear of dehydration or a belief that one&#8217;s health improves with excessive consumption&#46; It can also be observed in patients with hypothalamic sequelae of cranioencephalic trauma&#44; vascular diseases&#44; or infiltrative diseases of the hypothalamus such as sarcoidosis<a class="elsevierStyleCrossRef" href="#bib0095"><span class="elsevierStyleSup">19</span></a>&#46; Its incidence is not known&#44; but it seems to primary affect women &#40;80&#37; of cases&#41; and its onset occurs in the third decade of life&#46; Up to 40&#37; of patients with schizophrenia present with it<a class="elsevierStyleCrossRef" href="#bib0090"><span class="elsevierStyleSup">18</span></a>&#46; Nevertheless&#44; the prevalence of psychogenic polydipsia is increasing in the general population due to a belief in the beneficial health effects of high fluid consumption<a class="elsevierStyleCrossRef" href="#bib0100"><span class="elsevierStyleSup">20</span></a>&#46;</p><p id="par0155" class="elsevierStylePara elsevierViewall">When polyuria is due to water diuresis&#44; conducting a water deprivation test has classically been suggested in order to differentiate between diabetes insipidus and psychogenic polydipsia&#46; This test&#44; initially described by Miller et al&#46; in 1970<a class="elsevierStyleCrossRef" href="#bib0105"><span class="elsevierStyleSup">21</span></a>&#44; has demonstrated a limited diagnostic precision of 70&#37;&#46; It has even been found that just 41&#37; of patients with psychogenic polydipsia have the correct diagnosis<a class="elsevierStyleCrossRef" href="#bib0005"><span class="elsevierStyleSup">1</span></a>&#46; For this reasons&#44; other diagnostic methods such as magnetic resonance imaging of the hypophysis and copeptin measurements are used&#44; achieving sensitivities and specificities of greater than 90&#37; in differentiating between psychogenic polydipsia and partial central diabetes insipidus with each of these tests<a class="elsevierStyleCrossRef" href="#bib0005"><span class="elsevierStyleSup">1</span></a>&#46;</p><p id="par0160" class="elsevierStylePara elsevierViewall">Copeptin is a glycopeptide formed by a chain of 39 amino acids&#46; It is the terminal fraction of the provasopressin molecule &#40;precursor of vasopressin or antidiuretic hormone&#41;&#46; There is a high correlation between levels of copeptin and levels of vasopressin &#40;coefficient of correlation 0&#46;8&#41;&#46; Due to the difficulty of measuring vasopressin levels&#44; measurements of copeptin levels are used in clinical practice&#46; Their blood values in normal individuals range from 1 to 12&#160;pmol&#47;L<a class="elsevierStyleCrossRefs" href="#bib0110"><span class="elsevierStyleSup">22&#44;23</span></a>&#46;</p></span><span id="sec0030" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0050">Polyuria due to osmotic diuresis and&#47;or mixed polyuria</span><p id="par0165" class="elsevierStylePara elsevierViewall">The most frequent cause of polyuria due to osmotic diuresis in outpatients is hyperglycemia&#46; However&#44; there are also cases due to consumption of nutritional supplements that are high in protein&#44; mainly in athletes<a class="elsevierStyleCrossRef" href="#bib0120"><span class="elsevierStyleSup">24</span></a>&#46;</p><p id="par0170" class="elsevierStylePara elsevierViewall">In order to diagnose polyuria due to osmotic diuresis or mixed polyuria&#44; it is necessary to collect a 24-h urine sample and measure electrolytes&#44; glucose&#44; creatinine&#44; and urea nitrogen&#46; With these values&#44; it is possible to calculate the daily excretion of osmoles and measure Osm<span class="elsevierStyleInf">u</span> in order to detect solutes that generate intratubular water movement &#40;<a class="elsevierStyleCrossRef" href="#tbl0005">Table 1</a>&#41;&#46;</p><p id="par0175" class="elsevierStylePara elsevierViewall">Daily osmole excretion &#40;Osm<span class="elsevierStyleInf">u</span> multiplied by 24-h urine volume&#41; is the sum of the excretion of electrolyte and nonelectrolyte solutes&#44; all expressed as milliosmoles per day&#46; Then&#44; the next step in the study is to determine the type of solute responsible for the polyuria &#40;<a class="elsevierStyleCrossRef" href="#fig0010">Fig&#46; 2</a>&#41;&#46;</p><elsevierMultimedia ident="fig0010"></elsevierMultimedia><p id="par0180" class="elsevierStylePara elsevierViewall">The contribution of electrolytes to the polyuria can be estimated by multiplying the sum of Na<span class="elsevierStyleInf">u</span>&#160;&#43;&#160;K<span class="elsevierStyleInf">u</span> measured in a 24-h urine sample by 2&#44; assuming that there are no other quantitatively significant cations in the daily excretion of osmoles<a class="elsevierStyleCrossRef" href="#bib0125"><span class="elsevierStyleSup">25</span></a>&#46; Values greater than 600&#160;mOsm&#47;day suggest that electrolytes are the solutes that generate the polyuria whereas a value lower than 600&#160;mOsm&#47;day points toward the diuresis being due to a nonelectrolyte solute&#44; typically glucose or urea&#44; as we will explain later on&#46;</p><p id="par0185" class="elsevierStylePara elsevierViewall">This can be confirmed if an osmometer-measured Osm<span class="elsevierStyleInf">u</span> value is available&#59; if there is concordance with the osmometer-measured Osm<span class="elsevierStyleInf">u</span> value&#44; the polyuria is due to electrolytes&#46; On the contrary&#44; if the osmometer-measured Osm<span class="elsevierStyleInf">u</span> is greater than what is calculated using the formula&#44; it can be assumed that it is an osmotic diuresis not mediated by electrolytes<a class="elsevierStyleCrossRef" href="#bib0025"><span class="elsevierStyleSup">5</span></a>&#46;</p><p id="par0190" class="elsevierStylePara elsevierViewall">Polyuria due to electrolyte washout is usually measured by a sodium salt &#40;often chloride&#41; as a consequence of excessive administration of saline solution&#44; intravenous sodium bicarbonate administration&#44; excessive salt intake&#44; or use of loop diuretics&#46; However&#44; there may be other possibilities&#46; Measuring Na<span class="elsevierStyleInf">u</span>&#44; K<span class="elsevierStyleInf">u</span>&#44; and urinary chloride &#40;Cl<span class="elsevierStyleInf">u</span>&#41; values can be of help&#44; as these values are used to calculate the urine anion gap&#44; which allows for searching for an anion other than chloride which may be associated with the sodium&#46; The urine anion gap is calculated by adding sodium and potassium and subtracting chloride &#40;&#91;Na<span class="elsevierStyleInf">u</span>&#160;&#43;&#160;K<span class="elsevierStyleInf">u</span>&#93;&#160;&#8722;&#160;&#91;Cl<span class="elsevierStyleInf">u</span>&#93;&#41;&#46;</p><p id="par0195" class="elsevierStylePara elsevierViewall">A positive value indicates the presence of one or more anions apart from chloride in urine<a class="elsevierStyleCrossRef" href="#bib0130"><span class="elsevierStyleSup">26</span></a>&#46; This anion tends to be bicarbonate&#44; therefore a pH of around 7&#46;4 indicates large quantities of this anion in the urine<a class="elsevierStyleCrossRef" href="#bib0135"><span class="elsevierStyleSup">27</span></a>&#46; A urine pH value of less than 6&#46;4 rules out the bicarbonate anion as the cause and makes it necessary to search for others&#44; such as ketoacids and an excess of anions related to toxins or drugs such as salicylates<a class="elsevierStyleCrossRef" href="#bib0130"><span class="elsevierStyleSup">26</span></a>&#46;</p><p id="par0200" class="elsevierStylePara elsevierViewall">Osmotic diuresis not mediated by electrolytes can be observed in patients who are catabolizing a large quantity of protein&#44; whether due to enteral or parenteral nutrition&#44; hypercatabolic states&#44; or the resolution of obstructive uropathy&#46; In these patients&#44; the urea is dragged by the water&#46; When this occurs&#44; values of daily nonelectrolyte osmole excretion of less than 600&#160;mOsm can be abnormal and be enough to generate polyuria&#44; depending on patient&#39;s pathophysiological state&#46; Urea nitrogen values of 0&#46;7&#160;g&#47;dL or its equivalent of 1500&#160;mg&#47;dL of urine urea are able to generate solute diuresis<a class="elsevierStyleCrossRef" href="#bib0125"><span class="elsevierStyleSup">25</span></a>&#46;</p><p id="par0205" class="elsevierStylePara elsevierViewall">In daily practice&#44; particularly in critical care units&#44; it should be suspected that these patients lose hypotonic fluid in the urine due to urea-induced osmotic diuresis&#46; At the same time&#44; these losses are replaced with isotonic fluids that are in fact hypertonic compared to their urine&#44; resulting in an increase in sodium and secondary hypernatremia&#46; In this case&#44; it is again useful to calculate C<span class="elsevierStyleInf">water</span>&#40;e&#41; as it allows for guiding the quantity of free water necessary for maintaining natremia at a desired value&#46;</p><p id="par0210" class="elsevierStylePara elsevierViewall">Glucose becomes present in urine if there is a decrease in the capacity to reabsorb filtered glucose or when there are plasma glucose concentrations greater than 200&#8211;250&#160;mg&#47;dL &#40;exceeding the maximum transport capacity of SGLT-2 and SLGT-1 transporters in the proximal tubule&#41;<a class="elsevierStyleCrossRef" href="#bib0140"><span class="elsevierStyleSup">28</span></a>&#46; The glycosuria observed in diabetic ketoacidosis or hyperglycemic hyperosmolar syndrome can generate excretion of more than 833&#160;mmol&#44; corresponding to 150&#160;g of glucose per day&#44; which is able to produce an additional 1&#46;7&#8211;2&#46;8&#160;L of urine<a class="elsevierStyleCrossRef" href="#bib0025"><span class="elsevierStyleSup">5</span></a>&#46;</p><p id="par0215" class="elsevierStylePara elsevierViewall">In clinical studies&#44; pharmacological inhibition of SGLT-2 generated an increase in urine volume just a few days after initiating treatment&#44; leading to osmotic diuresis mediated by natriuresis with glycosuria&#44; achieving an increase of 1&#8211;1&#46;5 times the baseline level<a class="elsevierStyleCrossRef" href="#bib0145"><span class="elsevierStyleSup">29</span></a>&#46;</p><p id="par0220" class="elsevierStylePara elsevierViewall">In these cases&#44; the results of the urine study must be evaluated individually according to the clinical context<a class="elsevierStyleCrossRefs" href="#bib0130"><span class="elsevierStyleSup">26&#44;30</span></a>&#46; Likewise&#44; it should be remembered that an approach using the C<span class="elsevierStyleInf">water</span>&#40;e&#41; formula based on osmolarity &#40;influenced by urea concentration&#41; may not correctly evaluate the renal management of water<a class="elsevierStyleCrossRef" href="#bib0155"><span class="elsevierStyleSup">31</span></a>&#46;</p></span></span><span id="sec0035" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0055">Clinical case 1</span><p id="par0225" class="elsevierStylePara elsevierViewall">A 31-year-old male consulted for intense&#44; progressive thirst that had been ongoing for six months&#44; with consumption of 18&#160;L of water per day associated with nocturia and polyuria of 18&#160;L&#47;day&#46; He did not take protein supplements&#46; Upon physical examination&#44; he did not present with any relevant findings&#46;</p><p id="par0230" class="elsevierStylePara elsevierViewall">The study found an Na<span class="elsevierStyleInf">p</span> of 144&#160;mEq&#47;L&#44; Osm<span class="elsevierStyleInf">p</span> of 283&#160;mOsm&#47;kg&#44; 24-h urine volume of 11&#44;660&#160;mL&#44; and Osm<span class="elsevierStyleInf">u</span> of 79&#160;mOsm&#47;kg&#46; On the 24-h urine test&#44; an Na<span class="elsevierStyleInf">u</span> of 20&#160;mEq&#47;L and K<span class="elsevierStyleInf">u</span> of 6&#46;8&#160;mEq&#47;L were found&#46;</p><p id="par0235" class="elsevierStylePara elsevierViewall">As the Osm<span class="elsevierStyleInf">u</span> was hypotonic&#8212;less than 150&#160;mOsm&#47;kg&#8212;the polyuria was due to water diuresis&#46;</p><p id="par0240" class="elsevierStylePara elsevierViewall">Given that the patient had not increased water intake in association with a particular diet&#44; did not have a psychiatric disease&#44; and his levels of blood sodium were within the upper normal limits&#44; a diagnosis of diabetes insipidus was proposed&#46; A water deprivation test was performed to differentiate between central or nephrogenic diabetes insipidus or primary polydipsia &#40;<a class="elsevierStyleCrossRef" href="#fig0015">Fig&#46; 3</a>&#41;&#46; It was interpreted as polyuria due to water diuresis secondary to central diabetes insipidus&#46;</p><elsevierMultimedia ident="fig0015"></elsevierMultimedia><p id="par0245" class="elsevierStylePara elsevierViewall">In the case of our patient&#44; despite not having reached a concentration greater than 800&#160;mOsm&#47;kg&#44; perhaps due to the mechanisms of medullary concentration washout secondary to the polyuria&#44; an increase in the Osm<span class="elsevierStyleInf">u</span> of greater than 50&#37; was achieved&#44; which was enough to diagnose central diabetes insipidus&#46;</p><p id="par0250" class="elsevierStylePara elsevierViewall">When we calculated the electrolyte-free water clearance using the C<span class="elsevierStyleInf">water</span>&#40;e&#41; equation&#44; the result was positive&#58; 6&#46;6&#160;mL&#47;min&#46; In other words&#44; the patient had a loss of 9504 cc of free water in a total urine volume of 11&#44;660 cc&#44; concordant with the hypernatremia observed due to a large loss of free water&#46;</p><p id="par0255" class="elsevierStylePara elsevierViewall">For the central diabetes insipidus study &#40;<a class="elsevierStyleCrossRef" href="#tbl0005">Table 1</a>&#41;&#44; magnetic resonance imaging of the sella turcica with gadolinium was performed to search for a CNS tumor&#46; The results were suggestive of lymphocytic infundibular neurohypophysitis&#46; Treatment was started with intranasal desmopressin with a good response&#59; the natremia&#44; urinary frequency&#44; and thirst normalized&#46;</p></span><span id="sec0040" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0060">Clinical case 2</span><p id="par0260" class="elsevierStylePara elsevierViewall">An 85-year-old male with a medical history of benign prostatic hyperplasia&#46; Consulted due to anuria and abdominal pain&#46; Of note on the blood test were a plasma creatinine level of 8&#160;mg&#47;dL and a plasma urea level of 192&#46;6&#160;mg&#47;dL&#46; The kidney ultrasound showed bilateral hydroureteronephrosis&#46;</p><p id="par0265" class="elsevierStylePara elsevierViewall">A urinary catheter was placed&#44; which drained 5500&#160;mL of urine in 90&#160;min&#59; an improvement in renal function was observed in the following days&#46; Replacement was started with 0&#46;9&#37; saline solution at a ratio of 75&#37; of the diuresis&#46; However&#44; polyuria of 6000&#160;mL in 24&#160;h persisted&#46;</p><p id="par0270" class="elsevierStylePara elsevierViewall">The study found a Na<span class="elsevierStyleInf">p</span> of 148&#160;mEq&#47;L&#44; Osm<span class="elsevierStyleInf">p</span> of 285&#160;mOsm&#47;kg&#44; and Osm<span class="elsevierStyleInf">u</span> of 289&#160;mOsm&#47;kg&#46; The 24-h urine collection test showed a urine volume of 6000&#160;mL&#44; Na<span class="elsevierStyleInf">u</span> of 110&#160;mmol&#47;L&#44; K<span class="elsevierStyleInf">u</span> of 30&#160;mmol&#47;L&#44; Cl<span class="elsevierStyleInf">u</span> of 149&#160;mmol&#47;L&#44; and urea of 828&#46;9&#160;mg&#47;dL&#44; without glycosuria&#46; The urine anion gap &#40;&#91;Na<span class="elsevierStyleInf">u</span>&#160;&#43;&#160;K<span class="elsevierStyleInf">u</span>&#93;&#160;&#8722;&#160;&#91;Cl<span class="elsevierStyleInf">u</span>&#93;&#41; was negative&#46;</p><p id="par0275" class="elsevierStylePara elsevierViewall">Given that the Osm<span class="elsevierStyleInf">u</span> was 289&#160;mOsm&#47;kg&#44; it was considered to be mixed polyuria&#46; To define the type of solute that generated the polyuria &#40;electrolyte or nonelectrolyte&#41;&#44; the total quantity of urine solutes in 24&#160;h was estimated as electrolytes &#40;Ue&#41;&#58;<elsevierMultimedia ident="eq0035"></elsevierMultimedia><elsevierMultimedia ident="eq0040"></elsevierMultimedia></p><p id="par0280" class="elsevierStylePara elsevierViewall">Upon comparing this value to the urine solute load&#8212;Osm<span class="elsevierStyleInf">u</span>&#160;&#215;&#160;6&#160;L &#40;289&#160;&#215;&#160;6&#41;&#8212;the result was 1734&#160;mOsm&#46; Given the above&#44; it can be concluded that out of the total solute load &#40;1734&#160;mOsm&#41;&#44; 1680&#160;mOsm corresponded to electrolytes&#46; This indicates that it was polyuria due to electrolyte-dependent solutes&#46;</p><p id="par0285" class="elsevierStylePara elsevierViewall">The next step in this clinical case was to determine the predominant electrolyte in the urine&#46; This was obtained by calculating sodium and chloride excretion in the urine&#44; which is obtained by multiplying the concentration of each of these electrolytes by the urine volume &#40;in liters&#41;&#58;<elsevierMultimedia ident="eq0045"></elsevierMultimedia><elsevierMultimedia ident="eq0050"></elsevierMultimedia></p><p id="par0290" class="elsevierStylePara elsevierViewall">These values exceed the relatively normal figures for a patient who follows a typical American diet &#40;Na<span class="elsevierStyleInf">u</span> 150&#160;mmol&#44; Cl<span class="elsevierStyleInf">u</span> 120&#160;mmol&#41;<a class="elsevierStyleCrossRef" href="#bib0025"><span class="elsevierStyleSup">5</span></a>&#46; Therefore&#44; Na<span class="elsevierStyleInf">u</span> and Cl<span class="elsevierStyleInf">u</span> were the main solutes in the patient&#8217;s urine&#46; The above&#44; together with the negative urine anion gap value&#44; means that there was little excretion of nonchloride anions&#44; which indicates that the mechanism of the polyuria was secondary to the administration of saline solution as a fluid replacement solution&#44; which perpetuated the polyuria&#46; In this case&#44; there was no mechanism mediated by a nonelectrolyte solute &#40;urea&#41;&#44; as is expected in obstructive uropathy&#46;</p><p id="par0295" class="elsevierStylePara elsevierViewall">The electrolyte-free water clearance calculated using the C<span class="elsevierStyleInf">water</span>&#40;e&#41; equation was positive&#58; 0&#46;2&#160;mL&#47;min&#46; In other words&#44; there was a loss of 288&#160;mL of free water in a total urine volume of 6000&#160;mLc together with electrolyte-free water diuresis&#44; which was concordant with the mild hypernatremia observed&#46;</p></span><span id="sec0045" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0065">Conclusion</span><p id="par0300" class="elsevierStylePara elsevierViewall">The evaluation of polyuric states is a challenge in internal medicine due to a lack of familiarity with the formulas presented herein&#46; However&#44; their understanding and use allow us to organize the diagnostic study of polyurias and estimate free water losses with a very high degree of precision&#46;</p><p id="par0305" class="elsevierStylePara elsevierViewall">Therefore&#44; measured and calculated urine osmolarity&#44; the estimation of daily urine osmole excretion&#44; their nature&#44; the water deprivation test in water and mixed polyurias&#44; and electrolyte-free water clearance are essential diagnostic tests that must be included in the evaluation of polyuria-polydipsia syndrome&#46;</p></span><span id="sec0050" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0070">Funding</span><p id="par0310" class="elsevierStylePara elsevierViewall">The research has not received specific grants from agencies in the public&#44; commercial&#44; or non-profit sectors&#46;</p></span><span id="sec0055" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0075">Conflicts of interest</span><p id="par0315" class="elsevierStylePara elsevierViewall">The authors of this article have no conflicts of interest to declare&#46;</p></span></span>"
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          "titulo" => "Introduction"
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            0 => array:2 [
              "identificador" => "sec0010"
              "titulo" => "Physiology of urine concentration"
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            1 => array:2 [
              "identificador" => "sec0015"
              "titulo" => "Determination of urine osmolarity"
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            2 => array:2 [
              "identificador" => "sec0020"
              "titulo" => "Determination of free water losses"
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            3 => array:2 [
              "identificador" => "sec0025"
              "titulo" => "Polyuria due to water diuresis"
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            4 => array:2 [
              "identificador" => "sec0030"
              "titulo" => "Polyuria due to osmotic diuresis and&#47;or mixed polyuria"
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          "identificador" => "sec0035"
          "titulo" => "Clinical case 1"
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    "fechaAceptado" => "2021-03-18"
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            1 => "Hypernatremia"
            2 => "Electrolyte free water clearance"
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          "clase" => "keyword"
          "titulo" => "Palabras clave"
          "identificador" => "xpalclavsec1506762"
          "palabras" => array:3 [
            0 => "Poliuria"
            1 => "Hipernatremia"
            2 => "Aclaramiento de agua libre de electrolitos"
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    "resumen" => array:2 [
      "en" => array:2 [
        "titulo" => "Abstract"
        "resumen" => "<span id="abst0005" class="elsevierStyleSection elsevierViewall"><p id="spar0045" class="elsevierStyleSimplePara elsevierViewall">Polyuria is a common clinical condition characterized by a urine output that is inappropriately high &#40;more than 3&#160;L in 24&#160;h&#41; for the patient&#8217;s blood pressure and plasma sodium levels&#46; From a pathophysiological point of view&#44; it is classified into two types&#58; polyuria due to a greater excretion of solutes &#40;urine osmolality &#62;300&#160;mOsm&#47;L&#41; or due to an inability to increase solute concentration &#40;urine osmolality &#60;150&#160;mOsm&#47;L&#41;&#46; Sometimes both mechanisms can coexist &#40;urine osmolality 150&#8211;300&#160;mOsm&#47;L&#41;&#46; Polyuria is a diagnostic challenge and its proper treatment requires an evaluation of the medical record&#44; determination of urine osmolality&#44; estimation of free water clearance&#44; use of water deprivation tests in aqueous polyuria&#44; and measurement of electrolytes in blood and urine in the case of osmotic polyuria&#46;</p></span>"
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      "es" => array:2 [
        "titulo" => "Resumen"
        "resumen" => "<span id="abst0010" class="elsevierStyleSection elsevierViewall"><p id="spar0050" class="elsevierStyleSimplePara elsevierViewall">La poliuria es una condici&#243;n cl&#237;nica frecuente caracterizada por un volumen de orina inapropiadamente alto para los niveles de presi&#243;n arterial y sodio plasm&#225;tico del paciente &#40;volumen de orina &#62;3&#160;L&#47;24&#160;h&#41;&#46; Desde el punto de vista fisiopatol&#243;gico se clasifica en 2 tipos&#58; debido a una mayor excreci&#243;n de solutos &#40;osmolaridad urinaria &#62;300&#160;mOsm&#47;L&#41; o debido a una incapacidad de aumentar la concentraci&#243;n de solutos &#40;osmolaridad urinaria &#60;150&#160;mOsm&#47;L&#41;&#46; En ocasiones pueden coexistir ambos mecanismos &#40;osmolaridad urinaria 150&#8211;300&#160;mOsm&#47;L&#41;&#46; La poliuria supone un reto diagn&#243;stico y su tratamiento correcto exige una evaluaci&#243;n de la historia cl&#237;nica&#44; la determinaci&#243;n de la osmolaridad urinaria&#44; la estimaci&#243;n del aclaramiento de agua libre&#44; el uso de pruebas de deprivaci&#243;n h&#237;drica en la poliuria acuosa y la medici&#243;n de electr&#243;litos en sangre y orina en el caso de la poliuria osm&#243;tica&#46;</p></span>"
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    "NotaPie" => array:1 [
      0 => array:2 [
        "etiqueta" => "&#9734;"
        "nota" => "<p class="elsevierStyleNotepara" id="npar0005">Please cite this article as&#58; Ram&#237;rez-Guerrero G&#44; M&#252;ller-Ortiz H&#44; Pedreros-Rosales C&#46; Poliuria en el adulto&#46; Una aproximaci&#243;n diagn&#243;stica basada en la fisiopatolog&#237;a&#46; Rev Clin Esp&#46; 2022&#59;222&#58;301&#8211;308&#46;</p>"
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          "en" => "<p id="spar0005" class="elsevierStyleSimplePara elsevierViewall">Free water and electrolyte-free water clearance flowchart and formula&#46;</p> <p id="spar0010" class="elsevierStyleSimplePara elsevierViewall">C<span class="elsevierStyleInf">water</span>&#40;e&#41;&#58; electrolyte-free water clearance&#59; C<span class="elsevierStyleInf">osm</span>&#58; osmolar clearance&#59; K<span class="elsevierStyleInf">u</span>&#58; urine potassium&#59; Na<span class="elsevierStyleInf">p</span>&#58; plasma sodium&#59; Na<span class="elsevierStyleInf">U</span>&#58; urine sodium&#46;</p>"
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          "en" => "<p id="spar0015" class="elsevierStyleSimplePara elsevierViewall">Suggested flowchart for the differential diagnosis of polyuria&#46;</p> <p id="spar0020" class="elsevierStyleSimplePara elsevierViewall">UAG&#58; urine anion gap&#46; Difference in milliequivalents per liter between the sum of Na<span class="elsevierStyleInf">u</span>&#160;&#43;&#160;K<span class="elsevierStyleInf">u</span> and Cl<span class="elsevierStyleInf">u</span>&#59; Ue&#58; urine electrolytes&#46; 2&#215; &#40;Na<span class="elsevierStyleInf">u</span>&#160;&#43;&#160;K<span class="elsevierStyleInf">u</span>&#41;&#46;</p>"
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          "en" => "<p id="spar0025" class="elsevierStyleSimplePara elsevierViewall">Water deprivation test&#46;</p> <p id="spar0030" class="elsevierStyleSimplePara elsevierViewall">In the figure&#44; it can be observed that the patient started the deprivation test with a reduced Osm<span class="elsevierStyleInf">u</span> and continued with diluted urine despite 240&#160;min of water deprivation&#46; Following administration of desmopressin&#44; a urine concentration appropriate for the Osm<span class="elsevierStyleInf">p</span> was achieved&#46;</p>"
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          "leyenda" => "<p id="spar0040" class="elsevierStyleSimplePara elsevierViewall">DKA&#58; diabetic ketoacidosis&#59; iSGLT-2&#58; sodium&#47;glucose cotransporter 2 inhibitors&#59; ATN&#58; acute tubular necrosis&#59; HHS&#58; hyperglycemic hyperosmolar syndrome&#59; CNS&#58; central nervous system&#59; OU&#58; obstructive uropathy&#46;</p>"
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                  \t\t\t\t\tvoid\n
                  \t\t\t\t" class=""><thead title="thead"><tr title="table-row"><th class="td" title="\n
                  \t\t\t\t\ttable-head\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t" scope="col" style="border-bottom: 2px solid black">Osmotic&nbsp;\t\t\t\t\t\t\n
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                  \t\t\t\t\ttable-head\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t" scope="col" style="border-bottom: 2px solid black">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t\t\t</th><th class="td" title="\n
                  \t\t\t\t\ttable-head\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t" scope="col" style="border-bottom: 2px solid black">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t\t\t</th></tr></thead><tbody title="tbody"><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t"><span class="elsevierStyleItalic">Electrolytes</span>&nbsp;\t\t\t\t\t\t\n
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                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
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                  \t\t\t\t">Sodium&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Infusion of iso- or hypertonic sodium chloride&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Renal sodium losses&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Anion&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Chloride&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Diuretics&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Bartter syndrome&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Bicarbonate&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Exogenous administration&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Acetazolamide&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Ketoanion&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">DKA&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " colspan="3" align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t"><span class="elsevierStyleVsp" style="height:0.5px"></span></td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t"><span class="elsevierStyleItalic">Nonelectrolyte</span>&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Glucose&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Exogenous loading&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">DKA-HHS&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">iSGLT-2&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Urea&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Exogenous loading&#44; protein or amino acids&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Hypercatabolism&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">ATN&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">After OU&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Mannitol&#47;sorbitol&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t"><span class="elsevierStyleBold">Water</span>&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t"><span class="elsevierStyleItalic">Excess intake</span>&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Psychogenic polydipsia&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Iatrogenic&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t"><span class="elsevierStyleItalic">Diabetes insipidus</span>&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Central&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Cranioencephalic trauma&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">CNS tumors&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">CNS infections&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Sheehan syndrome&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Subarachnoid hemorrhage&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">CNS lupus&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Sarcoidosis&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Nephrogenic&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Hypokalemia&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Hypercalciuria&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Lithium&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Sarcoidosis&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Sickle cell anemia&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Obstructive uropathy&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr><tr title="table-row"><td class="td-with-role" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t ; entry_with_role_rowhead " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td><td class="td" title="\n
                  \t\t\t\t\ttable-entry\n
                  \t\t\t\t  " align="left" valign="\n
                  \t\t\t\t\ttop\n
                  \t\t\t\t">Polycystic kidney disease&nbsp;\t\t\t\t\t\t\n
                  \t\t\t\t</td></tr></tbody></table>
                  """
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      "