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Evaluate electrolyte composition of urine, acid-base balance studies. Distinguish whether or not a case of metabolic alkalosis is chloride-responsive (salt responsive). Sherman and Eisinger1,2 discuss bicarbonate excretion, blood volume, potassium depletion, and the differential diagnosis of metabolic alkalosis with loss of gastric juice (emesis, intubation) and after diuretics. Chloride depleted patients excrete urine with low chloride, <10 mmol/L. Such patients are chloride-responsive (ie, they respond to chloride sufficient to return body stores to normal). Metabolic alkalosis with low urine chloride is also found with villous tumors of the colon.
Endogenous or exogenous corticosteroids produce urine chloride values >20 mmol/L. Such patients are chloride resistant. The finding of chloride resistant metabolic alkalosis may provide a stimulus to identify an ACTH or aldosterone producing neoplasm (eg, Cushing syndrome or Conn syndrome). In Bartter syndrome with metabolic alkalosis, there is usually increased urine chloride. The complex relationships of chronic pulmonary disease with metabolic alkalosis are mentioned by Sherman and Eisinger.
Halogens other than chloride (bromide), which are also present in urine may erroneously elevate the chloride result. Isolated urine chloride, without urine sodium or potassium or without serum electrolytes, can provide misleading information. Discussion of electrolyte balance is beyond the scope of this manual (eg, effect of profound potassium depletion on impairment of chloride reabsorption). Fetal urinary electrolytes are an unreliable guide to evaluate fetal renal function.3
Colorimetric; ion-selective electrode (ISE)
110−250 mmol/24 hours
Urine chloride is often ordered with sodium and potassium as a timed urine. The urinary anion gap [Na+ − (Cl− + HCO3−)] or [(Na+ + K+) − (Cl−)] is useful in the initial evaluation of hyperchloremic metabolic acidosis.4
10 mL aliquot of entire collection
0.5 mL aliquot
For a 24-hour collection, instruct patient to void at 8 AM (or 8 PM), and discard the specimen. Then collect all the urine including the final specimen voided at the end of the 24-hour collection period (ie, 8 AM [or 8 PM] the following day). Container must be labeled with patient's name and date and time collection started and finished.
Causes for Rejection
State 24-hour volume on the test request form.
|Order Code||Order Code Name||Order Loinc||Result Code||Result Code Name||UofM||Result LOINC|
|003160||Chloride, 24 hr Urine||013656||Chloride, Urine||mmol/L||21194-6|
|003160||Chloride, 24 hr Urine||013284||Chloride Urine||mmol/24 hr||2079-2|