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.
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
10 mL aliquot of entire collection
0.5 mL aliquot
Plastic urine container, no preservative
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.
Room temperature 14 days
Frozen 14 days
Freeze/thaw cycles Stable x3