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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
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
1. Sherman RA, Eisinger RP. The use (and misuse) of urinary sodium and chloride measurements. JAMA. 1982 Jun 11; 247(22):3121-3124. PubMed 7077808
2. Sherman RA, Eisinger RP. Urinary sodium and chloride during renal salt retention. Am J Kidney Dis. 1983 Sep; 3(2):121-123. PubMed 6613992
3. Elder JS, O'Grady JP, Ashmead G, Duckett JW, Philipson E. Evaluation of fetal renal function: Unreliability of fetal urinary electrolytes. J Urol. 1990 Aug; 144(2 Pt 2):574-578. PubMed 2197439
4. Batlle DC, Hizon M, Cohen E, Gutterman C, Gupta R. The use of the urinary anion gap in the diagnosis of hyperchloremic metabolic acidosis. N Engl J Med. 1988 Mar 10; 318(10):594-599. PubMed 3344005
