Chloride, 24-Hour Urine

CPT: 82436
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Test Details

Use

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.

Limitations

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

Methodology

Colorimetric; ion-selective electrode (ISE)

Reference Interval

110−250 mmol/24 hours

Additional Information

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

Specimen Requirements

Specimen

Urine (24-hour)

Volume

10 mL aliquot of entire collection

Minimum Volume

0.5 mL aliquot

Container

Plastic urine container, no preservative

Collection

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.

Storage Instructions

Room temperature

Stability Requirements

Temperature

Period

Room temperature

14 days

Refrigerated

14 days

Frozen

14 days

Freeze/thaw cycles

Stable x3

Causes for Rejection

Improper labeling

Clinical Information

Special Instructions

State 24-hour volume on the test request form.

Footnotes

1. Sherman RA, Eisinger RP. The use (and misuse) of urinary sodium and chloride measurements. JAMA. 1982 Jun 11; 247(22):3121-3124. 7077808
2. Sherman RA, Eisinger RP. Urinary sodium and chloride during renal salt retention. Am J Kidney Dis. 1983 Sep; 3(2):121-123. 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. 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. 3344005

LOINC® Map

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

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