Creatinine, 24-Hour Urine

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Category:

Turnaround Time: Within 1 day
CPT Code:

82570

Test Type: 10 mL aliquot of entire collection, Urine
Stability Time:

Temperature

Period

Room temperature

7 days

Refrigerated

14 days

Frozen

14 days

Freeze/thaw cycles

Stable x3

Overview:

Renal function test when used as part of creatinine clearance; crude marker for completeness of 24-hour urine collections when collected for other purposes.

Complete urine collections require vigilance on the part of nursing personnel. Ingestion of meat may increase creatinine values of urine collections as well as serum creatinine values. Drugs interfering with tubular creatinine secretion include cimetidine, trimethoprim, and probenecid. Creatinine reabsorption occurs with very low urine flow rates. Entities in which reabsorption occurs include severe congestive heart failure, uncontrolled diabetes mellitus, and acute renal failure.1

Urine creatinine is not ordered alone. Creatinine clearance, which requires a serum creatinine, offers useful renal function data. Serum creatinine alone is not an adequate index of glomerular filtration rate.1

1. Levey AS, Perrone RD, Madias NE. Serum creatinine and renal function. Annu Rev Med. 1988; 39:465-490 (review). PubMed 3285786

Collection Details:

Collection Instructions:

Record total 24-hour urine volume on the request form.

Plastic urine container, with or without 6N HCl.

If the specimen is a 24-hour collection instruct the patient to void at 8 AM and discard the specimen. Then collect all urine including the final specimen voided at the end of the 24-hour collection period (ie, 8 AM the next morning). Screw the lid on securely. Transport the specimen promptly to the laboratory. Container must be labeled with patient's full name, date and time collection started, and date and time collection finished.

Room temperature.