Potassium, 24-Hour Urine

Casandra

Casandra Test Code LC93348Version 1 (DRAFT)

Performing Lab

Lab LabcorpLab Test ID 003186CPT Code 84133

Potassium, 24-Hour Urine

Clinical Use

Use

Evaluate electrolyte balance, acid-base balance; evaluate hypokalemia; Carroll and Oh point out that urinary loss of 40 mmol/24 hours in the presence of hypokalemia 50 mmol/L in a hypokalemic, hypertensive patient not on a diuretic may indicate primary or secondary aldosteronism. The kidneys do not respond quickly to potassium deprivation. There is renal wastage of potassium in secondary aldosteronism. Glucocorticoids, including endogenous steroids in Cushing's syndrome, are among the causes of kaliuresis.

Special Instructions

Ensure the 24-hour urine collection is complete, and state the 24-hour volume on the test request form. Label the container with the patient's full name and the dates and times of the collection.

Limitations

The kidneys do not respond quickly to potassium deprivation, which should be considered when interpreting results. Urinary potassium may be elevated due to dietary intake, medications, or conditions such as hyperaldosteronism or renal tubular acidosis. Incomplete or inaccurately timed specimen collection can lead to misleading results.

Test Details

Methodology

Automated Analyzer (Clinical Chemistry)

Biomarkers

Potassium

Analyte

Potassium, Urine • Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

LOINC Codes

Order Codes

2829-0

Result Codes

2828-2
2829-0

Result Turnaround Time

1 day

Specimen

Urine

Volume

10 mL aliquot of entire collection

Minimum Volume

1 mL aliquot (Note: This volume does not allow for repeat testing.)

Container

Plastic urine container, no preservative

Collection Instructions

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. Mix well. Container must be labeled with the patient's full name and dates and times of collections.