Potassium, 24-Hour Urine

CPT: 84133
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Test Details

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 <3 mmol/L is excessive.1 In the presence of such hypokalemia, urine excretion is helpful to separate renal from nonrenal losses. Excretion <20 mmol/24 hours is evidence that hypokalemia is not from renal loss.1 Renal loss >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.

Methodology

Ion-selective electrode (ISE); flame photometer

Reference Interval

25−125 mmol/24 hours

Additional Information

Urinary potassium may be elevated with dietary (food and/or medicinal) increase, hyperaldosteronism, renal tubular acidosis, onset of alkalosis, and with other disorders. Time relationships are important in interpretation. Potassium will decrease in Addison's disease and in renal disease with decreased urine flow (nephrosclerosis, pyelonephritis, glomerulonephritis).

Specimen Requirements

Specimen

Urine (24-hour)

Volume

10 mL aliquot of entire collection

Minimum Volume

1 mL aliquot

Container

Plastic urine container, no preservative

Collection

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.

Storage Instructions

Maintain specimen at 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. Carroll HJ, Oh MS. Water Electrolyte and Acid-Base Metabolism: Diagnosis and Management. Philadelphia, Pa: JB Lippincott Co;1978.

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
003186 Potassium, 24 hr Urine 013334 Potassium, Urine mmol/L 2828-2
003186 Potassium, 24 hr Urine 013276 Potassium, Urine mmol/24 hr 2829-0

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