Potassium Lab Test

Potassium, 24-Hour Urine

CPT Test code: 83945

Specimen: Urine (24-hour)
Volume: 10 mL aliquot of entire collection
Container: Plastic urine container, no preservative
Special Instructions: State 24-hour volume on the test request form.
Collection: If the specimen is a 24-hour collection instruct thepatient to void at 8 AM and discard the specimen. Then collect allurine including the final specimen voided at the end of the 24-hourcollection period (ie, 8 AM the next morning). Screw the lid on securely. Mix well. Container mustbe labeled with the patient’s full name and dates and times of collections.
Storage Instructions: Maintain specimen at room temperature.
Causes for Rejection: Improper labeling
Use: Evaluate electrolyte balance, acid-base balance;evaluate hypokalemia; Carroll and Oh point out that urinary loss of40 mmol/24 hours in the presence of hypokalemia <3 mmol/L isexcessive.1In 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.