Potassium, Urine

Urinary potassium levels are helpful in the evaluation of patients with unexplained hypokalemia, electrolyte, and acid " base balance. 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. Renal loss >50 mmol/L in a hypokalemic, and hypertensive patient not on a diuretic may indicate primary or secondary aldosteronism.

Normal range:

Twenty-four " hour urine:

Male:

Less than 10 years: 17 " 54 mmol/day

10 " 14 years: 22 " 57 mmol/day

Greater than 14 years: 25 " 125 mmol/day

Female:

6 " 10 years: 8 " 37 mmol/day

10 " 14 years: 18 " 58 mmol/day

Greater than 14 years: 25 " 125 mmol/day

Random urine:

Male: 13 " 116 mmol/g creatinine

Female: 8 " 129 mmol/g creatinine

Use

Evaluation of patients with unexplained hypokalemia, electrolyte, and acid " base balance.

Interpretation

Increased In

Dehydration

Primary and secondary aldosteronism

Diabetic acidosis

Mercurial and thiazide diuretic administration

Ammonium chloride administration

Renal tubular acidosis

Chronic renal failure

Starvation

Cushing syndrome

Decreased In

Acute renal failure

Malabsorption

Chronic potassium deficiency states

Addison disease

Severe GN

Pyelonephritis

Nephrosclerosis

Limitations

Urinary potassium may be elevated with dietary (food and/or medicinal) increase, hyperaldosteronism, renal tubular acidosis, onset of alkalosis, and with other disorders.

Urine chloride is often ordered with sodium and potassium as timed urine. The urinary anion gap [Na+ ข (Cl ข + HCO3 ข ]) or [(Na+ + K+) ข (Cl ข )] is useful in the initial evaluation of hyperchloremic metabolic acidosis.