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.