Initial diagnostic studies to assess unexplained hyperkalemia in a child

In a child with no obvious risk factor for hyperkalemia and normal volume status, repeat testing of serum/plasma potassium from a free flowing venous sample to differentiate true significant hyperkalemia from pseudohyperkalemia

In a child with unexplained true hyperkalemia based on repeated testing:

Complete blood count, platelets, and serum LDH to assess for blood dyscrasia or hemolysis

Serum creatine kinase to detect muscle injury

Blood electrolytes (sodium, potassium, bicarbonate, chloride) to detect other electrolyte abnormalities such as metabolic acidosis

Serum creatinine and BUN to assess kidney function

Urinalysis to detect kidney disease

Urine chemistries (urine should be obtained at same time or within a brief time of blood studies):
- Urine potassium values should be greater than 20 mEq/L
- Urine sodium values less than 20 mEq/L suggest increased proximal sodium absorption and a decrease in sodium delivery in the distal tubule, resulting in impaired potassium excretion due to limited availability of sodium for exchange

If there is a clinical concern for endocrinopathy, obtain serum aldosterone and plasma renin activity

BUN: blood urea nitrogen; LDH: lactic dehydrogenase.

Graphic 85976 Version 3.0

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Initial diagnostic studies to assess unexplained hyperkalemia in a child