Which of the following is a recognized cause of hyperkalemia?

• A. Renal failure
• B. Hyperaldosteronism
• C. Hypokalemia
• D. Metabolic alkalosis

Answer: (A)

Potassium balance is controlled mainly by the kidneys, which excrete potassium in the distal nephron. When renal function is impaired, the ability to excrete potassium diminishes, so potassium accumulates in the blood even with normal intake. This makes renal failure a classic and recognized cause of hyperkalemia, especially in acute injury or advanced chronic kidney disease.

Hyperaldosteronism drives potassium loss, leading to hypokalemia rather than hyperkalemia. Hypokalemia is, by definition, low potassium, so it cannot explain high serum potassium. Metabolic alkalosis also tends to be associated with lower potassium (potassium shifts into cells with alkalosis), not hyperkalemia.