Edema treated with furosemide; which electrolyte abnormality is most likely?

• A. Hyponatremia
• B. Hyperkalemia
• C. Hypokalemia
• D. Hypernatremia

Answer: (C)

When a patient with edema is treated with furosemide, a loop diuretic, it blocks the Na-K-2Cl transporter in the thick ascending limb of the loop of Henle. This causes increased loss of sodium, chloride, and water, and delivers more sodium to the distal nephron. The heightened sodium delivery to the collecting duct stimulates potassium secretion, and the aldosterone surge that accompanies volume depletion further drives potassium loss. The net result is hypokalemia, which is the electrolyte abnormality most commonly associated with loop diuretics like furosemide. Hyponatremia or hypernatremia are not as directly expected from this mechanism in the typical setting.