Which describes the primary mechanism by which diuretics promote diuresis?

• A. Inhibiting sodium and water reabsorption in renal tubules
• B. Increasing water reabsorption
• C. Causing vasoconstriction
• D. Increasing aldosterone release

Answer: (A)

Diuretics promote diuresis by blocking sodium reabsorption in the renal tubules, which prevents water from being reabsorbed as well. Since water follows sodium, keeping more Na+ (and thus water) in the filtrate increases urine formation. Different diuretics act on different parts of the nephron to inhibit Na+ reabsorption, but the shared outcome is more Na+ and water excretion.

Increasing water reabsorption would reduce urine output, vasoconstriction isn’t a diuretic mechanism, and increasing aldosterone release would promote Na+ reabsorption, opposing diuresis.