A patient with kidney stones requires medication to decrease urinary calcium excretion. Which diuretic is most suitable?

Hydrochlorothiazide is the most suitable diuretic for this patient because it has a unique mechanism that reduces urinary calcium excretion. Thiazide diuretics, like hydrochlorothiazide, work primarily by inhibiting sodium reabsorption in the distal convoluted tubule of the nephron. This action leads to enhanced sodium and water excretion but at the same time decreases the amount of calcium that is excreted in the urine.

In cases of hypercalciuria (excess calcium in urine), which can contribute to the formation of kidney stones, hydrochlorothiazide is particularly beneficial because it lowers urinary calcium levels, thereby helping to prevent the formation of new stones. This makes it a preferred choice for patients with a history of calcium-containing kidney stones.

Other diuretics like torsemide, spironolactone, and triamterene do not have the same effect on calcium excretion. Torsemide is a loop diuretic that primarily promotes sodium and water excretion, potentially increasing calcium loss. Spironolactone is a potassium-sparing diuretic that works on the aldosterone pathway and does not have a direct effect on calcium excretion. Triamterene is also a