Review Question - QID 217055

This patient presents with renal colic (intermittent crampy flank pain that radiates to the groin) secondary to recurrent kidney stones that appear envelope-shaped on microscopy, suggestive of calcium oxalate stones. Thiazide diuretics such as hydrochlorothiazide can be used to lower urine calcium to prevent recurrent calcium oxalate kidney stones.

Thiazide diuretics inhibit sodium reabsorption in the distal convoluted tubule, thereby promoting natriuresis, but also promote calcium-sodium exchange to increase calcium reabsorption. This can result in mild hypercalcemia but also decreases urinary calcium concentration, thereby preventing calcium kidney stone formation. Thiazide diuretics are commonly used in the treatment of essential hypertension because of their natriuretic effects but can also be used in the treatment of calcium nephrolithiasis due to their hypocalciuric effects. All patients with kidney stones are also counseled to have adequate fluid intake and decreased sodium intake because calcium is reabsorbed in the proximal tubule along with sodium.

Zisman reviews the treatment modalities for nephrolithiasis. The author emphasizes the importance of fluid intake for all types of kidney stones and highlights other modalities including thiazide diuretics.

Incorrect Answers:
Answer 1: Acetazolamide is a carbonic anhydrase inhibitor that has a mild diuretic effect via renal loss of bicarbonate and sodium. It is commonly used in treating altitude sickness but does not affect kidney stone formation.

Answer 2: Allopurinol is a xanthine oxidase inhibitor that is used to treat hyperuricemia and prevent gout flares and uric acid stones. Uric acid stones are needle-shaped, not envelope-shaped.

Answer 3: Furosemide is a loop diuretic that inhibits the Na-K-Cl transporter in the thick ascending limb of the loop of Henle to cause natriuresis. It is often used for its diuretic effect in the treatment of heart failure. However, it also increases urinary calcium excretion; thus, it would not prevent calcium stones.

Answer 5: Spironolactone is a potassium-sparing diuretic that antagonizes the effect of aldosterone at the distal convoluted tubule, promoting sodium excretion and potassium retention. It is used in the treatment of heart failure but is not used to prevent kidney stones.

Bullet Summary:
Recurrent calcium kidney stones can be prevented with thiazide diuretics, which increase calcium reabsorption.