A 46-year-old man comes to the emergency department with flank pain and hematuria. The pain is similar to several previous episodes of kidney stones. Abdominal imaging reveals a radiopaque calculus in the right ureter. The patient is admitted to the hospital and given intravenous hydration and analgesics. He subsequently passes the stone with rapid relief of his symptoms. Chemical analysis reveals that the stone is composed primarily of calcium oxalate. Which of the following medications is most likely to prevent recurrent stone formation in this patient?

Question

A 46-year-old man comes to the emergency department with flank pain and hematuria.  The pain is similar to several previous episodes of kidney stones.  Abdominal imaging reveals a radiopaque calculus in the right ureter.  The patient is admitted to the hospital and given intravenous hydration and analgesics.  He subsequently passes the stone with rapid relief of his symptoms.  Chemical analysis reveals that the stone is composed primarily of calcium oxalate.  Which of the following medications is most likely to prevent recurrent stone formation in this patient?

Quizplus · Accepted Answer

11ec160b_3c76_4d1d_9249_4bc3185b9b29_MD0001_00 Hypercalciuria increases the formation of calcium (calcium oxalate and calcium phosphate) stones, the most common types of kidney stone. In patients with recurrent calcium nephrolithiasis, thiazide diuretics can help prevent stone formation by decreasing urine Ca²⁺ excretion. Thiazides increase Ca²⁺ reabsorption through 2 major mechanisms: (Choice A) Acetazolamide is a carbonic anhydrase inhibitor that acts on the proximal convoluted tubule to cause bicarbonate wasting, raising urine pH and decreasing the risk of uric acid stones. However, the resulting systemic acidosis may increase release of calcium phosphate from bone, which is then cleared by the kidneys. Some studies have found that acetazolamide use may raise the risk of calcium stone formation. (Choice B) Ca²⁺ reabsorption in the loop of Henle occurs through both the transcellular and paracellular pathways. Paracellular Ca²⁺ reabsorption depends on concurrent, transcellular Na⁺/K⁺/Cl⁻ reabsorption. Loop diuretics (eg, furosemide) block the Na-K-2Cl cotransporter and increase urinary Ca²⁺ excretion. (Choice D) Mannitol is an osmotic diuretic. It is not used as maintenance therapy for any indication as it causes volume depletion and hypernatremia with prolonged use. It has no effect on Ca²⁺ homeostasis. (Choice E) Triamterene and amiloride are potassium-sparing diuretics that inhibit Na⁺ reabsorption in the collecting duct by blocking the epithelial sodium channel. This decreases net Na⁺/K⁺ exchange, reducing serum K⁺ losses. Educational objective: Thiazide diuretics effectively increase renal calcium reabsorption. In patients with recurrent calcium nephrolithiasis, thiazide diuretics can help prevent stone formation by decreasing urine Ca²⁺ excretion. __________ References: The mechanism of hypocalciuria with NaCl cotransporter inhibition. (http://www.ncbi.nlm.nih.gov/pubmed/21947122)

A 46-Year-Old Man Comes to the Emergency Department with Flank