A patient with recurrent calcium oxalate kidney stones is started on hydrochlorothiazide for prophylaxis. The mechanism by which thiazides reduce stone recurrence is:
- A Increased urinary citrate excretion
- B Alkalinization of urine preventing crystal formation
- C Reduction in urinary calcium excretion by enhancing distal tubular calcium reabsorption ✓
- D Increased urinary volume alone without altering calcium excretion
Correct answer: C. Reduction in urinary calcium excretion by enhancing distal tubular calcium reabsorption
Explanation
Thiazides reduce urinary calcium excretion by enhancing calcium reabsorption in the distal convoluted tubule, thereby reducing supersaturation of calcium salts in urine. This is the basis for their use in idiopathic hypercalciuria and calcium stone prophylaxis. Loop diuretics increase calcium excretion and would worsen stone risk.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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