The use of thiazides in the prevention of renal calculi.

The efficacy of hydrochlorothiazide, in a usual dosage of 50 mg. twice daily, in preventing further stone formation was evaluated in 67 patients with recurrent calcium stones. Fifty-three of these patients had idiopathic hypercalciuria (11 with associated urinary infection), one had medullary sponge kidneys and urinary infection, and two had urinary infection only; no cause for stone formation was detected in 11 patients. Urinary infection was also treated when present. Thirty-three patients (Group 1) were stone-free and 34 patients (Group 2) had stones in the urinary tract when treatment was started. In Group 1 during a total of 343 patient years (py) between the onset of stone symptoms and the institution of thiazide therapy there were 194 episodes (.57 per py) including 83 stones passed spontaneously and 30 major operations, but during 72 py on treatment there were only two episodes (.03 per py), both of which resulted in spontaneous passage of stones. The 34 patients in Group 2 had 365 episodes (1.1 per py) during the 343 py before thiazide therapy but only 34 episodes (.53 per py) during the 64 py on treatment. Many episodes in the Group 2 patients were related to previous stones, and in only four of these patients was there clear-cut evidence of new stone formation. Side effects, usually mild, were experienced by 25 patients; in three patients treatment was discontinued because of side effects.