--Disease Characteristics-- Absorptive hypercalciuria Intestinal hyperabsorption of calcium, i.e.: Exaggerated calciuric response to oral calcium load OR Fractional calcium-47 absorption greater than 0.61 Calciuria greater than 200 mg/day on random and calcium-restricted diet Normal or high fasting urinary calcium Normal serum calcium Normal serum parathyroid hormone No primary hyperparathyroidism At least 1 calcium oxalate stone within the past 3 years No struvite or carbonate apatite stones No noncalcareous stones No numerous stones making precise quantitation difficult No renal tubular acidosis --Prior/Concurrent Therapy-- No concurrent drug therapy for nephrolithiasis --Patient Characteristics-- Creatinine clearance at least 0.7 mL/min per kilogram No hyperkalemia No hyperphosphatemia No urinary tract infection Other: No predisposition to hyperkalemia, including concurrent use of the following drugs: Potassium-sparing diuretics Angiotensin-converting enzyme inhibitors Nonsteroidal anti-inflammatory drugs No active peptic ulcer disease No chronic diarrhea