Uric acid and calcium oxalate nephrolithiasis

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A 33-year-old man was examined because he formed recurrent renal calculi. At age 22, he had been hospitalized and had undergone ureterolithotomy for a right-sided calculus composed of calcium oxalate monohydrate and uric acid. During the ensuing Ii years, he passed 12 new stones, for which he was hospitalized eight more times, underwent five cystoscopic procedures for stone removal, and had two more ureterolithotomies, one on each side. His most recent x-ray films disclosed three renal stones, of which two were on the left. Of the nine that had been passed or removed, four were mixtures of calcium oxalate and uric acid, three were pure calcium oxalate, and two were pure uric acid. The remainder of his medical history was negative. His diet was unremarkable except for a daily one-pound total intake of meat, fish, and poultry. Physical examination was within normal limits; the patient weighed 82.3 kg. Blood concentrations of calcium, uric acid, and creatinine were normal. Three 24-hr urine samples were collected on an outpatient basis while he followed his regular diet (Table 1). Urine calcium excretion exceeded the normal upper limit of 300 mg/day for men, and uric acid excretion exceeded the normal upper limit of 800 mg/24 hr. Urine concentration of undissociated uric acid was uniformly above the