Fasting uric acid and phosphate in urine and plasma of renal calcium-stone formers.

Clearance experiments in calcium-stone patients (n = 60) and controls (n = 60) demonstrated significantly higher urinary uric acid (UA) in younger (less 40 years) stone patients than controls (median: 480 vs. 351 mug/min) but not in older (greater than 40 years) patients. Serum UA and urinary oxypurines were comparable in health and stone disease. Conversely urinary phosphate was significantly lower in younger patients than matched controls (males: 224 vs. 304 mug) and presumably is responsible for the more alkaline pH. It is suggested that calcium-stone formation in humans is represented by two different populations.