Uricemia and urinary acidification in renal calcium stone disease

Serum urate concentrations were determined in 487 consecutive patients with stone disease and in 89 controls. Male controls had higher concentrations than female controls but men and women with stones had lower concentrations than controls. Renal acidification defects, incomplete and complete forms, were found in 25 per cent of the patients with stones, with the highest frequency in patients with hyperuricemia. Patients with proximal renal acidification defects had a higher serum urate concentration than patients with normal acidification of the urine. The urinary excretion of urate was higher in hyperuricemic than in normouricemic patients but lower in patients with hyperuricemia and renal acidification defects than in those with hyperuricemia and normal acidification of the urine. This finding indicates that underexcretion rather than overproduction contributes to the higher serum urate concentration in patients with renal acidification defects. Stone patients with high serum urate levels, especially in combination with renal acidification defects, had more severe stone disease and underwent more operations than other patients with stones. Thus, hyperuricemia does not appear to be a common feature in patients with calcium stone disease, although it is associated with formation of large stones for unknown reasons.