[Evaluation of uric acid transport in nephrons of patients with calcium nephrolithiasis and hyperuricosuria].

Renal excretion of uric acid was studied in 48 patients with recurrent calcium nephrolithiasis. Hyperuricosuria was found in 16 patients (33%) and among them 10 patients had increased values of urate clearance and fractional excretion. The tubular transport of urate was evaluated by means of pharmacological tests with pyrazinamide (PZA) and benzbromarone (BB) in these 11 patients with hyperuricosuria of renal origin. PZA suppression test was normal in 10 patients while in one case uric acid excretion was not suppressed sufficiently by PZA. Maximal uricorusirc response to BB was increased in two patients, normal in one patient and impaired in eight patients. PZA and BB tests revealed isolated defect of uric acid postsecretory reabsorption in seven patients, impaired reabsorption at both pre- and postsecretory site in one case and enhanced tubular secretion of uric acid in two patients. This study indicates that different defects of uric acid transport in nephron are the frequent cause of hyperuricosuria in patients with recurrent calcium nephrolithiasis.