Renal handling of urate in patients with calcium stone disease

The renal handling of urate was investigated in 28 recurrent calcium stone formers and 12 healthy controls. 12 patients were hyperuricosuric and 16 patients had incomplete proximal or distal acidification defects. Measurements of the glomerular filtration and the tubular reabsorption of filtered urate were made through the pyrazinamide (PZA)-suppression test of urate secretion. Hyperuricosuria could not be explained by defects in the renal handling of urate. Patients with proximal acidification defects had a higher tubular reabsorption of filtered urate than the other subjects. Tubular reabsorption of filtered urate was inversely correlated, and filtered urate escaping reabsorption positively correlated to the 24-hour excretion of urate. In contrast, the PZA-suppressible fraction of urate excretion, which is the net effect of tubular secretion and post-secretory reabsorption and thought to be the main regulator of urate excretion, was not correlated to the 24-hour excretion of urate. It is concluded that the renal handling of urate is basically normal in calcium stone disease, whereas minor deviations may co-exist with renal tubular acidification dysfunction.