[Uric acid metabolism in patients with chronic glomerulonephritis]

Serum uric acid (SUA), creatinine clearance (Ccr), urinary excretion of uric acid (UUAV) and uric acid clearance (CUA) were determined in 357 patients with IgA nephritis (IgAN) and 81 patients with membranous nephropathy (MGN) in an attempt to clarify uric acid metabolism in patients with chronic glomerulonephritis, and UUAV/Ccr and CUA/Ccr levels were measured to investigate their correlations. As a result, hyperuricemia that could hardly be explained with a decline of Ccr alone was recognized in many cases, since the patients with hyperuricemia exceeding 7.0 mg/100 ml of SUA registered even as high as 25.5% in IgAN and 33.3% in MGN, whereas those with the Ccr levels higher than 80 ml/min registered 22.3% in IgAN and 38.0% in MGN. Although the SUA level increased and the UUAV and CUA levels decreased along with a decline of Ccr in IgAN, no similar trends were recognized in MGN. When the distribution of UUAV was studied in the patients with the Ccr levels higher than 80 ml/min, the patients whose UUAV levels higher than 800 mg/24 hrs that suggested excessive uric acid production were markedly as low as 3.9% in IgAN and 3.7% in MGN. Thus, the cause of hyperuricemia could not be attributed to an amount in the uric acid production. On the other hand, the patients whose CUA levels lower than 6.0 ml/min in the distribution of CUA that suggested a decrease of uric acid excretion registered 47.4% in IgAN and 63.0% in MGN, respectively, which equally appeared to be a type of lowered excretion in a majority of patients whose hyperuricemia was recognized in IgAN and MGN. The mechanism of the lowered excretion of uric acids from the kidney despite the normal level of Ccr has yet to be clarified.