Mechanisms of hyperuricemia in cyclosporine-treated renal transplanted children.

Mechanisms of hyperuricemia were investigated in 19 pediatric renal transplant recipients 6 months after transplantation. 51Cr-EDTA, PAH, lithium and sodium clearances, 24-hour urinary creatinine and urate excretions were measured. Ten patients had hyperuricemia. The hyperuricemic patients had lower EDTA, PAH, and urate clearances (mean 69.5 vs. 92.5, p < 0.05, 234 vs. 421, p < 0.05 and 4.3 vs. 10.6 ml/min/1.73 m2, p < 0.001, respectively). Serum urate concentration correlated with cyclosporine dose (r = 0.46, p < 0.05) and inversely with urate (r = -0.88, p < 0.001), and lithium (r = -0.55, p < 0.05) clearances. Urate clearance showed a significant positive correlation with lithium clearance (r = 0.66, p = 0.01) and an inverse correlation with fractional proximal tubular reabsorption (r = -0.63, p = 0.02). Results were not influenced by diuretic administration. Our data support increased proximal tubular urate reabsorption rather than decreased secretion as the mechanism in cyclosporine-induced hyperuricemia.