Early diagnosis of rejection. Correlation of enzymuria and histological findings after renal transplantation in the rat.

One hundred renal transplants were performed between different rat strain combinations. Posttransplant renal function was monitored using serum creatinine levels, creatinine clearance rates, and N-acetyl-beta-D-glucosaminidase (NAG) enzymuria. These biochemical measurements were compared with the morphological appearances of the transplanted kidney. Rises in NAG enzymuria proved to be useful diagnostic indicators of graft rejection with a false positive rate of only 6%. In 78% of the rejection episodes, the urinary NAG level rose 2 days before any elevation in serum creatinine concentration. There was a close correlation among increasing NAG enzymuria, decreasing renal function, and the structural events of rejection--indicating that the routine measurement of tubular enzymuria would be of value in the prediction and diagnosis of renal allograft rejection.