Serum creatinine does not distinguish between various causes of graft dysfunction. Serial assay of proximal tubular enzymes N-Acetyl-D-glucosaminidase (NAG), Alanine aminopeptidase (AAP) and Gamma glutamyl transferase (GGT) in urine was done to assess their usefulness in distinguishing various causes of graft dysfunction. Daily serum creatinine and enzymuria were measured in 32 consecutive renal allograft recipients for first 15 postoperative days. Graft dysfunction was defined as >20% increase in serum creatinine and >100% increase in enzymuria over the baseline. The diagnosis of graft dysfunction was based upon clinical criteria, ultrasonography, cyclosporin trough level, allograft biopsy, response to anti-rejection therapy and alteration of cyclosporin dosage. Fifteen episodes of graft dysfunction were identified in 15 patients. The sensitivity and specificity of the enzymes (NAG, AAP and GGT) for predicting graft dysfunction were 87.5%, 86.9%, 88.5% and 98.2%, 98.2%, 97.9% respectively. There was a significant increase in enzymuria during acute tubular necrosis (ATN) and acute rejection episode compared to cyclosporin nephrotoxicity (p<0.01). Enzymuria assay provides a simple, reliable and noninvasive method to distinguish cyclosporin nephrotoxicity from acute tubular necrosis and acute rejection in renal allograft recipients.
Keywords: Acute rejection; acute tubular necrosis; cyclosporin nephrotoxicity; renal transplantation; urinary enzymes.