Pancreas Allograft Rejection: Analysis of Concurrent Renal Allograft Biopsies and Posttherapy Follow-Up Biopsies

Abstract

Pancreas and kidney allograft function is routinely monitored with serum studies (amylase, lipase, and creatinine). Increased levels commonly prompt tissue biopsy, to diagnose cause of graft dysfunction. Historically, pancreas allografts were infrequently biopsied, although serum enzymes and renal rejection may be poor surrogates for pancreas status. Pancreas allograft biopsies at our center were reviewed and reclassified according to University of Maryland (UMD) and Banff criteria; C4d immunostaining was performed. Findings were correlated with clinical data and renal allograft biopsies. Fifty-six pancreas allograft biopsies from 27 patients were evaluated. UMD and Banff grading were similar, although two UMD "indeterminate" biopsies were Banff grade 1 rejection. There were 21 concurrent pancreas and renal biopsies, all from simultaneous pancreas-kidney allograft recipients. Thirteen pairs were concordant for rejection; eight pairs were discordant for rejection (38%); six pairs showed pancreas rejection without kidney rejection, and two pairs showed the converse. Fourteen patients had a total of 21 follow-up pancreas allograft biopsies. Seven biopsies showed a lower grade of rejection on follow-up biopsy, 4 biopsies showed more severe rejection, and 10 had unchanged grade. In only 9 of these 21 (43%) cases, did the interval serum amylase or lipase trend parallel the subsequent biopsy diagnosis. With a high biopsy discordance rate, our data suggest that renal allograft rejection is a poor surrogate for pancreas allograft status. Likewise, serum amylase and lipase levels do not predict response to rejection therapy. Surveillance or posttherapy pancreas allograft biopsies may be a useful means to monitor pancreas allograft status.