Concurrent biopsies of both grafts in recipients of simultaneous pancreas and kidney demonstrate high rates of discordance for rejection as well as discordance in type of rejection - a retrospective study

It is commonly assumed that in simultaneous pancreas and kidney (SPK) recipients, rejection of the two organs is concordant. As a result, concurrent biopsies of both organs are rarely performed and there are limited histological data on how often rejection is in fact discordant. We reviewed all SPK recipients transplanted at the University of Wisconsin between January 01, 2001, and December 31, 2016, that underwent biopsy of both organs. We included all patients whose biopsies were within 30 days. If patients were treated for rejection between biopsies, they were excluded if the biopsies were more than 4 days apart. Ninety-one simultaneous biopsies were performed within 30 days of each other, and 40 met our inclusion criteria. A total of 25 (62.5%) patients had concordance of biopsy findings: 11 had rejection of both organs, and 14 had no rejection of either organ. The other 15 (37.5%) were discordant for rejection, with 10 having pancreas-only rejection and five kidney-only rejection. It was striking to find that four of the 11 patients with concordance for rejection (36%) had different types (AMR, ACR, or mixed) of rejection in the two organs. This large series of simultaneous pancreas and kidney biopsies demonstrates the continued utility of performing biopsies of both organs.