The frequency of rejection episodes after combined kidney-pancreas transplant--the impact on graft survival.

The recipients of combined kidney-pancreas transplants (SPK) are unique because they routinely receive two allografts from the same donor. In a previous study, we found that the long-term graft survival of the two allografts was different, with better graft survival seen in the pancreas allograft. In an attempt to understand the reason for the different graft survival in the recipients of organs from the same donor, we have reviewed the incidence and timing of rejection episodes in 160 consecutive technically successful whole-organ bladder-drained SPK performed at a single institution using a uniform immunosuppressive regimen. Rejection episodes were common. A total of 53% of the recipients had at least one episode of rejection in one of the organs. Multiple rejection episodes requiring hospitalization occurred in 23% of the recipients. The kidney allograft had more frequent rejection episodes than the pancreas allograft: 78 patients had 130 renal rejection episodes while only 50 patients had 65 episodes of pancreas rejection. No rejection episodes occurred in 111 pancreas and 82 kidney grafts (P = 0.0014). Multiple rejection episodes were three times as common in the kidney grafts (20%) than in the pancreas grafts (6%; P = 0.0001). The timing of the first rejection episode was also different. The median time to the first kidney rejection episode was 29 days compared with 39 days to the first pancreas rejection episode (P = 0.0191). Graft survival in the organs was equal when stratified by the number of rejection episodes (none, one, > one) per organ (P = 0.9378). These data suggest that the worse long-term kidney graft survival seen in SPK recipients is due to the greater risk of rejection (relative risk: 2.04; [95% conf. interval: 1.29-3.23]) and a greater frequency of rejection episodes of rejection episodes in the kidney (0.81/patient) compared with the pancreas (0.41/patient). The implications for patient management and the possible reasons for the different rates of rejection are discussed.