Background: Late allograft failure is one of the critical issues in renal transplantation today. The relative importance of immunological versus non-immunological causes of chronic kidney allograft failure remains controversial.

Objective: The goal of the current study was to determine the degree of correlation of functional kidney and pancreas graft loss among patients undergoing SPK.

Methods: We analyzed the SRTR database of SPK transplants performed October 1987 to May 2012. Using Kaplan-Meier and proportional hazards methods, we calculated patient and death-censored kidney and pancreas graft survival from the day of transplant and also conditioned on survival of the patient and graft for at least 4 months. Correlation of functional kidney and pancreas graft loss was examined by contingency tables and the Chi-square statistic.

Results: There were 18,695 SPKs performed in the study period. The chance of pancreas graft failure in the first 4 months after the SPK transplant was much higher than the chance of kidney graft failure. However, after 4 months, the relative risk (RR) of a pancreas failure to that of a kidney failure was 0.75 (95% C.I.: 71 – 79%; p<0.0001), and this further decreased after 5 years to a RR=0.58 (95% C.I.: 53% – 62%; p<0.0001). Analysis of the graft failures occurring after 5 years demonstrated that, while kidney and pancreas functional graft loss were significantly correlated (p<0.0001), only 34% of these patients whose kidney failed also had a pancreas graft failure.

Conclusion: SPK patients have a high risk of pancreas failure in the first 4 months, likely secondary to technical factors such as vascular thrombosis. However, after 4 months, the RR of pancreas failure is significantly less than that of kidney failure. Only one-third of kidney graft failures after 5 years are associated with pancreas graft failure. Assuming that cellular or humoral rejection of the kidney graft will also be associated with injury to the pancreas graft, this suggests that the majority of late kidney graft failures after SPK are non-immunological in nature.

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