Sirolimus Versus Mycophenolate Mofetil in Simultaneous Pancreas–Kidney Transplantation: Impact on Urinary Tract Infection Rates

Background Urinary tract infections (UTIs) are common complications following simultaneous pancreas and kidney transplantation (SPK). The role of specific immunosuppressive agents in modulating UTI incidence and recurrence remains poorly understood. Methods In this retrospective, single‐center study, we analyzed 164 SPK recipients randomized to receive either sirolimus or mycophenolate mofetil (MMF) in combination with tacrolimus. The incidence of UTIs, relapses, recurrences, and UTI‐related hospitalizations was assessed over a 10‐year follow‐up. Univariable and multivariable negative binomial regression models were used to evaluate associations with immunosuppressive regimens and clinical outcomes in both intention‐to‐treat (ITT) and per‐protocol analyses. Results A total of 572 UTI episodes were recorded during follow‐up (0.102 per 100 recipient‐transplant days). No significant differences in overall UTI incidence or UTI‐related hospitalizations were observed between the sirolimus and MMF groups. However, in the multivariable per‐protocol analysis, the sirolimus group experienced significantly fewer UTI‐related hospitalizations (IRR 0.46; 95% CI, 0.23–0.94; p = 0.034) and relapses (IRR 0.54; 95% CI, 0.30–0.97; p = 0.039). Significant risk factors for UTIs included female sex, JJ stent placement, and pretransplant urological abnormalities. Recurrent UTIs were associated with lower 10‐year kidney graft survival (52% vs. 75%; p = 0.01) but had no impact on pancreas graft or patient survival. Conclusions While overall UTI incidence did not differ between immunosuppressive regimens, sirolimus use was associated with fewer hospitalizations and relapses. These findings indicate a potential clinical benefit of sirolimus in selected high‐risk SPK recipients, highlighting the need for further prospective investigation. Trial Registration: ClinicalTrials.gov identifier: NCT00140543