A Tale of Two Kidneys: Differences in Graft Survival for Kidneys Allocated to Simultaneous Liver Kidney Transplant Compared with Contralateral Kidney from the Same Donor.

BACKGROUND: Renal graft lifespan in simultaneous liver kidney transplant (SLK) is generally thought to be shorter than in kidney transplant (KT) alone, raising questions about the utility of SLK. This study aims to estimate what the outcomes would be for a kidney allocated to SLK if it were allocated to KT instead.

METHODS: Using United Network for Organ Sharing data, recipients of SLK from 2003 to 2012 were paired with the recipient who received the partner kidney from the same donor in a kidney or kidney pancreas transplant for analysis. The primary outcomes were long-term patient and renal graft survival. This was investigated using modified multivariable Cox regression, which allowed for changes in the hazard ratio (HR) associated with SLK over time (non-proportional hazards), accounted for the paired nature of the study, and adjusted for differences in recipient characteristics.

RESULTS: There were 3,721 recipients in each group. Ninety-day mortality was 8.0% for SLK vs 1.9% for KT recipients (p < 0.001). Median unadjusted renal graft survival was 11 years for the SLK group vs 10.5 years for KT (p < 0.001). The baseline adjusted HRs for death and renal graft loss associated with SLK were 3.03 and 2.05. These HRs became equal to 1 at 6.5 years for death and 5 years for renal graft loss. The HRs for death and renal graft loss associated with SLK at 10 years were 0.55 and 0.50.

CONCLUSIONS: Although kidneys allocated to SLK vs KT demonstrate worse short-term survival, this risk appears to be reversed when follow-up is extended long-term.