Graft Survival and Segment Discards Among Split-Liver and Reduced-Size Transplantations in the United States, 2008-2018.

Split-liver transplantation has allocation advantages over reduced-size transplantation due to its ability to benefit two recipients. However, prioritization of split-liver transplantation relies on three major assumptions that have never been tested in the United States: similar long-term transplant recipient outcomes, lower incidence of segment discard among split-liver procurements, and discard of segments among reduced-size procurements that would be otherwise "transplantable." We utilized UNOS-STAR data to identify all split-liver (n=1,831) and reduced-size (n=578) transplantation episodes in the United States between 2008-2018. Multivariable Cox proportional hazards modeling was used to compare 7-year all-cause graft loss between cohorts. Secondary analyses included etiology of 30-day all-cause graft loss events as well as incidence and anatomy of discarded segments. We found no difference in 7-year all-cause graft loss (aHR 1.09, 95%CI 0.82-1.46) or 30-day all-cause graft loss (aHR 1.13, 95%CI 0.70-1.80) between split-liver and reduced-size cohorts. Vascular thrombosis was the most common etiology of 30-day all-cause graft loss for both cohorts (56.4% vs 61.8% of 30-day graft losses, P=.85). Finally, reduced-size transplantation was associated with a significantly higher incidence of segment discard (50.0% vs 8.7%) that were overwhelmingly right-sided (93.6% vs 30.3%). Our results support the prioritization of split-liver over reduced-size transplantation whenever technically feasible.