Propensity score-based survival benefit of simultaneous liver-kidney transplant over liver transplant alone for recipients with pretransplant renal dysfunction.

The survival benefit of simultaneous liver-kidney transplantation (SLKT) over liver transplantation alone (LTA) is unclear from the current literature. Additionally, the role of donor kidney quality, measured by the kidney donor risk index (KDRI), in survival benefit of SLKT is not studied. We compared survival benefit after SLKT and LTA among recipients with similar pretransplant renal dysfunction using novel methodology, specifically with respect to survival probability and area under the survival curve by dialysis status and KDRI. Data were obtained from the Scientific Registry of Transplant Recipients. The study cohort included patients with pre-liver transplantation (LT) renal dysfunction who were wait-listed and received either a SLKT (n = 1326) or a LTA (n = 4283) between March 1, 2002 and December 31, 2009. Inverse Probability of Treatment Weighting-SLKT and LTA survival curves, along with the 5-year area under the survival curve, were computed by dialysis status at transplant. The difference in the area under the curve represents the average additional survival time gained via SLKT over LTA. For patients not on dialysis, SLKT resulted in a significant 3.7-month gain in 5-year mean posttransplant survival time. The decrease in mortality rate differs significantly by KDRI, and an estimated 76% of SLKT recipients received a kidney with KDRI sufficiently low for mortality. The mortality decrease for SLKT was concentrated in the first year after transplant. The difference between SLKT and LTA 5-year mean posttransplant survival time was 1.4 months and was nonsignificant for patients on dialysis. In conclusion, the propensity score-adjusted survival among SLKT and LTA recipients was similar for those who were on dialysis at LT. Although statistically significant, the survival advantage of SLKT over LTA was of marginal clinical significance among patients not on dialysis and occurred only if the donor kidney was of sufficient quality. These results should be considered in the ongoing debate regarding the allocation of kidneys to extra-renal transplant candidates.