Introduction: Transplantation of pediatric livers to adult recipients, a measure which places the graft at higher risk of hepatic artery thrombosis (HA), is frequently necessitated by the shortage of available livers. Studies have demonstrated a consistently increased thrombotic risk but have failed to reach a consensus on whether this early morbidity ultimately leads to decreased graft or patient survival. We aimed to examine a national transplant registry for evidence of whether this treatment should be avoided or embraced as another means of obtaining a life-saving treatment.

Methods: We analyzed the United Network for Organ Sharing registry for all records between October 1, 1987 and December 31, 2013. 14,804 cases of pediatric-to-adult liver transplantation (PA-OL x) were isolated. Pediatric patients were defined as younger than 19. Primary outcomes were considered to be graft rejection, graft failure, and patient mortality. Statistical analysis was performed using Fisher's exact test and logistic regression in R.

Results: Overall rates of rejection, graft failure, and survival were all decreased in adult recipients who received a pediatric allograft when compared to those who received an adult liver. Rejection was significantly increased in the PA-OL x group when compared to controls at both 6 months (27.6% vs. 21.1%, p<0.0001) and 12 months (22.6% vs. 20.1%, p<0.0001). Graft failure was also significantly higher in the PA-OL x group when compared to control (43.8% vs. 41.7%, p<0.0001). Hepatic artery thrombosis was a more common cause of failure (21.6% vs. 18.0%, p<0.0001). Survival rates were significantly lower in the PA-OL x group (21.6% vs. 18.0%, p<0.001) compared to controls. When adjusted for height mismatch as a surrogate of liver size mismatch, all differences remained significant except graft failure (p=0.612).

Conclusions: Transplantation of pediatric livers into adult recipients places the graft at higher risk of HA . Studies have not conclusively demonstrated the effect of this clotting propensity on graft or patient survival. We have shown that the risks of early graft rejection, graft failure due to vascular thrombosis, and death are significantly higher in the PA-OL x population even when controlled for BMI and height mismatch. PA-OL x should be avoided whenever possible to prevent liver-size independent morbidity and mortality.

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