It has been shown that recipients receiving grafts from both undersized and oversized donors have worse clinical outcomes. However, donor-recipient size (DR) mismatch is an understudied metric in pediatric whole-liver deceased donor liver transplantation (DDLT). Here, we analyzed the utility of both DR weight ratio (WR) and body surface area ratio (BSAR) in predicting outcomes among all pediatric whole-liver DDLT recipients. We also performed subgroup analyses for patients with biliary atresia (BA) as well as for other diagnoses with ascites to evaluate these ratios’ utility among patients with increased abdominal domain.

We evaluated all pediatric patients undergoing primary whole-liver DDLT within the UNOS database from 3/1/2002–1/23/2023. We identified 5286 patients <18 years old and divided them into five groups based on increasing DR weight ratios (WRs) and body surface area ratios (BSARs) (<10th percentile, 10th–20th percentile, 20th–80th percentile [reference], 80th–90th percentile, and >90th percentile). Subgroup analyses were performed for patients with BA and other diagnoses with ascites. Chi-square tests were also used to compare patients with and without BA. A Cox proportional hazards model adjusted for both donor and recipient factors was used to identify associations between WR and BSAR percentiles and graft survival, patient survival, and length of stay (LOS). Kaplan–Meier curves and log-rank test were used to compare each of the time-to-event outcomes among the percentiles.

In multivariable analysis, both WR and BSAR impacted clinical outcomes. However, WR remains to be explored in pediatric transplant and is easier to calculate. We therefore focused our analysis on WR.

The <10th WR percentile (WR ≤ 0.70) and >90th WR percentile (WR > 2.0) were associated with increased hazard of graft failure and death. The <10th percentile WR hazard ratio (HR) for graft survival was 1.45 (95 % confidence interval [CI] 1.12, 1.87, p = 0.004). The >90th percentile WR for graft survival was 1.61 (95 % CI 1.22, 2.13, p = 0.001). Bottom 10th WR percentile for patient survival was 1.46 (95 % CI 1.14, 1.88, p = 0.01), while the >90th WR for patient survival was 1.54 (95 % CI 1.28, 2.23, p < 0.001). Only the >90th percentile WR (HR 0.86, 95 % CI 0.77, 0.96, p = 0.007) was associated with increased LOS.

The relationship between WR and outcomes did not hold in patients with BA or in other diagnoses with ascites (p > 0.05).

DR WR is a significant predictor of adverse outcomes in pediatric whole-liver DDLT recipients, and WR is a superior metric to BSAR. The utility of size-matching metrics is decreased in patients with BA or significant ascites. Transplant surgeons should exercise caution if they encounter a WR ≤ 0.70 or >2.0 in pediatric whole-liver DDLT.