Is 0.6% Reasonable as the Minimum Requirement of the Graft-to-recipient Weight Ratio Regardless of Lobe Selection in Adult Living-donor Liver Transplantation?

Background. Several studies reported favorable outcomes of small-for-size grafts with graft-to-recipient weight ratio (GRWR) <0.8% in living-donor liver transplantation (LDLT). However, their indications should be carefully determined because they must have been indicated for low-risk cases over larger grafts with 0.8% <= GRWR. Furthermore, evidence for minimum requirements of GRWR remains inconclusive. We investigated the safety of small-for-size grafts against larger grafts by adjusting for confounding risk factors, and minimum requirement of graft volume in adult LDLT. Methods. We enrolled 417 cases of primary adult-to-adult LDLT in our center between 2006 and 2019. The outcomes of small grafts (0.6% <= GRWR < 0.8%, n = 113) and large grafts (0.8% <= GRWR, n = 289) were mainly compared using a multivariate analysis and Kaplan-Meier estimates. Results. The multivariate analysis showed that small grafts were not a significant risk factor for overall graft survival (GS). In the Kaplan-Meier analysis, small grafts did not significantly affect overall GS regardless of lobe selection (versus large grafts). However, GRWR < 0.6% was associated with poor overall GS. Although there were no significant differences between the 2 groups, unadjusted Kaplan-Meier curves of small grafts were inferior to those of large grafts in subcohorts with ABO incompatibility, and donor age >= 50 years. Conclusions. Similar outcomes were observed for small and large graft use regardless of lobe selection. 0.6% in GRWR was reasonable as the minimum requirement of graft volume in LDLT. However, small grafts should be indicated carefully for high-risk cases.