From large-for-size to large-for-flow: a paradigm shift in liver transplantation.

Liver graft-recipient matching remains challenging and both morphological and hemodynamic characteristics have been shown to be relevant indicators of post-transplant outcomes. However, no combined analysis is available to date. To study the impact of both morphological and hemodynamic characteristics of liver grafts on transplantation outcomes, we retrospectively evaluated all consecutive 257 liver transplantations (LT) with prospective hemodynamic measurements from 2017 to 2020 in a single center perspective. First, a morphological analysis compared recipients with or without large-for-size (LFS), defined by a Graft/Recipient Weight Ratio > 2.5% and excluding extreme LFS. Second, a hemodynamic analysis compared recipients with or without low portal flow (LPF; < 80 mL/min per 100g of liver tissue). Third, an outcome analysis combining LPF and LFS was performed, focusing on liver graft related morbidity (LGRM), graft and patient survival. LGRM was a composite endpoint including primary non function, high risk L-Graft7 category, and portal vein thrombosis. Morphological analysis showed that LFS (n = 33; 12.9%) was not associated with an increased LGRM (12.1% vs. 9.4%; p = 0.61) or impaired graft and patient survival. However, hemodynamic analysis showed that LPF (n = 43; 16.8%) was associated with a higher LGRM (20.9% vs. 7.5%, p = 0.007) and a significant impaired 90-day graft and patient survival. Multivariable analysis identified LPF but not LFS as an independent risk factor for LGRM (OR: 2.8%; CI [1.088-7.413]; p = 0.03), 90-day (HR: 4%; CI [1.411-11.551]; p = 0 .01) and 1-year patient survival. Low portal flow is a significant predictor of post-LT morbi-mortality, independently of LFS when defined as a morphological metric alone. Consequently, we propose the novel concept of large-for-flow which may guide graft selection and improve perioperative management of LPF.