Mechanisms and management of graft inflow and outflow in liver transplantation

Abstract

Effective management of the liver graft's dual vascular supply is increasingly recognised as critical to optimising graft function in liver transplantation (LT). In this narrative review, we explore the relationship between graft inflow and outflow within the context of hepatic haemodynamic autoregulation, highlighting key mechanisms such as the hepatic artery buffer response (HABR) and the influence of portosystemic circulatory changes on graft perfusion. This review synthesises current literature and incorporates the authors' clinical experience to provide guidance on the surgical management of both common and complex vascular conditions post-transplantation. Portal hyperperfusion - often due to reduced intrahepatic adenosine and HABR-mediated arterial vasoconstriction - is the most frequent issue and a primary cause of small-for-size syndrome. Portal inflow modulation strategies such as splanchnic vasodilators, splenic embolisation, or splenectomy are recognised treatments for portal hyperperfusion. In contrast, management of portal hypoperfusion remains poorly defined, with only isolated reports of portal inflow augmentation. Graft outflow is also examined, particularly its role in enhancing graft function in living donor LT. Overall, a deep understanding of hepatic vascular regulation is essential for improving graft outcomes and expanding access to LT globally.

Keywords: Liver transplantation; hepatic artery buffer response; liver hemodynamics; living donor liver transplantation; portal in-flow modulation; small-for-size syndrome.