Regulation of hepatic blood flow: the hepatic arterial buffer response revisited

Abstract

The interest in the liver dates back to ancient times when it was considered to be the seat of life processes. The liver is indeed essential to life, not only due to its complex functions in biosynthesis, metabolism and clearance, but also its dramatic role as the blood volume reservoir. Among parenchymal organs, blood flow to the liver is unique due to the dual supply from the portal vein and the hepatic artery. Knowledge of the mutual communication of both the hepatic artery and the portal vein is essential to understand hepatic physiology and pathophysiology. To distinguish the individual importance of each of these inflows in normal and abnormal states is still a challenging task and the subject of ongoing research. A central mechanism that controls and allows constancy of hepatic blood flow is the hepatic arterial buffer response. The current paper reviews the relevance of this intimate hepatic blood flow regulatory system in health and disease. We exclusively focus on the endogenous interrelationship between the hepatic arterial and portal venous inflow circuits in liver resection and transplantation, as well as inflammatory and chronic liver diseases. We do not consider the hepatic microvascular anatomy, as this has been the subject of another recent review.

Figure 1

Hepatic hemodynamics in normal and reduced-size livers. A: Preoperative hepatic blood flow in a donor liver or before extended hepatectomy representing a normal portal vein blood flow-hepatic artery blood flow (PVBF/HABF) ratio of 2.5; B: As a consequence of portal hyperperfusion, hepatic arterial buffer response (HABR) leads to hepatic arterial hypoperfusion of reduced-size liver that is characterized by a dramatically increased PVBF/HABF ratio of 29; C: Surgical reduction of the portal venous inflow, for example, by splenectomy or hepatic artery ligation, leads to HABR-induced dilation of the hepatic artery and results in a reduced PVBF/HABF ratio of 22; D: Possible effects of pharmacological interventions to preserve hepatic artery supply. PVBF/HABF ratios are adopted from[59]. HA: Hepatic artery; IVC: Inferior vena cava; PV: Portal vein.

Figure 2

Surgical interventions for modulation of the hepatic inflow, showing the portocaval shunt (short arrow), ligation of the splenic artery (thin long arrow) and splenectomy (thick long arrow). BD: Bile duct; HA: Hepatic artery; IVC: Inferior vena cava; PV: Portal vein; SpA: Splenic artery.