Liver anatomy: microcirculation of the liver.

Comprehension of the structural and functional characteristics of the hepatic microcirculation can help improve the design, planning, and practice of imaging-guided treatment for hepatic tumors and for portal vein embolization (PVE). The hepatic microcirculation derives dual blood supply from the portal vein and the hepatic artery. The terminal portal venules directly connect to the hepatic sinusoids, but the terminal hepatic arterioles connect to arterioportal communications before entering the sinusoids: the peribiliary plexus, the terminal arteriosinus twigs, the vasa vasorum on the portal vein, and the direct arterioportal anastomosis. These communications play important roles in the balance of blood perfusion to the liver parenchyma and in controlling the blood supply to hepatic tumors and the anticipated remnant liver (in cases of PVE). At the microcirculatory level, various embolic agents present different distribution patterns. To further our understanding, iodized oil has been found to pass into the portal vein after hepatic arterial administration through the peribiliary plexus and subsequently traverses the sinusoids to enter the lungs and then the systemic circulation. Ultimately, a thorough knowledge of the host environment at the microcirculatory level is essential in developing strategies for both tumor treatment and for inducing liver regeneration.