Arterial infarcts are pale. They have irregular shape and the margins are hyperemic and infiltrated by inflammatory cells. The necrosis in the infarcted area involves hepatocytes, portal fields and hepatic veins. In less severe ischemia the portal fields and periportal hepatocytes may be spared. The most common causes of ischemic infarctions are polyartertis nodosa, embolization and accidental ligation of hepatic artery.
Small infarcts heal by scar.
The red hemorrhagic infarcts of Zahn are due to occlusion of small intrhepatic portal vein branches. The infarcted area is usually peripheral, triangular, with the base toward the glissonian capsule. The sinusoids become distended. There is no ischemic necrosis. The area becomes red, congested, because of back-flow from the hepatic veins and from the artery.