The size of the infarct depends on the size of the occluded vessels. Pale Ischemic infarcts may result from arterial occlusion, portal vein occlusion or only from low flow, in cases of shock, without any vascular occlusion. While the left lobe in the fetus is supplied by the umbilical vein, which is well oxygenated, the right lobe is entirely supplied by the portal vein, which is poorly oxygenated. Any maneuver, which decreases further the oxygen supply to the fetus, may cause necrosis of the right lobe and may be fatal. This same mechanism, deprivation of oxygen during delivery, may also be the cause of multiple ischemic infarcts which when they heal by scar will result in the so-called congenital hepatic fibrosis.
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.