Hepatic haemodynamics and microvascular architecture after portal venular embolization in the rat

To clarify the relationship between hepatic damage and alterations of hepatic microvascular architecture and haemodynamics following portal venule occlusion, the present study was performed in rats which had been injected into the portal vein with 700,000 plastic beads (30-35 microns in diameter). When the occluded segment of the portal venule was short, infarction did not occur because of the prompt development of vascular channels bypassing the obstructed venules. On the other hand, when the occluded segment was long, infarction usually occurred. In this case, formation of collateral vascular channels began as dilatation of the sinusoids in the vicinity of the occluded portal venules and increased in diameter and developed into new portal venules in 5 days. Increased portal vascular resistance after embolization was normalized after 5 days in parallel with the progression of reconstruction of vascular channels. Reduced bile production returned to a normal level 3 days after embolization. Necrotic tissue was resorbed completely and replaced by fibroblasts 5 days after embolization. These findings indicate that the development of infarct following portal venule occlusion depends on the length of the occluded segment, and that hepatic microvasculature has a great capacity for adaptation and rapid reconstruction of vascular channels which leads to speedy recovery from hepatic circulatory disturbances and resulting hepatic damage.