Changes in rat liver microcirculation after experimental hepatic arterial embolization: Comparison of different embolic agents

PURPOSE: To evaluate the effects of hepatic arterial embolization on hepati c microcirculation in the rat liver by using different particulate agents. MATERIALS AND METHODS: Polylactic acid microspheres, polyvinyl alcohol part icles, and absorbable gelatin powder were injected into the hepatic artery of 50 rats. Saline was used as the control agent. Flow characteristics of h epatic microcirculation were qualitatively assessed on days 0 and 7 after e mbolization by using in vivo microscopy. Histologic specimens of the rat li ver were analyzed. RESULTS: The polylactic acid (1-5 mu m) injected into the hepatic artery wa s seen circulating through the sinusoids into the central venules. The slow ing of flow observed with the injection of larger (50-200-mu m) particles r eflected the arterial occlusion occurring more proximally. After 7 days, al l embolic agents caused vascular occlusion that led to necrosis and fibrosi s. Networks of irregular, high-speed vessels that resembled arterioles and bypassed the normal sinusoids were observed. CONCLUSION: The necrotic areas observed after experimental distal occlusion of the hepatic arteries in the rats were bypassed by vessels similar to th e capillarized sinusoids observed in the cirrhotic liver in humans. These v essels acted as sinusoidal shunts in the embolized territories.