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

Abstract

To evaluate the effects of hepatic arterial embolization on hepatic microcirculation in the rat liver by using different particulate agents. Polylactic acid microspheres, polyvinyl alcohol particles, and absorbable gelatin powder were injected into the hepatic artery of 50 rats. Saline was used as the control agent. Flow characteristics of hepatic microcirculation were qualitatively assessed on days 0 and 7 after embolization by using in vivo microscopy. Histologic specimens of the rat liver were analyzed. The polylactic acid (1-5 microns) injected into the hepatic artery was seen circulating through the sinusoids into the central venules. The slowing of flow observed with the injection of larger (50-200-micron) particles reflected the arterial occlusion occurring more proximally. After 7 days, all embolic agents caused vascular occlusion that led to necrosis and fibrosis. Networks of irregular, high-speed vessels that resembled arterioles and bypassed the normal sinusoids were observed. The necrotic areas observed after experimental distal occlusion of the hepatic arteries in the rats were bypassed by vessels similar to the capillarized sinusoids observed in the cirrhotic liver in humans. These vessels acted as sinusoidal shunts in the embolized territories.