The livers of rats subjected to end-to-side portacaval anastomoses were studied 3 to 5 months postoperatively by in uiuo and electron microscopy. Compared with sham-operated controls, the livers of portacaval anastomoses animals contained dilated, tortuous networks of sinusoids. The velocity of blood flow in these vessels tended to be slower and more variable than controls, but always progressed toward the hepatic venules. Blood entered the sinusoids from portal venules and from arteriosinus twigs which terminated in the initial segments of some of the sinusoids at the periphery of the lobule. Together, the arteriosinus twigs and the short, initial segments of these sinusoids formed functional arterioportal anastomoses. These, in combination with the lack of portal venous inflow, resulted in retrograde blood flow in portal venules. Nevertheless, blood still flowed from these portal venules into the sinusoids unless the sinusoid was fed by an arteriosinus twig. In addition to these microcirculatory alterations, the number of Kupffer cells that phagocytized latex particles was less in the animals with portacaval anastomoses, as was the number of particles ingested by these cells. Scanning and transmission electron microscopy confirmed the paucity of Kupffer cells. Those seen appeared inactive since they were flattened, exhibited few microplicae and filopodia and contained few latex particles. The endothelial cells of the sinusoid lining were perforated by increased numbers of large fenestrae which may be a reflection of devated intrasinusoid pressures generated by the expanded arterialization of the sinusoid bed. The observed dilated sinusoid network interspersed by narrowed plates of hepatocytes is also consistent with this hypothesis. Finally, scattered nodular foci were observed which contained enlarged hepatocytes, narrow sinusoids, active Kupffer cells, and more normal rates of blood flow. Such sites may represent attempts by the liver to regenerate its normal architecture.Portacaval anastomosis (PCA) is performed selectively to relieve portal hypertension and bleeding esophageal varices in patients suffering from cirrhosis of the liver.Several studies have reported major changes in hepatic hemodynamics and reticulo-endothelial function in animals following PCA (1). To date, however, direct in vivo microscopic evaluation of the altered microvasculature and Kupffer cell function has not been reported for such animals. 'In addition, the ultrastructural changes in the sinusoid wall that occur under these conditions is not clear although the morphometric changes in the liver 3 weeks following PCA recently were reported by Muller and Schroder (2).As a result, the hepatic microvasculature and distribution of phagocytic Kupffer cells in rats subjected to PCA was investigated using high-resolution in vivo microscopic methods of McCuskey ( 3 , 4 ) and McCuskey et al. (5). Subsequently, these livers were studied by scanning electron microscopy (SEM) and transmission (TEM) electron microscopy. The results form the basis...

The vasculature of the hepatic lobule of the monkey was investigated by scanning and transmission electron microscopy. The vessel walls of the portal and terminal hepatic (central) veins consist of a closed endothelium, a continuous basement membrane and a connective tissue layer. Sinusoids, however, show endothelia with typical fenestrations, and connective tissue fibres are only sparsely distributed in the space of Disse. Kupffer cells are present in the sinusoids, and occasionally in the terminal hepatic and sublobular veins, but are never present in the portal veins. They are characterized by a ruffled surface and special processes--filopodia and lamellipodia--which anchor them to the endothelial cells and also connect them with adjacent Kupffer cells. Flat branches of perisinusoidal cells, which encircle the endothelia, occur in the space of Disse, and are presumed to have a pericyte-like function.

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The bile canalicular network of the monkey was studied by fracturing fixed liver tissue and examination by scanning electron microscopy. Bile canaliculi do not differ remarkably from those described in other species. Their course and luminal diameter vary, depending on their position in the liver lobule. In one specimen the continuity of a canaliculus with a terminal bile ductule (canal of Hering) is presented. Several constrictions occur in this part of the ductular lumen. The interlobular bile duct wall shows two kinds of niches. A single cilium arises from a primary niche. The walls of secondary niches contain numerous primary niches. Simple columnar epithelium lines the common bile duct, the main pancreatic duct and the Several constrictions occur in this part of the ductular lumen. The interlobular bile duct wall shows two kinds of niches. A single cilium arises from a primary niche. The walls of secondary niches contain numerous primary niches. Simple columnar epithelium lines the common bile duct, the main pancreatic duct and the Several constrictions occur in this part of the ductular lumen. The interlobular bile duct wall shows two kinds of niches. A single cilium arises from a primary niche. The walls of secondary niches contain numerous primary niches. Simple columnar epithelium lines the common bile duct, the main pancreatic duct and the gallbladder. A common feature is the presence of microplicae on their lateral cell surfaces.

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