Microvasculature in the small portal tracts in idiopathic portal hypertension. A morphological comparison with other hepatic diseases.

The morphology of the microvasculature in the small portal tracts was examined in normal livers, idiopathic portal hypertension (IPH) and other hepatic diseases. The microvasculature examined was arbitrary divided into two groups: that near the limiting plate and that within portal tracts, particularly around bile ducts. Based on comparisons of histology, immunohistochemistry and vascular casts, it is suggested that the former corresponded to inlet venules and the latter to distributing portal veins and peribiliary capillary plexus. Both of these microvasculatures were positive for Ulex europaeus lectin I, and (infrequently and weakly) for factor VIII-related antigen. Morphometry disclosed that inlet venules were reduced in number in IPH compared with normal livers and that distributing portal veins, peribiliary capillary plexus and inlet venules were increased in extrahepatic portal obstruction, chronic active hepatitis and extrahepatic obstructive cholestasis. We believe that the change in the microvasculature reflects abnormal microcirculation in the small portal tracts, and that the reduction of inlet venules plays an important role in the development of portal hypertension in IPH.