Experimental extrahepatic obstruction of portal vein: documentation of histopathological alterations in liver and extrahepatic tissues.

The histopathology of the portal vein in human extrahepatic portal vein obstruction (EHPVO) in the form of cavernomatous transformation of the portal vein is well documented. However, a similar detailed histopathology has not been documented in experimental EHPVO, even though the model has been in existence for many years. An experimental model of EHPVO was created by partial ligation of the portal vein in 20 rats. A control group of 11 sham operated (SO) rats was also studied. Development of portal hypertension was confirmed by measurement of intrasplenic pulp pressure (19.7 + 7.1 cm normal saline vs 12.9 + 1.1 cm of normal saline in SO rats). Histopathological evidence included varices in the oesophagus and congestion in the submucosa and mucosa of the stomach and capillarization of sinusoids in the spleen. Animals were killed at 22-265 days post-ligation. While SO animals showed mild focal sinusoidal congestion and a normal portal vein, the experimental group of animals with EHPVO showed oedema around the portal vein, multiple dilated vascular channels near the hilum resembling cavernomatous transformation and severe sinusoidal congestion. Jejunum and kidneys showed congested veins in the experimental group. None of the SO animals showed this change. Thus experimental EHPVO does reproduce some histological changes observed in human EHPVO.