Portohepatic bypass by splenohepatopexy in rats with prehepatic portal hypertension. A long-term (12-month) study of the development of splenohepatic collaterals and their effect on portal vein pressure.

Transposition to the liver of the spleen in rats with prehepatic portal hypertension due to a calibrated portal vein stenosis with a diameter of 1.2 mm resulted in the development of new venous collaterals from the spleen into the liver parenchyma. The collaterals were visualized macro- and microscopically as well as angiographically and were found to drain into intrahepatic branches of the portal vein, sinusoids, and hepatic veins. The portal pressure 12 months after stenosis and transposition was found to be significantly lower in rats with transposed spleens than in rats with portal vein stenosis alone. The collaterals were sufficiently well developed to significantly reduce the increase in portal vein pressure that follows acute occlusion of the portal vein and the natural splenorenal collaterals.