Prehepatic portal hypertension in the rat. Immediate and long-term effects on portal vein and aortic pressure of a graded portal vein stenosis, followed by occlusion of the portal vein and spleno-renal collaterals.

The creation of a portal vein stenosis with a diameter of 1.2 mm in Wistar rats resulted in a sustained elevation of the portal vein pressure to approximately twice the control value lasting for at least 8 weeks. The alterations in portal vein pressure following occlusion of the stenosed portal vein and splenorenal collaterals, either separately or in combination, indicate that a considerable quantity of portal blood is diverted into the inferior caval vein through the splenorenal collaterals, and that the development of these collaterals occurs during the first 3-4 weeks after the establishment of the stenosis. The concomitant reduction in aortic pressure and increase in heart rate following total occlusion of the portal vein were most pronounced during the first weeks after stenosis, and were probably due to diminished venous return to the heart.