Evaluation of hepatic venous balloon occluder to estimate portal pressure

The hepatic venous balloon occluder method of estimating portal venous pressure (PVP) was evaluated in cats and dogs, during basal state and active vasoconstriction, and during passive presinusoidal resistance elevation in cats. In the dog, the balloon catheter measured a pressure not different from PVP when the balloon was inflated both in basal state and during active vasoconstriction induced by hepatic nerve stimulation, intraportal infusion of histamine or norepinephrine, regardless of whether the balloon was distal or proximal to hepatic venous sphincters. In the cat, the inflated balloon measures a pressure not different from PVP in basal state but slightly overestimated PVP during nerve stimulation or norepinephrine infusion in some protocols. Blood clots were injected intraportally in cats to produce a pure, passive presinusoidal resistance as shown by unchanged intrahepatic pressure but elevated PVP. The balloon method accurately measured PVP in this condition and clearly cannot differentiate pre- from postsinusoidal resistance sites in cats or dogs. The balloon method and the classical wedged pressure method will represent PVP when resistance is primarily postsinusoidal; they provide different measurements when resistance is presinusoidal, the wedged method representing intrahepatic pressure but the balloon method reflecting portal pressure. These differences require confirmation in human presinusoidal cirrhosis.