The Budd-Chiari syndrome.

Obstruction of the hepatic venous outflow tract results in increased hepatic sinusoidal pressure and portal hypertension. In the early stages, portal venous perfusion of the liver is decreased, which may result in portal venous thrombosis. 2 The ensuing venous stasis and congestion lead to hypoxic damage to adjacent hepatic parenchymal cells. Furthermore, the ischemic injury to the sinusoidal lining cells results in the release of free radicals, and oxidative injury to the hepatocytes ensues. 3 These mechanisms culminate in the development of hepatocyte necrosis in the centrilobular regions (Fig. 1), with progressive centrilobular fibrosis, nodular regenerative hyperplasia, and ultimately, cirrhosis of the liver. 4 However, if the hepatic sinusoidal pressure is reduced by the creation of a portosystemic shunt or by the development of a portal venous collateral system, liver function improves. 5