Budd-Chiari syndrome is an uncommon condition of obstruction of intrahepatic veins. It is induced by thrombotic or nonthrombotic obstruction of hepatic venous outflow, leading to congestive hepatopathy. The hepatopathy results from large and small vein obstruction of venous outflow, producing hepatocellular injury from microvascular ischemia. It eventually results in portal hypertension and then liver insufficiency and failure.

Exact incidence of Budd-Chiari syndrome is not known; it is classified as a rare entity both in the United States and internationally.

Budd-Chiari syndrome frequently occurs in patients who already have some manner of thrombotic diathesis, including myeloproliferative disorders, pregnancy, tumors, chronic inflammatory diseases, clotting disorders, and infections.