Obstruction can be Extrahepatic— portal vein thrombosis due to a hypercoagulable state, a vessel wall lesion (eg, pylephlebitis, omphalitis), an adjacent lesion (eg, pancreatitis, tumor), or congenital atresia of the portal vein Intrahepatic—eg, microvascular portal vein obstruction as occurs in schistosomiasis, primary biliary cholangitis (PBC, previously called primary biliary cirrhosis), sarcoidosis, and noncirrhotic portal hypertension