Prehepatic

 Portal vein thrombosis

 Splenic vein thrombosis

 Massive splenomegaly (Banti's syndrome)

Hepatic

 Presinusoidal

  Schistosomiasis

  Congenital hepatic fibrosis

 Sinusoidal

  Cirrhosis-many causes

  Alcoholic hepatitis

 Postsinusoidal

  Hepatic sinusoidal obstruction (venoocclusive syndrome)

Posthepatic

 Budd-Chiari syndrome

 Inferior vena caval webs

 Cardiac causes

  Restrictive cardiomyopathy

  Constrictive pericarditis

  Severe congestive heart failure