DIAGNOSTIC CIRCUMSTANCES: Portal vein thrombosis is the second cause of portal hypertension after cirrhosis in Western countries. Diagnosis can be either made at the acute stage in the context of abdominal pain or after appearance of a porto-portal collateral venous circulation leading to the formation of a portal cavernoma, the diagnosis being made in the circumstance of rupture of oesophageal varicose veins or manifestations of hypersplenism. AETIOLOGICAL SURVEY: In the absence of hepatocellular carcinoma, causes that need to be investigated are cirrhosis, local factors (intra-abdominal sepsis, abdominal surgery, splenectomy or pancreatitis), and one or several prothrombotic affections (acquired or inherited prothrombotic states are present in 70% of cases, with myeloproliferative disease ranking first). REGARDING TREATMENT: Anticoagulant therapy generally allows recanalisation of the thombosed veins in recently constituted thrombosis. Some patients at the portal cavernoma stage can also benefit from anticoagulant therapy: patients with a prothrombotic state without large oesophageal-gastric varicose veins. In the case of large oesophageal-gastric varicose veins that have never bled, treatment to prevent haemorrhages due to portal hypertension according to the same modalities as in cirrhosis must be associated with the prescription of an anticoagulant. In the absence of prothrombotic affection or in patients having already suffered from haemorrhages due to portal hypertension, the benefit of anticoagulant therapy is less clearly established.