Abdominal vein thrombosis is a rare, but potentially life-threatening form of venous thrombosis. It mainly involves the hepatic veins (Budd Chiari syndrome, BCS),
portal veins (PVT) and mesenteric veins. In recent years
several large-scale studies have been performed to study the underlying aetiological factors in these thrombotic disorders. Both inherited and acquired thrombophilia factors are frequently observed in these patients. Factor V Leiden mutation is frequently found in patients with BCS and prothrombin gene variant is seen more frequently in PVT. Myeloproliferative neoplasms (MPNs), including polycythemia vera and essential thrombocythemia, are underlying disorders in 30-40% of patients with abdominal vein thrombosis. Other aetiological factors are paroxysmal nocturnal haemoglobinuria (PNH), autoimmune disorders and hormonal factors. Recently, several new risk factors have been reported and are discussed in this review. BCS and PVT are multi-factorial disorders. In nearly 50% of patients two, and in 16% even three prothrombotic risk factors were found at presentation. Because patients with abdominal vein thrombosis have a high risk of recurrence immediate anticoagulant treatment is necessary. The duration of treatment is still a matter of debate because these patients also have a high risk of bleeding, especially those with portal hypertension. For BCS patients life-long anticoagulant treatment is advised. In patients with PVT it is recommended to tailor treatment to the individual patient based on the presence of an underlying prothrombotic disorder and the risk of bleeding.