Recent advances have changed our understanding of this disease, as well as the outcomes. In this review, we confine our discussion to primary BCS. Budd Chiari syndrome definition Budd-Chiari syndrome is a rare liver condition that is defined as, obstruction to the outflow of blood in hepatic veins at any point, ranging from the small hepatic vein to the junction of the right atrium (heart chamber) and inferior vena cava (largest vein in the body carrying deoxygenated blood). Budd-Chiari syndrome is a condition caused by occlusion of hepatic veins. Learn about its causes, symptoms, and treatment options for effective management. Budd-Chiari syndrome, also known as hepatic venous outflow obstruction (HVOO), refers to the clinical picture that occurs when there is partial or complete obstruction of the hepatic veins.