Portal cavernoma or chronic non cirrhotic extrahepatic portal vein obstruction.

Chronic non cirrhotic extrahepatic portal vein obstruction (EHPVO) refers to the cavernomatous transformation of the portal vein (the so-called "portal cavernoma") which occurs following acute thrombosis of the portal vein in the absence of recanalization. In adults, EHPVO mainly occurs following thrombosis, while in children it may be related to congenital malformations and/or neonatal umbilical venous catheterization. However, 50% of the cases of EHPVO remain idiopathic [1].

Sinusoidal obstruction syndrome.

Sinusoidal obstruction syndrome (SOS), previously known as veno-occlusive disease, is characterized by concentric and non-thrombotic obstruction of the sinusoid and central vein lumen with no identified primitive or thrombotic hepatic vein lesions. The initial lesion is a result of endothelial denudation, corresponding to the migration of damaged sinusoidal cells to the central veins of the hepatic lobules, leading to sinusoidal and veno-occlusive congestive obstruction. SOS may be associated with other lesions such as centrilobular perisinusoidal fibrosis, peliosis, or nodular regenerative hyperplasia.