The aetiology of portal hypertension in children is classified as: -

	Cirrhotic - e.g. biliary atresia, cystic fibrosis
	Non- cirrhotic
	Pre-hepatic - e.g. portal vein thrombosis
	Intra-hepatic -
	Presinusoidal - e.g. congenital hepatic fibrosis
	Parasinusoidal - e.g. fatty liver, nodular hyperplasia
	Postsinusoidal - e.g. veno-occlusive disease of liver
	Supra-hepatic - e.g. Budd-Chiari syndrome

The most frequent surgical cause of cirrhosis in childhood is biliary atresia. Besides this cause alpha-1- antitrypsin deficiency and metabolic liver diseases are the commonest medical conditions leading up to cirrhosis of the liver. Many of these patients have the stigmata of their underlying disease and the diagnosis of portal hypertension is not difficult.

The diagnosis may not be so obvious in children with non-cirrhotic portal hypertension. Portal vein thrombosis (extra-hepatic portal hypertension), for example, may present within the first five years of life as a major haematemesis with only splenomegaly and a reduced platelet count as clues to the diagnosis. Many affected patients have no documented cause for their portal hypertension. However, at times, a history of umbilical vein canulation, abdominal infection, trauma or pancreatitis may be responsible for the portal thrombosis. The liver function tests in such patients are essentially normal. A confirmation of portal vein occlusion may be obtained by ultrasound demonstration of collateral venous channels in the porta hepatis replacing the portal vein. Approximately 40 % of these patients have a history of umbilical vein catheterization or abdominal sepsis in the neonatal period but the venous occlusion in the majority appears to be congenital in origin.

Congenital hepatic fibrosis may also present with an acute haematemesis and normal liver function tests but the clinical features include hepatomegaly. A liver biopsy shows bands of fibrous tissue joining the portal tracts and this condition may be associated with polycystic disease and other renal disorders.

There are several reports of portal hypertension in children presenting with haematemesis and splenomegaly in whom the liver histology is normal and in whom the portal vein is patent.

Further studies have shown a subendothelial thickening of intrahepatic branches of the portal vein causing presinusoidal obstruction to portal blood flow within the liver leading to the formation of collateral venous channels in the porta hepatis. The condition has been known under a variety of names such as non-cirrhotic portal hypertension but the best is perhaps 'hepato-portal sclerosis'. The aetiology is unknown.

Suprahepatic obstruction caused by either a web in the inferior vena cava above the entrance of the hepatic veins or thrombotic occlusion of the hepatic veins (Budd-Chiari syndrome) is extremely rare in childhood. The clinical features may be mimicked by constrictive pericarditis but echocardiography and venography should make the diagnosis clear.