Portal hypertension: prolonged elevation of portal venous pressure (normal 2-5mmHg). To develop clinical features or complications, patients usually have pressures >12mmgHg

Mechanism:

Increased vascular resistance in the portal venous system - from various mechanical causes , and also as an active process in which liver damage activates stellate cells and myofibroblasts, contributing to the abnormal blood flow patterns.
Increased blood flow in the portal veins - from splanchnic arteriolar vasodilatation, caused by an excessive release of endogenous vasodilators.

Causes:

Prehepatic - blockage of the portal vein before the liver

Congenital atresia or stenosis.
Portal-vein thrombosis (idiopathic, umbilical and portal sepsis, malignancy, hypercoagulable states -pregnancy, The Pill)
Pancreatitis
Splenic vein thrombosis.
Abdo trauma (inc surgery)
Extrinsic compression, eg tumours.

Hepatic

Cirrhosis.
Chronic hepatitis.
Schistosomiasis.
Myeloproliferative diseases.
Idiopathic portal hypertension.
Drugs
Granulomata, eg sarcoid.
Nodular (nodular regenerative hyperplasia, partial nodular transformation).
Toxins (arsenic, vinyl chloride).
Fibropolycystic disease (including congenital hepatic fibrosis).

Posthepatic - blockage of hepatic veins or venules

Budd-Chiari syndrome (hepatic vein obstruction).
Constrictive pericarditis.
Right heart failure.
Veno-occlusive disease of the smaller hepatic veins/venules (due to ingestion of pyrrolizidine alkaloids; antileukaemic drugs, radiation).

Other causes Increased hepatic blood flow:

Increased splenic blood flow, eg massive splenomegaly.
Hepatoportal arteriovenous fistula.
Idiopathic (a diagnosis of exclusion)

Left-sided (sinistral) portal hypertension Rare. It is confined to the left side of the portal system. It may present as bleeding from gastric varices.Usually it is due to pathology involving the splenic vein or the pancreas

	Created by bessimajamal almost 12 years ago

Note on Liver, created by bessimajamal on 14/06/2014.