Review article: the relevance of portal pressure and other risk factors in acute gastro-oesophageal variceal bleeding.

Gastro-oesophageal variceal bleeding is the last step in a chain of events that starts with an increased portal pressure, and is followed by the formation and progressive dilatation of gastro-oesophageal varices. When the tension of the thin wall of the varices exceeds its elastic limit, the varices rupture and bleed. Wall tension is directly proportional to variceal pressure (which is a function of portal pressure) and variceal radius, and inversely related to the thickness of the variceal wall. The above facts explain why a high portal pressure (usually determined by the hepatic venous pressure gradient, or HVPG) and the presence at endoscopy of large varices with red wheals, red spots or diffuse redness on the varices (signalling a reduced wall thickness) correlate with the risk of bleeding.