The epidemiology and pathogenesis of gastrointestinal varices

摘要

Gastrointestinal varices are a consequence of portal hypertension that can occur in the setting of cirrhosis or extrahepatic portal vein obstruction. Increased intrahepatic vascular resistance, a hyperdynamic circulation, and increased flow through the portal and collateral venous system lead to persistently elevated portal pressures that result in angiogenesis and formation of collaterals between the portal and systemic circulation. Despite this physiological attempt at decompression, portal hypertension persists as collateral vessels have higher resistance than the normal liver. Variceal wall tension is the main factor that determines vessel rupture and bleeding occurs when tension in the wall exceeds the limit of elasticity of the vessel. Progressive distension leads to increasing resistance to flow and hemorrhage ensues when the limits of resistance to further dilation are surpassed. Gastroesophageal varices are present in 50% of patients with cirrhosis and progress in size at a rate of 8%-10% per year. Hemorrhage occurs at a rate of approximately 12% per year and large esophageal varices carry a higher risk of rupture. Gastric varices occur in 20% of patients with portal hypertension and bleed less frequently, but more severely. Cardiofundal varices have a complex vascular anatomy that is important to consider as it pertains to the effectiveness of strategies used for management. Ectopic varices make up 2%-5% of all variceal bleeding, occur more frequently in patients with extrahepatic portal hypertension, and their identification should prompt assessment of the intra-abdominal vasculature. Varices in the setting of splenic vein thrombosis should be considered a distinct entity owing to their disparate etiologic basis and treatment approach.