portal-systemic anastomoses

por·tal-·sys·tem·ic a·nas·to·mo·ses

1. naturally occurring venous communications between tributaries of the portal venous system and tributaries of the systemic venous system. The major portal-systemic anastomoses include: 1) esophageal branches of left gastric vein with esophageal veins, 2) superior rectal vein with middle and inferior rectal veins, 3) paraumbilical veins with subcutaneous veins of anterior abdominal wall, 4) retroperitoneal veins with venous branches of veins of the colon and bare area of the liver, and 5) a patent ductus venosus connecting left branch of portal vein to inferior vena cava (rare). These anastomoses are important clinically, providing collateral circulation during portal obstruction or hypertension, although they may become varicose;
2. surgically created communications between the portal vein and the inferior vena cava or their tributaries, to relieve portal hypertension.