Sigmoid veins

At a glance

English

Sigmoid veins

Latin (TA2)

Venae sigmoideae

System

Vein

Region

Trunk

Side

Single, on the midline

About the sigmoid veins

The sigmoid veins drain the sigmoid colon, the S-shaped loop of large bowel that lies in the left lower abdomen and pelvis between the descending colon and the rectum. There are usually several of them. They run in the sigmoid mesocolon, the fold of peritoneum that suspends the loop from the back wall of the pelvis, and they lie alongside the sigmoid arteries, which they follow in reverse.

Each vein begins from small veins in the wall of the colon. Near the bowel these are linked by arcades, so that venous blood can pass along the gut from one vein to the next, matching the marginal arterial arcade. The sigmoid veins then pass upwards and to the left in the mesocolon and open into the inferior mesenteric vein, either one by one or after joining into a common trunk.

The inferior mesenteric vein carries the blood upwards, behind the peritoneum and to the left of the duodenojejunal flexure, to end in the splenic vein or at the junction of the splenic and superior mesenteric veins. From there it reaches the hepatic portal vein and the liver. Like the other veins of the gut, the sigmoid veins have no valves of any importance, and nutrients and other substances absorbed from the colon pass through the liver before they reach the general circulation.

In operations on the sigmoid colon, as in resection for cancer or for diverticular disease, the veins are divided with their arteries, and the lymph nodes along them are removed. Spread of tumour cells from the colon along these veins to the liver explains why the liver is the commonest site of distant spread from colorectal cancer.

Course and drainage

Begins at

Begin in the wall of the sigmoid colon, linked near the bowel by arcades.

Drains into

End in the inferior mesenteric vein, singly or by a common trunk.

Drains

Drain the sigmoid colon into the hepatic portal system.