CT appearance of the inferior mesenteric vein.

The CT appearance of the inferior mesenteric vein (IMV) was studied. It can best be identified by its location behind or to the left of the duodenojejunal flexure. Superiorly, it drains into either the splenic vein, superior mesenteric vein, or the splenoportal junction. Inferiorly, it continues to the left of the fourth stage of the duodenum, lying in the left anterior pararenal space. Occasionally, the left colic vein is seen draining into the IMV. In 14 normal cases the diameter of the IMV, measured behind or to the left of the duodenojejunal flexure, was 3-6 mm with a mean of 3.9 mm and a standard deviation of 0.83 mm. In a case of portal hypertension it measured 9 mm. Thus, the IMV can be used to suggest portal hypertension.