Cranial mesenteric vein

The cranial mesenteric vein begins in the mesentery of the jejunum, where it is formed by the confluence of multiple jejunal and ileal veins. It courses cranially in the root of the mesentery, closely accompanying the cranial mesenteric artery and its branches, although generally located ventromedial to it. The vein lies to the right of the midline and progresses cranially and slightly dorsally.

The cranial mesenteric vein continues cranially and ultimately joins with the splenic vein, often at the same location as the caudal mesenteric vein. These veins unite to form the hepatic portal vein, which proceeds cranially toward the liver at the porta hepatis. The convergence typically occurs caudal to the pancreas, ventral to the aorta, and slightly to the right of the midline.

Along its course, the cranial mesenteric vein receives tributaries that are mostly homologous to the branches of the cranial mesenteric artery. These include:

• Jejunal veins: Numerous small veins draining the jejunal loops and mesojejunum.

• Ileal veins: Draining the ileum, often joining the terminal jejunal tributaries.

• Ileocolic vein: A significant tributary that collects blood from the ileum, cecum, and ascending colon.

• Right colic vein: Drains the ascending colon and may join the ileocolic vein before entering the cranial mesenteric vein.

• Middle colic vein: Drains the transverse colon, and may anastomose with the left colic vein (from the caudal mesenteric vein).

• Pancreaticoduodenal veins: These drain portions of the duodenum and pancreas.