Caudal mesenteric vein

The caudal mesenteric vein is an unpaired, smaller terminal tributary to portal vein that courses in mesenterium towards colon descendens.

In horses and rabbits, the caudal mesenteric vein as a similar anatomy with the inferior mesenteric vein in humans. The caudal mesenteric vein is formed by the union of smaller veins from the descending colon and rectum, mainly the left colic vein and cranial rectal vein. It runs cranially and slightly to the right within the descending mesocolon, adjacent to the caudal mesenteric artery and empties into the cranial mesenteric vein or the portal vein.

In carnivores, the caudal mesenteric vein is not a satellite of the caudal mesenteric artery. It begins in the pelvic cavity as the cranial rectal vein, which is a satellite of the cranial rectal artery. In the rectal plexus of veins at the pelvic outlet, it anastomoses with the caudal rectal vein, which drains blood into the caval system of veins. The cranial rectal vein continues cranially from the pelvic inlet in the left mesocolon to the place where the cranial rectal artery becomes associated with it. Here it is continued as the left colic vein and collects approximately 25 left colic branches, which are satellites of the vasa recta of the left colic artery. Some of these may be double. The last tributary to enter the left colic vein is larger than the others, as it collects blood from the left colic flexure as well as from the adjacent middle and left parts of the colon. Its middle colic tributary anastomoses in an arcade with the middle colic vein. At the left colic flexure, the caudal mesenteric vein enters the mesojejunum, in which it crosses the left face of the cranial mesenteric artery and associated structures. It joins the cranial mesenteric vein to the right of the left lobe of the pancreas to contribute to the portal vein.