The inferior mesenteric vein
begins in the rectum
as the superior rectal vein
(superior hemorrhoidal vein
), which has its origin in the hemorrhoidal plexus
, and through this plexus communicates with the middle and inferior hemorrhoidal veins
The superior hemorrhoidal vein leaves the lesser pelvis and crosses the left common iliac vessels with the superior hemorrhoidal artery, and is continued upward as the inferior mesenteric vein.