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.