Superior rectal vein

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.

Superior rectal vein
The bloodvessels of the rectum and anus, showing the distribution and anastomosis on the posterior surface near the termination of the gut. (Labeled at top as superior hemorrhoidal vein.)
The veins of the right half of the male pelvis.
Details
Drains from	Rectum
Source	Hemorrhoidal plexus
Drains to	Inferior mesenteric vein
Artery	Superior rectal artery
Identifiers
Latin	vena rectalis superior
TA98	A12.3.12.035
TA2	5130
FMA	15393
Anatomical terminology [edit on Wikidata]

The superior rectal vein leaves the lesser pelvis and crosses the left common iliac vessels with the superior rectal artery, and is continued upward as the inferior mesenteric vein.

References

This article incorporates text in the public domain from page 681 of the 20th edition of Gray's Anatomy (1918)