The middle anorectal (rectal) veins originate from the anorectal venous plexus, which is a network of veins surrounding the rectum. Along with the superior rectal veins and inferior rectal veins, they play a key role in draining venous blood from the rectum.

These veins travel laterally through the mesorectum, running along the pelvic surface of the levator ani muscle. They are relatively short vessels that terminate in the internal iliac vein (Read more!). There is considerable variation in both the number and diameter of these veins.

Interestingly, veins located above the middle rectal vein in the colon and rectum drain into the portal venous system, ultimately reaching the liver. In contrast, veins at the level of the middle rectal vein and below drain into the systemic circulation, returning blood directly to the heart and bypassing the liver.

The middle rectal veins have a more significant role than their corresponding artery. They drain the portion of the rectum located above the internal anal sphincter and form both submucosal and perimuscular connections with the inferior rectal vein. Additionally, they form submucosal anastomoses with the superior rectal vein.

Branches of the middle rectal vein also communicate with the prostatic venous plexus in males, and with the vaginal and uterine venous plexuses in females. These veins serve as a major connection between the portal venous system and the systemic venous system.

Overall, the middle anorectal veins drain blood from the middle portion of the rectum, as well as receive blood from the prostate and seminal gland. They may also drain the urinary bladder and ureter.

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Middle anorectal (rectal) veins