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Rectal Venous Plexus

plexus venosus rectalis

The rectal venous plexus surrounds the rectum and anal canal and has two parts: an internal plexus in the submucosa and an external plexus outside the muscular wall and under the perianal skin. It drains upward through the superior rectal vein to the portal system and through the middle and inferior rectal veins to the systemic system. It is therefore an important portal-systemic connection.

Anatomical Data

Course & Branches

Origin	Submucosal and perimuscular veins of the rectum and anal canal
Course	The internal plexus lies in the submucosa above and below the pectinate line; the external plexus lies outside the muscle wall; both drain into the superior, middle and inferior rectal veins
Branches	Internal rectal venous plexus External rectal venous plexus Superior rectal vein (to the inferior mesenteric vein) Middle rectal veins (to the internal iliac veins) Inferior rectal veins (to the internal pudendal veins)

Clinical Relevance

Clinical Notes

The internal plexus forms the anal vascular cushions, and their enlargement and downward slipping produces internal haemorrhoids, which bleed bright red blood but are usually painless because they lie above the pectinate line. The external plexus below the pectinate line can thrombose, causing a painful perianal lump. In portal hypertension, true anorectal varices may develop, which are distinct from haemorrhoids.

Pathology

Common Injuries & Conditions

Haemorrhoids

Enlarged anal cushions of the internal plexus cause painless bright red bleeding and prolapse. Treatment ranges from fibre and fluids to banding, sclerotherapy or surgery.

Thrombosed External Haemorrhoid

A clot in the external rectal plexus produces a sudden, very painful bluish lump at the anal margin, which may be excised early or allowed to settle.

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