Rectal Venous Plexus
Rectal venous plexus drains rectal veins via superior, middle, and inferior rectal veins.
The rectal venous plexus is a network of interconnected veins surrounding the rectum. It serves as the primary venous drainage system for the rectum and anal canal and forms an important connection between the portal and systemic circulations. The plexus is subdivided into internal and external components, which lie in different layers of the rectal and anal wall. This venous arrangement is clinically significant as it is the site of hemorrhoid formation and a common route for portosystemic anastomosis.
Structure
The rectal venous plexus consists of two main components:
- Internal rectal venous plexus: Located in the submucosa of the anal canal, above the pectinate line
- External rectal venous plexus: Located in the subcutaneous tissue around the anus, below the pectinate line
These venous channels are thin-walled and valveless, making them vulnerable to pressure changes and distension.
Connections
- Superior rectal vein: Drains into the inferior mesenteric vein → portal circulation
- Middle rectal vein: Drains into the internal iliac vein → systemic circulation
- Inferior rectal vein: Drains into internal pudendal vein → internal iliac vein
Location
The rectal venous plexus surrounds the terminal part of the large intestine and is divided anatomically as follows:
| Plexus | Location |
|---|---|
| Internal plexus | Within submucosa of rectum and superior anal canal (above pectinate line) |
| External plexus | Within perianal subcutaneous tissue (below pectinate line) |
Function
- Venous Drainage: Drains deoxygenated blood from the rectum and anal canal
- Portosystemic Communication: Forms one of the major sites of portal-systemic venous anastomosis
- Pressure Equalization: Assists in adapting to pressure fluctuations during defecation and straining
Drainage Pathways
- Internal plexus: Mainly drains into superior rectal vein → inferior mesenteric vein → portal vein
- External plexus: Drains into middle and inferior rectal veins → systemic circulation (internal iliac vein)
Lymphatic Drainage
- Above pectinate line: Internal iliac lymph nodes
- Below pectinate line: Superficial inguinal lymph nodes
Clinical Significance
- Hemorrhoids: Dilatation of internal plexus causes internal hemorrhoids (painless); external plexus leads to external hemorrhoids (painful)
- Portal Hypertension: Can lead to engorgement of the superior rectal veins, contributing to hemorrhoidal varices
- Metastatic Spread: Rectal cancer may spread via the venous plexus to both portal and systemic systems
Last updated on May 11, 2025
