Origin and Course
The superior rectal artery arises as the direct continuation of the inferior mesenteric artery (a. mesenterica inferior). The inferior mesenteric artery branches off the anterior surface of the lower third of the abdominal aorta at the level of the third lumbar vertebra (LIII) and courses retroperitoneally.
A. rectalis superior is the terminal branch of this arterial trunk. The inferior mesenteric artery also gives rise to the left colic and sigmoid arteries. The superior rectal artery courses within the root of the mesentery and descends toward the ampulla of the rectum.
Rectal Blood Supply and Anastomoses
The rectum receives blood from five arteries: the superior rectal artery is unpaired, while the middle and inferior rectal arteries are paired.
It forms anastomoses with:
- The lower sigmoid artery.
- The middle rectal artery (a. rectalis media), a branch of the internal iliac artery (a. iliaca interna).
Vascularization feature: Along the mesenteric border of the bowel, typically only a single primary arcade (marginal or parallel vessel) is formed.
Topography and Related Structures
The upper part of the rectum is covered by peritoneum on all sides (intraperitoneal), while the supra-ampullary or rectosigmoid junction sometimes possesses a mesentery (mesorectum).
Extraorgan veins parallel the arteries and drain into the superior and inferior mesenteric veins. The inferior mesenteric vein (v. mesenterica inferior) runs to the left of the duodenojejunal flexure (flexura duodenojejunalis), passes inferior to the body of the pancreas, and empties into the splenic vein. The rectal veins form the internal and external rectal venous plexuses, which play a crucial role in portosystemic (portocaval) anastomoses.
Lymphatic Drainage and Clinical Significance
Regional lymph nodes are located along a. rectalis superior. When a tumor is located in the sigmoid colon or upper rectum, regional lymph nodes along the course of a. rectalis superior are critical sites for lymphatic spread.
In surgical management of pathologies affecting the rectosigmoid region, the vascular ligation strategy typically involves high ligation of the inferior mesenteric artery (a. mesenterica inferior) at its origin or immediately distal to the takeoff of the left colic artery (a. colica sinistra), depending on the required oncological margin and collateral perfusion.