Intraoperative Localization of the Superior Rectal Artery
The superior rectal artery can be most reliably located intraoperatively by identifying it as the continuation of the inferior mesenteric artery after the sigmoid branches have been given off, following it as it descends in the mesorectum enclosed in a fibrous sheath connected to the posterior rectal surface.
Anatomical Considerations
The superior rectal artery (SRA) is the direct continuation of the inferior mesenteric artery after the sigmoid branches have been given off, and is enclosed in a fibrous sheath connected to the posterior rectal surface by an anterior mesorectum containing the "transverse rectal branches" 1
The SRA typically gives rise to 4 branches: transverse rectal, descending rectal, rectosigmoid, and terminal branches 1
When the SRA reaches the rectum, it divides into multiple branches with four main patterns observed in angiographic studies:
- Four main branches (two left and two right) - most common pattern (46.8%)
- One right and two left branches (26.6%)
- Two branches to the right and one to the left (20%)
- One branch to the right and one to the left without further subdivision (6.6%) 2
Intraoperative Localization Technique
Identify the inferior mesenteric artery at its origin from the aorta, then trace it distally past the sigmoid branches to locate the beginning of the SRA 3
Follow the SRA as it descends in the mesorectum toward the posterior rectal wall, where it will be enclosed in a fibrous sheath 1
The SRA forms an "anterior mesorectum" containing the transverse rectal branches that connect to the posterior rectal surface, which serves as an important landmark 1
The terminal branches of the SRA extend downward and forward around the lower two-thirds of the rectum to the level of the levator ani muscle 4
Imaging Guidance for Localization
If available, review preoperative CT angiography (CTA) which can provide a detailed roadmap of the SRA and its branches with 95-100% sensitivity and specificity for detecting vascular abnormalities 5
CTA is particularly valuable for understanding the patient's specific vascular anatomy before surgery, as it can identify variations in the branching pattern of the SRA 5
For cases involving mesenteric ischemia, CTA of the abdomen and pelvis should be performed as the first-line diagnostic test prior to surgery to visualize the SRA and other mesenteric vessels 6, 5
Clinical Implications
Preservation of the SRA during colorectal resection significantly reduces the risk of anastomotic leakage compared to procedures where the inferior mesenteric artery is ligated at its origin 3
Understanding the branching pattern of the SRA is critical for procedures such as hemorrhoidal artery ligation, as some branches course through the outer layers of the rectal wall and enter just above the levator ani muscle 7
The SRA supplies the upper half of the rectum through transverse rectal arteries in an annular pattern, while the lower half receives blood through a plexiform pattern from the SRA terminal branches 1
When performing embolization procedures for hemorrhoidal disease, knowledge of the four main branching patterns of the SRA is essential for optimal results 2
Potential Pitfalls
The middle rectal artery is present in only about 50% of individuals, so relying on it as a landmark may be unreliable 1, 4
The SRA may have additional branches coursing in the outer layers of the rectal wall that enter just above the levator ani muscle, which should be taken into account during surgical procedures 7
Variations in the branching pattern of the SRA are common, so the surgeon should be prepared to encounter different anatomical configurations 2
In cases of mesenteric ischemia, the normal anatomy may be distorted, making identification more challenging 6