Anatomy, Abdomen and Pelvis: Ileocolic Artery

Structure and Function

The major branches of the SMA include the RCA, MCA, and the ileocolic and inferior pancreaticoduodenal arteries. Additional jejunal and ileal branches arise from the left aspect of the SMA.

The MCA is the 1st colic branch of the SMA and supplies the proximal 2/3 of the transverse colon. The RCA is the 2nd colic branch and supplies the right colon, predominantly the ascending colon.

The ileocolic artery is the most inferior branch of the SMA, often described as the terminal branch. After arising from the SMA, the ileocolic artery courses inferiorly in a retroperitoneal plane toward the right iliac fossa. Division into superior and inferior branches occurs in this region.

The superior branch of the ileocolic artery anastomoses with the RCA and supplies the terminal ileum, cecum, and appendix. The inferior branch gives rise to the anterior and posterior cecal arteries, the ileal branch of the ileocolic artery, and the appendicular artery. The anterior and posterior cecal arteries course anterior and posterior to the terminal ileum, respectively.

The ileal branch of the ileocolic artery forms an anastomosis with the last intestinal (ileal) artery. The ileocolic artery also anastomoses superiorly with the RCA. The appendicular artery courses within the mesoappendix and is located posterior to the terminal ileum.

Normal anatomic variations of the right colonic vasculature and SMA branches are well described, with the most common configuration consisting of separate origins of the RCA, MCA, and ileocolic artery, as previously described. Additional frequent variants include a common origin of the MCA and RCA with a separate origin of the ileocolic artery, as well as a common origin of the RCA and ileocolic artery with a separate origin of the MCA.

Arteries of the midgut and hindgut form an anastomotic arcade known as the marginal artery of Drummond. This blood vessel consists of an anastomosis between the terminal branches of the SMA and the inferior mesenteric artery (IMA), coursing along the inner colonic margin within the mesentery. Small colonic branches arise from this arcade and are termed "vasa recta."[1][2]][3][4][5][6]

The ileocolic artery and its branches supply the distal ileum, ileocecal valve, cecum, vermiform appendix, and proximal ascending colon. The ileocolic artery courses anterior to the right gonadal vessels and ureter. The anterior cecal artery lies anterior to the terminal ileum and cecum, while the posterior cecal artery is situated posterior to these structures. The appendicular artery traverses posterior to the terminal ileum. An anastomosis occurs between the ileocolic artery and the RCA. Terminal branches of the SMA and IMA form an anastomosis via the marginal artery of Drummond.

Embryology

The ileocolic artery is of midgut origin, arising as the most inferior branch of the SMA and supplying midgut derivatives. Consistent with general vascular development, the ileocolic artery is derived from mesoderm.[7]

Blood Supply and Lymphatics

The blood supply to the ileocolic artery is derived from the SMA, the 2nd major branch of the abdominal aorta, located just distal to the celiac trunk. The celiac trunk supplies the stomach, proximal small bowel, liver, spleen, and pancreas. The IMA arises from the abdominal aorta and supplies the hindgut. Lymphatic drainage associated with the ileocolic artery involves lymph nodes within the mesentery of the mesoileum, mesocecum, mesoappendix, and mesocolon.[8]

Nerves

The ileocolic artery supplies the portion of the myenteric plexus corresponding to its visceral distribution. The myenteric plexus extends along the territory supplied by the ileocolic artery from the distal ileum to the proximal ascending colon.[9]

Muscles

Muscles supplied by the ileocolic artery are located within the bowel walls. Adequate perfusion of the muscular layer, composed of inner circular and outer longitudinal layers, is required for peristalsis. In addition to the bowel wall musculature, the ileocolic artery supplies the intrinsic sphincter muscle of the ileocecal valve. The proximal portion of the taeniae coli also receives vascular supply, extending from their convergence at the vermiform appendix to the proximal ascending colon at the level of anastomosis with the RCA.[10]

Physiologic Variants

The ileocolic artery is present in more than 95% of individuals. In approximately 50% of patients, this blood vessel courses anterior and superior to the SMV. Common variations of the right colonic vasculature include a common origin of the RCA and MCA with a separate origin of the ileocolic artery, as well as a common origin of the RCA and ileocolic artery with a distinct origin of the MCA. An additional variation includes the absence of the RCA.[11][12]

Surgical Considerations

The appendicular artery courses within the mesoappendix, lying close to its free margin. The blood vessel terminates in multiple small branches supplying the appendix. Ligation of the inferior branch of the ileocolic artery at the base of the appendix is required during an appendectomy. Postoperative bleeding may result from inadequate vessel ligation. Complete hemostasis should be achieved, and mesoappendiceal integrity must be confirmed before closure. By the same principle, ileocolic arterial branches should be ligated during Meckel diverticulectomy to ensure hemostasis.[13]

Clinical Significance

Ileocecal intussusception may result in the occlusion of the ileocolic artery as the terminal ileum telescopes into the cecum. Progressive invagination of a bowel segment into another may compress the vascular supply, sufficient to occlude the ileocolic artery and produce ischemia within its distribution. The extent of ischemic involvement depends on the level of vascular compression and may include proximal or distal segments or individual arterial branches. Ischemia may involve a limited section of bowel or the full vascular territory of the ileocolic artery. Prolonged or recurrent intussusception may progress to necrosis and perforation, resulting in an acute abdomen and surgical emergency.

Intussusception occurs most frequently in young children, typically aged between 2 and 3 years. Clinical presentation may include intermittent abdominal pain, vomiting, a right upper quadrant mass, and bloody stools. A lead point is rarely found in young children, although commonly identified in older children and adults. These lead points include benign and malignant neoplasms. Management in most pediatric cases may include water-soluble contrast or air enema reduction. Surgical backup is required due to the risk of perforation. Recurrence rates as high as 30% have been reported.[14][15][16][17][18]

Ischemia may occur following SMA thromboembolism. Occlusion of the SMA can impair blood flow throughout its entire vascular territory. Smaller thromboemboli may lodge within distal SMA branches, including the inferior terminal branch and the ileocolic artery. Similar to intussusception, the extent of ischemia or necrosis depends on the level of vascular occlusion.[19][20]

A thorough understanding of right colonic vascular anatomy and its anatomic variations is essential for surgical intervention. Clinical contexts include appendicitis, Meckel diverticulitis, inflammatory bowel disease, colon cancer, and symptomatic benign neoplasms of the bowel or mesentery. Accurate anatomic knowledge supports effective hemostasis and optimal healing of bowel anastomoses. Anastomotic sites within the colon carry an increased risk of ischemia following tumor or bowel resection. Adequate vascular supply is particularly critical in patients who are of advanced age or have diabetes to support normal anastomotic healing.

Traumatic injury may rarely result in an isolated rupture of the ileocolic artery. This condition may occur in the setting of blunt abdominal trauma.[21]

Other Issues

Colic vessels include the ileocolic artery, and postcancer resection status may serve as a marker of the extent of resection. Arterial stumps identified on routine portal venous computed tomography have demonstrated potential as in vivo markers of surgical quality and the extent of mesenteric resection.[22]