The Anatomy of the Common Iliac Artery

The common iliac artery supplies the pelvis and lower limb

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The common iliac arteries are paired arteries running downwards to the pelvis. They originate at the bifurcation (splitting into two) of the abdominal aorta near the fourth lumbar (lower back) vertebra. At the level of the pelvic brim, this artery terminates as it splits into two major branches: the internal and external iliac arteries.

Primarily, the common iliac arteries supply the bones, organs, muscles, and other structures in the abdomen and pelvis, while playing an important role in lower limb circulation. Disorders or traumas here can lead to serious medical problems. Most notable of these is common iliac artery aneurysm, in which there is ballooning or even rupture in a section of the artery.

Anatomy

The common iliac arteries are a link between the aorta and the arteries of the pelvis and lower limbs.

Structure and Location

There are two common iliac arteries that split off from the abdominal aorta (which moves blood from the heart downward), coursing to the right and left side respectively. These emerge at the level of the fourth vertebrae, moving downward and to the sides of the body. They enter the pelvis at the psoas muscle, which connects the lower spine to the femur (upper leg bone) and run parallel to their corresponding veins: the common iliac vein.

In front of the sacroiliac joint—the juncture of between the sacrum and ilium bones of the pelvis—the common iliac artery then splits into external and internal iliac arteries—its two primary terminating branches. What do these branches do and where do they go? Here’s a quick breakdown:

  • Internal Iliac Artery: Running behind the ureter—a duct that allows urine from the kidneys to the bladder—in its upper portion, this artery courses downward with its corresponding vein in front of it. This artery splits into numerous posterior (rear) and anterior (front) branches that supply various muscle groups, bones, nerves, and organs in and around the pelvis.
  • External Iliac Artery: Also arising at the sacroiliac joint, the external iliac artery runs downward. As it passes the inguinal ligament (also known as the “groin ligament”)—and after splitting into two branches within the pelvis—this artery is renamed the femoral artery, which is a major source of blood supply to the lower limb. This artery’s branches are tasked with supplying major components of the leg.

Notably, the left common iliac artery is a little shorter than the right. The former runs parallel to the left of the left common iliac vein, whereas the latter passes in front of this vein, before following a parallel course to the right of the right common iliac vein.

Anatomical Variations

The most common variations in this artery are seen in the internal iliac branch of the common iliac artery. While most often this artery originates at the level of the lumbosacral joint at the base of the spine, sometimes it has a higher origin at the fifth lumbar vertebra, while in others this occurs at the sacrum (S1)—the tip of the tailbone. Furthermore, doctors have observed differential origins for the obturator artery—the first major branch of the internal iliac artery—wherein it sometimes arises lower down in the artery, from the inferior epigastric inferior artery, or the vesical artery. Finally, the iliolumbar artery—which supplies the abdomen—can emerge earlier than normal, right at the trunk of the internal iliac artery. 

In addition, irregular branching patterns from this artery have also been observed as a result of pregnancy. Most notably, in these cases the internal iliac artery may be seen emerging from the umbilical artery rather than the other way around. After delivery of the baby, the structure will continue to alter as the umbilical artery recedes, leading to a different final form.

Function

The primary task of the common iliac artery is to supply oxygenated blood to the pelvic area and lower limbs. Via its branches, the internal iliac artery delivers to the pelvic region, groin, and surrounding muscles and bones. As such, this branch ensures that the gluteus maximus and minimus (muscles of the buttocks), abdominal region, uterus and vagina (in women), prostrate (in men), and genitalia, among other structures, are supplied with blood.   

The external iliac artery, meanwhile, is tasked with supplying muscles, nerves, and bones of the legs. The femoral artery—which is what the external iliac artery becomes after passing through the pelvis—ensures that blood reaches the bones of the tibia, the femur, and other parts of the lower limb are supplied. It’s also a source for the knee area, and—via the anterior and posterior tibial artery that branches off of it—the lower leg, feet, and toes.

Clinical Significance

Disorder or trauma to the common iliac artery leads to serious medical issues. Common iliac artery aneurysm, in which there is a ballooning of a region of the artery due to weakness in its walls, accounts for 10 to 20 percent of aneurysms in the abdominal region. While this is frequently asymptomatic, shock and severe abdominal pain can result if there is rupture. Not only that, this condition can contribute to hydronephrosis (the swelling of the kidney) as well as compression of the sciatic nerve (which runs from base of spine through the pelvis to the lower limbs).

Endovascular aneurysm repair (EVAR) is a specialized, minimally-invasive surgical procedure that repairs damaged or ballooning parts portions of the artery seen in common iliac artery aneurysm. This involves implanting a special device—the “trouser leg graft”—that can expand and thereby plug up any leakage or rupture in the artery. Since this is done endoscopically—using smaller incisions and a special camera that can access the inside of the artery—recovery is quicker than it would be with open surgery.

Surgeons operating in the region need to take particular care with regards to this artery, as damage to it can lead to a cascade of negative effects. The most common complications in these cases occur during abdominal surgery or when the uterus is operated upon as in hysterectomy.

Since the common iliac artery is crucial to lower limb supply, doctors may ligate it (close it off) when there is severe hemorrhage in the leg to prevent excessive loss of blood. 

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