The Anatomy of the Common Iliac Artery

The artery supplies blood to the pelvis and lower limbs

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The common iliac arteries originate near the fourth lumbar vertebra in the lower back, where the abdominal aorta divides (bifurcation). From there, it runs down the pelvis where it ends at the level of the pelvic brim. Here, it splits into two major branches: the internal and external iliac arteries.

Primarily, the common iliac arteries supply blood to the bones, organs, muscles, and other structures in the abdomen and pelvis. These arteries play an important role in lower limb circulation.

Disorders or traumas affecting the common iliac arteries can have serious medical consequences. One example is a common iliac artery aneurysm, which causes ballooning of the artery and can lead to rupture.

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). One goes off to the left, and the other to the right.

The arteries come out at the level of the fourth vertebrae in the spine, then move down and to each side of the body. They enter the pelvis at the psoas muscle, which connects the lower spine to the upper leg bone (femur).

Each common iliac artery runs parallel to its corresponding vein (common iliac veins).

In front of the sacroiliac joint (the juncture between the sacrum and ilium bones of the pelvis) the common iliac artery splits into its two primary terminating branches: the external and internal iliac arteries.

  • Internal Iliac Artery: Running behind the duct that allows urine to flow from the kidneys to the bladder (ureter) in its upper portion, this artery courses down the body with its corresponding vein in front of it. The artery branches at the rear (posterior) and front (anterior) of the body and supplies blood to 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 down the pelvis to the groin (inguinal) ligament and divides into two branches. After the split, the external iliac artery is renamed the femoral artery and serves as a major source of blood supply to the lower limbs.

The left common iliac artery is often a little shorter than the right. The former runs parallel to the left of the left common iliac vein. The latter passes in front of the vein before taking a parallel course to the right of the right common iliac vein.

Anatomical Variations

The most common variations in the common iliac arteries are seen in the internal iliac branch.

While the artery typically originates at the level of the lumbosacral joint at the base of the spine, it sometimes comes out at a higher origin at the fifth lumbar vertebra. In others, it occurs at the tip of the tailbone (sacrum or S1).

Doctors have also observed different origins of the first major branch of the internal iliac artery (obturator artery). It can also arise lower down in the artery from the inferior epigastric inferior artery or the vesical artery.

The iliolumbar artery (which supplies blood to the abdomen) can also emerge earlier than normal at the trunk of the internal iliac artery. 

Function

The primary task of the common iliac artery is to deliver oxygenated blood to the pelvic area and lower limbs. Via its branches, the internal iliac artery supplies blood to the pelvic region, groin, and surrounding muscles and bones.

The internal branch ensures the muscles of the buttocks (gluteus maximus and minimus); abdominal region; uterus and vagina or prostate; and genitalia have a continuous blood supply.   

The external iliac artery brings blood to the muscles, nerves, and bones of the legs. The femoral artery (what the external iliac artery becomes after passing through the pelvis) ensures blood reaches the tibia, femur, and other bones of the lower limbs.

The anterior and posterior tibial arteries that branch off the external iliac artery supply blood to the knee area, the lower leg, the feet, and the toes.

Clinical Significance

Medical conditions or injuries affecting the common iliac arteries can have serious consequences.

One example is a common iliac artery aneurysm, which occurs when a section of the artery swells or "balloons" as a result of having weak walls. This type of aneurysm accounts for around 10-20% of aneurysms in the abdominal region.

The condition can also cause swelling of the kidneys (hydronephrosis) and compression of the sciatic nerve (which runs from the base of the spine through the pelvis to the lower limbs).

While frequently asymptomatic, shock and severe abdominal pain can occur if a common iliac artery aneurysm ruptures.

Endovascular aneurysm repair (EVAR) is a specialized, minimally-invasive surgical procedure to repair damaged or ballooning portions of the artery. A device called an endovascular graft ("endograft") is implanted where it can expand and plug up a leak or rupture in the artery.

The procedure is done using small incisions and a special camera that can see inside the artery (endoscopic surgery) the recovery period is usually less than it would be for open surgery.

Even if the procedure is minimally invasive, it's very important that surgeons work carefully when they are performing any surgery near the artery, as damaging it can have serious consequences.

These arteries are especially vulnerable to injury during abdominal or pelvic surgery (such as a hysterectomy to remove the uterus). Since the common iliac artery is crucial to supply blood to the lower limbs, surgeons may choose to close it off (ligate) to prevent severe blood loss (hemorrhage).

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