The Anatomy of the Internal Iliac Artery

The internal iliac arteries are the major arteries of the pelvis, and together with their many branches, supply the blood to the major organs and muscles of the pelvis. The internal iliac arteries are branches of the common iliac arteries, which themselves are branches from the aorta. At the pelvic brim, each common iliac artery splits into the internal and external iliac arteries. Each internal iliac artery courses downward into the pelvic cavity and is the main blood supply to the pelvic organs, gluteal muscles, and perineum.

Anatomy

The left side of the heart pumps oxygen-rich blood to the rest of the body. Blood leaving the left ventricle passes through the aorta, the largest artery in the body. The aorta passes down into the abdomen, where it is called the abdominal aorta.

In the lower abdomen, at about the level of the fourth lumbar vertebra, the aorta splits into two smaller arteries called the common iliac arteries. Each common iliac artery splits again into the external iliac artery and the internal iliac artery.

Each internal iliac artery is about 1.5 inches long and courses downward and medially into the pelvic cavity. Each internal iliac artery typically splits into an anterior and posterior division.

The anterior division passes forward along the pelvic wall and divides into multiple smaller arteries. These include the visceral branches which supply the bladder, rectum, and reproductive organs. The other large branches of the anterior division are the obturator and internal pudendal arteries, which help supply the muscles of the pelvis, perineum, and medial thigh.

The posterior division passes back along the pelvic wall and typically splits into multiple smaller branches (the iliolumbar artery, the superior gluteal artery, and the lateral sacral arteries) which supply blood to the muscles of the pelvic wall and buttocks.

Anatomical Variations

The internal iliac artery branches are subject to many normal variations and may have different arrangements in different patients. In some patients, the obturator artery, which typically arises from the anterior division of the internal iliac, can arise instead from another artery called the inferior epigastric artery. This variation can have implications on surgical approach if inguinal hernia surgery is being considered.

Function

The internal iliac arteries are blood vessels that carry oxygenated blood to the tissues. They have muscular walls to support the pulsatile, high-pressure blood on its way to its destination from the heart.

These arteries supply the organs of the pelvis, the external genitalia, the pelvic walls, the buttock muscles, and part of the thigh.

Blood flow to the pelvis is richly collateralized, which means that there are multiple interconnecting arteries which provide alternative paths of blood flow to pelvic structures. Because of this, injury or occlusion of one of the internal iliac arteries will not necessarily interrupt blood flow to the pelvic structures (see below). 

Clinical Significance

The internal iliac artery or its branches can be injured by penetrating trauma (stabbing or gunshot wound) or blunt force trauma (car accidents, falls, or crush injuries). Fractures of the pelvis are often associated with injuries to branches of the internal iliac artery. The superior gluteal and internal pudendal arteries are the most commonly injured branches, and patients with arterial injury after pelvic trauma may develop life-threatening bleeding.

Life-threatening pelvic hemorrhage may require surgical repair to control bleeding. Increasingly however, an angiography and embolization procedure is performed for this purpose. In this procedure, doctors access the patient’s arterial system by puncturing an artery (often at the groin or wrist) with a needle. Under guidance by fluoroscopy, a wire is passed into a vessel at or near the injury. The bleeding vessel can be occluded temporarily with a gelatinous material (Gelfoam) or permanently with metallic coils or plugs.

The pelvic structures can receive blood via multiple redundant pathways (collateralization). Surgeons or angiographers can safely occlude one internal iliac artery or its branches without severely compromising blood flow to the pelvic organs.

The internal iliac artery can be affected by atherosclerosis. Sometimes called “hardening of the arteries,” atherosclerosis is a disease of the large arteries characterized by the accumulation of fats and fibrous tissue (scar) in vessel walls. Atherosclerosis can cause narrowing, occlusion, or abnormal dilatation of affected vessels, and when it affects the arteries of the brain or heart, is the primary cause of heart disease and stroke.

Atherosclerosis can cause narrowing or even blockage of the internal iliac arteries. Internal iliac disease often occurs in association with common iliac artery disease. Symptoms often overlap and typically include pain in the lower back, hips, buttocks, or thighs with walking (claudication). Men may experience erectile dysfunction. The triad of claudication, erectile dysfunction, and decreased lower extremity pulses is called Leriche syndrome.

 Treatment depends on your specific symptoms as well as what coexisting diseases are present. Treatment may focus on medical therapy (such as blood pressure reduction and cholesterol-reducing medications). Quitting smoking is important.

More severe cases may be unresponsive to medical therapy or lifestyle changes and may require surgical or endovascular therapy. If disease is isolated to the internal iliac arteries, endovascular therapy (such as angioplasty or stenting) is usually preferred. More extensive disease (involving the aorta and common iliac arteries) may require creation of a surgical bypass.

Disease of the walls of a large artery can cause loss of mechanical integrity and ballooning of a vessel segment, called an aneurysm. The most common site of true aneurysm is the abdominal aorta. The iliac arteries can be affected as well, and iliac artery aneurysms are often associated with aneurysms of the abdominal aorta. The most common site of iliac artery aneurysm is the common iliac artery, followed by the internal iliac arteries.

When iliac artery aneurysms increase in size, they may cause symptoms such as compression of adjacent structures. Clots may develop in aneurysms that can obstruct the vessel or can break off and obstruct smaller arteries. Large aneurysms are at risk for rupture (bursting).

Aneurysms that are large, rapidly expanding, or cause symptoms are usually treated. Treatment may take the form of stenting or open surgical repair, and will depend on the specific patient presentation.