The common iliac arteries are the two large vessels that form when the abdominal aorta splits near the lower spine, and they serve as the main blood supply route to the pelvis and legs. A meta-analysis covering nearly 6,000 cases found that this split most often happens at the level of the fourth lumbar vertebra, roughly at or just below the navel line on the surface of the body.1PubMed Central. The anatomy of the common iliac artery: a meta-analysis based on 5785 cases Each common iliac artery is relatively short, running only a few centimeters before it divides again into an external iliac artery heading toward the leg and an internal iliac artery feeding the pelvic organs. Despite that brevity, this stretch of artery is a surprisingly common site for plaque buildup, aneurysm formation, and complications during surgery, making it one of the more clinically significant vessels in the body.
Where It Sits and What It Does
The aorta, after descending through the chest and abdomen, reaches its terminus by forking into the right and left common iliac arteries. That fork point, called the aortic bifurcation, sits in front of the lower lumbar spine. In about six out of ten people, this happens at the fourth lumbar vertebra (L4), though the bifurcation can range from L3 to L5 depending on the individual.2PubMed Central. The anatomy of the common iliac artery: a meta-analysis based on 5785 cases During fetal development, the bifurcation starts out lower and gradually migrates upward as the body grows.3PubMed. Development of the abdominal aorta and iliac arteries during the fetal period: a morphometric study
Each common iliac artery is a muscular conduit roughly 5 to 7 centimeters long in adults. Its job is deceptively simple: carry oxygenated blood downstream. But the volume is significant. Together, the two common iliacs deliver virtually all blood flow below the diaphragm aside from what the kidneys and abdominal organs already siphoned off higher up. When one of these arteries narrows or becomes blocked, the consequences can range from cramping in the buttock and thigh during walking to, in severe cases, tissue loss in the leg or pelvis.
Branches and Anatomical Variations
Textbooks usually describe the common iliac artery as a “clean” trunk with no branches of its own, saving all branching for the external and internal iliac arteries downstream. Reality is messier. An angiographic study of 200 common iliac arteries found that about one in five actually gave off at least one branch, with roughly half of those branches classified as aberrant, meaning they arose from the common iliac when they would normally originate elsewhere.4PubMed. Normal, accessory, and aberrant branches of the common iliac artery: angiographic prevalence and clinical implications These unexpected branches matter in surgery and interventional procedures. A surgeon planning to clamp or stent the common iliac artery needs to know if a small but important artery feeding the ureter or the pelvic wall happens to come off that segment instead of its usual origin.
Variations extend beyond branching patterns. In some people, the common iliac arteries are unusually short or long, the bifurcation sits notably high or low, or the angle at which the two vessels diverge is especially steep or shallow. These differences are usually harmless in daily life but become relevant when a radiologist interprets imaging or a vascular surgeon selects the size and shape of a stent graft.
What the Artery Wall Looks Like Up Close
The common iliac artery is classified as a muscular artery, but its wall structure has some distinctive features compared with other arteries of similar size. Research on the mechanical properties of major arteries found that the common iliac artery is one of the stiffest vessels tested, on par with the abdominal aorta, and that its elastic fibers are arranged differently from what you see in more compliant arteries. Instead of elastic tissue spread evenly through the vessel wall, the common iliac concentrates its elastin along the outer elastic layer and orients much of it lengthwise rather than in a circumferential ring.5PubMed. Biaxial mechanical properties of the human thoracic and abdominal aorta, common carotid, subclavian, renal and common iliac arteries
A more recent study comparing the common iliac with the external and internal iliac arteries found similar patterns: the common iliac had denser elastic fibers in its middle layer than its downstream counterparts, which showed wavier and more fragmented elastic sheets.6PubMed Central. Mechanical, structural, and morphological differences in the iliac arteries This stiffness likely reflects the hemodynamic demands at the aortic bifurcation, where blood flow abruptly changes direction and turbulence is high. But stiffness also has a downside: stiff arteries tend to accumulate atherosclerotic plaque more aggressively. The common iliac ranks among the most disease-prone arteries in the body, and its wall composition helps explain why.
Atherosclerosis and Peripheral Artery Disease
Atherosclerosis in the aortoiliac segment is common and carries consequences beyond the legs. People with narrowed or blocked iliac arteries face elevated cardiovascular risk across the board, with symptoms that can range from intermittent claudication, which is pain or cramping in the legs while walking, all the way to limb-threatening ischemia when blood supply drops critically low.7PubMed. Aorto-iliac peripheral artery disease The classic presentation is sometimes called Leriche syndrome when both common iliac arteries are severely blocked: absent femoral pulses, buttock claudication, and erectile dysfunction in men.
An autopsy study examining the iliac arteries of deceased patients found advanced atherosclerotic plaques in roughly three-quarters of common iliac arteries, along with high rates of calcification and intraplaque hemorrhage. People with advanced plaque in the common iliac artery had substantially higher odds of having experienced a heart attack, stroke, or renal failure during their lifetime. Importantly, these iliac plaques were strongly linked to advanced atherosclerosis in the coronary and carotid arteries as well, suggesting that disease in the common iliac artery is a marker of bodywide vascular damage rather than an isolated local problem.8PubMed. Asymptomatic Plaques of Lower Peripheral Arteries and Their Association with Cardiovascular Disease: An Autopsy Study
The location of the aortic bifurcation helps explain why plaque likes to settle here. Blood flowing through a straight tube experiences steady shear stress along the walls, which tends to keep the lining healthy. At a bifurcation, flow separates and recirculates, creating zones of low wall shear stress on the outer walls of each branch. Computational fluid dynamics models of the iliac bifurcation confirm that these low-shear zones correspond closely to where plaque tends to accumulate.9International Journal of Computational Methods. Fluid–Solid Interaction Analysis on Iliac Bifurcation Artery: A Numerical Study
Common Iliac Artery Aneurysms
An aneurysm is a balloon-like widening of an artery wall, and the common iliac artery is the most frequent site for isolated iliac aneurysms. These often coexist with abdominal aortic aneurysms but can also occur on their own. The risk of rupture depends heavily on size. A systematic review found that the average diameter of common iliac artery aneurysms at the time of treatment was about 41 millimeters, while those that had ruptured averaged closer to 58 millimeters. Rupture at diameters below 4 centimeters was extremely rare.10PubMed. A systematic review on endovascular repair of isolated common iliac artery aneurysms and suggestions regarding diameter thresholds for intervention
Those numbers guide clinical decision-making. Studies tracking iliac aneurysms over time have found that small ones grow slowly and rarely cause symptoms. Aneurysms below 3 centimeters can usually be monitored once a year with ultrasound. Between 3 and 3.5 centimeters, more frequent check-ups are warranted. At 3.5 centimeters or larger, elective repair becomes a consideration for patients who are good surgical candidates, and aneurysms reaching 5 centimeters or more carry a high enough rupture risk that prompt repair is generally recommended.11PubMed. Expansion rates and outcomes for iliac artery aneurysms Surgical experience has broadly confirmed this threshold approach, with separate clinical series noting that rupture risk concentrates among aneurysms exceeding 5 centimeters while those under 3 centimeters may not enlarge at all during follow-up.12PubMed. Management of isolated common iliac artery aneurysms
Stenting and Other Treatments for Blockages
When atherosclerosis narrows the common iliac artery enough to cause symptoms, the first-line treatment is usually endovascular: a catheter-based procedure in which a balloon is inflated inside the narrowed segment and a metal stent is placed to hold the artery open. The common iliac artery responds well to stenting compared with its downstream neighbor, the external iliac. One study reported primary patency rates of about 92% at one year and 76% at five years for common iliac stents, while external iliac stents fared worse, particularly in women.13Journal of Vascular Surgery. External iliac and common iliac artery angioplasty and stenting in men and women Longer-term data on iliac stenting generally show that shorter blockages do better than long ones, and narrowings that have not completely occluded the vessel respond better than total occlusions. In one series, three-year patency was about 88% for short lesions versus 63% for long ones.14PubMed. Flexible tantalum stents for the treatment of iliac artery lesions: long-term patency, complications, and risk factors
When blockages are too extensive or complex for stenting, open surgical options include endarterectomy (cleaning out the plaque from the inside of the artery) and bypass grafting (routing blood around the blockage with a synthetic tube). A comparison of the two approaches in patients whose disease was confined to the common iliac arteries found that both procedures were safe and produced high long-term patency without needing repeat intervention.15PubMed. Comparative Long-term Outcomes of Patients with Aortoiliac Occlusive Disease Limited to Common Iliac Arteries Who Underwent Endarterectomy versus Bypass Grafting Today, stenting is preferred whenever feasible because it avoids a major abdominal incision, but open surgery remains a reliable backup when anatomy or disease complexity demands it.
The Common Iliac Artery in Aortic Aneurysm Repair
When surgeons repair an abdominal aortic aneurysm using an endovascular stent graft (a procedure called EVAR), the common iliac arteries serve as landing zones: the lower ends of the graft need to seal against healthy artery wall to prevent blood from leaking back into the aneurysm sac. If the common iliac arteries themselves are dilated or aneurysmal, achieving a reliable seal becomes harder. Research has shown that using an aneurysmal common iliac artery as a landing zone may increase the risk of late complications, including ongoing dilation of the iliac segment and leaks around the bottom of the graft.16PubMed. Importance of Distal Sealing during Endovascular Aneurysm Repair Using Aneurysmal Common Iliac Artery as Landing Zone
Even common iliac arteries that appear acceptable at the time of EVAR can dilate significantly over the following years, particularly if they were already on the wider side of normal. One study tracking iliac artery behavior after EVAR found that dilation was more pronounced in ectatic arteries and concluded that ongoing surveillance is mandatory.17PubMed. Natural history of the iliac arteries after endovascular abdominal aortic aneurysm repair and suitability of ectatic iliac arteries as a distal sealing zone When the common iliac artery is too diseased to serve as a landing zone, surgeons sometimes extend the stent graft into the external iliac artery, but that means covering the origin of the internal iliac artery, which supplies the pelvic organs. Blocking that vessel can lead to buttock claudication, erectile dysfunction, or, in worst-case scenarios, ischemia of the colon or pelvic tissues.
Pelvic Blood Flow and Its Consequences
Because the common iliac artery feeds both the internal and external iliac branches, any procedure that alters flow through it can affect the pelvis. Interrupting the internal iliac artery (also called the hypogastric artery) during aortoiliac reconstruction is sometimes unavoidable, and while pelvic ischemia from this is uncommon, it does occur. Certain disease patterns or graft configurations leave collateral pathways unable to compensate, resulting in ischemia of the buttock muscles, the sigmoid colon, or the bladder.18PubMed. Pelvic ischemia following aortoiliac reconstruction In rare and extreme cases, compromised pelvic blood flow has led to gluteal gangrene, particularly when both internal iliac arteries are blocked simultaneously and collateral circulation is poor.19PubMed Central. Gluteal ischemic gangrene due to chronic aortoiliac occlusive disease
May-Thurner Syndrome
The common iliac artery does not just carry blood. Its physical position can also cause problems for the vein running beneath it. In May-Thurner syndrome, the right common iliac artery compresses the left common iliac vein against the lumbar spine.20PubMed Central. May-Thurner syndrome This chronic compression can damage the vein wall, promote the formation of internal scar tissue or “spurs,” and lead to deep vein thrombosis in the left leg.21PubMed Central. What the young physician should know about May-Thurner syndrome
May-Thurner syndrome disproportionately affects younger women and is probably underdiagnosed, since a degree of iliac vein compression is visible on imaging in many people who never develop symptoms. When it does cause a clot, the presentation is typically swelling, pain, and heaviness in the left leg. The diagnosis is often missed initially because left-sided deep vein thrombosis is simply attributed to other risk factors. Treatment usually involves clearing the clot, placing a venous stent to prop open the compressed vein, and sometimes anticoagulation therapy.22PubMed Central. May-Thurner syndrome: a not so uncommon cause of a common condition The key insight for patients is that if you have unexplained left-leg deep vein thrombosis, especially without typical risk factors like recent surgery or immobility, May-Thurner syndrome is worth investigating.
Iliac Artery Endofibrosis in Athletes
There is a condition almost exclusive to competitive endurance athletes, particularly cyclists, in which the wall of the iliac artery thickens and stiffens not from atherosclerosis but from a process called endofibrosis. The repeated hip flexion and extreme cardiac output sustained over years of high-intensity training appear to cause the inner lining of the artery to develop fibrous tissue, narrowing the vessel. The external iliac artery is the more commonly affected segment, but the common iliac artery can be involved as well.23PubMed. Short- and long-term outcomes after endarterectomy with autologous patching in endurance athletes with iliac artery endofibrosis
What makes endofibrosis tricky is that affected athletes have entirely normal blood flow at rest. Symptoms only appear during maximal exertion: a loss of power in one leg, a cramping or heavy feeling, sometimes numbness. Because the athletes are otherwise extremely fit and their resting exams are normal, diagnosis is often delayed.24PubMed Central. Arterial endofibrosis in professional cyclists When recognized and treated, usually by surgically removing the thickened tissue and patching the artery, most athletes are able to return to competition.
Injury During Spine Surgery
The common iliac arteries sit directly in front of the lower lumbar spine, separated from the vertebral bodies and intervertebral discs by only a thin layer of tissue. This proximity makes them vulnerable during lumbar disc surgery. Case reports and small series describe surgeons inadvertently perforating or lacerating a common iliac artery, or creating an abnormal connection between the artery and the adjacent vein, while removing a herniated disc at the L4-L5 level. In one series, six of seven vascular injuries from lumbar spine surgery involved the common iliac vessels.25European Journal of Vascular and Endovascular Surgery. Endovascular Treatment of Abdominal Aortic and Common Iliac Artery Injuries after Lumbar Spine Surgery
Some injuries announce themselves immediately as life-threatening bleeding during the operation. Others declare themselves days later when a patient develops unexplained leg swelling, lower back pain, or signs of a pseudoaneurysm (a pulsating blood collection outside the artery wall). Fortunately, many of these injuries can now be repaired with catheter-based stent grafts rather than open abdominal surgery, and outcomes in reported cases have been good.26PubMed. Iatrogenic Common Iliac Vessel Injury During Routine Degenerative Lumbar Spine Surgery: Report of 2 Cases and Review of Literature The complication remains rare, but spine surgeons and patients benefit from awareness that the major blood vessels to the legs are sitting just millimeters from the operative field.
How the Common Iliac Artery Is Imaged
When doctors need to evaluate the common iliac artery for blockages, aneurysms, or anatomical planning before surgery, several imaging tools are available. Ultrasound (duplex Doppler) is the simplest and cheapest, suitable for screening and for following known aneurysms over time. CT angiography (CTA) is the workhorse for detailed evaluation. A study comparing CTA with traditional catheter-based angiography found that CTA detected iliac artery occlusions with 100% sensitivity and identified high-grade narrowings with about 93% sensitivity when radiologists examined the full cross-sectional images. One caveat: when only the three-dimensional reconstructions were used, heavily calcified plaques obscured some narrowings, dropping sensitivity considerably.27PubMed. CT angiography versus intraarterial digital subtraction angiography for assessment of aortoiliac occlusive disease Magnetic resonance angiography (MRA) is an alternative that avoids radiation and iodinated contrast dye, making it useful for patients with kidney problems. Catheter-based angiography, once the gold standard, is now reserved mainly for situations where an intervention is planned at the same sitting.