Where Is an Iliac Stent Placed and How Does It Work?

An iliac stent is placed inside one of the iliac arteries or iliac veins in your pelvis, the large blood vessels that carry blood between your lower trunk and your legs. On the arterial side, the stent sits in the common iliac artery, the external iliac artery, or both, propping open a segment that has become narrowed or completely blocked by plaque buildup. On the venous side, a stent is placed in the iliac vein, typically the left common iliac vein, to relieve compression or scarring that blocks blood returning to your heart. In both cases the stent acts as a permanent internal scaffold, holding the vessel walls apart so blood can flow through at something closer to its normal volume and pressure.

Exactly Where in the Body the Stent Sits

Your aorta, the body’s main artery, splits into two branches at about the level of your navel. Each branch is a common iliac artery, one running to the left leg and one to the right. The common iliac artery then divides again into the internal iliac artery (which supplies organs in the pelvis) and the external iliac artery (which continues down into the leg and becomes the femoral artery at the groin). Iliac arterial stents are deployed somewhere along this pathway, from the common iliac artery down through the external iliac artery, depending on where the blockage sits.¹ Some patients have disease in both segments and receive stents that span the junction.

On the venous side, the anatomy is a mirror image running in the opposite direction. Blood returning from each leg flows through the external iliac vein into the common iliac vein and then up into the inferior vena cava. Venous iliac stents are placed most often in the left common iliac vein, because the right common iliac artery crosses directly over it and can compress it against the spine. That compression is the hallmark of May-Thurner syndrome, one of the main reasons people need venous iliac stents.²

Why Someone Needs an Iliac Stent

The arterial and venous reasons are quite different, though they share the common thread of obstructed blood flow in the pelvis.

Peripheral arterial disease is by far the most common reason for arterial iliac stenting. Fatty plaque accumulates inside the iliac arteries, narrowing them (stenosis) or blocking them entirely (occlusion). The classic symptom is intermittent claudication, a cramping pain in the buttocks, hips, or thighs that comes on with walking and fades with rest. In more severe cases the blood supply drops low enough to threaten the limb itself, a situation called critical limb ischemia. Worldwide, peripheral arterial disease affects over 230 million people, and endovascular stenting has become a standard option for iliac artery blockages.³

Venous iliac stenting targets a different set of problems. Besides May-Thurner syndrome, stents may be placed after a deep vein thrombosis has scarred and narrowed the iliac vein, or for chronic venous insufficiency where blood pools in the legs and causes swelling, pain, skin changes, or ulcers. The goal is to reopen the vein so blood can drain properly, reducing the chronic pressure that damages tissue in the lower leg.⁴

How the Stent Actually Works

Getting the stent into position is a minimally invasive procedure, usually performed under local anesthesia with sedation. A catheter is threaded into the femoral artery or vein at the groin (sometimes the arm) and guided to the blockage using real-time X-ray imaging called fluoroscopy. For venous cases especially, intravascular ultrasound is increasingly used during the procedure to get precise measurements of the vein diameter and to choose the right stent size.⁵ This matters because a stent that is too small can migrate or fail to hold the vessel open, while one that is too large can damage the vessel wall.

Once the catheter reaches the target, a balloon is typically inflated first to push the plaque or scar tissue aside and widen the channel. Then the stent, a small mesh tube made of metal alloy, is deployed at the treatment site. It locks into place against the vessel wall, maintaining the opening even after the balloon and catheter are withdrawn. In hemodynamic terms, the effect is immediate: pressure gradients across the treated segment drop sharply. One randomized study found that the average pressure difference across iliac lesions fell from about 15 mmHg before stenting to roughly 3 mmHg afterward, meaning blood could flow through with far less resistance.⁶

Types of Iliac Stents

There are two broad mechanical categories, plus an important design variation layered on top.

Self-expanding stents are made of a shape-memory alloy (usually nitinol) and are delivered in a compressed state. Once released from the delivery catheter, they spring open to a predetermined diameter and continue to exert gentle outward force. Balloon-expandable stents, by contrast, are crimped onto a balloon catheter and expanded only when the balloon is inflated; they hold whatever diameter the balloon creates. A randomized trial (the ICE trial) compared the two approaches head-to-head for iliac artery disease and found that self-expanding stents had a lower restenosis rate at twelve months, about 6% compared with roughly 15% for balloon-expandable stents.⁷ Self-expanding stents are generally preferred for longer or more tortuous segments where flexibility matters, while balloon-expandable stents are favored at the aortic bifurcation where precise positioning and radial strength are critical.

The other important distinction is whether the metal mesh is bare or covered with a thin layer of fabric (typically PTFE, a material related to Teflon). Covered stents seal over the plaque rather than just pushing it aside, and this seems to matter most when the disease is extensive. A meta-analysis using individual patient data found that covered stents had roughly 91% patency at four years versus about 84% for bare metal stents overall, and the advantage widened for more severe lesions.⁸ A matched cohort study confirmed a similar pattern: for the most complex complete blockages, covered stents maintained about 88% patency at three years versus roughly 54% for bare metal.⁹ For milder disease, though, the difference between covered and bare metal tends to shrink or disappear.¹⁰

How Long Iliac Stents Last

Long-term patency, meaning whether the stented vessel stays open, is a central question for anyone getting one of these devices. The answer depends on the severity of the original disease, the type of stent used, and how closely a patient is monitored afterward.

Results vary across studies, partly because patient populations and techniques differ. One long-running follow-up from the early stenting era reported primary patency of about 66% at five years and 46% at ten years, though secondary patency (meaning the vessel stayed open after any needed touch-up procedures) reached about 79% at five years and 55% at ten.¹¹ A more recent series using intravascular ultrasound guidance to optimize stent placement reported substantially better numbers: primary patency around 89% at five years, 83% at ten, and 75% at fifteen years, with secondary patency above 90% at all time points.¹² The gap likely reflects improvements in imaging, stent design, and patient selection over the past two decades.

What that means practically is that most iliac arterial stents do their job for years, but some fraction will narrow again over time. When restenosis happens, it is usually treatable with another catheter-based procedure (balloon dilation or placing an additional stent inside the old one). The secondary patency numbers show that these salvage procedures tend to work well. A study tracking patients out to seven years found assisted primary and secondary patency rates above 98%.¹³

Venous Stent Outcomes

Venous iliac stenting is a newer field than its arterial counterpart, and the outcome measures are different because the goals are different. Instead of preventing amputation or restoring walking distance, venous stenting aims to relieve chronic swelling, pain, and skin ulcers caused by poor venous drainage.

The evidence here is encouraging. In patients with leg swelling from iliac vein obstruction, stenting significantly reduced swelling grades and pain scores, with quality-of-life improvements across every measured category.¹⁴ A multicenter randomized trial testing a dedicated venous stent found swelling remission rates near 79%, pain relief in about 69-77% of patients, and ulcer healing rates around 87-90%.¹⁵ Stent sizing guided by intravascular ultrasound has been linked to excellent patency and low reintervention rates in chronic venous obstruction cases as well.¹⁶

What Can Go Wrong

Iliac stenting is considered safe relative to open surgery, but it carries real procedural risks. The most feared acute complication is vessel rupture. In one institutional review of aortoiliac stenting, rupture occurred in about 2.5% of cases, and all ruptures happened in the external iliac artery, where the vessel is thinner-walled and more prone to tearing. Less calcified lesions were paradoxically a risk factor, possibly because heavily calcified arteries resist overdilation. All the ruptures in that series were treated successfully with covered stents placed over the tear.¹⁷

Distal embolization is another concern. Bits of plaque or clot can break free during the procedure and travel downstream, potentially blocking smaller arteries in the leg or foot. Reported embolization rates from angioplasty and stenting procedures range from about 8% to 24%, though most episodes are managed during the procedure itself.¹⁸ In rare cases, debris can travel into the internal iliac artery branches, potentially causing buttock pain or, uncommonly, erectile dysfunction.

Stent migration, where the device shifts from its intended position, is uncommon but well-documented. It tends to happen when a stent is undersized or deployed in a vessel that changes diameter abruptly. Most migration events can be addressed with a second catheter-based procedure to reposition or add another stent.³

Over the longer term, the main issue is restenosis, the gradual re-narrowing of the stented segment. This happens because the body treats the stent as a foreign object and mounts a healing response: smooth muscle cells proliferate inside the stent (a process called intimal hyperplasia), slowly encroaching on the open channel.¹⁹ This is why follow-up imaging and repeat interventions are sometimes needed.

Medications After Stenting

After an iliac arterial stent is placed, you will almost certainly be prescribed antiplatelet medication to prevent blood clots from forming on the new metal surface. The question is whether one drug is enough or two are better. A large study of over 22,000 patients compared outcomes depending on the discharge prescription. Patients on dual antiplatelet therapy (typically aspirin plus clopidogrel) had significantly better one-year amputation-free survival than those on aspirin alone, with a roughly 22% lower risk of amputation and a 21% lower risk of major adverse limb events.²⁰ Strikingly, patients discharged on no antiplatelet therapy had markedly worse outcomes across the board, including one-year survival rates roughly 12 percentage points lower than those on dual therapy.

The duration of dual therapy varies by practice and patient risk, but many vascular specialists keep patients on two antiplatelet drugs for at least a month or two and then step down to one drug long-term. For venous stents, the anticoagulation strategy differs: patients are often placed on blood thinners rather than antiplatelet drugs, since the venous system is more prone to clotting than plaque-related blockage.

Stenting Versus Supervised Exercise

For patients whose main symptom is claudication (leg pain with walking) rather than a threatened limb, the choice between stenting and a structured exercise program is worth discussing. The landmark CLEVER trial compared supervised exercise against primary stenting for claudication from aortoiliac disease and found that patients in the supervised exercise arm achieved better treadmill walking performance than those who got stents.²¹ That finding surprised many clinicians, since stenting produces an immediate improvement in blood flow while exercise takes weeks to months to show benefit.

The results do not mean stenting is unnecessary. Many patients cannot access or adhere to a structured exercise program, and those with more severe disease or critical ischemia are not candidates for exercise alone. A broader evidence review noted that despite high immediate technical success rates, stenting for claudication did not show clear advantages over conservative management in patency, quality of life, or complication rates across moderate-quality evidence.²² In practice, many vascular teams use a combined approach: exercise therapy first, with stenting reserved for patients who do not improve enough or who have anatomy that limits collateral blood flow development.

How Doctors Decide Who Gets a Stent

Not every narrowed iliac artery calls for a stent. Lesion classification plays a major role in decision-making. The TransAtlantic Inter-Society Consensus (TASC) system grades iliac disease from A (short, simple narrowings) through D (long or complete blockages). For simple lesions, balloon angioplasty alone often works, with a stent placed only if the result is inadequate. For moderate lesions, the best approach has been debated for years, with neither stenting nor surgical bypass clearly proven superior.²³ For the most complex disease, covered stents and surgical bypass both remain in play, and the decision increasingly hinges on patient fitness for open surgery, anatomy, and local expertise.

Cost factors into the equation as well. A recent economic analysis compared endovascular stent techniques against open surgical repair for aortoiliac disease and found that the endovascular approach dominated from a cost-effectiveness standpoint, delivering a small quality-of-life advantage while costing substantially less, primarily because open surgery carries higher perioperative mortality and longer hospital stays.²⁴ The trade-off is that stented patients face a higher chance of needing a repeat procedure down the road, while surgical bypasses tend to be more durable when they survive the initial recovery. For most patients who are reasonable candidates for either, the less invasive option wins on the combined metric of outcomes and cost.