Deep in the pelvis, the left iliac vein — carrying blood up from the left leg — passes directly beneath the right iliac artery. In many people the artery presses on the vein against the spine, narrowing it. When that compression is significant, it slows venous outflow from the leg and can cause chronic swelling, heaviness, and a markedly higher risk of deep vein thrombosis. This pattern is called May-Thurner syndrome, and the modern treatment is a dedicated venous stent that props the vein open. This guide explains the anatomy, how it is diagnosed, and how venous stenting differs from the arterial stents most people have heard of.
What Is May-Thurner Syndrome?
May-Thurner syndrome is compression of the left common iliac vein by the overlying right common iliac artery. The constant pulsation of the artery against the vein also creates internal webs and scarring over time, worsening the narrowing. Many people have some degree of compression without symptoms; it becomes a syndrome when it produces leg swelling, pain, varicose veins, skin changes, or — most importantly — a deep vein thrombosis, classically an extensive clot in the left leg of a younger woman.
How It's Diagnosed
Because the obstruction is deep in the pelvis, ordinary leg ultrasound can miss it. Diagnosis usually requires cross-sectional imaging — CT or MR venography — or intravascular ultrasound (IVUS) during a venous procedure, which directly measures the degree of compression from inside the vein. IVUS has become the reference standard because surface imaging underestimates how much the vein is squeezed.
Why Venous Stents Are Different
A vein is not a small artery. Veins are larger in diameter, thin-walled, low-pressure, and subject to external compression and bending — so an arterial stent is the wrong tool. Dedicated venous stents are engineered for this environment: larger diameters, high crush resistance to withstand the arterial pressure from outside, and enough flexibility to sit across the pelvic bend without kinking. INVAMED's Atlas venous stent is designed for exactly this iliofemoral application, within the dedicated venous stent portfolio. The procedure is endovascular — through a vein puncture, under imaging — and typically same-day.
Treatment: Stenting and What Comes With It
When symptomatic compression is confirmed, the vein is opened with a balloon and held open with a venous stent; if a clot is present, it is usually cleared first with catheter-based thrombus removal before stenting. A period of blood-thinning medication follows to keep the stented segment clear while it heals. Most patients notice reduced swelling and heaviness as outflow is restored. As with any stent, follow-up imaging monitors patency.
Frequently Asked Questions
What are the symptoms of iliac vein compression?
Chronic left-leg swelling and heaviness, pain, varicose veins, skin changes, and an elevated risk of deep vein thrombosis. Many people with mild compression have no symptoms at all.
Can you use a regular stent in a vein?
No — veins need dedicated venous stents with larger diameters, high crush resistance, and flexibility. Arterial stents are not built for the low-pressure, externally compressed venous environment.
How is May-Thurner syndrome diagnosed?
With CT or MR venography, or intravascular ultrasound (IVUS) during a procedure — the reference standard, because ordinary ultrasound often misses the pelvic compression.
Is venous stenting permanent?
The stent is a permanent implant that holds the vein open; blood thinners are used temporarily during healing, and follow-up imaging checks that the segment stays patent.
Related on INVAMED
Patient hub: deep vein thrombosis (DVT). Portfolio: venous stents.
This article is for education only and is not medical advice, diagnosis, or treatment — always consult a qualified physician about your situation. Device availability and regulatory status vary by country; contact INVAMED or your authorized local distributor for current regulatory information applicable to your region.