Names & Terms You Will Hear
Plain-language meanings for the terms your care team may use.
| Term | Meaning |
|---|---|
| May-Thurner Syndrome (MTS) | the formal name we use in your chart |
| Iliac vein compression syndrome | the descriptive name — the left iliac vein is squeezed |
| Cockett syndrome | named for Frank Cockett, who described the same finding in 1965 |
| Iliocaval compression | broader term that includes the inferior vena cava (IVC) area |
| Left iliac vein compression | anatomic short form — the left vein is the one almost always affected |
| Non-thrombotic iliac vein lesion (NIVL) | MTS without an active blood clot — chronic compression and scarring |
| Post-thrombotic syndrome (PTS) | the chronic leg-swelling and skin changes that can follow a missed MTS-driven DVT |
What Is May-Thurner Syndrome?
- May-Thurner Syndrome is when the right iliac artery presses on the left iliac vein where they cross in the pelvis. Imagine a soft drinking straw under a heavier rope.
- The squeezed vein narrows. Blood from the left leg has trouble getting back to the heart.
- Slow blood flow plus a damaged vein wall sets the stage for a deep-vein thrombosis (DVT) - a blood clot in the left leg.
- It is more common in women aged 20-50 and in pregnancy. Men can also have it; we look for it after any unexplained left-leg DVT.
- Many people have some compression without symptoms. The syndrome is the compression PLUS leg symptoms or a clot.
Why It Matters
- MTS is the most common reversible cause of left-leg DVT. Missing it means the clot keeps coming back even on blood thinners.
- Without treatment, up to half of people develop post-thrombotic syndrome - chronic swelling, aching, and skin changes for life.
- MTS-related clots can dislodge and travel to the lungs (pulmonary embolism) - a life-threatening event.
- A simple stent can fix the underlying compression. Patency at 5 years is over 90 percent in experienced centers.
- Pregnancy raises MTS risk because the gravid uterus adds outside compression. Untreated MTS in pregnancy can cause large clots.
Treatment Options
Shown in English for your safety — this section is not automatically translated. Confirm with your doctor or call the office.
- Anticoagulation (blood thinner): the foundation. DOACs (apixaban, rivaroxaban) for 3-6 months minimum after a DVT; longer if clot extends or compression remains.
- Compression stockings (20-30 or 30-40 mmHg, knee-high or thigh-high): reduce swelling and lower post-thrombotic syndrome risk.
- Catheter-directed thrombolysis (CDT): for new, large iliofemoral DVTs - dissolves clot to prevent post-thrombotic syndrome (CaVenT, ATTRACT trials).
- Iliac vein stenting: opens the squeezed segment with a metal mesh tube. Done after a clot is cleared, or for chronic non-thrombotic disease causing symptoms.
- IVC filter: temporary metal cage placed in the vena cava to catch clots. Used only when anticoagulation cannot be given.
- Surgical bypass or cross-pubic graft: rarely needed; reserved for failed stenting in complex anatomy.
- Long-term low-dose aspirin (or continued anticoagulation) for up to 12 months after stenting helps keep the stent open.
Risks, Benefits, and Alternatives
Shown in English for your safety — this section is not automatically translated. Confirm with your doctor or call the office.
Every choice has trade-offs. Use this table to start the shared decision conversation with your care team.
| Option | Risks | Benefits | Alternatives |
|---|---|---|---|
| Anticoagulation alone | Bleeding (1-3% major bleeding/yr), bruising, drug interactions. | Cuts new-clot risk by 70-90%. Once-daily or twice-daily pill. No procedure. | Add stenting if compression is significant; mechanical thrombectomy if early presentation. |
| Iliac vein stenting | Bleeding at access site, stent migration (rare), in-stent re-thrombosis (5-10%/yr without anticoagulation). | Patency 80-95% at 5 years. Resolves chronic swelling. Reduces clot recurrence dramatically. | Anticoagulation alone (slower symptom relief), conservative care with compression. |
| Catheter-directed thrombolysis | Bleeding (intracranial 0.5%, major 4%); not used in pregnancy or recent surgery. | Clears acute clot fast; reduces post-thrombotic syndrome by 30-50% in iliofemoral DVT (ATTRACT, CaVenT). | Anticoagulation alone (symptoms resolve more slowly), surgical thrombectomy. |
| IVC filter (retrievable) | Filter migration, fracture, IVC perforation. Long-term filters increase DVT risk. | Catches breakaway clots when blood thinners cannot be given. | Use only when anticoagulation truly cannot be started; remove as soon as feasible. |
Common Misconceptions
| Myth | Reality |
|---|---|
| If I had May-Thurner I would know - my leg would always hurt. | Most people with anatomic compression have no symptoms. The syndrome shows up suddenly as a DVT, or gradually as worsening leg swelling and aching. |
| DVTs always come from sitting too long on a plane. | Travel is one trigger. Anatomy (May-Thurner), pregnancy, hormones, and clotting disorders are equally important — especially when the left leg is involved. |
| Once my clot dissolves on blood thinners, I am cured. | If May-Thurner is the underlying cause, the compression is still there. Without addressing it, recurrence rate is high. |
| A stent inside a vein will fail like leg artery stents do. | Iliac vein stents have excellent long-term patency (>90% at 5 years in experienced hands) because veins are larger and lower pressure than arteries. |
| I should sit still and rest until the clot is gone. | Modern guidelines say walking is safe and helps. Rest only if you cannot tolerate walking. Compression stockings help during activity. |
| Pregnancy guarantees I will get May-Thurner. | Pregnancy raises risk but most pregnancies pass without DVT. Watch for left-leg swelling, especially after the second trimester. |
| The blood thinner pill is enough — I do not need imaging. | We need a CT or MR venogram (sometimes IVUS) to see the compression. Without imaging, the diagnosis is just a guess and the right treatment is missed. |
| Aspirin alone is enough after a stent. | After iliac vein stenting we usually use full anticoagulation (3-6 months) followed by aspirin or low-dose anticoagulation, depending on your bleeding risk. |
Possible Complications
Knowing what can go wrong helps you spot problems early. Most complications are uncommon, especially with treatment.
| Where / What | What Can Happen |
|---|---|
| Recurrent DVT | If the iliac compression is not relieved, the same leg can clot again. Stenting plus anticoagulation cuts recurrence dramatically. |
| Pulmonary embolism (PE) | Clots can break off from the left leg and travel to the lungs. PE is life-threatening - call 911 for sudden shortness of breath, chest pain, or fainting. |
| Post-thrombotic syndrome (PTS) | Chronic leg swelling, aching, brown-stained skin, and (in severe cases) ulcers. Can be lifelong. Stenting + compression stockings reduce risk. |
| Bleeding from anticoagulation | GI bleeding most common. Intracranial hemorrhage is rare but most feared. Treat reflux and ulcer disease, avoid NSAIDs, limit alcohol. |
| In-stent re-thrombosis | A clot can form inside the stent (5-10% per year without anticoagulation). Anticoagulation for 3-6 months after stenting cuts this dramatically. |
| Skin ulceration (advanced PTS) | Late complication of severe chronic venous hypertension. Prevention is the key — early diagnosis, early treatment of the underlying compression. |
Points to Know
Shown in English for your safety — this section is not automatically translated. Confirm with your doctor or call the office.
If you remember nothing else, remember these key points.
- Unexplained left-leg swelling, especially with aching or skin discoloration, deserves an evaluation for May-Thurner.
- After any unprovoked left-leg DVT, ask whether iliac compression has been imaged. CT venogram or MR venogram is the test.
- Take your anticoagulant exactly as prescribed. Missed doses are the most common reason a clot recurs.
- Walk daily. Wear graduated compression stockings during waking hours, especially long flights and long workdays.
- Stay hydrated. Avoid prolonged sitting without moving your legs.
- Tell every dentist, surgeon, and ER doctor that you take a blood thinner before any procedure or shot.
- Pregnancy and hormonal contraception change clotting risk. If you have MTS, discuss the safest option with your cardiologist or hematologist.
- After stenting, bring the stent ID card to every appointment. Imaging follow-up is at 1, 6, and 12 months.
When to Call Us — and When to Call 911
Shown in English for your safety — this section is not automatically translated. Confirm with your doctor or call the office.
If you are not sure, call. We would rather hear from you twice than miss a real problem.
- Sudden swelling, redness, or tightness in one leg (especially the left) - call us today.
- Severe shortness of breath, chest pain, or coughing blood - call 911 (possible pulmonary embolism).
- Painful new lump in the leg or visible vein - tell us.
- Bleeding that does not stop with 10 minutes of pressure, blood in stool or urine, vomiting blood, or severe headache while on a blood thinner - call us right away.
- Stent area suddenly feels different (severe pain, new swelling) after stenting - call us.
- Pregnancy with new leg swelling or shortness of breath - tell your obstetrician AND us today.
- Missed dose of your blood thinner - call us before you decide what to do.
- Fever, chills, or hot/red skin over the affected leg - rule out infection.
Office: (727) 943-5200
Trusted Resources
Independent, evidence-based pages we recommend for deeper reading.
- Cleveland Clinic - May-Thurner Syndrome — Plain-language overview of MTS for patients.
- Mayo Clinic - Deep Vein Thrombosis — Comprehensive DVT overview - symptoms to watch and prevention tips.
- National Blood Clot Alliance - Stop the Clot — Patient community, anticoagulation tips, travel guidance.
- CDC - Venous Thromboembolism — US prevalence and prevention information.
Sources Used to Build This Guide
- May R, Thurner J. The cause of the predominantly sinistral occurrence of thrombosis of the pelvic veins (1957) [Landmark paper] — Original anatomical description of left iliac vein compression by the overlying right iliac artery; defines the named syndrome.
- Cockett FB, Thomas ML. The iliac compression syndrome (1965) [Landmark paper] — Larger clinical series establishing iliac compression as a cause of left-leg deep-vein thrombosis.
- ATTRACT Trial — Vedantham S et al. Pharmacomechanical Catheter-Directed Thrombolysis for DVT (NEJM 2017) [Clinical trial] — Defines when adding catheter-directed thrombolysis (often paired with iliac stenting) reduces post-thrombotic syndrome severity.
- CaVenT Trial — Enden T et al. Long-term outcome after additional catheter-directed thrombolysis vs anticoagulation alone (Lancet 2012) [Clinical trial] — Showed reduced post-thrombotic syndrome at 24 months after thrombolysis for ileofemoral DVT — relevant for May-Thurner-driven clots.
- Hartung O et al. — Late results of stenting for chronic iliac vein obstruction [Cohort] — Long-term patency data for iliac vein stenting in May-Thurner; supports stenting as a durable treatment.
- AVF / SVS — Practice Guidelines on the Management of Iliac Vein Compression / May-Thurner Syndrome (2018) [Guideline] — Society of Vascular Surgery / American Venous Forum criteria for diagnosis (IVUS, MRV) and indications for stenting.
- Cleveland Clinic — May-Thurner Syndrome [Patient education] — Plain-language patient overview used to align our explanations with familiar phrasing.
- Mayo Clinic — Deep vein thrombosis (DVT) [Patient education] — Referenced for DVT symptom recognition and red-flag criteria patients can act on.
- National Blood Clot Alliance — Stop the Clot [Patient education] — Patient community resources for living with chronic anticoagulation.
