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Medically Reviewed By:

2026-05-01

  • Condition
  • Venous
  • Severity: Urgent

May-Thurner Syndrome

Also Known As: MTS; DVT; iliac vein compression syndrome
May-Thurner syndrome (MTS) — also called iliac vein compression syndrome — is an anatomical condition in which the right iliac artery compresses the left common iliac vein against the lumbar spine. This chronic compression causes scarring and narrowing of the vein, which restricts venous outflow from the left leg and significantly increases the risk of deep vein thrombosis (DVT), chronic leg swelling, and pelvic venous congestion.

Who Gets May-Thurner Syndrome?

May-Thurner syndrome is most commonly diagnosed in women between the ages of 18 and 50, though it can affect men as well. It is frequently underdiagnosed because its symptoms — left-leg swelling, DVT, and varicose veins — overlap with other venous conditions. The true prevalence is estimated at 20–30% of the general population having some degree of iliac vein compression, though only a subset develop clinically significant disease.

May-Thurner Syndrome Symptoms

The hallmark presentation is left leg swelling, pain, and heaviness that is asymmetric — meaning the right leg is unaffected. Many patients with May-Thurner are diagnosed after developing a left-sided DVT, often without a clear provoking cause. Other symptoms include prominent varicose veins of the left leg, pelvic pain or heaviness (due to associated pelvic venous congestion), and chronic venous insufficiency changes.

Diagnosing May-Thurner Syndrome in Sarasota & Bradenton

Diagnosis begins with duplex ultrasound to evaluate the venous system and assess for DVT. When May-Thurner is suspected, cross-sectional imaging — CT venography or MRI venography — is used to visualize the iliac vein anatomy and quantify the degree of compression. In some cases, intravascular ultrasound (IVUS) performed at the time of intervention provides the most accurate assessment of vein narrowing.

May-Thurner Treatment: Venous Stenting

Definitive treatment for May-Thurner syndrome is catheter-based venous stenting. A self-expanding stent is placed across the compressed iliac vein segment, restoring normal lumen diameter and venous outflow. In patients who present with acute DVT, catheter-directed thrombolysis or mechanical thrombectomy is first performed to clear the clot before stenting. Most patients experience dramatic improvement in leg swelling and symptoms after successful stenting.

The procedure is performed under conscious sedation, typically requiring a short hospital observation period. Long-term anticoagulation is maintained after stenting to prevent in-stent thrombosis, with the duration determined individually.

SYMPTOMS

  • Left leg swelling, heaviness, and pain — asymmetric (right leg unaffected)
  • Recurrent left-sided DVT
  • Varicose veins or venous insufficiency primarily in the left leg
  • Pelvic pain or pressure (in women with concurrent pelvic venous congestion)
  • Chronic left leg discomfort worsening with prolonged standing

DIAGNOSIS METHODS

  • Duplex Venous Ultrasound +

    Screens for DVT and identifies left iliac vein flow abnormalities.

  • CT Venography +

    Defines the anatomy of iliac vein compression and guides stent planning.

  • MRI Venography +

    Non-contrast alternative for young patients or those with contrast allergy.

  • Intravascular Ultrasound (IVUS) +

    Gold-standard intraoperative tool for measuring the degree of compression at the time of stenting.

TREATMENTS

RELATED CONDITIONS

FREQUENTLY ASKED QUESTIONS

  • How is May-Thurner syndrome different from ordinary DVT? +

    Ordinary DVT is usually caused by a temporary provoking factor (surgery, immobility, travel) and resolves with anticoagulation. May-Thurner syndrome is a structural cause of DVT — the underlying vein compression persists and leads to recurrent or treatment-resistant DVT without stenting to correct the anatomy.

  • Can May-Thurner syndrome cause pelvic pain? +

    Yes. When iliac vein compression causes elevated venous pressure in the pelvis, it can contribute to pelvic congestion syndrome — a cause of chronic pelvic pain in women, particularly around menstruation or after prolonged standing.

  • Is May-Thurner syndrome a surgical emergency? +

    Chronic May-Thurner syndrome is not an emergency, but acute DVT associated with May-Thurner syndrome warrants prompt evaluation and often urgent catheter-directed treatment to minimize post-thrombotic complications. Call our office or seek emergency care if you develop sudden, severe leg swelling.