Medically reviewed by Nachiket J. Patel, MD, FACC, FSCAI. Last reviewed July 2026.
May-Thurner syndrome is a pattern of pelvic vein compression. Most often, the right iliac artery crosses over the left iliac vein and presses it against the spine.
Some degree of compression can exist without symptoms. It becomes clinically important when it limits venous outflow, contributes to left-leg swelling or pain, or plays a role in an extensive DVT.
The diagnosis should connect the anatomy with the patient’s symptoms. Treating an image without that connection can expose someone to a procedure that does not solve the real problem.
What symptoms suggest iliac vein compression?
Right-sided and other anatomic compression patterns also occur. Symptoms and imaging determine whether the label is clinically useful.
- Persistent swelling of the left leg
- Heaviness, aching, or tightness that worsens while standing
- Pelvic or upper-thigh venous discomfort
- New varicose veins or visible lower-abdominal veins
- Skin change from chronic venous pressure
- An extensive left-leg DVT
- Ongoing symptoms after a previous DVT
When is urgent evaluation needed?
Sudden one-sided swelling, pain, warmth, or discoloration may indicate acute DVT and deserves prompt assessment. Severe swelling with a blue or very painful leg can signal a threatened venous outflow problem.
Call 911 for sudden shortness of breath, chest pain, coughing blood, or fainting because these can be signs of pulmonary embolism.
How is May-Thurner syndrome diagnosed?
A leg ultrasound is excellent for DVT and venous reflux but may not fully show the pelvic iliac vein. CT venography or MR venography can demonstrate anatomy and collateral veins.
When an intervention is being considered, catheter venography and intravascular ultrasound can provide more precise information about the location and severity of obstruction. Intravascular ultrasound looks from inside the vein and can help size a stent.
How is iliac vein compression treated?
A person with an anatomic compression but no meaningful symptoms may need no procedure. Conservative care can include walking, elevation, compression when appropriate, and management of other venous disease.
If acute DVT is present, anticoagulation is central. Selected patients with extensive clot may benefit from thrombectomy, followed by treatment of a significant underlying iliac obstruction when appropriate.
For persistent symptoms from a confirmed outflow obstruction, an iliac vein stent can hold the compressed segment open. Follow-up includes symptom assessment, medication planning, and imaging when indicated.
What should I bring for a second opinion?
Bring ultrasound, CT, MR, venogram, or intravascular-ultrasound reports and the actual images when available. Include records from any DVT, prior venous procedure, and current anticoagulant treatment.
The review should distinguish superficial reflux, post-thrombotic damage, lymphedema, and pelvic obstruction because more than one problem may be contributing.
Frequently asked questions
Is May-Thurner syndrome always on the left?
The classic pattern affects the left iliac vein, but other compression patterns can occur.
Does every compression need a stent?
No. Treatment is based on symptoms, clot history, collateral flow, imaging, and expected benefit—not compression percentage alone.
Can symptoms continue after a technically successful stent?
Yes, if post-thrombotic valve damage, superficial reflux, lymphedema, or another cause also contributes. Follow-up should reassess the whole leg.
Related heart and vascular information
Schedule an appointment
If you have a stable heart or circulation concern, request an appointment with Flow Heart & Vascular in Mesa, Arizona. Call 911 for emergency symptoms.
This page provides general education and does not replace individualized medical advice.
