Anatomy can be incidental
A compressed-looking vein on a scan does not prove that it is causing symptoms.
Pelvic venous outflow · Los Angeles
May-Thurner syndrome evaluation & treatment starts by mapping the outflow.
Persistent swelling, heaviness, pain, or visible veins in one—often left—leg can happen when the left common iliac vein is compressed in the pelvis. Because DVT and other conditions can look similar, EVSLA checks for clot and maps venous outflow before discussing treatment.
- One-leg swelling assessed for clot first
- Pelvic venous imaging when indicated
- Stenting only for selected patients
A clot warning worth checking
Is one leg suddenly more swollen?
- New swelling, pain, warmth, or color change affects one leg
- The leg feels markedly heavier or tighter than the other
- Chest pain, breathlessness, fainting, or coughing blood appears
Compression anatomy is not the whole diagnosis.
Symptoms, clot history, imaging, and alternative causes all matter.
What is May-Thurner syndrome?
May-Thurner syndrome, also called iliac vein compression syndrome, is a symptomatic pelvic venous outflow problem. In the classic pattern, the right common iliac artery presses the left common iliac vein against the spine. The narrowed vein may make it harder for blood to leave the left leg, contributing to chronic swelling, heaviness, pain, varicose veins, skin changes, or deep vein thrombosis (DVT).
Many people have some iliac-vein compression on imaging without symptoms. That anatomy alone does not automatically require a stent. A useful diagnosis connects symptoms and clot history with the location and significance of the obstruction while excluding other causes.
Clinical references: Society for Vascular Surgery and 2024 multisociety NIVL consensus
The anatomy in plain language
The vein can be compressed where an artery crosses it
The left common iliac vein carries blood from the left leg toward the heart. In the classic May-Thurner configuration, it passes between the right common iliac artery and the lumbar spine. Repeated arterial pulsation and limited space may narrow the vein and encourage collateral veins or clotting in susceptible patients.
The left side is classic—not exclusive
Other iliac-vein compression patterns can occur, including right-sided or bilateral obstruction.
Clot changes the treatment question
Acute DVT, old clot damage, and nonthrombotic compression are evaluated differently.
Clinical reference: Society for Vascular Surgery.
Classic left iliac vein compression
A simplified orientation—not a diagnostic image.
Compression pointThe crossing artery and spine can narrow the vein’s outflow channel.
Blue: iliac vein
Coral: iliac artery
Tan: spine
May-Thurner syndrome symptoms
The clue is often a one-sided pattern
Symptoms may be mild, build through the day, worsen with prolonged standing or exercise, or appear suddenly if a DVT forms. One symptom cannot diagnose iliac-vein compression.
Same symptom, different cause
One swollen leg is a diagnostic question
May-Thurner syndrome is one possibility. The evaluation also looks for conditions that require a different or more urgent plan.
Acute DVT
A new deep-vein clot can cause sudden swelling, pain, warmth, and discoloration.
Superficial venous reflux
Valve failure closer to the skin can cause varicose veins, aching, and ankle swelling.
Post-thrombotic syndrome
Old clot damage may leave chronic obstruction, reflux, swelling, skin changes, or ulcers.
Lymphedema
Lymphatic fluid buildup has a different exam pattern and may need compression-focused care.
Infection or inflammation
Spreading redness, fever, severe tenderness, or drainage needs prompt clinical assessment.
Musculoskeletal or systemic causes
Joint injury, medication, heart, kidney, and other conditions can also contribute to swelling or pain.
DVT and pulmonary embolism warning signs
Sudden swelling should not wait for a routine vein visit
Call a clinician promptly for new one-sided leg swelling, pain, warmth, or discoloration. Call 911 for symptoms that could mean a pulmonary embolism, including sudden shortness of breath, chest pain, fainting, a fast or irregular heartbeat, or coughing blood.
Clinical reference: American Heart Association, , .
The reason to classify the pattern
Four ways iliac-vein compression can present
The anatomy can be silent, cause chronic symptoms, contribute to an acute clot, or coexist with damage left by an old clot. The category changes the urgency, tests, and treatment discussion.
Anatomy only
Incidental compression
Imaging shows narrowing, but there are no meaningful leg or pelvic venous symptoms.
Chronic symptoms
Nonthrombotic obstruction
Persistent one-leg swelling, heaviness, venous claudication, varices, or skin changes without acute DVT.
Acute clot
Iliofemoral DVT
Sudden swelling and pain may reflect a deep clot extending through the pelvis.
After a prior clot
Post-thrombotic obstruction
Scarred or narrowed veins may cause lasting swelling, heaviness, skin change, or ulcer risk.
No treatment based on anatomy alone
Urgency rises with clot and tissue risk
Patient selection should be symptom-driven and should integrate clinical and imaging findings.
2024 multisociety NIVL consensusWhy symptoms can surface
Compression plus a trigger or vulnerability
The crossing-vessel anatomy may exist for years. Symptoms or DVT can emerge when additional factors slow flow or increase clot risk. Not every patient has an identifiable trigger.
Clot history
Prior DVT changes the workup
Old clot damage can scar the iliac vein or damage valves, creating a post-thrombotic pattern rather than a purely nonthrombotic lesion.
- Prior DVT or pulmonary embolism
- Recurrent clot
- Current anticoagulation
- Previous thrombectomy or stent
Temporary risk
Pregnancy, estrogen, surgery, or immobility
Changes in venous flow and clot risk can make a previously silent anatomy clinically important.
- Pregnancy or recent delivery
- Estrogen-containing medication
- Recent surgery or hospitalization
- Long travel or prolonged immobility
Whole-patient review
Other clot and pelvic factors
Active cancer, inflammation, clotting disorders, pelvic procedures, radiation, or a mass can alter the differential and treatment plan.
- Known thrombophilia or family clot history
- Active cancer or inflammatory illness
- Pelvic procedure or radiation
- Alternative pelvic compression
May-Thurner syndrome diagnosis
Imaging should answer a clinical question
The evaluation begins with history and examination, then chooses the least invasive test that can answer the next question. Pelvic outflow is harder to see than the lower leg, so no single test fits every patient.
Treatment is considered only after symptom severity, alternatives, imaging, and patient goals are aligned.
May-Thurner diagnostic pathway
Step 1
History and focused examination
Compare both legs, skin, varices, pulses, symptom timing, clot history, medications, pregnancy, and prior procedures.
Step 2
Venous duplex ultrasound
Check for acute or old DVT, reflux, and flow clues that may suggest a pelvic outflow problem.
Step 3
CT or MR venography
Define pelvic anatomy, collateral veins, alternative compression, and other pelvic findings when appropriate.
Step 4
Venography and IVUS
During a selected invasive evaluation, these tests can assess the lumen and guide treatment.
Decision
Match symptoms to the obstruction
Do not treat an imaging percentage without a defensible clinical relationship.
Clinical references: Society for Vascular Surgery.
May-Thurner syndrome treatment
Treat the patient—not the compression percentage
A stent is not preventive treatment for every compressed-looking vein. The plan depends on symptoms, DVT, chronic scarring, bleeding risk, anatomy, previous care, and how much the condition affects daily life.
Path 1 · Observe or support
No meaningful symptoms or mild symptoms
When anatomy is incidental or symptoms are limited, the plan may focus on observation, movement, symptom management, and follow-up.
- No prophylactic stent for anatomy alone
- Compression when safe and helpful
- Review clot-risk situations
- Return precautions for DVT and PE
Path 2 · Treat the clot
Acute iliofemoral DVT
Anticoagulation is central. Selected patients may be considered for catheter-based clot removal after symptom duration, extent, bleeding risk, and goals are reviewed.
- Anticoagulation plan
- Selected thrombectomy or thrombolysis
- Evaluate underlying outflow obstruction
- PE and bleeding precautions
Path 3 · Restore outflow
Significant symptomatic obstruction
For carefully selected chronic nonthrombotic or post-thrombotic obstruction, a dedicated venous stent may be used to support the iliac vein.
- Confirm symptom-obstruction match
- IVUS-guided sizing and placement
- Medication plan individualized
- Structured imaging follow-up
Procedures that may enter the plan
From confirming the outflow to keeping it open
Not every patient needs every step. The exact combination depends on whether the problem is nonthrombotic compression, acute DVT, chronic clot damage, or another diagnosis.
- Symptom-driven decisions
- Clot status defined first
- Pelvic outflow mapped
- IVUS when intervention is planned
- Medication plan individualized
- Surveillance scheduled
Venography and IVUS
Contrast imaging and ultrasound from inside the vein can define the channel, reference size, and landing zones during a selected procedure.
Thrombectomy or thrombolysis
Selected acute iliofemoral DVT may be treated with catheter-based clot removal when potential benefit outweighs bleeding and procedural risk.
Iliac vein stenting
A self-expanding venous stent may support a clinically significant iliac obstruction after the anatomy and symptom relationship are confirmed.
Duplex surveillance
Follow-up imaging can assess stent flow, recurrent obstruction, residual clot, or another reason for persistent symptoms.
After iliac vein treatment
Recovery is a plan—not a single finish line
Timelines vary with acute clot, procedure type, access site, medications, other health conditions, and work demands. The treating clinician should provide the actual schedule.
First days
Move as directed
Walking, hydration, access-site care, compression, lifting, and return-to-work advice are individualized.
Medication safety
Follow the exact regimen
Anticoagulant or antiplatelet decisions depend on clot history, procedure, and bleeding risk. Do not stop medication without guidance.
Scheduled surveillance
Check flow and symptoms
Visits compare swelling, pain, function, skin, and imaging rather than relying on appearance alone.
Long term
Watch for recurrence
New one-sided swelling, worsening pain, chest symptoms, or bleeding concerns should be reported promptly.
Procedure day
Long-term surveillance
Postprocedure medication and surveillance should be individualized to clot history, procedure, and bleeding risk.
2024 multisociety NIVL consensusWho should be evaluated
When a pelvic outflow workup may be reasonable
The strongest signal is a persistent or recurrent one-sided venous pattern that has not been explained by a lower-leg study alone.
Bring these patterns to the visit
- Persistent left-leg swelling, heaviness, or pain
- Prior left iliofemoral DVT or recurrent DVT
- Venous claudication—tightness or pain with sustained activity
- Recurrent varicose veins after appropriate surface treatment
- Unilateral skin changes, venous ulcer, or pelvic collaterals
- An outside CT or MR report mentioning iliac-vein compression
What happens
From side-to-side pattern to a defensible plan
Bring prior imaging discs and reports, clot records, medication list, procedure notes, compression garments, pregnancy history, and photographs of changing swelling or skin.
- Screen DVT and PE symptoms Urgent clot or chest symptoms are separated from a routine chronic-vein visit.
- Measure the clinical pattern The exam compares both legs, varices, skin, tenderness, pulses, and swelling distribution.
- Review lower-extremity duplex The study looks for acute clot, old clot changes, reflux, and pelvic-flow clues.
- Escalate pelvic imaging selectively CT or MR venography may clarify anatomy and alternative pelvic causes.
- Use invasive imaging only when justified Venography and IVUS are considered when the result can change an intervention decision.
- Discuss alternatives and follow-up The plan explains observation, medication, compression, clot therapy, stenting, uncertainties, and surveillance.
Your care team
Who evaluates iliac-vein obstruction at EVSLA
This concept positions EVSLA’s physicians around venous imaging review, DVT assessment, candidacy for image-guided treatment, and postprocedure surveillance. Physician credentials, exact services, and location availability must be confirmed before publication.
Harout Dermendjian, MD
Endovascular Specialist
Featured in this concept for pelvic venous imaging review and minimally invasive treatment planning. Confirm approved credentials and scope before publication.
Kartik Kansagra, MD
Endovascular Specialist
Featured in this concept for DVT and iliac-outflow assessment, procedure candidacy, and image-guided venous care. Confirm current services.
Sipan Mathevosian, MD
Endovascular Specialist
Featured in this concept for ultrasound-led assessment and venous treatment planning. Confirm training, specialty description, and approved claims.
Where to request a vein evaluation
Three clinics across Los Angeles County
Call before traveling to confirm where venous duplex, pelvic venous consultation, DVT treatment, venography, IVUS, or iliac vein stenting is performed. Services may differ by location.
Glendale
445 W Broadway
Glendale, CA 91204
Simi Valley
2750 Sycamore Dr, Ste 200
Simi Valley, CA 93065
La Cañada Flintridge
1407 Foothill Blvd
La Cañada, CA 91011
Questions patients ask
May-Thurner syndrome, answered plainly
What is May-Thurner syndrome?
May-Thurner syndrome is a symptomatic iliac-vein outflow problem. In the classic anatomy, the right common iliac artery crosses over and compresses the left common iliac vein against the spine.
Some compression is common in people without symptoms. A diagnosis should connect symptoms or DVT with meaningful obstruction and exclude other causes.
What are the early signs and symptoms of May-Thurner syndrome?
Possible early signs include persistent swelling in one leg, heaviness, aching, pressure, visible veins, or discomfort that builds with standing or activity. The left leg is classic.
Sudden one-leg swelling, warmth, pain, tenderness, or discoloration may be DVT and needs prompt assessment.
Why does May-Thurner syndrome usually affect the left leg?
The classic crossing pattern places the left common iliac vein between the right common iliac artery and the spine. That can narrow the channel carrying blood out of the left leg.
Other pelvic vein compression patterns can affect the right side or both sides, so laterality is a clue rather than an absolute rule.
What causes May-Thurner syndrome, and is it genetic?
The core issue is an anatomic relationship among the iliac vein, crossing artery, and spine. Why one person becomes symptomatic while another does not is not fully explained.
It is not usually described as a straightforward inherited disorder. Family clot history can still matter because separate clotting risks may affect DVT risk.
How is May-Thurner syndrome diagnosed? Will an ultrasound find it?
Duplex ultrasound is useful for checking DVT, old clot changes, reflux, and flow clues, but the pelvic iliac veins can be difficult to see completely from the surface.
CT or MR venography may define pelvic anatomy. Venography and intravascular ultrasound may be used during a selected invasive evaluation.
What is the treatment for May-Thurner syndrome? Does everyone need a stent?
No. People with incidental compression and no meaningful symptoms generally do not need a prophylactic stent. Mild symptoms may be managed conservatively.
Acute DVT requires a clot-treatment plan. A venous stent may be considered for selected patients with significant symptoms and confirmed iliac outflow obstruction.
What are possible iliac vein stent complications?
Potential problems include bleeding or bruising at the access site, medication-related bleeding, stent thrombosis or restenosis, migration or placement issues, injury to nearby structures, contrast or kidney concerns, and persistent symptoms if another condition is contributing.
How long is recovery after iliac vein stenting?
Many patients walk soon after an uncomplicated endovascular procedure, but return to driving, work, exercise, lifting, compression, and travel varies with the access site, clot treatment, medications, and overall health.
Follow the treating clinician’s schedule and attend surveillance imaging.
Can pregnancy cause or worsen May-Thurner syndrome?
Pregnancy does not create the classic crossing anatomy, but pregnancy and the postpartum period can change venous flow and increase clot risk. Symptoms or a prior DVT should be reviewed with the obstetric and vascular teams.
How should I sleep with May-Thurner syndrome?
No sleeping position can remove iliac-vein compression or treat a DVT. A comfortable position and modest leg elevation may help some people’s swelling, but symptom relief does not establish the diagnosis.
Do not rely on sleep position for new or worsening one-leg swelling, pain, warmth, or color change.
Clinical review required before publication
Assign an EVSLA physician reviewer and confirm physician credentials; May-Thurner/NIVL terminology; DVT and PE instructions; duplex, CT, MR, venography, and IVUS protocols; anticoagulation language; thrombectomy, thrombolysis, and iliac stent capabilities; pregnancy guidance; medication and surveillance protocols; recovery timelines; location availability; and every outcome or risk claim. Add reviewed and next-review dates.
One swollen leg deserves a clear outflow map.
Bring prior ultrasound, CT, or MR images and reports; DVT and procedure records; medication list; compression garments; and photographs of changing swelling or skin. EVSLA can separate clot, reflux, and pelvic obstruction and explain the next step.
Request a Vein Evaluation
Call (818) 626-3710
For sudden chest pain, shortness of breath, fainting, coughing blood, or rapidly worsening one-leg swelling, seek emergency care.