One-sided leg swelling is easy to dismiss. Maybe you stood too long, maybe you slept awkwardly. But when the swelling keeps coming back — always in the same leg, always worse by the end of the day — there is often something more specific behind it. May-Thurner Syndrome is one of the most commonly overlooked causes of one-sided leg swelling, and understanding it can make a meaningful difference in how quickly you find answers and relief.
What Is May-Thurner Syndrome?
May-Thurner Syndrome is a structural vascular condition in which the right iliac artery compresses the left iliac vein against the spine. That compression restricts blood flow returning from the left leg to the heart, creating the conditions for swelling, pain, and, in more serious cases, people develop deep vein thrombosis (DVT).
Because the anatomy involved is internal and the symptoms can seem non-specific, the condition is frequently missed or misattributed to other causes.
Who Is Most Affected by May-Thurner Syndrome?
May-Thurner Syndrome is diagnosed most often in women between the ages of 20 and 50, though it can affect anyone. According to research published in the Journal of Vascular Surgery, May-Thurner Syndrome may account for up to 2–3% of all lower extremity venous disorders — and is believed to be significantly underdiagnosed.
People who are pregnant, sedentary for long periods, or have a history of blood clots are at higher risk of experiencing symptoms.
What Symptoms Should You Watch For?
The most recognizable sign is persistent swelling in the left leg that is not mirrored on the right side. You may also notice:
- A feeling of heaviness or pressure in the left leg, especially after standing or sitting for extended periods
- Aching or tenderness along the inner thigh or calf
- Visible varicose veins or surface vein changes on the left leg
- Skin discoloration near the ankle in more advanced cases
Pain that worsens throughout the day and improves with leg elevation is a particularly common pattern.
Understanding One-Sided Leg Swelling with May-Thurner Syndrome
One-sided leg swelling with May-Thurner Syndrome occurs because the compressed iliac vein cannot drain blood from the left leg efficiently. As venous pressure builds, fluid leaks into surrounding tissue — and that is what causes the visible swelling.
What makes May-Thurner Syndrome distinct from general venous insufficiency is its anatomical origin. The problem is not valve damage throughout the leg veins; it is a single, structural point of compression higher up in the pelvis. That is why symptoms tend to be isolated to one leg, and why standard vein treatments may not resolve the underlying issue without addressing that compression directly.
Left untreated, the reduced blood flow can lead to DVT — a blood clot in the deep veins of the leg. DVT carries serious risks, including pulmonary embolism if a clot breaks free and travels to the lungs. Recognizing one-sided leg swelling with May-Thurner Syndrome early is one of the most important steps you can take.
Diagnosis and When to See Vascular Doctors
A general practitioner may not immediately identify May-Thurner Syndrome, particularly if leg swelling is attributed to lifestyle factors. Vascular doctors — specialists in the circulatory system — are best equipped to investigate structural causes of venous obstruction.
Diagnosis typically involves:
- Duplex ultrasound to assess blood flow and identify areas of restriction
- CT venography or MRI venography to visualize the iliac vein and confirm compression
- Intravascular ultrasound (IVUS), which provides a detailed cross-sectional view of the vein and is considered the gold standard for diagnosing this condition
If your leg swelling is persistent, affects only one side, or is accompanied by pain, warmth, or redness, reaching out to vascular doctors sooner rather than later is the right move. Early diagnosis leads to a wider range of treatment options and reduces the risk of clot formation.
Treatment Options
The good news is that May-Thurner Syndrome is treatable. A vascular clinic can offer targeted interventions that address the compression directly, rather than managing symptoms alone.
Common treatment approaches include:
- Anticoagulation therapy to reduce clot risk, particularly when DVT is present or suspected
- Catheter-directed thrombolysis to dissolve existing clots and restore flow
- Venoplasty and stenting, in which a small stent is placed in the iliac vein to hold it open and prevent recompression — this is the most widely used definitive treatment for May-Thurner Syndrome.
- Compression therapy to support venous return and manage swelling during and after treatment
Treatment is tailored to each patient based on severity, symptoms, and overall vascular health. A vascular clinic with experience in venous disease will assess your specific anatomy before recommending a plan.
Take the First Step Through Our Department
Swelling in one leg is your body communicating that something needs attention. You do not have to wait until symptoms become severe to seek care.
Our vascular team provides comprehensive evaluation and treatment for conditions like May-Thurner Syndrome. Whether you are experiencing new symptoms or have been dealing with unexplained leg swelling for months, our vascular doctors are here to help you find answers. Reach out today by calling 1-347-384-5690 or visiting us at 1797 Pitkin Avenue, Brooklyn, New York 11212 to schedule a consultation.
