What is May-Thurner Syndrome?
May-Thurner Syndrome (MTS), also known as Iliac Vein Compression Syndrome, is a rare but potentially serious condition that affects the veins in the pelvis. This condition occurs when the left iliac vein is compressed or squeezed by the adjacent right iliac artery, potentially causing back-pressure in the leg. This condition was first described in 1851 by Drs. May and Thurner, hence the long-winded name. It is somewhat an obscure disease in the medical community and is thought to be under-diagnosed and under-treated.
What causes May-Thurner Syndrome?
In human anatomy, major pelvic veins called the iliac veins serve as the major highways for blood to return from the legs back to the heart. These veins naturally sit between your spine and your arteries. A small amount of vein compression by these adjacent structures is to be expected and is perfectly normal, and we typically see this effect more on the left side. However, this “natural” compression can be more exaggerated in some individuals. When a person develops symptoms from it, the diagnosis of the syndrome is made. Although the left leg is most commonly affected, the right leg or even both legs can be involved.
Illustration of May-Thurner Syndrome
What are the symptoms of May-Thurner Syndrome?
The symptoms of May-Thurner Syndrome can range widely from mild discomfort to severe blood clots. Many patients present with one-sided leg pain and swelling for many years despite having a history of negative or missed workup by doctors. Some patients develop varicose veins, chronic venous insufficiency, and skin pigmentations and ulcers from the chronic back pressure. In more extreme cases, the “bottleneck” effect of the compression can limit blood flow to the point of stagnation, causing blood to congeal and clot, resulting in an iliofemoral deep vein thrombosis (DVT). In practice, we frequently see MTS-driven DVT in the setting of acute illness and trauma, where heightened body stress causes the blood to thicken and exacerbate the flow limiting effect of the iliac vein compression.
Who is at risk for May-Thurner Syndrome?
MTS is more common in women than men and often presents in individuals between the ages of 20 and 50.
How to Diagnose May-Thurner Syndrome?
May-Thurner Syndrome can be diagnosed in a number of ways. Patients who have leg swelling issues tend to start with venous ultrasound of the leg. While venous ultrasound infrequently looks at the iliac vein directly, the downstream effects on the leg can be assessed and can guide the physician to the next step. CT or MRI scan of the abdomen and pelvis are good ways to look at the iliac veins and are probably the most popular studies to look for May-Thurner Syndrome. The gold standard diagnostic test for MTS is formal venography with intravascular ultrasound, which is a procedure performed by the physician. This is discussed next.
What are the Treatments for May-Thurner Syndrome?
Fortunately, vascular surgeons today are highly educated on the topic and have a number of tools to help patients with this condition. Most vascular surgeons will start the patient on compression stockings to help reduce swelling non-invasively. There are a number of procedures and techniques available to correct the physical compression of the iliac vein. Most physicians:
- Start with diagnostic venogram, where a large IV is inserted in the leg vein and imaging is performed live by the physician. This is usually done with a combination of IV contrast injection and specialized ultrasound probe called intravascular ultrasound (IVUS).
- If there are any blood clots in the veins, the surgeon will use a number of methods to clear the clots. These techniques include dripping clot-busting medication into the vein, suction removal of the clots, or dragging a clot retrieval device across the blockage.
- Once the clot is cleared, your surgeon may choose to place a stent in the vein to open up the narrowing.
- In rare cases where above techniques do not work, surgical bypass around the blockage may be offered.
May-Thurner Syndrome with Left Iliac Stents
This is an example of a May-Thurner Syndrome affecting a female patient in her 80s. She presented with left leg swelling and non-healing skin ulcers. A diagnostic venogram in the cath lab confirmed left common to external iliac vein compression. She was treated with several stents in the left iliac vein. Her leg swelling improved drastically and her skin ulcers healed quickly after.
May-Thurner Syndrome with Bilateral Iliac Stents
This is a more extensive version of May-Thurner Syndrome. A female patient in her 20s suffered from left leg swelling and blood clots, which causes significant functional limitations. Venogram imaging demonstrated occlusions of both iliac systems with small amount of blood through venous collaterals. We treated this by declotting both iliac veins and placing stents into the inferior vena cava (IVC) in a kissing fashion. The patient had excellent resolution of swelling and is leading a normal lifestyle.