May Thurner Syndrome (MTS), also known as Iliac Vein Compression Syndrome, is caused by the right iliac artery squeezing the left iliac vein. Both blood vessels are located in the pelvis, and the iliac arteries start as a fork at the base of the aorta.
MTS increases the risk of deep vein thrombosis (DVT) in the left leg. DVT is a blood clot that can impede blood flow in the vein. While the blood clot by itself is not life-threatening, a piece can break off and travel through the bloodstream. If it ends up in a blood vessel in the lungs, it can cause a pulmonary embolism, which is potentially lethal.
What are the Symptoms of May Thurner Syndrome?
May-Thurner Syndrome can be difficult to diagnose because it does not always produce symptoms, even if the iliac vein is markedly compressed. Some people aren’t diagnosed until they develop DVT. In such cases, smaller veins called collaterals that bypass the blocked area grow larger and drain the blood from the blocked vein.
In severe cases, the patient can develop chronic venous insufficiency. Such people have painful swollen legs. If the patient has a DVT, their leg will be painful and swollen, and the pain will be similar to that of a cramp or Charley horse. Their skin will be red or purple and feel warm.
Other patients may feel pain in the abdomen or pelvis or pain in the leg that worsens as the day progresses. They may also develop varicose veins, especially in the upper left leg.
How is May Thurner Syndrome Diagnosed?
In many cases, MST isn’t diagnosed until the patient has developed DVT. It is usually diagnosed through imaging studies of the pelvis or lower back. In ultrasound imaging, the doctor uses soundwaves to create an image of veins and look for blood clots.
The patient may have to fast about 8 to 12 hours beforehand, since undigested food can block the soundwaves and thus interfere with the image. The technician will apply a lubricating jelly to the patient’s skin which helps transmit the soundwaves and prevents friction. He will then rub the ultrasound transducer over the skin, and it will send soundwaves through the patient’s body.
The soundwaves echo when they hit something solid like a bone or organ, and a computer records the echoes. The whole procedure usually takes about 30 minutes.
In Magnetic Resonance Imaging (MRI) or Computed Tomography (CT) scans, the machines create images that enable the doctor to spot blood clots and determine if the iliac vein is being compressed.
During an MRI or CT scan, the patient lies on a motorized bed in a tube containing a scanner. They will have to stay still while being scanned, so the images don’t come out blurry.
In a venogram or phlebogram, the doctor injects a dye into a foot vein to make the blood flow visible. He will then X-ray the relevant area and measure the blood flow there. He will also look for signs of blood clots and compression of the iliac vein.