In normal anatomy, blood flows through the deep veins of the leg, into the pelvis, and then to the heart. Sometimes, however, the deep vein in the left leg, called the left common iliac vein, is pushed into the vertebra behind it by the big pelvic artery that crosses over it. This compression can cause the vein to narrow, and this is called May-Thurner Syndrome (MTS). A slight narrowing of the vein may produce no symptoms at all because there are a number of bypassing veins in the area that can take over and transport the blood. If major narrowing occurs, however, the individual is at increased risk for deep vein thrombosis (DVT) in the left leg.

When DVT occurs, blood cannot flow through the vein as quickly as needed. This causes blood to pool in the vein and a blood clot may form. DVT itself is not life threatening, but if the blood clot breaks free and travels into the lungs it can become quite dangerous.

While MTS itself does not present obvious symptoms, it is often diagnosed when people present symptoms of DVT in their left leg. Those symptoms include swelling, pain or tenderness, a feeling of increased warmth, redness or discoloration of the skin, or vein enlargement.

It’s important to consult a physician if you are experiencing May Thurner Syndrom symptoms. As stated above, DVT can cause serious discomfort and potentially serious complications if left untreated.