Colorado Rep. Lauren Boebert has announced that she underwent emergency surgery and was diagnosed with a rare condition called May-Turner syndrome.

The 37-year-old Republican congresswoman was admitted to UCHealth Medical Center of the Rockies in Loveland, Colorado, after doctors detected an acute blood clot in her leg with a CT scan and diagnosed May-Turner syndrome (MTS), says the New York Post. The condition disrupts blood flow. Doctors operated to remove the blood clot and inserted a stent to restore blood flow.

MTS is a rare vascular disorder in which the right artery compresses the left iliac vein in the pelvis, blocking off blood flow from the leg back to the heart, according to UPMC. The effect is like stepping on a hose, says the Cleveland Clinic. Experts are not sure why this happens.

In Boebert’s case, her campaign says “dehydration, travel, and extended periods of sitting” were identified as potential factors, says the Post.

When the left iliac vein is compressed, it is difficult for blood to flow freely through it. According to StatPearls, MTS accounts for only 2% to 5% of all patients presenting with deep vein thrombosis, or DVT. However, multiple autopsy studies have shown that the actual prevalence of the syndrome is as high as 14% to 32% in the general population. Despite the high prevalence, MTS remains clinically silent in most patients.

Very often there are no symptoms, but sufferers can develop DVT or potentially life-threatening blood clots in the leg. Boebert noticed swelling in her upper leg, which prompted the congresswoman to seek medical help.

Sometimes the syndrome causes discolored skin on the leg, or swollen, enlarged veins. It could trigger pain, throbbing or tenderness in the leg as well as swelling and feelings of heaviness. MTS appears to affect more women than men and is more common in adults ages 20 to 50.

While iliac vein compression can affect one in five people, a formal diagnosis of MTS is rare. It’s diagnosed with CT scans, MRIs, ultrasounds and venograms that use a contrast dye into veins with x-rays following the blood flow through the veins.

Surgeons treat the syndrome with angioplasty and stenting to keep the vein open and may perform bypass surgery to build a new route around the compressed portion of the vein. Another surgical technique could be to remove the right artery to reduce compression on the left iliac vein.

If you have DVT due to MTS, doctors may prescribe oral blood thinners to help break up the clots, clot busting medication delivered though a catheter to dissolve the clots or insert a vena cava filter into the large vein that takes blood to your heart that traps clots, so they don’t travel to the lungs.

The main concern of MTS, says the Cleveland Clinic, is DVT. If a blood clot in your legs breaks off and travels to your lungs, it’s called a pulmonary embolism and is a life-threatening emergency. The prognosis with MTS is good, with many people living long, healthy lives with the disorder.