<unk>  (MTS), also known as the iliac vein compression syndrome, is a condition in which compression of the common venous outflow tract of the left lower extremity<unk>  cause discomfort, swelling, pain or clots (deep venous thrombosis) in the iliofemoral veins. Specifically, the problem is due to left common iliac vein compression by the overlying right common iliac artery. This leads to stasis of blood, which predisposes to the formation of blood clots. Uncommon variations of MTS have been described, such as the right common iliac vein getting compressed by the right common iliac artery. In the 21st century the<unk>  definition has been expanded to a broader disease profile known as nonthrombotic iliac vein lesions (NIVL) which can involve both the right and left iliac veins as well as multiple other named venous segments. This syndrome frequently manifests as pain when the limb is dependent (hanging down the edge of a bed/chair) and/or significant swelling of the whole limb.
May–Thurner syndrome
Van Wyk and Grumbach syndrome
Helsmoortel-Van der Aa syndrome
Wells-Jankovic syndrome
Jeavons syndrome
Crome syndrome
Bogart–Bacall syndrome
Keutel syndrome