May-Thurner syndrome

The May-Thurner syndrome is the symptomatic compression of the left common iliac vein between the right common iliac artery and the lumbar vertebrae.

The normal anatomy is that the artery which runs to the right leg (= right common iliac artery) lies on top of the vein coming from the left leg (= left common iliac vein). This close proximity leads, in some people, to pressure of the artery onto the vein and to varying degrees of narrowing of the vein. This is referred to as "May Thurner syndrome". It is not a disease but a congenital anatomic variant. Mild and moderate degrees of narrowing are typically asymptomatic. More severe degrees can lead to obstruction of blood flow from the leg and thus to leg swelling and pain. The narrowed vein can also clot, resulting in left leg DVT.

The syndrome is named after the authors R. May and J. Thurner, who first described this phenomenon in 1957. It has also been termed the iliac compression syndrome. It is probably the reason why more DVTs occur in the left than in the right leg.

Compression of the iliac vein has been documented in approximately 50% of patients with left iliac vein thrombosis.

Several surgical treatment strategies have been employed in the past:

1. venous bypass surgery of the narrowed area;
2. cutting of the iliac artery and repositioning of the artery behind the iliac vein;
3. construction of a tissue sling or flap to lift it off the iliac vein;

Since 1995 venous stents have been placed into the narrowed area, to pry them open . Unfortunately, there are no large studies that
(a) investigate the long-term success of the procedure, i.e. how often the stents improve symptoms and remain patent.
(b) whether patients should remain on long-term (lifelong) coumadin (warfarin) or not. Stents appear beneficial at least in the short-term improvement of symptoms, within the first 1-2 years of stent placement .