May-Thurner syndrome refers to a chronic compression of the left common iliac vein (CIV) against the lumbar vertebrae by the overlying right common iliac artery (CIA), with or without deep venous thrombosis 2.
Although both left and right CIVs lie deep to the right common iliac artery, the left CIV has a more transverse course and is predisposed to compression whereas the right CIV ascends more vertically and is therefore not similarly predisposed.
The presence of a spur, possibly from injury to the vein endothelium from the arterial pulsations, predisposes to the development of deep vein thrombosis (DVT) and differentiates this condition from bland DVT.
Cadaveric and CT studies show a prevalence of ~25% in the population 7. A predilection for this disorder is seen in young women in their 2nd to 4th decades, usually after prolonged immobilisation or pregnancy.
Patients can present with unilateral (left) lower extremity oedema and pain.
Portal venous or venographic phase is used for assessment and allows visualisation of the site and extent at the compression point.
Treatment and prognosis
Because of the high prevalence of asymptomatic iliac vein compression, follow up is not necessary unless the patient is symptomatic from the process.
First-line treatment is with thrombolysis and stenting 2, which removes the clot and relieves the compression to prevent recurrence.
History and etymology
It is named after R May and J Thurner who initially described the phenomenon anatomically in 1957 4,5. It was then clinically described by FB Cockett and M Lea Thomas in 1965 11.
In imaging modalities where cross-sectional anatomy is difficult to appreciate, the differential includes
- iliac vein compression from some other source (e.g. occult pelvic mass/lymph node)
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