A 15-year-old girl with history of Raynaud's disease and insulin-resistant diabetes mellitus presents with one day of acute left leg pain. The patient's mother noted progressive asymmetric increase in size of the left leg with discoloration and inability to bear weight.
Gray-scale and color Doppler sonography of the left common femoral vein/greater saphenous vein junction demonstrated normal compressibility and color flow. Spectral tracing, however, demonstrated diminished respiratory phasicity, which suggested a more central venous thrombus that is not visualized on the current examination. (Images 1 and 2.)
Selected images from a pelvic MRI, including an axial T2 SPAIR, coronal and axial T1 fat sat post-contrast images, demonstrated complete occlusion of the left common iliac vein extending into the external iliac and common femoral veins. The right common iliac artery crosses and compresses the left common iliac vein, resulting in a mechanical obstruction. (Images 3-5.)
Repeat left lower extremity gray scale and color Doppler sonography demonstrated rapid progression of clot burden, now with noncompressibility of the left common femoral vein/greater saphenous vein junction as well as complete lack of color flow in the left common femoral vein, corresponding to the MRI findings. (Images 6-7.)
The patient was diagnosed with May-Thurner syndrome (MTS), which is extrinsic compression of the left common iliac vein between the right common iliac artery and lumbar vertebrae. The true incidence of MTS is unknown because the majority of the cases may be subclinical and asymptomatic. Symptomatic MTS results from subsequent formation of iliofemoral venous thrombosis, and accounts for two to three percent of all lower extremity deep venous thromboses. The most common symptoms are unilateral lower extremity swelling, pain, and aching, which may be acute or chronic in etiology.
Prolonged disease may eventually result in post-thrombotic syndrome, including venous stasis and skin ulcers. It is most commonly described in young women with persistent left lower leg edema. Definitive diagnosis relies on characteristic imaging findings demonstrating compression of the left common iliac vein by the overlying and crossing right common iliac artery as well as deep venous thrombus in the common iliac vein. Ultrasound diagnosis may be difficult because direct visualization of the common iliac veins is often not possible. Loss of respiratory phasicity in the common femoral vein may help infer the presence of a nonvisualized and more central venous thrombus. Direct venography as well as contrast-enhanced computed tomography and MRI will provide better visualization of the pelvic venous anatomy as well as intraluminal filling defects that would suggest the presence of thrombus.
Patients with May-Thurner syndrome may be discharged with these instructions:
- In acute symptomatic cases, treatment goals are to prevent pulmonary embolism and post-thrombotic syndrome and to restore venous return to preserve venous function.
- Standard treatment involves anticoagulation therapy and mechanical thrombectomy combined with balloon venoplasty and stenting. After stenting, patients generally require at least six months of anticoagulation to prevent in-stent thrombus formation.
- Consider this diagnosis in all young patients with unilateral unexplained left lower extremity pain or swelling.
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