Case Presentation:

A 27–year–old African American woman without prior medical history reported 12 h of left lower extremity swelling associated with dull, throbbing pain. Her only daily medication was an oral contraceptive. She had no significant family history, rarely smoked, and denied alcohol or drug use but did recall a recent 8–h auto trip. Vital signs were normal. Her left leg was warm, swollen and erythematous from mid–calf to mid–thigh. Laboratory values were normal except for elevated D–dimer (24.3 mg/L). Right lower extremity ultrasound revealed ileofemoral deep venous thrombosis (DVT). Urgent venography revealed extensive thrombus in the left femoral and iliac veins with proximal compression of the left common iliac vein over the lumbar spine (presumably by the overlying right common iliac artery) consistent with May–Thurner Syndrome (MTS). A 5 French catheter was placed in the left femoral vein and tissue plasminogen activator (tPA), 1 mg/h, was infused over 18 h. Intravenous heparin was then begun and repeat venography 2 days later revealed resolution of the thrombus. A 14 × 40 mm smart stent was then placed in the compressed area of the left common iliac vein to prevent future DVT. Postoperatively, heparin was discontinued and the patient was started on warfarin. Subsequent hypercoagulability work up was unremarkable. She was discharged on long–term warfarin and has had no recurrence of DVT in the ensuing 18 months.

Discussion:

MTS was first described in 1957 as an anatomical variant where the right common iliac artery overrides the left common iliac vein, compressing the vein against the lumbar spine, predisposing to left ileofemoral DVT. The prevalence of MTS is unknown and likely underestimated because many patients with this anatomy are asymptomatic. Retrospective reviews of cadaveric studies and CT images revealed MTS in 22–24% of the population. The prevalence of MTS may also help to explain the predominance of left sided DVT (55.9%). MTS most commonly occurs in women (aged 25–50) and is manifested clinically by signs and symptoms of DVT. Ultrasound visualization of the high pelvic area may be difficult so contrast venography or MRI should be used if MTS is suspected. Both techniques allow identification of thrombus in that location and may show left common iliac compression by an overriding right common iliac artery. DVT associated with MTS tends to be recurrent and responds poorly to treatment with anticoagulation alone. Successful treatment typically requires catheter–directed thrombolytics and intravascular stenting. After stent deployment, oral anticoagulation for a minimum of 6 months is recommended.

Conclusions:

Although oral contraceptive use and prolonged recent travel have been traditionally implicated in the pathogenesis of DVT in young women, this case highlights the importance of considering MTS in this population. Successful treatment requires a more aggressive diagnostic and therapeutic approach than standard DVT.