A Prolonged Presentation of May-Thurner Syndrome With Extensive Deep Vein Thrombosis.

An 18-year-old female presented to the emergency department with progressive bilateral lower extremity pain and swelling. She reported a two-week history of back pain radiating down both legs, initially treated with steroids and muscle relaxants without improvement. Initial imaging, including an MRI and hip X-rays, was unremarkable. She subsequently developed worsening left leg swelling, prompting further evaluation for deep vein thrombosis (DVT). She had no history of oral contraceptive use, recent travel, surgery, or prolonged immobility. A family history of "thick blood" in her mother and aunt raised concerns for an underlying hypercoagulable state. Physical examination revealed diffuse bilateral leg swelling with warmth and erythema. A venous duplex ultrasound confirmed extensive left lower extremity DVT, which was further characterized on CT as extending from the common femoral vein through the iliac veins and infrarenal inferior vena cava. Imaging also identified compression of the left common iliac vein by the right common iliac artery, consistent with May-Thurner Syndrome (MTS). Management included systemic anticoagulation, catheter-directed thrombolysis, venous stenting, and Inferior Vena Cava (IVC) filter placement. This case highlights the importance of recognizing MTS as a potential cause of unprovoked DVT in young patients, emphasizing the need for early diagnosis and intervention to prevent long-term complications.