Persistent Left Lower Extremity Swelling as a Presentation of May‐Thurner Syndrome After Deep Vein Thrombosis: A Case Report and Literature Review

May‐Thurner syndrome (MTS) is an anatomic variant where the right common iliac artery compresses the left common iliac vein against the lumbar spine. This chronic pulsation promotes intimal fibrosis and venous spur formation, increasing the risk of deep vein thrombosis (DVT) and post‐thrombotic syndrome (PTS). Despite an estimated anatomical prevalence of 22%–24% in asymptomatic individuals, MTS remains an underdiagnosed cause of unilateral left leg symptoms, often due to reliance on initial ultrasound alone which may miss iliac vein pathology. We present the case of a 60‐year‐old female with a history of left lower extremity DVT who presented with recurrent swelling and pain. Despite initial point‐of‐care ultrasound suggesting MTS but showing no acute DVT, subsequent computed tomography (CT) confirmed both MTS and thrombosis in the left external iliac and common femoral veins (CFVs). She was successfully managed with anticoagulation. This case corroborates literature findings that a high index of suspicion and timely cross‐sectional imaging are crucial. MTS should be considered in patients with unexplained unilateral left leg swelling, regardless of initial ultrasound findings, to prevent long‐term complications.