May-Thurner Syndrome and Its Possible Influence on Pulmonary Embolism Severity: A Case Report.

The management of recurrent venous thromboembolism requires a high index of suspicion for underlying structural anomalies such as May-Thurner syndrome (MTS). Although the prothrombotic consequences of venous compression are well established, its influence on embolization dynamics has not been clearly defined. We report the case of a 38-year-old female with recurrent left-sided iliofemoral deep vein thrombosis (DVT) who presented with progressive calf pain without cardiopulmonary symptoms. Venous Doppler ultrasound demonstrated extensive thrombosis of the iliac, femoral, popliteal, and tibial veins. Pulmonary computed tomography angiography (CTA) revealed a clinically silent distal pulmonary embolism (PE). Abdominal CTA, using a triple-phase acquisition protocol, showed an 80% diameter stenosis of the left common iliac vein due to compression by the right common iliac artery, consistent with MTS. Thrombophilia testing was negative. The patient was treated successfully with oral anticoagulation and graduated compression stockings (GCS) as she declined endovascular stenting. This case confirms the established association between MTS and recurrent left-sided thrombosis. It also raises the theoretical possibility that severe iliac vein stenosis could modulate embolus size through altered venous flow dynamics. However, this hypothesis remains speculative and requires confirmation in mechanistic and epidemiologic studies.