May-Thurner Syndrome Presenting as Extensive Left Iliofemoral Deep-vein Thrombosis with Inferior Vena Cava Extension Following Lower Limb Fracture Fixation: A Computed Tomography Venography.

May-Thurner syndrome is an anatomical condition in which the left common iliac vein is compressed between the right common iliac artery anteriorly and the lumbar spine posteriorly, predisposing to predominantly left-sided deep-vein thrombosis (DVT). It is frequently subclinical and typically becomes evident only at the time of a thrombotic event, often with a disproportionately extensive thrombus burden. We report the case of a 32-year-old male who developed acute swelling and pitting edema of the left lower limb approximately 18 days after intramedullary nail fixation of a left femoral shaft fracture. Doppler ultrasonography confirmed DVT and computed tomography (CT) lower limb angiography and venography were subsequently performed. Imaging demonstrated focal compression of the proximal left common iliac vein between the right common iliac artery and the L4 vertebral body, with extensive thrombosis of the entire left deep venous system from the pelvis to the calf and a small nonocclusive mural thrombus in the inferior vena cava. The arterial study was unremarkable. Management comprised therapeutic anticoagulation, catheter-directed mechanical thrombectomy, balloon angioplasty, and endovascular iliac vein stenting. Follow-up CT venography at 1 month confirmed the complete resolution of thrombus with a patent stent. This case demonstrates the value of CT venography in defining both the extent of thrombosis and the underlying anatomical predisposing factor in a single examination, directly informing a combined endovascular management strategy.