May-Thurner Syndrome (MTS), also known as iliac vein compression syndrome, was diagnosed in this patient.  The patient presented with left lower extremity pain, swelling, and edema, consistent with chronic venous insufficiency.  Symptoms included persistent aching and heaviness in the left leg, exacerbated by prolonged standing or sitting.  Physical examination revealed left leg edema, dilated superficial veins, and mild tenderness to palpation along the iliofemoral venous segment.  Duplex ultrasound of the left lower extremity demonstrated compression of the left common iliac vein by the overlying right common iliac artery, confirming the diagnosis of May-Thurner Syndrome.  Differential diagnoses considered included deep vein thrombosis (DVT), chronic venous insufficiency (CVI) without compression, and lymphedema.  DVT was ruled out by the absence of an acute thrombus on ultrasound.  The patient's symptoms and imaging findings were most consistent with May-Thurner Syndrome.  Treatment plan includes conservative management with compression stockings and leg elevation.  Endovascular intervention, such as iliac vein stenting, will be considered if conservative measures fail to provide adequate symptom relief.  Patient education regarding the pathophysiology of May-Thurner Syndrome, risk factors, and treatment options was provided.  Follow-up appointment scheduled in four weeks to assess treatment response and discuss further management if necessary.  ICD-10 code I87.2, Compression of vein, unspecified, is documented for this encounter.