A 67-year-old man with history of hypertension and diabetes presented with progressive left leg swelling and calf discomfort. He denied any recent trauma, major surgery, or periods of immobility. He initially attributed the discomfort to an increase in his exercise routine. However, after it persisted despite a hiatus from exercise, he presented to his Primary Care Physician. A venous ultrasound was performed and documented left popliteal DVT (Fig. 10.1). The patient was treated with rivaroxaban 15 mg orally twice daily for 3 weeks and then 20 mg daily thereafter for a total of 6 months of anticoagulation. Six months after discontinuing rivaroxaban, he developed recurrent left leg swelling and discomfort this time involving the whole lower extremity. Again, he noted no recent trauma, major surgery, or immobility. The pain was so severe that the patient was having difficulty ambulating. He presented to the Emergency Department where he was noted to have a tender and tensely edematous left thigh and calf. Venous ultrasound demonstrated new left common femoral and femoral deep vein thrombosis (Figs. 10.2 and 10.3). Because of the severity of his symptoms, Vascular Medicine was consulted and recommended catheter-directed fibrinolysis. The patient noted marked improvement in his lower extremity symptoms following overnight catheter-based fibrinolysis. May-Thurner compression was not observed on repeat venography the following day. He was restarted on rivaroxaban 15 mg twice daily for 3 weeks followed 20 mg daily thereafter. He was referred to Vascular Medicine clinic after hospital discharge to determine the optimal duration of anticoagulation. His Vascular Medicine physician recommended extended duration anticoagulation with rivaroxaban 20 mg daily because of the patient’s recurrent unprovoked DVTs and high risk for recurrence.