Review Question - QID 214531

A 38-year-old woman presents to the emergency department for progressively worsening right leg pain and swelling over the course of 2 days. She denies any trauma to the leg and reports to be otherwise healthy. She has no past medical history and currently takes a daily multivitamin and oral contraceptive pill. She smokes approximately 1 pack of cigarettes per week and works as a commercial truck driver. On physical examination, the right lower extremity is warm and tender with evidence of pitting edema up to the knee. There is no pain elicited with passive dorsiflexion of the right foot. The left lower extremity is normal. Compression ultrasonography with Doppler is performed, which demonstrates non-compressibility up to the right popliteal vein. Which of the following is the most appropriate treatment for this patient?