Colorectal cancer Quiz: Ace Your Exams

A 66-year-old woman presents to her primary care physician for a routine checkup. She has been feeling tired over the past few months. She also reports constipation which is new for her. She has not had abdominal pain, nausea, or vomiting. Past medical history is significant for type 2 diabetes managed with metformin and a hysterectomy 10 years ago for fibroids. Family history is significant for colon cancer in her maternal aunt at the age of 71. Her temperature is 36.5°C (97.7°F), blood pressure is 128/80 mm Hg, pulse is 76/min, respiratory rate is 15/min, and oxygen saturation is 98% on room air. Physical examination reveals pale conjunctiva and unremarkable abdominal findings. Digital rectal examination shows no hemorrhoids or anal fissures. Laboratory studies show a hemoglobin level of 10.2 g/dL, and an MCV of 71 fl. Iron studies indicate low serum iron, low ferritin, and increased total iron-binding capacity. Which of the following is the best next step in management?