Review Question - QID 214221

A 50-year-old man presents to the emergency room with a 1-month history of diarrhea. He is originally from Puerto Rico but moved the US 15 years ago. He reports occasional bright red blood in his stools for the past 3 weeks. He denies any nausea, vomiting, constipation, or pain with bowel movements at this time. He does report mild abdominal pain and has noticed that his clothes seem to be fitting more loosely during the last month. He has never seen a primary care doctor and admits to using IV drugs for the past 5 years. His only other trip to the hospital was 3 years ago for painful bloody bowel movements, which were attributed to hemorrhoids and treated with over the counter medications. His temperature is 100.1°F (37.8°C), blood pressure is 130/70 mmHg, pulse is 70/min, and respirations are 14/min. On exam, he appears thin with temporal wasting. His ophthalmic exam is notable for the findings in Figure A. He has mild, generalized abdominal pain to palpation with no rebound tenderness. Rectal exam is significant for bloody stool in the rectal vault. The remainder of the exam is unremarkable. Routine labs are sent, and a colonoscopy is scheduled for biopsy. Which of the following is the most likely diagnosis?