Bloody diarrhea years after resection of a rib

A 32-year-old man presented with bloody diarrhea of new onset. For three days he had had 10 to l5 bowel movements per day containing bright red blood. He also had had one black, tarry stool, but no fever, chills, nausea, vomiting, or constipation. Upper gastrointestinal endoscopy revealed acute gastritis, and colonoscopy was interpreted as unremarkable; he was then transferred to our institution for further workup.