This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Small & Large Intestine, Subject name: Surgery
[{'content': "A 60-year-old man complains of recurrent attacks of painless rectal bleeding. Colonoscopy reveals normal mucosa between the cecum and the anal verge. What is the most helpful test to determine the cause of bleeding? \nSelect and explain. \nA. Angiography to look for angiodysplasia, B. Technetium scan for Meckel's diverticulum, C. Upper GI endoscopy for peptic ulcer, D. Small-bowel series for tumor", 'role': 'user'}, {'content': "Answer: A \nExplanation: A common cause of lower GI bleeding that is recurrent and painless is angiodysplasia of the colon. In the absence of diverticula or hemorrhoids, the suspicion is even higher for these lesions. Peptic ulcer and Meckel's diverticulum can cause predominantly lower GI bleeding. However, the bleeding is usually in the form of melena rather than bright red.", 'role': 'assistant'}]