This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
[{'content': 'A 50 year old male known case of ulcerative colitis presents with distention of the abdomen of acute onset with vomiting. The next investigation would be \nSelect and explain. \nA. Abdominal X ray, B. USG, C. CT scan, D. MRI abdomen', 'role': 'user'}, {'content': "Answer: A \nExplanation: Answer- A. Abdominal X rayToxic megacolon is defined as a transverse colon with a diameter of more than 5.0 to 6.0 cm with loss ofhaustration.Although usually associated with ulcerative colitis, toxic megacolon can also be seen in Crohn's disease.Plain abdominal railiographs are essmtial for the iliagnosk and management of toxic megacolon (toxic colitis)", 'role': 'assistant'}]