This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Colon and Rectum - Benign Colonic Disorders, Subject name: Surgery
[{'content': 'Commonest site for volvulus is? \nSelect and explain. \nA. Caecum, B. Stomach, C. Proximal jejunum, D. Sigmoid colon', 'role': 'user'}, {'content': 'Answer: D \nExplanation: ANSWER: (D) Sigmoid colonREF: Schwarz 8th ed p-1098, Sutton\'s 7th ed p-677, Sabiston 16th ed p-1422, Maingot\'s 10deg\' ed p-1404"Most common site of volvulous is the colon. In colon sigmoid colon is the most common site of volvulous"Volvulous:Twisting of one segment of intestine on an axis formed by its mesentry # Results in partial of complete intestinal obstructionPlain radiography of volvulous shows :Large inverted U shaped loop of massively distended sigmoid colon emerging from the pelvis, k/a bent inner tube sign or coffee bean sign.Absence of haustraApex of loop under diaphragmContrast with gastrografhn showrs bird of prey or bird\'s beak sign', 'role': 'assistant'}]