This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T, Subject name: Anatomy
[{'content': 'False about gallstone ileus \nSelect and explain. \nA. 90% patients give history of biliary disease, B. Causes 1% of all SBO ; around 25% cases in >70 years, C. Tumbling obstruction, D. Fistula is mostly formed between duodenum and gallbladder', 'role': 'user'}, {'content': "Answer: A \nExplanation: Option B: Rigler's triad - Classic plain abdominal film of triad of small bowel obstruction, pneumobilia & ectopic gallstone Option C: pain may be episodic and recurrent as the impacted stone temporarily obstructs the bowel lumen and then dislodges and moves distally, known as tumbling obstruction Option D: most common site of biliary enteric fistula is gallbladder and duodenum So opting for option A. Ref: Sabiston 20th edition Pgno : 1506-1507", 'role': 'assistant'}]