This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Medicine
[{'content': 'A 75-year old woman with chronic atrial fibrillation presented to the hospital with a 2-day of colicky abdominal pain. The physical examination revealed hypoactive bowel sounds and diffuse abdomina tenderness. Laboratory tests showed a white cell count of 19,400 per cubic millimeter with 92 /o neutrophils, a blood urea nitrogen level of 42 mg per deciliter (15 jimol per liter) and a syrum creatinine level of 3.0 mg per deciliter (267 per liter). The common cause for this problem would be- \nSelect and explain. \nA. Occlusion of the poal vein, B. Occlusion of the superior mesenteric vessel, C. Occlusion of the inferior mesenteric vessel, D. Perforation of the duodenum back.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Acute occlusion of the superior mesenteric aery (SMA) causes extensive bowel necrosis, resulting in a poor prognosis with an extremely high moality rate. As a result, the residual thrombus disappeared and all branches of the SMA became well visualized. Ref Davidson 23rd edition pg 790', 'role': 'assistant'}]