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: Medicine
[{'content': 'A posteriorly perforating ulcer in the pyloric antrum of the stomach is most likely to produce initial localized peritonitis or abscess formation in the following: \nSelect and explain. \nA. Omental bursa (lesser sac), B. Greater sac, C. Right subphrenic space, D. Hepato renal space (pouch of Morison)', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Answer is A (Omentum bursa) "Gastric ulcers perforate into the lesser sac, which can be paicularly difficult to diagnose" - Bailey "A gastric ulcer perforates into the lesser sac, then no signs of generalised peritonitis can be seen but misleading symptoms may appear" - Schwaz As can be seen from the figure, a posteriorly perforating ulcer of the stomach will localize in the lesser sac or omental bursa only. (lesser sacis synonymous with omental bursa)', 'role': 'assistant'}]