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': 'Which among the following is not a ultrasound feature of Congenital Hypertrophic Pyloric Stenosis? \nSelect and explain. \nA. 95% sensitivity by ultrasound, B. Thickness of pylorus > 4mm, C. Canal length > 16mm, D. High gastric residue', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ultrasound is the investigation of choice. It can diagnose BPS accurately in 95% of patients.\nCriteria for ultrasound diagnosis of HPS:\n\nchannel length of > 16mm\npyloric thickness of > 4mm\n\n"The diagnosis of pyloric stenosis usually can be made on physical examination by palpation of the typical "olive" in the right upper quadrant and the presence of visible gastric waves on the abdomen. When the olive cannot be palpated, ultrasonography can diagnose the condition accurately in 95% of patients. Criteria for ultrasonographic diagnosis include a channel length of >16 mm and pyloric thickness of >4 mm."- Schwartz', 'role': 'assistant'}]