This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gastro Intestinal System, Subject name: Pediatrics
[{'content': 'A three week old infant presented in the paediatric outpatient department having non bilious vomiting; which is projectile in nature. O/E child is found to be slightly dehydrated. A vigorous peristaltic wave was seen to move from left hypochondrium to umbilicus after feeding. The most likely diagnosis in the infant is: \nSelect and explain. \nA. Pyloric stenosis, B. Abdominal Tuberculosis, C. Gastro-esophageal reflux disease, D. Cyclical vomiting', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. A. Pyloric stenosisThis is a classical presentation of Idiopathic HPS. It is the most common surgical disorder of gastrointestinal tract in infants.This disorder is 4-6 times more common in boys than girls. In 75-80% of affected infants, a firm olive shaped mass is palpable in the medgastrium. USG abdomen is the diagnostic investigation and shows muscle thickness of >4mm & pylorus length>16mm.', 'role': 'assistant'}]