This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gastrointestinal tract, Subject name: Pediatrics
A 6 year old boy presenting with palpable abdominal mass in the epigastrium. The clinical diagnosis is (There is no bile in vomitus) ? 
Select and explain. 
A. Duodenal Atresia, B. Choledochal cyst, C. Pyloric stenosis, D. Oesophageal Atresia
C: Pyloric stenosis
Answer: C: Pyloric stenosis 
Explanation: Features of pyloric stenosis : non bilious vomiting malnutrition,dehydration,hypochloremic alkalosis constipation is common peristaltic waves moving from left hypochondrium to umbilicus is visible a small mass due to pyloric thickening palpable in the transpyloric plane on the right side. Ref : ESSENTIAL PEDIATRICS,O.P.GHAI,PG NO:253,7 th edition