A 4-week-old male infant is brought to the clinic because of increasingly frequent vomiting after meals. He had been feeding without any problems for the first 2 weeks of life. The vomit is not bilious. His skin appears yellow. A round, movable mass can be palpated in the epigastrium. What is the most likely etiology of this patient's condition?

Ans. (d) Pyloric stenosis.Pyloric stenosis is a disorder of unknown etiology but appears to have a strong genetic component. Most cases occur in male individuals, in whom pyloric stenosis is about four times as common as in female individuals. Presentation usually involves the development of vomiting after meals that was not present at birth. The vomiting is nonbilious and progresses to projectile vomiting, jaundice occurs in about 10% of cases. An olive-shaped mass may be palpated in the epigastric area in these patients. Such palpation is greatly aided by decompression of the stomach and practice. A barium study shows dilation of the stomach with pyloric channel narrowing. Surgical treatment of this condition involves cutting into the pylorus longitudinally into the muscularis down to but not through the mucosa.Image source- style="font-family: Times New Roman, Times, serif">