You have a 1 month old male admitted to the PICU with severe protein-calorie malnutrition and infant failure to thrive. The mother reports that the infant vomits within 1 hour of every feed and is hungry after. The child's front fontanelle is depressed, and the skin tents when pulled up. Upon abdominal assessment, you can see a mass in the ULQ and visible peristalsis.
Which of the following diagnoses would you expect for this child?
Select one of the following: