A 3 week-old male infant presented to the emergency department with a chief complaint of vomiting for 3-4 days. His mother stated that the vomiting has gotten progressively worse and now seems to "shoot out of his mouth." The emesis always occurs after feeding, sometimes vomiting the entire volume of his feed. The vomitus is non-bilious and non-bloody. After vomiting, the infant remains hungry and is still eager to feed. He is exclusively bottle fed with formula. There is no history of fever, URI symptoms, or diarrhea.
He is less active than normal. He is making fewer wet diapers and less stool than usual. There is no history of trauma or recent travel. There are no ill contacts. Physical Exam: VS T 37.0, P 170, R 50, BP 80/50, O2 saturation 99% on RA. Length is 54 cm (50th percentile) and weight is 3.6 kg (25th percentile; previously 50th) and head circumference is 37 cm…
