Hypertrophic Pyloric Stenosis
Nonbilious projectile emesis between weeks of life 2–5 with hypochloremic, hypokalemic metabolic alkalosis is the cardinal feature of hypertrophic pyloric stenosis (HPS). The vomiting often happens soon after feeding, with the child continuing to act hungry and appearing vigorous without fevers. The health of the child at presentation can vary widely due to hydration status, from well appearing to lethargic and severely dehydrated. Not uncommonly, children present with HPS relatively late in the disease course after changes in feedings or formulas have been made with the thought that the emesis was secondary to feed intolerance or reflux.