Pyloric stenosis (PS) is characterized by abnormal hypertrophy of the antropyloric muscles, which can progress to gastric outlet obstruction leading to forceful vomiting, dehydration, and hypochloremic, hypokalemic metabolic alkalosis.
Precise etiology is unclear, but risk factors include male sex, preterm birth, maternal smoking, family history of PS (especially in the mother), and early postnatal exposure to macrolides.
Most commonly presents in newborns and infants 3 to 6 weeks of age.
Until late stages of dehydration, most infants are alert, active, and hungry despite frequent emesis.
Management is almost always surgical after correction of electrolyte abnormalities, and postoperative prognosis is excellent.