This document discusses infantile hypertrophic pyloric stenosis (IHPS), a condition where the pylorus becomes thickened and obstructed. It presents in infants 2-8 weeks old with projectile vomiting. Risk factors include being male and a firstborn. Diagnosis involves physical exam finding an olive-sized mass and testing for metabolic alkalosis. Treatment is typically pyloromyotomy surgery to divide the thickened muscle. Post-op care focuses on rehydration and monitoring for complications like apnea.