Congenital hypertrophic pyloric stenosis

**Definition:** A not uncommon congenital malformation of the stomach of unknown cause in which there is hypertrophy and hyperplasia of the circular muscle of the pylorus. Symptoms of gastric outlet obstruction usually appear between the third and sixth weeks of life. The anomaly is manifested by intermittent vomiting (which increases in frequency and becomes projectile), regurgitation, weight loss, dehydration, electrolyte imbalance, sometimes a small palpable pyloric mass, and visible peristaltic contractions across the epigastrium; there may also be jaundice. Some cases appear to be familial (possibly of autosomal dominant inheritance).