Monarch Disease Ontology term MONDO_0001560 (hypertrophic pyloric stenosis) is an abnormality characterized by thickening of the muscle in the wall of the pylorus. It results in the narrowing of the pyloric channel. The overlying mucosa may appear hypertrophic as well. Clinical signs and symptoms appear early in life and include projectile vomiting and dehydration. Also known as: IHPS, congenital Hypertrophy of the pylorus, congenital constriction of the pylorus, congenital hypertrophic pyloric stenosis, congenital or infantile stricture of pylorus, congenital pyloric stenosis, congenital stricture of the pylorus, infantile Hypertrophy of the pylorus.