A 6-week-old infant is brought to see his GP as he is suffering from more frequent episodes of projectile vomiting. His mother is nervous as she has not had any other children and he appears to be hungry immediately after vomiting unaltered milk

b. This is a case of pyloric stenosis. It is most common in first born males and most frequently occurs between the ages of 2 and 10 weeks. Vomiting is characteristically projectile in nature with progressive dehydration and constipation. The vomiting is unaltered food and in severe cases a hypochloraemic acidosis may be seen. On examination a palpable mass in the epigastrium may represent the thickening of the pylorus – it is most easily felt during a feed. The diagnosis can be confirmed on ultrasound scan and surgical management is necessary to relieve the obstruction.