In this anomaly there is marked hypertrophy of the circular muscle of the pyloric canal, resulting in marked reduction of its lumen. The infant appears normal at birth. However, two to three hours after feeding, the stomach contents are ejected with considerable force (projectile vomiting). Congenital pyloric stenosis is a very common anomaly; the incidence is 1 in 350 live
births and 80% of the affected children are males.The condition can be treated surgically by making a longitudinal incision through the hypertrophied muscle fibers.