What is the most characteristic of congenital hypertrophic pyloric stenosis -

Option (a) HPS classically presents in a firstborn male child between 3 and 6 weeks of age. However, children outside this age range also are commonly seen, and the disease is not restricted to either male or first borne children. Option (d) After vomiting the child has a voracious appetite, that leads to a cycle of feeding and vomiting. Option (c) "Greater awareness of pyloric stenosis has led to earlier identification of patients with fewer instances of chronic malnutrition and severe dehydration" -Nelson 17/e Option (b) The diagnosis of pyloric stenosis is usually made by palpation - of the typical olive shaped hard pyloric mass located in the right upper quadrant. In healthy infants when palpation is difficult, feeding can help in the diagnosis. After feeding, gastric peristalsis waves may be visible. After the infant vomits, the abdominal musculature is more relaxed and the mass is easier to palpate. Sedation can also be used to facilitate examination but is usually unnecessary. In cases of doubt, ultrasound can confirm the diagnosis.