Which of the following is most characteristic of congenital hyperophic pyloric stenosis?

Congenital hyperophic pyloric stenosis is more common in first born males.Symptoms usually sta after 3 weeks of age.Nonbilious vomiting is the initial symptom. After vomiting, the infant becomes hungry and wants to feed again.The metabolic disturbance is hypochloremic metabolic alkalosis.Clinical diagnosis is by palpation of hyperophic mass, confirmed by USG.The surgical procedure of choice is Ramstedt pylorotomy.Ref: Nelson 17th/e p1229