Vomiting is the first symptom in most children:

• Vomiting may occur after every feeding or only after some feedings
• Vomiting usually starts around 3 weeks of age, but may start any time between 1 week and 5 months of age
• Vomiting is forceful (projectile vomiting)
• The infant is hungry after vomiting and wants to feed again

Other symptoms generally appear several weeks after birth and may include:

• Abdominal pain
• Belching
• Constant hunger
• Dehydration (gets worse with the severity of the vomiting)
• Failure to gain weight or weight loss
• Wave-like motion of the abdomen shortly after feeding and just before vomiting occurs

The condition is usually diagnosed before the baby is 6 months old.

A physical exam may reveal signs of dehydration. The infant may have a swollen belly. The doctor may detect the abnormal pylorus, which feels like an olive-shaped mass, when touching the stomach area.

An ultrasound of the abdomen may be the first imaging test performed. Other tests that may be done include:

• Barium x-ray -- reveals a swollen stomach and narrowed pylorus
• Blood chemistry panel -- often reveals an electrolyte imbalance