Pyloric stenosis is a narrowing of the pylorus, the opening of the stomach into the small intestine.

Pyloric stenosis is caused by a thickening of the muscles of the pylorus. This thickening prevents the stomach from emptying into the small intestine.

The cause of the thickening is unknown, although genetic factors may play a role. Pyloric stenosis occurs more commonly in boys than in girls, and is rare in patients older than 6 months. The condition is usually diagnosed by the time a child is 6 months old.

Symptoms generally appear several weeks after birth:

• Vomiting
  • Usually mild at first
  • Becomes more forceful within 30 minutes of feeding
  • Projectile vomiting
• Infant appears constantly hungry
• Diarrhea (loose green stools)
• Wave-like motion of the abdomen shortly after feeding and just before vomiting occurs
• Dehydration (becoming more profound with the severity of the vomiting)
• Failure to gain weight or weight loss
• Abdominal fullness prematurely after meals
• Belching
• Abdominal pain

Physical examination may show signs of dehydration. The infant may have a distended abdomen. Palpation of the abdomen may reveal the abnormal pylorus, which feels like an olive-shaped mass.

• Chemistry panel often reveals electrolyte imbalances.
• Ultrasound of abdomen may be the first imaging test performed.
• Barium x-ray reveals a distended stomach and narrowed pylorus.