Pyloric stenosis

Pyloric stenosis is an uncommon condition affecting the opening (pylorus) between the stomach and small intestine in infants. The pylorus is a muscular valve that holds food in the stomach until it is ready for the next stage in the digestive process.

In pyloric stenosis, the pylorus muscles thicken, blocking food from entering the baby's small intestine. Pyloric stenosis can lead to forceful vomiting, dehydration and weight loss. Babies with this condition may seem to always be hungry.

Pyloric stenosis can be fixed with surgery.

Symptoms Causes Risk factors Complications

Signs of pyloric stenosis usually appear within three to six weeks after birth. Pyloric stenosis is rare in babies older than age 3 months.

Watch for these signs and symptoms:

  • Projectile vomiting. Pyloric stenosis often causes projectile vomiting — the forceful ejection of milk or formula up to several feet away. Vomiting occurs within 30 minutes after your baby eats. Vomiting may be mild at first and gradually become more severe as the pylorus opening narrows. The vomit may sometimes contain blood.
  • Persistent hunger. Babies who have pyloric stenosis often want to eat soon after vomiting.
  • Stomach contractions. You may notice wave-like contractions (peristalsis) that ripple across your baby's upper abdomen soon after feeding but before vomiting. This is caused by stomach muscles trying to force food through the narrowed pylorus.
  • Dehydration. Your baby may cry without tears or become lethargic. You may find yourself changing fewer wet diapers or diapers that aren't as wet as you expect.
  • Changes in bowel movements. Since pyloric stenosis prevents food from reaching the intestines, babies with this condition may be constipated.
  • Weight problems. Pyloric stenosis can keep a baby from gaining weight, and sometimes can cause weight loss.

When to see a doctor

Contact your baby's doctor if your baby is:

  • Frequently vomiting after feeding
  • Projectile vomiting
  • Less active or seems unusually irritable
  • Urinating much less frequently or is having noticeably fewer bowel movements
  • Not gaining weight, or even losing weight

The causes of pyloric stenosis are unknown, but genetic and environmental factors probably play a role.

Risk factors for pyloric stenosis include:

  • Sex. Pyloric stenosis occurs more often in males than in females.
  • Family history. Studies found higher rates of this disorder among certain families and also among offspring of mothers who had pyloric stenosis.
  • Early antibiotic use. Babies given certain antibiotics, such as erythromycin, in the first weeks of life for whooping cough (pertussis) have an increased risk of pyloric stenosis. In addition, babies born to mothers who were given certain antibiotics in late pregnancy also may have an increased risk of pyloric stenosis.

Pyloric stenosis can lead to:

  • Failure to grow and develop at a normal, healthy rate.
  • Dehydration from frequent vomiting, One effect of dehydration is an electrolyte imbalance. Electrolytes are minerals, such as chloride and potassium, that circulate in the body's fluids to help regulate many vital functions. When a baby loses more fluid from vomiting than he or she takes in from eating, an imbalance of electrolytes eventually occurs.
  • Stomach irritation. Repeated vomiting can irritate your baby's stomach. This irritation may even cause mild bleeding.
  • Jaundice. Rarely, infants who have pyloric stenosis develop a yellowish discoloration of the skin and eyes (jaundice) caused by a buildup of a substance secreted by the liver called bilirubin.
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