Normally, food passes easily from the stomach into the first part of the small intestine through a valve called the pylorus. With pyloric stenosis, the muscles of the pylorus are thickened. This prevents the stomach from emptying into the small intestine.
The cause of the thickening is unknown. Genes may play a role, since children of parents who had pyloric stenosis are more likely to have this condition.
Pyloric stenosis occurs most often in infants younger than 6 months. It is more common in boys than in girls.
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 appear several weeks after birth and may include:
Dehydration (gets worse as vomiting gets worse)
Failure to gain weight or weight loss
Wave-like motion of the abdomen shortly after feeding and just before vomiting occurs
Exams and Tests
The condition is usually diagnosed before the baby is 6 months old.
A physical exam may reveal:
Signs of dehydration, such as dry skin and mouth, less tearing when crying, and dry diapers
Olive-shaped mass when feeling the upper belly, which is the abnormal pylorus
Treatment for pyloric stenosis involves surgery to widen the pylorus. The surgery is called pyloromyotomy.
If putting the infant to sleep for surgery is not safe, a device called an endoscope with a tiny balloon at the end is used. The balloon is inflated to widen the pylorus.
In infants who cannot have surgery, tube feeding or medicine to relax the pylorus is tried.
Surgery usually relieves all symptoms. As soon as several hours after surgery, the infant can start small, frequent feedings.
When to Contact a Medical Professional
Call your health care provider if your baby has symptoms of this condition.
Hunter AK, Liacouras CA. Pyloric stenosis and congenital anomalies of the stomach. In: Kliegman RM, Stanton BF, St. Geme JW III, et al., eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, Pa: Elsevier Saunders; 2011: chap 321.
Pandya S, Heiss K. Pyloric stenosis in pediatric surgery. Surg Clin N Am. 2012;92:527-553.
Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.