Pyloric stenosis is a narrowing of the pylorus, the opening from the stomach into the small intestine. This article describes the condition in infants.
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 exact 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. Other risk factors include certain antibiotics, too much acid in the first part of the small intestine (duodenum), and certain diseases a baby is born with, such as diabetes.
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:
- Abdominal pain
- Constant hunger
- 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
- Swollen belly
- Olive-shaped mass when feeling the upper belly, which is the abnormal pylorus
Ultrasound of the abdomen may be the first imaging test. Other tests that may be done include:
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.
If pyloric stenosis isn't treated, a baby won't get enough nutrition and fluid, and can become underweight and dehydrated.
When to Contact a Medical Professional
Call your health care provider if your baby has symptoms of this condition.
Congenital hypertrophic pyloric stenosis; Infantile hypertrophic pyloric stenosis; Gastric outlet obstruction; Vomiting - pyloric stenosis
Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM. Pyloric stenosis and other congenital anomalies of the stomach. In: Kliegman RM, St Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 355.
Seifarth FG, Soldes OS. Congenital anomalies and surgical disorders of the stomach. In: Wyllie R, Hyams JS, Kay M, eds. Pediatric Gastrointestinal and Liver Disease. 5th ed. Philadelphia, PA: Elsevier; 2016:chap 25.
Review Date 8/7/2019
Updated by: Neil K. Kaneshiro, MD, MHA, Clinical Professor of Pediatrics, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.