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Pyloric Stenosis

Last updated May 6, 2018

Approved by: Krish Tangella MD, MBA, FCAP

BruceBlaus

Pyloric Stenosis is the thickening of the muscle layer of the pyloric region resulting in the narrowing of the pyloric sphincter, which prevents the food from leaving the stomach.


What are the other Names for this Condition? (Also known as/Synonyms)

  • Congenital Hypertrophic Pyloric Stenosis
  • Gastric Outlet Obstruction
  • Infantile Hypertrophic Pyloric Stenosis

What is Pyloric Stenosis? (Definition/Background Information)

  • The pylorus or pyloric canal forms the lower-end of the stomach, connecting to the duodenum (the first part of the small intestine). In this canal, there is a small muscular layer, called the pyloric sphincter, which controls the flow of partially digested food out of the stomach and into the duodenum
  • Pyloric Stenosis is the thickening of the muscle layer of the pyloric region resulting in the narrowing of the pyloric sphincter, which prevents the food from leaving the stomach
  • The condition is congenital in nature and usually seen within the first few months of life. The characteristic signs and symptoms of Pyloric Stenosis are projectile vomiting (vomitus ejected with great force), poor feeding, and dehydration due to loss of fluids
  • The diagnostic method of choice is ultrasonography, along with detailed medical history and physical examination
  • A common complication of Pyloric Stenosis is fluid and electrolyte imbalance that may be very dangerous, because infants are highly vulnerable to even a minor change in their normal fluid and electrolyte balance
  • The treatment of choice is a surgical correction of the pyloric sphincter defect. The prognosis of Pyloric Stenosis with appropriate surgery is excellent

Who gets Pyloric Stenosis? (Age and Sex Distribution)

  • Pyloric Stenosis typically occurs in infants, within the first 3-4 weeks of life
  • It occurs more often in males than in females
  • People of Jewish decent have a higher prevalence of Pyloric Stenosis

What are the Risk Factors for Pyloric Stenosis? (Predisposing Factors)

The risk factors associated with Pyloric Stenosis are

  • Having a positive family history
  • Male gender
  • Jewish decent
  • Exposure to  azithromycin (an antibiotic to treat infections) in the first few weeks of life
  • Infants born to mothers, who are exposed to certain antibiotics in late pregnancy
  • It is seen more frequently in individuals with blood groups type O and B (for reasons unknown)

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Pyloric Stenosis? (Etiology)

  • Currently, the exact cause of Pyloric Stenosis is unknown
  • It is speculated that genetic factors may influence its development

What are the Signs and Symptoms of Pyloric Stenosis?

The signs and symptoms of Pyloric Stenosis include the following:

  • Projectile vomiting: Vomiting that occurs with great force, resulting in the vomitus being thrown to a great distance
  • Poor feeding
  • Burping
  • Weight loss
  • Dehydration that is often observed when the baby produces fewer wet diapers
  • Weakness and lethargy
  • Persistent hunger
  • Changes in bowel movements, such as constipation
  • Waves like motion of the abdomen shortly after feeding
  • Presence of round mass (olive mass) in the upper abdomen

How is Pyloric Stenosis Diagnosed?

The diagnosis of Pyloric Stenosis requires:

  • Physical examination of the infant along with thorough evaluation of history. During physical exam the physician will look for:
    • The presence of a mass in the upper abdomen
    • Waves like movements in the upper abdomen, when the stomach is trying to push its contents down

Specific diagnostic tests for Pyloric Stenosis may include:

  • Ultrasound scan - that shows thickening of the pylorus
  • X-ray of the abdomen using barium contrast: The infant is made to swallow barium and a thinning of the material is seen at the pyloric sphincter. This is called a string sign or railroad track sign

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Pyloric Stenosis?

The possible complications of Pyloric Stenosis are:

  • Weight loss or problems with appropriate weight gain according to age: The child weighs much less than what is expected for a normal growing child
  • Dehydration, which can be severe enough to cause multiple organs to fail
  • Metabolic alkalosis: As acid is lost from the stomach due to vomiting, the body becomes less acidic and more alkaline, resulting in metabolic alkalosis. This can be fatal, if it is not recognized early and treated appropriately
  • Excessive loss of electrolytes due to vomiting, which can result in poor functioning of nervous system and muscular system
  • Severe electrolyte imbalance: This can result in heart arrhythmias that can be fatal, if the condition is not detected and treated early
  • Jaundice (which is yellowing of the skin and eyes) due to improper functioning of the liver. It is a rare complication

How is Pyloric Stenosis Treated?

The treatment of Pyloric Stenosis consists of the following steps:

  • Surgery (pyloromyotomy) is the definitive treatment method of Pyloric Stenosis. During the surgery, an incision is made in the muscle layer, to relieve tension in the pyloric sphincter
  • Correction of fluid and electrolyte imbalance by appropriate intravenous fluid in an hospital setting

How can Pyloric Stenosis be Prevented?

  • Currently, there are no specific methods or guidelines to prevent Pyloric Stenosis, as it may be a genetic condition
  • Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
  • If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
  • Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders

What is the Prognosis of Pyloric Stenosis? (Outcomes/Resolutions)

Pyloric Stenosis has an excellent prognosis with appropriate surgical intervention.

Additional and Relevant Useful Information for Pyloric Stenosis:

  • Pyloric Stenosis can occur within the first 6 months of life. But, it usually presents within the first 3-4 weeks of life and is noticed by the classic sign of projectile vomiting
  • In case of any signs of poor feeding, projectile vomiting with feedings, or weight loss, it is important to seek medical advice, as quickly as possible

What are some Useful Resources for Additional Information?


References and Information Sources used for the Article:


Helpful Peer-Reviewed Medical Articles:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Nov. 3, 2014
Last updated: May 6, 2018