What Is Pyloric Stenosis?


The pylorus is a muscle present at the end of the stomach before the intestines. It is present between the stomach and the intestines. The pylorus functions as a valve and allows the partly digested food to move from the stomach to the intestines.1 In infants, this valve swells and thus impedes the passage of partly digested food from the stomach to the intestines, resulting in vomiting and dehydration in babies. It is also known as hypertrophic pyloric stenosis. Hypertrophic comes from the swelling that occurs in the pylorus, making the passageway too narrow or congested for liquids such as breast milk or water to go through which leads to vomit and weight loss.2 The word stenosis comes from the narrowing of the opening that connects the stomach to the intestines. This narrowing due to swelling of the pylorus muscle in infants is then called infantile hypertrophic pyloric stenosis. 

Causes of pyloric stenosis

Pyloric stenosis is a multifactorial trait. A multifactorial trait is controlled by several factors including environmental and genetic. In multifactorial inheritance, more than one factor is involved in causing the disease. The chances of the disease are increased in a particular gender. The chances of pyloric stenosis are four times more likely to occur in people assigned male at birth (AMAB) than in people assigned female at birth (AFAB).3 In the literature, no clear cause of infantile hypertrophic pyloric stenosis has been mentioned. It is known that there is nothing that can be done to prevent its occurrence.4 

Signs and symptoms of pyloric stenosis

The following can be the possible signs and symptoms of infantile hypertrophic pyloric stenosis: 

  • Non-bloody, non-bilious vomiting at 4 to 8 weeks of age.5 
  • Initially, it can be possible that vomiting is infrequent. But later on, it turns out to be frequent, after each feeding to the infant.5 
  • Haematemesis of either bright-red flecks or a coffee-ground appearance is sometimes observed.5 
  • If a delay in diagnosis occurs, it causes weight loss, possible dehydration of infants, and malnutrition.5 
  • Irritability.2 
  • Small stools.2 

Management and treatment for pyloric stenosis

When infantile hypertrophic pyloric stenosis occurs in an infant, a surgical procedure is recommended. The surgical procedure lacks complications.5 The only difficult task here is getting the baby ready for surgery. Pyloromyotomy is a surgical procedure used to treat neonates with pyloric stenosis. 

In preoperative management, the following steps are followed: 

  • Fluid balance and electrolyte imbalance are corrected. 
  • The fluid balance correction may take up to 24 hours. But in some cases, the fluid balance of a severely dehydrated patient may take up to several days. 
  • Initially, if recommended, an IV bolus of 0.45 isotonic sodium chloride solution is administered. 
  • The IV therapy is continued until the fluid balance has been corrected, and the infant is ready for the surgery. 
  • To correct metabolic alkalosis, adequate amounts of chloride and potassium are needed. 
  • KCl (unless renal insufficiency is not the concern) and chloride levels are also corrected here. 

The surgical management of infantile hypertrophic pyloric stenosis is as follows: 

  • Ramstedt pyloromyotomy remains the standard procedure to be adopted here. 
  • Laparoscopic pyloromyotomy may also be used. 
  • An endoscopic pyloromyotomy is a simple procedure that can be used. 

The postoperative management is as follows: 

  • IV fluid is maintained until adequate tolerance of the infant to feeding is developed. 
  • Feedings can begin 8 hours after the surgery. 
  • H2 receptor blocker is sometimes given to get benefits. 
  • Persistent vomiting is expectantly treated as it is resolved within 1 to 2 days. 

All these form the management of pyloric stenosis. 

Diagnosis of pyloric stenosis

In a superficial diagnosis, the physician can ask about a child's eating habits. Due to the swelling of the pylorus, an olive-sized lump is felt in your child’s stomach. Another way of diagnosing pyloric stenosis is through blood tests. The blood tests tell us about possible electrolyte imbalance due to frequent vomiting and dehydration.2 

Risk factors

There are many risk factors of pyloric stenosis such as2

  • Gender of the baby: It occurs more in AMAB babies that are firstborn. 
  • Race: It is more prevalent in white babies, particularly of European descent. 
  • Family history: If the parents or anyone in the family has had pyloric stenosis then there are increased chances that the child will also have pyloric stenosis. These chances are up to 15% more likely. If the mother has had pyloric stenosis then the child is 3 times more likely to acquire pyloric stenosis. 
  • Smoking: If the mother has smoked during the pregnancy then the chances of pyloric stenosis are increased in the newborn. 
  • Antibiotics: If the mother has taken antibiotics during the pregnancy then the chances of developing pyloric stenosis are increased in the baby. The baby can also get pyloric stenosis if they were on antibiotics shortly after birth. 


Currently, there are no severe complications involved with the surgery (pyloromyotomy) to treat hypertrophic pyloric stenosis.5 


How common is pyloric stenosis?

Pyloric stenosis is a rare condition. 3 out of 1,000 babies born in the United States suffer from pyloric stenosis. However, the chances of developing pyloric stenosis become three times more likely if the mother had it. Smoking and the intake of certain antibiotics during pregnancy can also cause pyloric stenosis. 

How can I prevent pyloric stenosis?

In the literature, there are no particular causes of pyloric stenosis. Multifactorial inheritance may be the cause of pyloric stenosis where more than one factor is involved in causing the disease. However, it is believed that there is no definite cause of pyloric stenosis and nothing can be done to prevent its occurrence.  

Can older children get pyloric stenosis?

Pyloric stenosis is a characteristic of infants and only in rare cases may an older child get it. However, it occurs predominantly in infants and is thus known as infantile hypertrophic pyloric stenosis. 

When should I see a doctor?

You should see a doctor if your child has an olive-sized lump on the stomach. It is due to the swelling of the pylorus muscle. If your child vomits out the liquid or any feeding and suffers from frequent weight loss, dehydration, and vomiting, you should seek medical assistance from your doctor. 


The pylorus is a muscle present between the stomach and intestines and it functions as a valve. It allows the passage of partly digested food from the stomach to the intestines. In infants, it can swell due to unknown reasons or due to multifactorial inheritance and thus it blocks or narrows the passageway of food from the stomach to the intestine. This results in vomiting and dehydration of the infant. The symptoms of pyloric stenosis are irritability, small stools, weight loss, and dehydration. It can be detected by a physician observing an olive-sized lump on the stomach. The physician can prescribe blood tests that can indicate electrolyte imbalance. This imbalance predominantly results from severe dehydration. In management, preoperative care deals with the correction of the electrolytes that were lost in the dehydration and vomiting of the infant. This management is done for 24 hours and in severe cases it can last up to several days. Once the correction has been made, surgery can proceed which takes up to an hour. There are several variations of the surgery such as Ramstedt, laparoscopic, and endoscopic techniques. Ramstedt is the standard procedure that is commonly followed. These surgical procedures are straightforward and occur without any complications. There are many risk factors such as family history, race, gender, smoking, and antibiotics during pregnancy that can increase the risk of pyloric stenosis in babies.


  1. The Children’s Hospital of Philadelphia. Pyloric stenosis [Internet]. Chop.edu. 2014 [cited 2023 Apr 11]. Available from: https://www.chop.edu/conditions-diseases/pyloric-stenosis
  2. Pyloric stenosis (HPS) [Internet]. Cleveland Clinic. [cited 2023 Apr 11]. Available from: https://my.clevelandclinic.org/health/diseases/4524-pyloric-stenosis-hps
  3. Pyloric stenosis [Internet]. Nationwidechildrens.org. [cited 2023 Apr 11]. Available from: https://www.nationwidechildrens.org/conditions/pyloric-stenosis
  4. Pyloric stenosis | causes, symptoms, diagnosis & treatment [Internet]. Cincinnatichildrens.org. [cited 2023 Apr 11]. Available from: https://www.cincinnatichildrens.org/health/p/pyloric-stenosis
  5. Pediatric hypertrophic pyloric stenosis: practice essentials, background, pathophysiology [Internet]. Medscape.com. 2019 [cited 2023 Apr 11]. Available from: https://emedicine.medscape.com/article/929829-overview?icd=login_success_gg_match_norm
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Syed Sharf ud Din

Doctor of Pharmacy, University of Central Punjab

Syed Sharf ud Din is a fourth-year pharmacy student. While still in pharmacy school, he has vast interests in biopharmaceutics and pharmacy practise. With an ardent skill of writing combined with background of health sciences, he is curating perfectly designed health-related articles for the general public. He aims to continue his skills and interests in the future to contribute to breakthroughs in pharmaceutical sciences.

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