Pyloric Stenosis

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Pyloric Stenosis

Topic Overview

What is pyloric stenosis?

Pyloric stenosis is a problem with a baby’s stomach that causes forceful vomiting. It happens when the baby's pylorus, which connects the stomach and the small intestine, swells and thickens. This can keep food from moving into the intestine.

A baby may get pyloric stenosis any time between birth and 5 months of age. It usually starts about 3 weeks after birth. If your baby was born early (premature), symptoms may start later.

See a picture of pyloric stenosis.

What causes pyloric stenosis?

Experts don't know what causes pyloric stenosis. It may be passed down through families.

What are the symptoms?

The main symptom of pyloric stenosis is throwing up (vomiting) all or most of feedings. Vomiting usually starts gradually. As the pylorus becomes tighter over time, your baby's vomiting will become more forceful. If your baby keeps vomiting, he or she can become dehydrated. If your baby's vomit is yellow or green, he or she may have a more serious problem than pyloric stenosis.

Call your doctor if your baby is vomiting yellow or green liquid or has signs of pyloric stenosis. A baby with pyloric stenosis:

  • Throws up formula or breast milk shortly after a feeding.
  • Has a swollen upper belly after a feeding.
  • Acts fussy and hungry, even right after being fed.
  • Has fewer wet diapers and fewer, harder stools.

How is pyloric stenosis diagnosed?

Your doctor will do a physical examination and ask you about your baby's symptoms. Your baby may need imaging tests, such as an upper gastrointestinal (UGI) series or an abdominal ultrasound. Your baby also may need blood tests to see if he or she is dehydrated.

How is it treated?

Pyloric stenosis is treated with surgery to widen the opening between the stomach and the small intestine. Your baby likely will be ready to go home within 2 days after surgery. Almost all babies recover completely. After surgery, your baby probably won't get pyloric stenosis again.

Frequently Asked Questions

Learning about pyloric stenosis:

Being diagnosed:

Getting treatment:

Ongoing concerns:


Vomiting all or most of feedings on a repeated basis is the main symptom of pyloric stenosis. Vomiting usually begins between a few days after birth and 5 months of age. But if your baby was premature, the start of symptoms may be delayed.

Vomiting caused by pyloric stenosis usually starts gradually and gets worse over time. As the pylorus, the connection between your baby's stomach and intestine, becomes tighter, the vomiting becomes more frequent and more forceful (projectile vomiting). Your baby likely has a problem different from pyloric stenosis if his or her vomit is yellow or green.

A baby with pyloric stenosis:

  • Vomits formula or breast milk shortly after a feeding.
  • Has a full (distended) upper belly after a feeding.
  • Acts irritable and hungry.
  • Has fewer and harder stools (constipation) than normal.
  • Passes smaller amounts of urine than normal.

As the vomiting continues, your baby will:

  • Lose weight.
  • Develop symptoms of not getting enough fluids (dehydration).
  • Be sleepier than normal and very fussy when awake.

When to call a doctor

Call your doctor if your baby:

  • Has vomited most or all of his or her feeding for two feedings in a row.
  • Is vomiting yellow or green liquid (bile). This could indicate a problem more serious than pyloric stenosis.
  • Has symptoms of dehydration.
  • Is 5 months of age or younger and has symptoms of pyloric stenosis, such as repeated forceful vomiting shortly after feedings, irritability, hunger, and less urine.

Examinations and Tests

Pyloric stenosis is diagnosed by a physical examination and your baby's medical history and symptoms. An upper gastrointestinal (UGI) series or an abdominal ultrasound can be used to diagnose pyloric stenosis.

During the physical examination, the doctor will check your baby's belly for:

  • A wave-like motion shortly after feeding and before vomiting.
  • An olive-sized lump between the stomach and the intestine. Your doctor feels for this lump in the upper part of your baby's belly.

The doctor will also examine your baby for signs of dehydration. Blood tests may be done to check for dehydration.

Treatment Overview

Pyloric stenosis is always treated with surgery (pyloromyotomy). After your baby has the surgery, pyloric stenosis usually will not develop again.

Types of surgery

Two methods of surgery are used to correct pyloric stenosis—open surgery and laparoscopic surgery. Your doctor will choose which one is best for your baby.

  • During open surgery, a small incision is made in the baby's abdominal wall. The ring of muscle (pyloric sphincter) is then cut to widen the channel between the stomach and the intestine.
  • During laparoscopic surgery, an instrument called a laparoscope is inserted through a small incision made in the baby's belly button. The laparoscope provides access to the pyloric muscle so the muscle can be cut. Several other small incisions are usually needed.

Before surgery

Your baby may not go to surgery immediately after being diagnosed with pyloric stenosis. If your baby is dehydrated, he or she may need to receive fluids through a vein (intravenous, or IV) for 24 to 48 hours. Another tube may be put through your baby's nose to drain fluids from the stomach (nasogastric tube).

After surgery

After surgery, your baby may be fed fluids with electrolytes for one or two feedings and then formula or breast milk within 24 hours. Your baby likely will go home within 2 days after surgery.

It is normal for a baby to vomit a small amount during the first day or two after surgery. But if your baby continues to vomit after you return home, call your doctor. In some cases, persistent vomiting indicates an incomplete cutting of the pyloric muscle.

Complications from surgery (which may include infection at the incision site) are rare. A red or raised incision, with or without drainage, may indicate an infection.

Home Treatment

After surgery for pyloric stenosis

While your baby is in the hospital for pyloric stenosis, be actively involved in his or her care so that you will feel more comfortable doing it on your own after you take your baby home. Don't be afraid of holding or handling your baby. After your baby has one or two feedings of fluid with electrolytes, breast milk or formula is usually okay.

When your baby comes home from the hospital, give small, frequent feedings, according to your doctor's instructions. Your baby may vomit occasionally for the first few days after surgery. If vomiting is frequent or persistent (lasts beyond 2 to 3 days after surgery), call your doctor.

Complications from surgery to correct pyloric stenosis are rare. But call your doctor if you are concerned about the wound healing properly. A red or raised incision, with or without drainage, may indicate an infection.

Other Places To Get Help


Canadian Association of Gastroenterology
1540 Cornwall Road
Suite 224
Oakville, ON  L6J 7W5
Phone: 1-888-780-0007
(905) 829-2504
Fax: (905) 829-0242
Web Address:

The Canadian Association of Gastroenterology (CAG) provides educational information and supports research about digestive health and disease.

Canadian Paediatric Society
2305 Saint Laurent Boulevard
Ottawa, ON  K1G 4J8
Phone: (613) 526-9397
Fax: (613) 526-3332
Web Address:

The Canadian Paediatric Society (CPS) promotes quality health care for Canadian children and establishes guidelines for paediatric care. The organization offers educational materials on a variety of topics, including information on immunizations, pregnancy, safety issues, and teen health.

KidsHealth for Parents, Children, and Teens
4600 Touchton Road East, Building 200
Suite 500
Jacksonville, FL  32246
Phone: (904) 232-4100
Fax: (904) 232-4125
Web Address:

This Web site is sponsored by Nemours Foundation. It has a wide range of information about children's health, from allergies and diseases to normal growth and development (birth to adolescence). This Web site offers separate areas for kids, teens, and parents, each providing age-appropriate information that the child or parent can understand. You can sign up to get weekly e-mails about your area of interest.


Other Works Consulted

  • Middlesworth W, Kadenhe-Chiweshe A (2006). Neonatal intestinal obstruction. In FD Burg et al., eds., Current Pediatric Therapy, 18th ed., pp. 289–293. Philadelphia: Saunders Elsevier.
  • Russo MA, Redel CA (2006). Anatomy, histology, embryology, and developmental anomalies of the stomach and duodenum. In M Feldman et al., eds., Sleisenger and Fordtran's Gastrointestinal and Liver Disease, 8th ed., vol. 1, pp. 981–998. Philadelphia: Saunders Elsevier.
  • Safford SD, et al. (2005). A study of 11,003 patients with hypertrophic pyloric stenosis and the association between surgeon and hospital volume and outcomes. Journal of Pediatric Surgery, 40(6): 967–973.
  • Wegner KJ (2006). Pyloric stenosis. In MR Dambro, ed., Griffith's 5-Minute Clinical Consult, pp. 940–941. Philadelphia: Lippincott Williams and Wilkins.


By Healthwise Staff
Primary Medical Reviewer Susan C. Kim, MD - Pediatrics
Primary Medical Reviewer Donald Sproule, MD, CM, CCFP, FCFP - Family Medicine
Specialist Medical Reviewer Brad W. Warner, MD - Pediatric Surgery
Last Revised February 10, 2010

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