When a baby starts vomiting repeatedly, especially after feeds, parents become understandably anxious. One possible cause is pyloric stenosis, a condition that affects how milk moves from the stomach into the small intestine.
The name sounds frightening and very medical. The good news is that pyloric stenosis in babies is well understood and treatable. If you know what to look for and how it is managed, it can make a very stressful situation a little less overwhelming.
A typical consultation
Alarm bells ring in my head when a consultation goes something like this:
Doctor: Hello, I am Dr Enrico. How can I help you today?
Parent: It is the strangest thing. My baby started to vomit after feeding a few days ago. At first I thought he had just overfed, but now he is projectile vomiting after almost every feed. Even after vomiting he is hungry again and wants to feed straight away.
Doctor: How old is your baby now?
Parent: My baby is six weeks old.
Doctor: Have you noticed any other symptoms?
Parent: Not really.
Doctor: Ok. Take your baby through to my examination bed and let us have a look.
On examination I might say something like:
“Your baby appears a bit dehydrated, and I can feel a small lump, about the size of an olive, in the upper part of the tummy. Can you see the little ripples moving across your baby’s stomach? That is the peristalsis. In other words, the muscles of the digestive system are contracting and trying to push the milk through. Given your baby’s age, the history you have described, and what I can feel and see, I am concerned that your baby may have pyloric stenosis.”
At this point most parents understandably say:
“Sorry, doctor, I have never heard of pyloric stenosis. What is it?”
What is pyloric stenosis?
Imagine the digestive tract as one long, cleverly designed tube. Milk goes in through the mouth, travels down the throat, into the stomach, then moves into the small intestine and along the rest of the gut, until the waste products are finally passed out as stool.
This journey happens because of muscular contractions in the walls of the digestive tract. The muscles squeeze behind the milk to push it forward, while the muscles in front relax to let the milk move into the next section. This wave-like movement is called peristalsis.
At the end of the stomach, just before the small intestine, there is a circular muscle that acts like a gate. This is called the pylorus. It closes while the stomach is busy digesting the milk, then opens to let the milk pass into the small intestine.
In pyloric stenosis, this pyloric muscle becomes thickened and narrowed. The opening is too tight, so the milk in the stomach cannot pass through properly into the intestine. The stomach tries harder and harder to push the milk through, which leads to the classic projectile vomiting.
To break down the terminology:
Pyloric refers to the pylorus (the muscular opening at the end of the stomach).
Stenosis means narrowing.
You may also hear the term hypertrophic pyloric stenosis. Hypertrophic means thickened. So the full name describes a thickened, narrowed pyloric muscle.
How common is pyloric stenosis in babies?
Pyloric stenosis is not rare. It affects about 1 to 5 babies in every 1 000. It is more common in boys than in girls, with a ratio of roughly four boys for every girl.
Why does age matter?
Pyloric stenosis usually develops between four and eight weeks of age.
Early onset, before this, is uncommon.
It is also unusual to see pyloric stenosis for the first time after three months of age.
So when I hear about a baby of around six weeks with projectile vomiting and constant hunger, pyloric stenosis is high on my list of possibilities.
Typical symptoms of pyloric stenosis
The symptoms often develop over a few days. Parents might notice:
Vomiting that gradually becomes more forceful. At first it may look like simple posseting. Over time it turns into projectile vomiting after feeds.
Baby is still hungry. After vomiting, the baby often wants to feed again enthusiastically because nothing is actually reaching the intestine.
No fever. This helps to distinguish pyloric stenosis from some infections.
Visible movement across the tummy. You may notice wave-like ripples moving across your baby’s stomach. These are the muscles trying to push the milk out of the stomach.
Signs of dehydration if vomiting continues. These may include:
Fewer wet nappies
No tears when crying
Dry mouth
Sunken fontanel
Sunken eyes
Weakness or lethargy
Constipation. If little or no milk reaches the intestine, the bowel movements will decrease.
Poor weight gain or weight loss. A baby who cannot keep feeds down will not grow well.
Not every baby will show all of these signs, but the combination of age, projectile vomiting, ongoing hunger and visible tummy movements is very suggestive.
How is pyloric stenosis diagnosed?
Your doctor will use a combination of history, examination and tests.
1. Physical examination
The first step is a thorough examination.
The doctor will check for signs of dehydration.
They will feel the baby’s tummy to look for a small, firm lump in the region of the pylorus.
They may also watch for visible peristaltic waves.
If the story and examination point strongly toward pyloric stenosis, further tests will be arranged.
2. Ultrasound
An ultrasound is the most common and useful test.
Your baby will go to the radiology department.
A small probe is moved gently over the tummy.
The radiologist will look for a thickened pyloric muscle and a narrowed opening.
If the pylorus is enlarged and narrowed, the diagnosis is confirmed.
3. X-ray studies
X-rays are used less often than ultrasound, but in some cases a contrast study may be done.
The baby drinks a special liquid.
Images are taken in sequence to see if the fluid enters the stomach and then passes into the small intestine.
If the contrast stays in the stomach because it cannot pass the pylorus, this supports the diagnosis of pyloric stenosis.
4. Blood tests
Blood tests may be done to check:
Hydration status
Electrolyte levels (for example sodium, potassium and chloride), which can become abnormal with persistent vomiting
These results can guide fluid management before surgery.
Treatment of pyloric stenosis in babies
Once the diagnosis of pyloric stenosis is made, treatment is necessary. The aim is to relieve the blockage so milk can pass freely from the stomach into the intestine again.
Stabilising your baby
Before any operation, your baby’s hydration and electrolytes need to be corrected.
Your baby will be admitted to hospital.
A drip (intravenous line) will be placed.
Fluids will be given for about 24 to 48 hours, depending on how dehydrated your baby is.
This step is very important. A well hydrated baby is much safer for anaesthetic and surgery.
Surgery: pyloromyotomy
The most effective treatment for pyloric stenosis is surgery, called a pyloromyotomy.
The surgeon usually uses a keyhole (laparoscopic) approach.
Three small incisions are made in the tummy.
A tiny camera goes through one incision, and instruments through the other two.
The surgeon carefully cuts along the length of the thickened pyloric muscle and gently spreads it apart.
This loosens the muscle so that the pylorus can open wider. The lining of the gut remains intact, so the muscle can still open and close, but no longer blocks the passage of milk.
Medication: when surgery is not possible
There is a medicine called atropine sulfate that can sometimes be used to treat pyloric stenosis. However, it is not the preferred option.
Treatment with atropine requires a prolonged hospital stay.
The baby needs a drip for fluids and nutrition for several weeks until the vomiting settles.
Long hospital stays bring their own risks and challenges.
For these reasons, medication is usually only considered if surgery would be too dangerous in a specific baby.
What happens after surgery?
Most babies recover very well after a pyloromyotomy.
Your baby will usually stay in hospital for at least 24 hours after the operation so the team can monitor closely.
Feeding often starts again 12 to 24 hours after surgery. Doctors usually begin with small amounts of clear fluid, then gradually reintroduce milk.
Some babies may still vomit a little in the early days while the stomach settles, but this should improve quickly.
Follow-up appointments are important to:
Check wound healing
Monitor weight gain
Make sure your baby is reaching developmental milestones
Most parents are relieved to see their baby feeding comfortably and gaining weight again.
Final thoughts for parents
Pyloric stenosis can be a difficult diagnosis for parents at first. Before they arrive at the correct diagnosis, many parents try to change formulas or feeding methods because they think their baby has reflux, an allergy or an intolerance.
My advice is to keep the following in mind:
Look at the age of your baby.
Notice the pattern and force of the vomiting.
Watch for visible movement across the tummy.
Pay attention to signs of dehydration and poor weight gain.
Most importantly:
If you are concerned, please seek medical advice.
Pyloric stenosis can lead to severe dehydration and electrolyte imbalances. Over time, it can result in malnutrition if not treated. The reassuring news is that once surgery is performed and your baby is properly hydrated, the condition is unlikely to come back. Most babies return to full feeds and normal growth within a few days.
You know your baby best. If something does not feel right, it is always worth having it checked.
