What is pyloric stenosis?
The pylorus is the muscle that closes the stomach off from the intestine and keeps food in the stomach. Pyloric stenosis is thickening of the pylorus muscle that partly or fully blocks food from passing out of the baby’s stomach into the intestine.
Babies with pyloric stenosis eat well but throw up forcefully soon after eating
Pyloric stenosis usually happens when a baby is 1 or 2 months old
Babies can become dehydrated Dehydration in Children Everyone needs water and certain chemicals (electrolytes) to be healthy. Normally, you drink fluids to meet the need, and being thirsty tells you when you need more fluids. But babies and very... read more (have too little fluid in their bodies) and not get enough nutrients
To tell if your baby has pyloric stenosis, doctors do an ultrasound
Doctors do surgery to cut and loosen the thickened muscle
There's a higher risk of pyloric stenosis in:
Male, first-born babies
Babies whose mothers smoked while pregnant
Babies given specific antibiotics
Babies with family members who had it
What are symptoms of pyloric stenosis?
Babies with pyloric stenosis are hungry, eat well, and then forcefully throw up (projectile vomiting) after eating. Unlike babies who throw up because they're sick, babies with pyloric stenosis want to eat and drink right away after they throw up.
Sometimes, babies throw up so much they:
Lose weight
Usually, babies are still able to absorb liquids enough that they don't become dehydrated. However, they may lose a lot of weight and look very thin before doctors figure out what's wrong.
How can doctors tell if my child has pyloric stenosis?
The doctor may be able to feel a small lump in your baby’s belly. Doctors do an ultrasound Ultrasonography Ultrasonography is a safe imaging test that uses sound waves to create a moving picture of the insides of your body. Ultrasonography doesn't use radiation (x-rays). Ultrasonography is also called... read more 
to be sure your baby has pyloric stenosis.
How do doctors treat pyloric stenosis?
Doctors will:
Give your baby fluids into the vein
Do surgery to cut the muscle that's blocking the stomach so formula or breast milk can move through
Your baby can usually return to eating normally the day after surgery.
