Pyloric stenosis

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at July 26, 2016
StartDiseasesPyloric stenosis

The pylorus is a muscular valve located between the stomach and the small intestine. It typically holds food in the stomach until it is ready to move into the small intestine for the next step in the digestive process. However, when an infant has pyloric stenosis, food cannot move from the stomach to the small intestine, causing significant problems. Fortunately, this condition can be cured.


Definition & Facts

Pyloric stenosis is an uncommon condition affecting infants. While food is typically held in the stomach by the pylorus before it travels to the small intestine for the next step in the digestive process, in pyloric stenosis, the muscles of the pylorus become abnormally large and thicken, blocking food from being able to pass to the small intestine. While pyloric stenosis can have some serious medical complications, surgery cures the condition.

Symptoms & Complaints

Pyloric stenosis is typically not present at birth. Symptoms usually develop between three to five weeks of age, and the condition is rare in infants three months of age or older.

Vomiting after eating is common for babies who have pyloric stenosis. The vomiting may be mild initially and may become more severe over time as the opening of the pylorus narrows.

The baby may also projectile vomit, spewing milk up to many feet away. The vomit may contain blood at times as well. Babies will often appear to be hungry shortly after vomiting. 

The baby may have stomach contractions before he vomits. One may observe wave-like contractions that move across the infant's abdomen shortly after he eats. These contractions are caused by the stomach muscles attempting to force food through the pylorus. 

Babies with pyloric stenosis may become constipated because food is unable to move to the intestines. In addition, babies with pyloric stenosis may not gain weight. Sometimes weight loss can even occur.

Dehydration may also occur with pyloric stenosis. Signs of dehydration in infants include crying without tears, lethargy, urine that is darker or smells stronger than usual, and dry lips, dry skin, and dry mouth. Parents of dehydrated babies may also find themselves changing fewer wet diapers.

When dehydration becomes severe, an infant may have sunken eyes; hands and feet that look splotchy and feel cold; sunken fontanelles (the soft spots on an infant's head); or be excessively fussy or sleepy

Pyloric stenosis can lead to some medical complications. For instance, frequent vomiting can lead to dehydration and an electrolyte imbalance. Electrolytes serve important functions in the human body. For example, sodium regulates the amount of water in the body and helps maintain proper functioning of the muscular system and central nervous systems.

Potassium is essential for heartbeat regulation and muscle function. Too much or too little potassium can lead to irregular heartbeat, which can be fatal. Babies with pyloric stenosis may also fail to grow and develop normally. Though rare, bilirubin, a substance secreted by the liver, may build up in the body, causing yellowing of the skin and eyes (jaundice). 


The exact cause of the condition is unknown. However, experts believe that both genetic factors and environmental factors play a role in the development of pyloric stenosis. There are some known factors that put an infant at risk for developing the condition.

Males, especially firstborn children, are more likely to develop pyloric stenosis than females. Additionally, the condition develops more often in premature babies than in full-term infants. The condition is also more common in Caucasians of north Eastern descent, less common among African-Americans, and rare in Asians. 

Some studies have found that infants who are bottle fed are more likely to develop pyloric stenosis than those who are breastfed. However, most of the babies in the studies were bottle fed with formula rather than breast milk, so it isn't clear whether the increased risk for the condition is due to being bottle fed or being fed formula

Infants who take certain antibiotics in their first weeks of life are also at higher risk of developing the condition. Additionally, infants born to mothers who were on antibiotics in late pregnancy are at higher risk of getting pyloric stenosis.

Babies who are born to mothers who smoked during their pregnancies are nearly twice as likely to develop pyloric stenosis than those who are born to non-smoking mothers. A family history of the condition also puts infants at higher risk of developing pyloric stenosis. 

Diagnosis & Tests

Parents who notice signs of pyloric stenosis in their infants should take them to the doctor. The doctor will initially perform a physical examination on the infant. Sometimes an olive-shaped lump indicating an enlarged pylorus can be felt during an examination. A doctor may recommend other tests to confirm a diagnosis of pyloric stenosis.

Blood tests may be ordered to check for an electrolyte imbalance and dehydration. An ultrasound can be utilized to look at the pylorus to confirm a diagnosis of the condition. Finally, a doctor may order X-rays of an infant's digestive system if an ultrasound cannot definitively diagnose pyloric stenosis. 

Treatment & Therapy

Surgery is the cure for pyloric stenosis. In a pyloromyotomy, a surgeon cuts through the outside layer of the pylorus muscle, which allows the inner lining to bulge out. This opens a channel to allow food to pass from the stomach to the small intestine. A pyloromyotomy can usually be done as a minimally invasive surgery, which requires a smaller incision and has a quicker recovery period than traditional surgery. 

A pyloromyotomy is typically scheduled for the same day a diagnosis of pyloric stenosis is made. An infant who is dehydrated or has an electrolyte imbalance will receive fluids before surgery is done. A baby may also receive intravenous fluids following surgery until she can eat again, which is usually 12 to 24 hours after the procedure. Vomiting may persist for a few days after a pyloromyotomy, but this is normal. 

As with any surgery, there are risks with a pyloromyotomy. Specifically, bleeding or infection may occur. However, complications with this surgery are unusual, and pyloromyotomies generally have good results. 

Prevention & Prophylaxis

There is no consensus on how to prevent pyloric stenosis. Preventative approaches involve early detection to address and ultimately cure the problem.

Pregnant women or new mothers should absolutely refrain from smoking and the use of tobacco for a variety of health reasons, and to the extent that smoking during pregnancy or while breastfeeding may increase the risk of pyloric stenosis, this commonsense measure may also reduce the risk of the child having pyloric stenosis.

Pregnant mothers should also exercise caution about taking antibiotics. Azithromycin and erythromycin while taken during pregnancy are associated with an increased risk of an infant developing pyloric stenosis.