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Hypertrophic Pyloric Stenosis

Hypertrophic pyloric stenosis (HPS) is a narrowing of the lower portion of the stomach (pylorus) that leads into the small intestine. It is actually an enlargement of the muscles in this area of the stomach that contributes to the narrowing problem, and as a result food, does not move easily into the intestine for digestion.

HPS is a disease of newborns with an incidence of one in 300 to one in 900 live births. Symptoms of HPS in infants generally present between the second or third week of life to 2 months old. Rare cases have been reported throughout childhood and into adult life. It is most commonly found in Caucasians of northern European descent. Throughout the world, HPS appears to be less common in Africans, African Americans and Asians. HPS is more common in infants with blood types B and O.


Despite extensive clinical and laboratory research, the cause of pyloric stenosis remains unknown. Although a genetic predisposition to HPS is suspected, the exact mode of inheritance is unknown. Males are affected four times as often as females, and first born males are at highest risk. A family history is HPS makes it more likely that an infant will have the disorder. When parents (mother or father) have had HPS, it occurs in 5-20% of their male children but in only 3-7% of their female children. 


Symptoms begin as mild vomiting that gradually worsens. With time, the emesis becomes more frequent and forceful (often described as "projectile"). After vomiting epidoses, infants can usually be quieted, but they are obviously hungry. In a small number of cases, the vomitus will be brown or even bloody due to irritation of the esophagus and/or stomach lining.

If not treated promptly, infants become dehydrated, lose weight and fail to thrive because they are not getting enough fluids or nutrition because of the blockage. Gastric secretions contain significant quantities of potassium, hydrogen and chloride.

When the surgeon examines the ill infant, one of the classical findings in HPS is the presence of a nodule about the size of olive that the surgeon can feel while palpating the baby's upper abdomen. This olive-size nodule is in fact the over-developed muscle that surrounds the opening of the channel emptying from the stomach into the intestine.


The enlarged muscle (the "olive") can be felt by the surgeon on clinical exam in about 75 percent to 90 percent of infants with HPS. If the "olive" cannot be felt or the diagnosis is in doubt, your physician may order an ultrasound. 

If for some reason, the ultrasound is not conclusive, another x-ray called an upper gastrointestinal study (UGI) may be done.


The treatment generally starts with intravenous fluids given to the infant to rebalance the body's normal chemistry. Once this is done, an operation called a pyloromyotomy is performed. This procedure loosens the tight musculature blocking the normal passageway from the stomach into the intestine. Most pyloromyotomies at Lurie Children's are performed laparoscopically, through pen-tip sized incisions and tiny instruments.

Most infants can be operated upon within 24 hours of admission.

Long-term Effects

Infants tolerate pyloromyotomy very well. Recurrence of HPS is extremely rare.