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Hypertrophic Pyloric Stenosis

Hypertrophic pyloric stenosis (HPS) is a narrowing of the lower portion of the stomach 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. These muscles are referred to as the pylorus. As a result, a blockage occurs, making food difficult to move into the intestine for digestion and leading to persistent vomiting. The vomiting ultimately leads to dehydration, malnutrition, and electrolyte disturbances, all of which are especially serious in an infant.

HPS is a disease found in newborns with an incidence that varies from one in 300 to one in 900 live births. This makes HPS one of the most common conditions in newborns that requires the need for surgery. Symptoms of HPS in infants generally present anywhere between the second week of life to two months old. However, it is possible for HPS to occur at any time up until six months old. Rare cases have been reported throughout childhood and into adult life. Throughout the world, HPS appears to be less common in Africans, African-Americans and Asians. It is most commonly found in Caucasians of northern European descent. HPS is more common in infants with blood types B and O.

What Causes HPS?

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 of 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. Nothing can be done to prevent HPS from occurring.

What Are the Symptoms of HPS?

Symptoms begin as mild vomiting that gradually worsens. With time, the emesis becomes more frequent and forceful (often described as "projectile"). After vomiting episodes, 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. Dehydration can cause infants to sleep an excessive amount, have a lack of energy, and the inability to release tears when crying. They also will begin to lose weight and fail to thrive because they are not getting enough fluids or nutrition because of the blockage. The infant will experience less bowel movements since they are not getting proper nutrients in their system. Constipation is also a symptom of HPS. 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.

How Is HPS Diagnosed?

The enlarged muscle, commonly referred to as the "olive", can be felt by the surgeon on clinical exam in about 75 to 90 percent of infants with HPS. If the "olive" cannot be felt or the diagnosis needs confirmation, a physician may order an ultrasound. An ultrasound will reveal how thick the pyloric muscle is and how long it is as well. 

If for some reason, the ultrasound is not conclusive, another x-ray called an upper gastrointestinal study (UGI) may be done. A UGI takes a look at the esophagus, stomach, and the small intestine. It will show if the contents of the stomach are not emptying at the usual pace and can tell if the pylorus is narrowing.

Blood tests must also be checked to determine the presence and severity of dehydration and to guide fluid and electrolyte replacement. These results are critical in order to determine the timing of the infant’s surgery and safety for general anesthesia. 

How Is HPS Treated?

HPS can be treated in two stages. The treatment generally starts with intravenous fluids given to the infant to rebalance the body's normal chemistry. This treats the extreme dehydration and loss of nutrients the infant has experienced. 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. Laparoscopic surgery minimizes scarring for the infant. The chance of potential infections decreases and less recovery time is needed.

Most infants can be operated upon within 24 hours of admission. Once a pyloromyotomy is performed, food can begin to digest properly again.

What Is the Follow-up Care for After Surgery?

Doctors will administer a pain medication into the incision by injection. This medication allows the infant to remain pain-free for six to eight hours after the surgery. After that, acetaminophen is given for the pain. The incision will need to be kept clean and dry for two to three days after the surgery. A surgeon will provide instructions on how to care for the incision.

The infant can start feeding again within two hours after the surgery. Only small amounts of liquid will be given to start and gradually increase over the next 48 hours. Once the infant can digest the average amount of liquid for their weight, they will be discharged from the hospital.

Vomiting is common after surgery and may continue for 24 to 48 hours post-surgery. For some infants, vomiting may continue for up to five days until their gastrointestinal tract has settled down. A doctor can prescribe an antacid if the vomiting continues frequently for a long period of time.

What Are the Long-term Effects of HPS?

Infants tolerate pyloromyotomy very well. There are no long-term effects. Recurrence of HPS is extremely rare with only a one percent chance. The rare baby with recurrent pyloric stenosis is still expected to have a normal gastro-intestinal tract long term, but may need additional surgery or nutritional therapy to recover.