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Pyloric Stenosis

  • A rare condition in infants in which food cannot move into the small intestine
  • Symptoms include forceful vomiting and a continuing desire to eat
  • Treatment includes surgery to split the pylorus muscle
  • Involves Pediatric Surgery, Pediatric Radiology, and Pediatrics
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Pyloric Stenosis


All babies spit up, so it can be difficult for parents of newborns to know what is normal. But if the vomiting is forceful and occurs after every single meal—and the child is still hungry, or worse, dehydrated—a condition called pyloric stenosis could be the problem.

Pyloric stenosis typically first appears in babies between ages 4 and 6 weeks. The condition is rare, occurring in about 3 out of 1,000 babies born in the United States. The good news, says Yale Medicine’s Michael G. Caty, MD, chief of Pediatric Surgery, is that trained pediatricians, pediatric surgeons and pediatric radiologists can reliably diagnose the condition. In addition, pediatric surgeons are able to offer minimally invasive techniques to cure pyloric stenosis.

“It’s an uncommon condition, but it’s common for us to treat,” Dr. Caty says. “We perform about 20 to 30 surgeries a year.”

Because they do so many of these surgeries, Dr. Caty and his team of pediatric surgeons have gained valuable experience and are highly skilled at the procedure, which is performed laparoscopically (in a minimally invasive way) almost all of the time. 

"I tell families that nobody ever wants their baby to need surgery, but if you have to have a condition that requires an operation, pyloric stenosis is not a bad condition to have. Surgery is profoundly effective," says Daniel Solomon, MD, a pediatric surgeon. "Babies can go home eating normally within one to two days and continue to grow. The vast majority of our babies start eating right in the recovery room."

What is pyloric stenosis?

The pylorus, which means “gate” in Latin, is the lower part of the stomach, forming the connection to the small intestine. The term “stenosis” describes the abnormal narrowing of a channel in the body.

When a baby has pyloric stenosis, the muscles in the pylorus enlarge, causing the opening to the small intestine to narrow. That, in turn, stops food from moving from the stomach into the intestine. Instead, the food comes back up.   

“The so-called projectile vomiting, which goes pretty far out, happens right after eating,” says Dr. Caty,

“Normal” spit-up, which Dr. Caty calls “physiological reflux,” is the result of either gastroesophageal reflux (GERD) or plain old “wet burps”—and doesn’t cause any symptoms. “We call those babies ‘happy spitters,’” says Dr. Caty. “With pyloric stenosis, there is more of it, and it’s much more forceful.” 

Still parents are often at their wits' end, Dr. Solomon says. "One of our deepest instincts as new parents is to feed and nourish our babies, and when a baby is constantly hungry yet throwing up everything they eat, it can be emotionally devastating to parents," he says. "But I reassure them that there is nothing they could have done to prevent it. It's a blockage at the end of the stomach that does not allow feeds through. The best approach to therapy is an operation."

What causes pyloric stenosis?

“Pyloric stenosis is an acquired condition, meaning it happens after birth,” Dr. Caty says. “There is no proven reason or cause, and boys are at a slightly higher risk for it. It does seem to have forms of inheritance. And possibly something environmental contributes to it.” 

What are the symptoms of pyloric stenosis?

The signature symptom of pyloric stenosis is forceful vomiting, which may travel several feet across a room. The vomit may look curdled, because it stayed in the stomach, where there is acid, and never made it to the small intestine.

“We almost always see it between 4 to 6 weeks of age,” Dr. Caty says. “The vomiting becomes more forceful, and then it becomes everything that the baby eats. Plus, the baby is still hungry afterward. Usually, if you have a stomach bug, when you are throwing up, you don’t feel well and you don’t want to eat. But that is not the case with pyloric stenosis.”

Another distinguishing factor, Dr. Caty notes, is that pyloric stenosis is not accompanied by diarrhea.

“A point of confusion that general pediatricians need to first work through when a parent brings a child to them is whether it’s a formula allergy, since babies this young don’t have cow’s milk yet,” Dr. Caty says. “So the pediatrician will often have the parents change the formula a few times to see if that helps.” 

How is pyloric stenosis diagnosed?

If a baby with pyloric stenosis is no longer wetting his or her diaper, it’s a serious sign of dehydration that requires immediate medical attention. “At that point, the pediatrician knows to order an abdominal ultrasound, which will show if the muscle is thickened and how long it is,” Dr. Caty says.

Most pediatricians are familiar with the condition and quick to refer the family to specialty care. “There is a sensitivity around pyloric stenosis and it’s readily diagnosed and ultrasound is easily available,” Dr. Caty says. 

How is pyloric stenosis treated?

Once the diagnosis of pyloric stenosis is confirmed via ultrasound, a child will be admitted to the hospital and hooked up to IV fluids to counteract any dehydration.

After any dehydration and electrolyte disturbances are corrected, surgery is scheduled—usually the next day.

The procedure (called pyloromyotomy) can be performed two ways: a traditional, open surgery, or laparoscopically. Either way, a board-certified pediatric anesthesiologist will put the baby to sleep.

Laparoscopic surgery for pyloric stenosis is the preferred method at Yale Medicine. After a small incision is made near the baby’s belly button, a viewing instrument with a camera at the tip (laparoscope) is inserted.

“We make two additional small incisions (3 millimeters) in the left and right upper quadrants of the abdomen and use small instruments to split the pylorus muscle, making sure the lining is left intact,” Dr. Caty says. “It only takes 5 to 10 minutes. Total, with the baby going to sleep and waking up, the procedure takes 30 to 45 minutes.”

As soon as the baby awakens, he or she can eat again. “If the baby is nursing, we first do a few measured feedings by bottle to make sure everything is OK,” Dr. Caty says. “After that, they can return to regular nursing, and they usually go home the next day.” 

What are the risks of surgery?

There are few risks to surgery for pyloric stenosis, but one of them includes tearing of the mucosa—the thin, inner layer of the pyloric muscle. “It’s very rare, but it does happen, probably in less than 1 percent of cases,” Dr. Caty says. “And if it did happen, we would simply stitch the hole up.”

The other risk, he says is something called an “incomplete pyloromyotomy,” which means the child continues to vomit. This can result from areas of muscle remaining that were not divided during the operation. “This is also very rare, and if it happens, we would have to go back in and do another operation to open more of the muscle,” Dr. Caty says.

What stands out about Yale Medicine’s approach to pyloric stenosis?

A distinguishing factor about Yale Medicine’s approach is that the surgery is “almost universally done with laparoscopic repair,” Dr. Caty says. “That means the baby has minimal scarring. And because we are very progressive with our feeding schedule post-surgery, it’s a short length of stay for the child and their family.”

Plus, Dr. Caty adds, “We have full-time, talented pediatric sonographers who perform the ultrasounds,” which leads to fast, accurate diagnoses.

Additionally, at Yale New Haven Children’s Hospital, babies are treated by anesthesiologists, physicians, surgeons and nurse practitioners who are all highly trained to care for children.