Pyloric stenosis is a condition in infants where the pylorus, a muscle connecting the stomach and the small intestine, thickens abnormally. This thickening creates a blockage, preventing food from moving properly into the small intestine.
Typical Age of Onset and Symptoms
Symptoms of pyloric stenosis typically begin to appear when a baby is between 2 weeks and 6 months old. While it can occur anytime within this window, symptoms most often become noticeable between 3 and 6 weeks of age. It is uncommon for symptoms to manifest in babies older than 3 months.
The main symptom of pyloric stenosis is forceful, projectile vomiting. This vomiting occurs shortly after feeding and does not contain bile. The thickened pylorus prevents food from passing into the small intestine.
Babies with this condition remain hungry and want to feed again after vomiting. As the condition progresses, vomiting becomes more frequent and severe, potentially leading to dehydration and poor weight gain or weight loss. Other signs include visible wavelike stomach contractions across the baby’s belly. Infrequent bowel movements may also occur as little food reaches the intestines.
Understanding Causes and Risk Factors
The exact cause of pyloric stenosis is not fully understood, but genetic and environmental factors play a role. The thickening of the pyloric muscle develops after birth.
Certain factors increase an infant’s likelihood of developing pyloric stenosis. Male infants, particularly first-born boys, are at a higher risk, with the condition being about four times more common in males than females. A family history of pyloric stenosis also increases the risk, with siblings of affected infants having a significantly higher chance of developing the condition.
Other risk factors include being Caucasian. Exposure to certain antibiotics, such as erythromycin or azithromycin, has also been linked to an increased risk. Additionally, bottle-feeding and a mother who smoked during pregnancy are considered potential risk factors.
Diagnosis and Treatment
Diagnosing pyloric stenosis often begins with a physical examination by a healthcare professional, who will inquire about the baby’s symptoms. During the examination, the doctor might feel a firm, non-tender mass in the upper right abdomen, often described as “olive-shaped,” which is the enlarged pyloric muscle. Sometimes, wavelike contractions of the stomach may be visible across the abdomen, especially after a feeding.
The diagnosis is most commonly confirmed with an abdominal ultrasound, which is the preferred imaging method due to its accuracy and non-invasive nature. An ultrasound provides clear images of the pylorus, allowing measurement of its muscle thickness and length. A pyloric muscle thickness of 3 mm or more, and a pyloric length greater than 15 mm, are common diagnostic criteria, though some studies suggest lower measurements can also indicate the condition. Blood tests may also be performed to check for dehydration and electrolyte imbalances, which can result from persistent vomiting.
The standard treatment for pyloric stenosis is a surgical procedure called pyloromyotomy. This surgery involves making a cut through the thickened outer muscle layer of the pylorus, allowing the inner lining to bulge through and relieving the obstruction. The procedure is often performed minimally invasively through small incisions using a laparoscope. Before surgery, it is important to correct any dehydration or electrolyte imbalances, which may take 24 to 48 hours. Outcomes after successful pyloromyotomy are generally excellent, both in the short and long term.