The pyloric canal is the opening between the stomach and the duodenum, which is the first section of the small intestine. In pyloric stenosis, the circumferential muscle of the sphincter becomes thickened, resulting in elongation and narrowing of the pyloric canal. This produces an outlet obstruction which leads to projectile vomiting, dehydration, metabolic alkalosis and growth failure. The precise etiology is unknown.
This condition usually develops in the first 2 to 5 weeks of life. The reported incidence is 1 to 3 per 1000 live births with a male-to-female ratio of 4 to 6: 1. There is a genetic predisposition, so many times the siblings and offsprings of the affected child are at increased risk of developing hypertrophic pyloric stenosis. It is more common in full term than in preterm infants. It is not seen as often in African-American and Asian infants, than in white infants.
The diagnosis is usually made after a history and physical examination. The olive-like mass is easily palpated when the stomach is empty (usually the result of persistent vomiting), the infant is quiet, and the abdominal muscles are relaxed. Vomiting occurs within 30 to 60 minutes of feeding and will become projectile in nature as the obstruction progresses. The emesis consists of stale formula / milk and is non-bilious (doesn’t consist of bile or the green colored contents of the stomach). If this condition is not diagnosed early, the infant may become dehydrated and appear malnourished.
If the diagnosis is inconclusive from the history and physical exam, and ultrasound may be in order. The ultrasound will reveal an elongated, sausage-shaped mass with an elongated pyloric canal. If ultrasonography doesn’t produce a conclusive diagnosis, then and upper Gastrointestinal radiography should be done. Laboratory findings (i.e., blood sample analysis) usually supports the diagnosis in revealing the metabolic alteration (low blood chloride levels / elevated blood carbon dioxide level) created by depletion of fluid and electrolytes and hydrogen ions from the prolonged vomiting.
Therapeutic Management and Prognosis
Relief of the pyloric obstruction is achieved through surgical intervention, known as a pyloromyotomy. This procedure is often performed by laparoscope. The procedure consists of making a longitudinal incision through the circular muscle fibers of the pylorus down to, but not including the sub-mucosa layer. The procedure has a high success rate. The infant is kept NPO (nothing by mouth) for a 4-6 hours, postoperatively. When feedings are re-introduced, it will began with an electrolyte replenishing solution, such as Pedialyte. The amount will be small and frequent. If the child is able to retained the Pedialyte after a few feedings, then formula or breast milk may be re-introduced into the diet. The amount, type and the frequency of the feedings will be determined by the surgeon. The amount and the interval between feedings are gradually increased. The parent is also instructed to burp the infant frequently during the feedings and keep the child upright for 30 minutes after the feedings.