Pyloric stenosis (or infantile hypertrophic pyloric stenosis) Pyloric stenosis is a birth defect that typically affects infants two to eight weeks old, involves an inability to pass food from the stomach into the duodenum, part of the small intestine. Babies with Pyloric stenosis experience progressively worsening vomiting within the first weeks of life. The vomiting is often described as non-bile stained ("non bilious") and "projectile vomiting", because it is more forceful than the usual spittiness. The condition is the most common reason for surgery in the first months of life.
Males are more commonly affected than females, with firstborn males affected about four times as often, and there is a genetic predisposition for the disease.
Among whites, there are 1.5 to 3 cases of pyloric stenosis per 1,000 live births.
Pyloric Stenosis Study
A study of nearly two million children born in Denmark between 1977 and 2008 found that pyloric stenosis is more common among twins and siblings. During the study period, 3,362 of the children had surgery for the birth defect. The researchers found that 46% of children with an affected identical (monozygotic) twin and 7.7% of children with an affected fraternal (dizygotic) twin also had pyloric stenosis.
The findings regarding Pyloric Stenosis highlight a strong family risk of pyloric stenosis, with a nearly 200-fold increased risk among identical twins and a 20-fold increase among siblings. Even more distant relatives had an increased risk, wrote the researchers.
"Our findings argue for a hereditary component of pyloric stenosis," wrote Dr. Camilla Krogh, of the Statens Serum Institute in Copenhagen, and colleagues, in a news release. Not only was it [Pyloric Stenosis] predominant in boys, the Pyloric Stenosis risk was higher among identical twins and fraternal twins and cropped up among even third-degree relatives. There was a difference in Pyloric Stenosis risk between siblings and half-siblings (and cousins and half-cousins), and there was "a heritability [estimate] of 87%," whose most likely explanation was shared genes that affected individuals' responses to various factors after birth, Krogh noted.
The researchers conclude that "the high rates for twins and siblings should be considered in counseling families with affected children."