Duodenal atresia is a congenital condition defined by the complete blockage of the duodenum, the first segment of the small intestine immediately following the stomach. This obstruction develops before birth and prevents the passage of food and fluid, leading to characteristic symptoms shortly after a newborn begins feeding. Infants typically present with vomiting within the first 24 to 38 hours of life, often featuring a greenish bile color if the blockage is past the bile duct. This anomaly occurs in approximately 1 in every 5,000 to 10,000 live births, making it a significant cause of intestinal obstruction in newborns.
Failure of Fetal Duodenal Recanalization
The physical cause of duodenal atresia is a failure of normal developmental processes during the first trimester of pregnancy. Between the fourth and sixth weeks of gestation, endodermal cells rapidly proliferate, temporarily filling the duodenal lumen and creating a solid cord of tissue. This temporary blockage is a normal part of human embryonic development.
This solid phase must be followed by recanalization, where epithelial cells undergo programmed cell death (apoptosis) to re-establish a hollow channel for digestion. Duodenal atresia occurs when this process fails, leaving a physical barrier. The duodenum is particularly susceptible because its recanalization is slightly delayed.
The obstruction manifests in distinct anatomical forms. The most frequent type involves a mucosal web or diaphragm spanning the lumen, often causing the proximal section to balloon out in a characteristic “windsock” deformity. Other forms include segments connected only by a short, fibrous cord, or, in severe cases, the two ends are completely separated. This mechanical obstruction causes fluid buildup in the stomach and duodenum, visible on imaging as the classic “double bubble” sign.
The Strong Link to Chromosomal Syndromes
While mechanical failure is the immediate cause, an underlying genetic predisposition is a major factor in many cases. Duodenal atresia shows a pronounced association with chromosomal abnormalities, suggesting the developmental error is often genetically triggered. The most significant connection is with Trisomy 21 (Down Syndrome), where the infant has an extra copy of chromosome 21.
Infants with Down Syndrome are significantly more likely to have duodenal atresia; estimates suggest that between 25% and 40% of all babies diagnosed with duodenal atresia also have Trisomy 21. Conversely, about 3% of infants with Down Syndrome are born with the condition. This correlation suggests that the genetic changes disrupt the molecular signaling required for the duodenal lumen to re-open.
A chromosomal abnormality is detected in up to 38% of patients. While Trisomy 21 is the most common, other syndromes like Trisomy 18 have also been reported. In these genetically linked cases, the chromosomal issue is considered a powerful risk factor leading to the mechanical failure.
Other Associated Congenital Anomalies and Maternal Factors
Duodenal atresia is frequently not an isolated finding, as over half of affected infants have at least one other major congenital anomaly. This suggests a shared developmental timing or underlying cause for multiple defects during the early weeks of gestation.
Associated Congenital Anomalies
Cardiac defects are the most common co-occurring anomaly, affecting 20% to 25% of infants with duodenal atresia who have normal chromosomes. The risk of heart defects is substantially higher when paired with Trisomy 21, where the incidence can exceed 60%. Other associated malformations include annular pancreas, where pancreatic tissue encircles the duodenum and contributes to the obstruction. Defects in the kidneys, skeleton, and anus (VACTERL association) are also seen in some cases.
Maternal Factors and Prenatal Findings
Certain maternal conditions and prenatal findings are associated with duodenal atresia, though they are not considered direct causes. A significant finding is polyhydramnios, an excessive accumulation of amniotic fluid in the womb. Because the fetal intestine cannot absorb the amniotic fluid it swallows due to the blockage, the fluid builds up, observed in 50% to 84% of affected pregnancies. Maternal diabetes has also been studied, but it is generally regarded as an association or marker rather than a direct trigger for the malformation.