Duodenal atresia is a rare congenital condition characterized by a complete blockage in the upper part of the small intestine. This structural malformation occurs during fetal development, preventing the normal passage of food and fluid through the digestive tract. Understanding the underlying causes requires an examination of the intricate processes of embryonic development.
Defining Duodenal Atresia
Duodenal atresia is the congenital absence or complete closure of a segment of the duodenum, the first section of the small intestine immediately following the stomach. The duodenum is a C-shaped tube that receives partially digested food from the stomach, along with bile and pancreatic enzymes. The resulting mechanical obstruction of the gastrointestinal tract presents with clear clinical signs shortly after birth. Newborns typically begin vomiting within the first day or two of life, often immediately following their first feeding. The vomit is frequently bilious (green, containing bile), indicating the blockage is located past the point where the bile duct enters the small intestine, leading to upper abdominal distension.
The Embryological Origin of Duodenal Atresia
The primary cause of duodenal atresia is a failure in the normal process of embryonic development known as recanalization. During the fifth to sixth week of gestation, the proliferating cells of the inner lining (epithelium) of the fetal duodenum temporarily fill the lumen, turning the tube into a solid cord. Following this solid phase, programmed cell death and vacuolization should begin, creating channels that merge to re-establish a single, open passage. This re-opening is typically complete by the 11th week of gestation. Duodenal atresia results when this process fails, leaving a residual obstruction.
The physical manifestation of this failure is classified into three main types. The most common type involves a mucosal diaphragm or web obstructing the passage while the outer muscular wall remains intact. Other forms include the two ends of the duodenum being connected only by a fibrous cord, or completely separated. There is also a strong genetic association, as 25% to 40% of affected infants also have Trisomy 21 (Down syndrome).
Diagnosis and Related Congenital Conditions
The condition is often first suspected during pregnancy through routine prenatal ultrasound screening. A classic finding is the “double bubble sign,” representing two fluid-filled, enlarged structures: the stomach and the proximal duodenum. This appearance is caused by trapped fluid and air that cannot pass the obstruction, and it is frequently accompanied by polyhydramnios (excess amniotic fluid) because the fetus cannot swallow and absorb the fluid normally.
Following birth, the diagnosis is confirmed with an abdominal X-ray, which visually confirms the characteristic double bubble sign created by air trapped in the stomach and the dilated duodenal bulb. Once duodenal atresia is diagnosed, healthcare providers must screen for other conditions, as the defect rarely occurs in isolation; up to 62% of affected infants have additional anomalies.
Associated Anomalies and Treatment
Associated congenital anomalies are common and can involve multiple organ systems. Cardiac defects are among the most frequent, occurring in 20% to 33% of cases. Other co-occurring malformations include renal anomalies and intestinal malrotation, where the intestines have not rotated correctly. The definitive treatment is surgical correction, typically performed shortly after birth, to remove the obstruction and restore the continuity of the digestive tract.