Duodenal Atresia is a congenital digestive disorder where the duodenum, the first part of the small intestine immediately following the stomach, is completely blocked. This condition arises from a failure in the normal developmental process where the solid cord of cells that forms the duodenum fails to properly hollow out, or recanalize, during the eighth to tenth week of gestation. Since the blockage prevents food and digestive fluids from passing into the rest of the bowel, intervention is required soon after birth.
Detection During Pregnancy
The earliest indication of Duodenal Atresia often presents during routine prenatal care. The condition may be suspected during a standard prenatal ultrasound scan, though signs of the obstruction typically become apparent during the late second or third trimester of pregnancy. It is usually not visible during the routine 20-week anatomy survey.
One of the most frequent findings associated with Duodenal Atresia is polyhydramnios, which is an abnormally large amount of amniotic fluid surrounding the fetus. This excess fluid accumulates because the fetus normally swallows amniotic fluid, which is then absorbed by the small intestine and passed back into the maternal circulation. The obstruction in the duodenum prevents this process, leading to a build-up of fluid in the amniotic sac.
The ultrasound may show a dilated, fluid-filled stomach and a dilated first part of the duodenum. These two fluid-filled structures, separated by the pyloric sphincter, create the distinct appearance known as the “double bubble” sign on the prenatal scan. While this finding is highly suggestive of a proximal intestinal obstruction, a definitive diagnosis cannot be made until after the baby is born.
Signs Immediately After Birth
Once the baby is born, the clinical presentation of Duodenal Atresia usually becomes clear within the first 24 to 48 hours of life. The most prominent sign is persistent, often forceful, vomiting that occurs shortly after the newborn’s first feeding. This happens because the milk or formula cannot pass the obstruction and backs up into the stomach.
The color of the vomit provides an important clue to the location of the blockage. If the obstruction is located below the ampulla of Vater, where the bile duct enters the small intestine, the vomit will appear bilious, meaning it is green or yellow-green due to the presence of bile. Bilious vomiting requires immediate medical attention. A less common finding is non-bilious vomiting, which suggests the obstruction is located above the bile duct entrance.
The baby will quickly show feeding intolerance and may experience swelling in the upper part of the abdomen. Another significant sign is the absence of normal meconium passage. While a baby may pass one or two initial meconium stools, the complete blockage prevents any further contents from traveling through the bowel, resulting in little or no subsequent bowel movements.
Diagnosis and Confirmation Methods
Following the presentation of characteristic postnatal symptoms, the next step is to confirm the diagnosis using medical imaging. The initial and most common diagnostic tool is a plain abdominal X-ray. This simple test is highly effective for visualizing the classic pattern associated with the condition.
The abdominal X-ray typically reveals the pathognomonic “double bubble” sign. This appearance is caused by air becoming trapped and distending the two segments immediately above the obstruction: the stomach and the proximal duodenum.
A finding of the double bubble sign with a complete absence of air in the rest of the small and large intestines strongly indicates a complete Duodenal Atresia. If the X-ray shows the double bubble sign but also reveals some air in the distal bowel, this may suggest a partial obstruction, such as duodenal stenosis.