What is the most common cause of duodenal obstruction in children under 1 week old?

Duodenal atresia is recognized as the most common cause of duodenal obstruction in neonates, particularly those under one week old. This condition occurs when there is a congenital disruption in the normal development of the duodenum, leading to a complete blockage. The obstruction typically presents with bilious vomiting shortly after birth, a key clinical sign that raises suspicion for this condition.

Duodenal atresia is often associated with other congenital anomalies, particularly Down syndrome, which adds to its prevalence in the neonatal population. The characteristic "double bubble" sign seen on X-ray, where there are two distended air-filled spaces (the stomach and proximal duodenum) indicates the presence of this atresia.

Addressing the other conditions, while malrotation can also lead to duodenal obstruction, it is less common than duodenal atresia in the first week of life. Intestinal atresia encompasses various forms, not just in the duodenum, and while it is a significant cause of obstruction, it is not specific to the duodenum. Pyloric stenosis, while a notable condition that causes gastric outlet obstruction, typically presents later than the first week of life and is much less likely to cause du