Which sign is indicative of duodenal atresia in a newborn?

The double-bubble sign seen on an abdominal X-ray is a classic radiological finding indicative of duodenal atresia in a newborn. This sign represents two distinct air-filled areas: one in the stomach and the other in the proximal duodenum, with a lack of air in the distal duodenum and the rest of the gastrointestinal tract. This pattern occurs because the obstruction at the duodenum prevents the passage of air and fluid further along the intestinal tract, which leads to the accumulation of air in just these proximal areas, hence creating a "double-bubble" appearance.

The presentation of duodenal atresia is typically noted shortly after birth, often accompanied by symptoms such as bilious vomiting and abdominal distension. Recognition of the double-bubble sign plays a critical role in diagnosing this condition promptly, allowing for appropriate intervention.

In contrast, the other options mentioned do not specifically indicate duodenal atresia. For example, the triple-bubble sign would suggest a different type of obstruction involving more distal sections of the bowel, while air in the rectum and the presence of meconium in the stool usually indicate a patent gastrointestinal tract, suggesting that the obstruction is not present or that the gut is functioning adequately