Double-bubble sign on abdominal X-ray is seen in :
**Core Concept**
The double-bubble sign is a radiological finding on abdominal X-ray, characterized by the presence of two air-filled structures in the upper abdomen. This sign is typically associated with intestinal obstruction, particularly in the context of duodenal atresia or stenosis.
**Why the Correct Answer is Right**
The double-bubble sign occurs due to the accumulation of air in the stomach and the proximal duodenum, resulting from an obstruction at the level of the duodenojejunal junction or the ampulla of Vater. In cases of duodenal atresia, the obstruction prevents the normal passage of intestinal contents, leading to the formation of air-filled structures. The duodenum and stomach become distended with air, producing the characteristic double-bubble appearance on X-ray.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the double-bubble sign is not typically associated with gastric outlet obstruction, which would more likely result in a single air-filled structure (the stomach).
**Option B:** This option is incorrect because pyloric stenosis would result in a single air-filled structure (the stomach), and the pyloric canal would not produce a distinct air-filled bubble.
**Option C:** This option is incorrect because small bowel obstruction would result in multiple air-filled structures along the length of the intestine, rather than the characteristic double-bubble appearance.
**Clinical Pearl / High-Yield Fact**
The double-bubble sign is a classic radiological finding in duodenal atresia, and its presence should prompt a high index of suspicion for this diagnosis. It is essential to consider the clinical context and other imaging findings to confirm the diagnosis.
**Correct Answer: C. Duodenal atresia.**