“Double bubble” sign with absent distal bowel air shadows on X-ray abdomen is characteristic of
**Core Concept**
Duodenal atresia is a congenital anomaly characterized by the complete or partial obstruction of the duodenum, leading to an accumulation of gas proximal to the obstruction. The "double bubble" sign on X-ray abdomen is a classic radiographic finding in duodenal atresia, indicating the presence of two distinct gas-filled structures within the upper abdomen.
**Why the Correct Answer is Right**
The "double bubble" sign is caused by the accumulation of gas in the stomach (the first bubble) and the duodenum proximal to the atresia (the second bubble). The absence of distal bowel air shadows is due to the complete obstruction of the duodenum, preventing gas from passing into the rest of the intestine. The diagnosis of duodenal atresia can be confirmed by a barium study or surgical exploration, which demonstrates the complete or partial obstruction of the duodenum.
**Why Each Wrong Option is Incorrect**
**Option A:** Duodenal webs are a different congenital anomaly characterized by a thin membrane or web that partially obstructs the duodenum. While duodenal webs can cause partial obstruction and lead to a "double bubble" sign, they are not the most characteristic cause of this radiographic finding.
**Option C:** CHPS (Congenital Hypertrophic Pyloric Stenosis) is a condition characterized by hypertrophy of the pyloric muscle, leading to gastric outlet obstruction. While CHPS can cause gastric distension and a "double bubble" sign, it is not typically associated with the absence of distal bowel air shadows.
**Option D:** This option is incorrect because duodenal atresia is the most characteristic cause of the "double bubble" sign with absent distal bowel air shadows.
**Clinical Pearl / High-Yield Fact**
The "double bubble" sign is a classic radiographic finding in duodenal atresia, but it can also be seen in other conditions such as duodenal webs and gastric outlet obstruction. A careful evaluation of the X-ray and clinical context is necessary to make an accurate diagnosis.
**✓ Correct Answer: B. Duodenal atresia**