X-ray feature of pyloric stenosis is: March 2013 (c)
**Core Concept**
Pyloric stenosis is a condition characterized by hypertrophy of the pyloric muscle, leading to narrowing of the pyloric channel and obstruction of gastric outflow. The X-ray feature of pyloric stenosis is a radiological finding that can aid in its diagnosis.
**Why the Correct Answer is Right**
The characteristic X-ray feature of pyloric stenosis is the "string sign" or "olive sign" on a barium study, but the key feature on an X-ray is the "double bubble sign" or the presence of a "single bubble" due to the obstruction of the pylorus. This occurs due to the hypertrophied pyloric muscle, which causes the gastric air bubble to be displaced upwards and the duodenal air bubble to be absent or smaller. The pyloric canal may also appear narrowed or "string-like" in appearance.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not a characteristic X-ray feature of pyloric stenosis. While gastric dilatation may be present, it is not a specific sign for pyloric stenosis.
**Option B:** The "olive sign" is a clinical finding, not an X-ray feature. It refers to the palpable mass of hypertrophied pyloric muscle.
**Option C:** The "double bubble sign" is actually a feature of duodenal obstruction, not pyloric stenosis. It is characterized by two air-filled structures (the stomach and the duodenum) in the upper abdomen.
**Clinical Pearl / High-Yield Fact**
The "string sign" or "olive sign" is a clinical finding that can be used to diagnose pyloric stenosis, but it is not as specific as the radiological findings on an X-ray. A high index of suspicion and clinical correlation with symptoms such as projectile vomiting and weight loss are essential for diagnosis.
**Correct Answer: A. The double bubble sign**