What is a common radiologic finding in pyloric stenosis?

The string sign is a common radiologic finding in pyloric stenosis. This sign reflects the narrow channel created in the pylorus due to the hypertrophy of the pyloric muscle. On imaging studies, particularly ultrasound or upper gastrointestinal series, the string sign appears as a thin, elongated channel through which contrast material can pass. This is indicative of the marked narrowing that occurs in patients with pyloric stenosis and highlights the difficulty that food and liquids face when moving from the stomach into the duodenum.

In the context of pyloric stenosis, this finding is very useful for diagnosis, as it directly correlates with the classical symptoms often observed in affected infants, such as projectile vomiting and dehydration. The other signs listed, while associated with different gastrointestinal conditions, do not specifically pertain to pyloric stenosis, making the string sign a defining feature of this particular condition.