What is the characteristic symptom of Pyloric Stenosis?

Pyloric stenosis is a condition typically seen in infants, characterized by the narrowing of the pylorus, which is the opening from the stomach into the small intestine. The primary symptom that distinguishes this condition is projectile vomiting. This occurs because the narrowing makes it difficult for food to pass from the stomach into the intestines, leading to forceful, often arc-like vomiting shortly after feeding.

Projectile vomiting in pyloric stenosis is usually non-bilious, meaning it does not contain bile, which contrasts with vomiting seen in other gastrointestinal issues like intestinal obstruction. The behavior of the vomiting—being sudden and powerful—often leads to pediatric patients appearing hungry shortly after vomiting, as they have not been able to retain their feedings.

In terms of the other symptoms listed, currant jelly stools are commonly associated with intussusception in children, asymmetric neck swelling can be related to conditions such as a hematoma or congenital torticollis, and drooling with trismus (jaw rigidity) can occur due to dental issues or infections such as tetanus or mumps, but they do not relate to pyloric stenosis. Therefore, identifying the correct symptom of projectile vomiting is crucial for diagnosis and appropriate management of pyloric stenosis.