Which symptom indicates priority attention in an infant with pyloric stenosis?

Projectile vomiting is a key symptom that indicates priority attention in an infant with pyloric stenosis because it represents a significant and concerning manifestation of the condition. Pyloric stenosis is characterized by a narrowing of the pylorus, the opening between the stomach and the small intestine, which can lead to severe vomiting. This vomiting is typically forceful and occurs shortly after feeding, which can result in dehydration and electrolyte imbalances.

In an infant, projectile vomiting signals that the body is unable to properly process food due to the obstruction, and it can quickly escalate into a life-threatening situation if not addressed. Prompt recognition ensures timely intervention, which is crucial given the potential for dehydration and the need for surgical correction of the stenosis.

Other symptoms, while they may be concerning, do not present the same immediate risk as projectile vomiting. Loss of appetite may occur but can be more commonly found in various conditions. Explosive diarrhea and constipation are also potential symptoms but are not as directly associated with pyloric stenosis and do not usually indicate the immediate need for intervention as projectile vomiting does. Thus, projectile vomiting stands out as the symptom that necessitates urgent care in this scenario.