Which symptom might suggest a diagnosis of pyloric stenosis in infants?

Projective vomiting is a classic symptom associated with pyloric stenosis in infants. This condition involves a narrowing of the pylorus, which is the opening from the stomach into the small intestine. As a result, when food or formula is ingested, the narrowing can prevent it from passing into the intestine, leading to forceful, projectile vomiting. This vomiting typically occurs shortly after feeding and can be quite vigorous, distinguishing it from normal spitting up or mild vomiting that some infants experience.

The behavior of the vomit in these cases may also indicate that it is primarily stomach contents without bile, as the obstruction prevents the passage of material into the duodenum. This symptom, in conjunction with a "hungry" appearance of the infant shortly after vomiting, can help healthcare professionals narrow down the diagnosis to pyloric stenosis. Other symptoms that may accompany include dehydration and weight loss, but the hallmark feature remains the projectile vomiting.