An infant diagnosed with pyloric stenosis recently developed projectile vomiting. Which finding indicates to the practical nurse that the infant is becoming dehydrated?

A. Bulging fontanel: A bulging fontanel may indicate increased intracranial pressure rather than dehydration. In dehydration, the fontanel is typically sunken rather than bulging. B. Weak cry without any tears: Absence of tears when crying and a weak cry are classic signs of dehydration in infants. These findings indicate fluid loss and inadequate hydration, which is especially concerning in conditions like pyloric stenosis with frequent vomiting. C. Visible peristaltic wave: A visible peristaltic wave across the abdomen is characteristic of pyloric stenosis itself but does not indicate dehydration. It reflects gastric contractions trying to move contents past the narrowed pylorus. D. Palpable mass in the right upper quadrant: The palpable “olive-shaped” mass in the right upper quadrant is a hallmark diagnostic finding for pyloric stenosis but is unrelated to the infant’s hydration status.