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

A. Visible peristaltic wave: This finding is a characteristic sign of pyloric stenosis, reflecting strong gastric contractions before vomiting. It does not indicate dehydration but rather the mechanical obstruction in the pylorus. B. Weak cry without any tears: A weak cry and absence of tears are clinical indicators of dehydration in infants. Fluid loss from repeated vomiting leads to decreased tear production and lethargy, signaling significant volume depletion. C. Palpable mass in the right upper quadrant: The “olive-shaped” mass represents hypertrophy of the pyloric sphincter, a diagnostic feature of pyloric stenosis. It is unrelated to hydration status. D. Bulging fontanel: A bulging fontanel suggests increased intracranial pressure or fluid overload, not dehydration. In dehydration, the fontanel would typically appear sunken rather than bulging.