Final answer:
When assessing a toddler with gastroenteritis and signs of dehydration, the nurse's priority finding is signs of dehydration.
Step-by-step explanation:
The nurse's priority finding when assessing a toddler with gastroenteritis and manifestations of dehydration would be signs of dehydration. These signs include a marked decrease in urination, a very dry mouth and throat, or feeling dizzy when standing up. Dehydration can be serious and requires immediate intervention to rehydrate the toddler and prevent further complications.