Final answer:
The nurse's priority finding when assessing a toddler with gastroenteritis and signs of dehydration is hypotension, or low blood pressure.
Step-by-step explanation:
When assessing a toddler with gastroenteritis and signs of dehydration, the nurse's priority finding would be hypotension, or low blood pressure. Hypotension is a symptom of hypovolemic shock, which can occur due to fluid losses from severe vomiting and diarrhea. Hypovolemic shock requires immediate intervention to restore fluids and raise blood pressure.