After a family picnic, which member should the nurse be most concerned about if they have moderate diarrhea?

The reasoning for focusing on the toddler with moderate diarrhea is grounded in the developmental and physiological considerations of different age groups. Young children, particularly those around 2 years old, are more susceptible to dehydration due to their smaller body size and higher surface area-to-volume ratio. Their fluid reserves are also less than those of older children and adults, which makes them vulnerable to the rapid onset of dehydration from diarrhea.

In addition, young children may not be able to effectively communicate their symptoms or hydrate themselves, which increases the nurse's concern for their well-being. Diarrhea can lead to significant fluid and electrolyte loss, and in toddlers, this loss can quickly escalate to a critical condition if not addressed promptly.

Older adults and healthy children have a greater ability to manage and recover from such symptoms, provided they have no underlying health issues. While all individuals experiencing diarrhea need monitoring and care, the toddler's age, size, and developmental stage make them the highest priority in terms of potential complications from moderate diarrhea.