A 3-month-old cries inconsolably with poor feeding and diarrhea; the fontanel is sunken and there are no tears. Which finding best supports dehydration?

• A. Sunken fontanel.
• B. Teary eyes.
• C. Normal skin turgor.
• D. Moist mucous membranes.

Answer: (A)

In infants, signs of dehydration center on reduced body fluid volume, and a sunken fontanel is a classic, reliable cue. The fontanel is a soft spot on the head where the skull bones meet; when a baby is dehydrated and fluid volume drops, the fontanel can sink because the supporting tissues lose turgor and the skull’s soft spots appear recessed. This finding directly reflects overall hydration status.

Other signs listed are less specific: teary eyes suggest tear production and hydration more than not, so “teary eyes” would not support dehydration. Normal skin turgor and moist mucous membranes indicate hydration rather than dehydration. Therefore, the sunken fontanel best supports dehydration in this scenario.