Infants with diabetes insipidus (DI) must be closely monitored for which electrolyte abnormality?

• A. Fluid retention
• B. Hypernatremia
• C. Hypoglycemia
• D. Hyponatremia

Answer: (B)

When infants have diabetes insipidus, their kidneys can’t concentrate urine, so they lose large amounts of free water. If fluid intake doesn’t keep up, this free-water loss concentrates the blood, leading to high serum sodium. That makes hypernatremia the electrolyte abnormality to watch closely. In DI, you’ll see dilute urine with low urine osmolality and dilute urine specific gravity, while the serum sodium rises as water is lost. Because infants can’t communicate thirst or access fluids easily, careful monitoring of fluid balance and serum sodium is essential, and treatment aims to replace water gradually (and administer ADH analog if appropriate) to avoid rapid shifts that could harm the brain.