Dilutional hyponatremia is best described as:

• A. Water poisoning which leads to brain edema, brain stem herniation, and death
• B. Dehydration due to excessive sweating
• C. Hypernatremia from salt wasting
• D. Hypokalemia causing arrhythmias

Answer: (A)

Dilutional hyponatremia happens when there is too much water relative to sodium, so plasma osmolality falls and water shifts into cells. In the brain this causes cellular swelling, leading to cerebral edema and, in severe cases, brainstem herniation and potentially death. This situation is often described as water intoxication or water poisoning because the excess water dilutes the sodium in the bloodstream. The other options point to dehydration, hypernatremia from salt loss, or potassium-related issues, none of which describe the excess water diluting sodium that defines dilutional hyponatremia.