Which of the following conditions can cause hypotonic hypervolemic hyponatremia?

• A. Stress/pain
• B. Water intoxication
• C. Renal failure
• D. SIADH

Answer: (C)

Hypotonic hyponatremia with hypervolemia happens when total body water increases more than total body sodium, leading to a diluted serum sodium and signs of fluid overload. Renal failure fits this pattern because the kidneys’ ability to excrete free water is impaired. With reduced filtration, water retention occurs, expanding the extracellular fluid and diluting sodium—so you get low sodium with a hypervolemic (edematous) state.

Stress or pain can trigger nonosmotic ADH release and cause hyponatremia, but the volume status is usually euvolemic. Water intoxication causes dilutional hyponatremia from excessive water intake; it can produce hypotonic hyponatremia but isn’t classically characterized by hypervolemia. SIADH causes hyponatremia with euvolemia because water is retained without overt fluid overload.