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Hypervolaemic hyponatraemia in heart failure — SCE Geriatric Medicine MCQ

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HardRenal medicineHypervolaemic hyponatraemia in heart failureSCE Geriatric Medicine

An 89-year-old man with heart failure is admitted with falls and confusion. Sodium is 121 mmol/L, serum osmolality is low, urine sodium is 18 mmol/L and he is clinically oedematous with raised JVP and bibasal crackles. He takes furosemide, spironolactone and sertraline. What is the most likely diagnosis?

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Correct answer: A — Hypervolaemic hyponatraemia due to decompensated heart failure

The low serum osmolality with oedema, raised JVP and pulmonary congestion is most consistent with hypervolaemic hyponatraemia from heart failure. SIADH can be drug-related but usually presents euvolaemically with higher urine sodium. Pseudohyponatraemia would not have low osmolality. The pearl is that volume status remains central when interpreting hyponatraemia in older adults with diuretics and multimorbidity.

Reference: NICE heart failure guidance; European hyponatraemia guideline