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Thiazide-associated severe hyponatraemia — SCE Acute Medicine MCQ

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HardAcute Renal and Metabolic EmergenciesThiazide-associated severe hyponatraemiaSCE Acute Medicine

An 83-year-old woman presents with confusion and a fall. Sodium is 118 mmol/L, serum osmolality is low, urine sodium is 62 mmol/L and urine osmolality is 520 mOsm/kg. She started bendroflumethiazide two weeks ago and is euvolaemic on examination. What is the most likely cause?

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Correct answer: E — Thiazide-associated hyponatraemia

Recent thiazide initiation with hypotonic hyponatraemia and inappropriately concentrated urine is typical of thiazide-associated hyponatraemia in an older woman. Primary polydipsia usually produces dilute urine. Diabetes insipidus causes hypernatraemia or high-normal sodium with dilute urine. The drug should be stopped and symptomatic severe hyponatraemia managed cautiously to avoid osmotic demyelination.

Reference: European hyponatraemia guideline, NICE CKS hyponatraemia, BNF