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SIADH from pneumonia — SCE Acute Medicine MCQ

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HardAcute Renal and Metabolic EmergenciesSIADH from pneumoniaSCE Acute Medicine

A patient with pneumonia has sodium 124 mmol/L, low serum osmolality, urine osmolality 520 mOsm/kg, urine sodium 52 mmol/L and apparent euvolaemia. What additional condition must be met before diagnosing SIADH?

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Correct answer: C — Exclude endocrine and volume causes before diagnosing SIADH

The best answer is “Exclude endocrine and volume causes before diagnosing SIADH”. This is correct because SIADH is a diagnosis of exclusion requiring hypotonic hyponatraemia, inappropriate urine concentration, clinical euvolaemia and absence of adrenal, thyroid, renal or diuretic explanations. Oedema, hypertonicity and maximally dilute urine point elsewhere, while thiazides confound rather than confirm the diagnosis.

Reference: NICE NG133 electrolyte and endocrine assessment recommendations: https://www.nice.org.uk/guidance/ng133/chapter/Recommendations