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SIADH — ESENeph MCQ

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HardAcute Kidney Injury, Electrolytes and Acid-BaseSIADHESENeph

A 72-year-old woman with small cell lung cancer is admitted after a fall. Sodium is 118 mmol/L, serum osmolality is low, urine osmolality is 620 mOsm/kg and urine sodium is 54 mmol/L. She is euvolaemic, alert and has had nausea for 2 weeks. What is the most appropriate management?

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Correct answer: A — Fluid restriction with careful sodium monitoring

Euvolaemic hypotonic hyponatraemia with inappropriately concentrated urine in small cell lung cancer suggests SIADH; chronic mild symptoms are usually managed with fluid restriction and close monitoring. Rapid normalisation risks osmotic demyelination and is reserved for severe neurological symptoms with controlled hypertonic saline. Desmopressin would worsen free-water retention unless used in specific overcorrection rescue protocols. The pearl is that chronic hyponatraemia should be corrected slowly and the treatment urgency follows symptoms, not the sodium value alone.

Reference: https://guidelines.ukkidney.org