Question

A 58-year-old man with small cell lung cancer develops serum sodium 118 mmol/L, low serum osmolality, urine sodium 60 mmol/L, and urine osmolality 500 mOsm/kg. He is euvolaemic on examination. Which diagnosis best explains these findings?

Accepted Answer

Syndrome of inappropriate antidiuretic hormone secretion (SIADH)

Answer

Hypovolaemic hyponatraemia from diuretics

Answer

Hypervolaemic hyponatraemia from heart failure

Answer

Primary polydipsia

Answer

Pseudohyponatraemia from hyperlipidaemia

Practice question

A 58-year-old man with small cell lung cancer develops serum sodium 118 mmol/L, low serum osmolality, urine sodium 60 mmol/L, and urine osmolality 500 mOsm/kg. He is euvolaemic on examination. Which diagnosis best explains these findings?