Question

A 72-year-old man is found to have sodium 120 mmol/L. He is euvolaemic, has small-cell lung cancer and is on no diuretics. Serum osmolality is low and urine osmolality is high. What is the most likely diagnosis?

Accepted Answer

Syndrome of inappropriate antidiuretic hormone secretion (SIADH)

Answer

Hypovolaemic hyponatraemia from gastrointestinal losses

Answer

Hypervolaemic hyponatraemia from heart failure

Answer

Pseudohyponatraemia due to hyperlipidaemia

Answer

Primary polydipsia

Practice question

A 72-year-old man is found to have sodium 120 mmol/L. He is euvolaemic, has small-cell lung cancer and is on no diuretics. Serum osmolality is low and urine osmolality is high. What is the most likely diagnosis?