A 68-year-old lady with bowel cancer who had been admitted to hospital following a fall had a persistent low plasma sodium including the following plasma results (refer- ence ranges are given in brackets): Sodium Potassium Urea Creatinine Glucose Osmolality 120 mmol/L 3.9 mmol/L 3.4 mmol/L 53 μmol/L 5.2 mmol/L 255 mOsm/kg (135-145) (3.5-5.0) (3.5-6.6) (70-150) (3.5-5.5) (285-305) In this patient, the urine volume was low and relatively concentrated, the urine osmo- lality was 374 mOsm/kg and its sodium concentration was 75 mmol/L. Comment on these results.

A 68-year-old lady with bowel cancer who had been admitted to hospital following a fall had a persistent low plasma sodium including the following plasma results (refer- ence ranges are given in brackets): Sodium Potassium Urea Creatinine Glucose Osmolality 120 mmol/L 3.9 mmol/L 3.4 mmol/L 53 μmol/L 5.2 mmol/L 255 mOsm/kg (135-145) (3.5-5.0) (3.5-6.6) (70-150) (3.5-5.5) (285-305) In this patient, the urine volume was low and relatively concentrated, the urine osmo- lality was 374 mOsm/kg and its sodium concentration was 75 mmol/L. Comment on these results.