23rd September 2020

A 77-year-old lady is admitted to the Medical Assessment Unit

A 77-year-old lady is admitted to the Medical Assessment Unit after a 3-day history of increasing breathlessness which has been complicated by increasing confusion, headaches, and reduced urine output. Her daughter noted that she had been passing very dark urine. Her urine osmolality raised, serum sodium low, and low serum osmolality. Plain film chest x-rays are consistent with a pneumonia, and empirical antibiotics are commenced.

What is the most likely cause of her hyponatraemia and raised urine osmolality?

Select the SINGLE most appropriate option from the list below. Select ONE option only.