5th June 2023

A 75-year-old man with retinitis pigmentosa is admitted to the general medical ward

A 75-year-old man with retinitis pigmentosa is admitted to the general medical ward with a fall. He lives with his partner and usually needs help with outside activities and keeping house. He has no other past medical history and only takes laxatives for constipation. During his inpatient stay, he becomes sleepy and withdrawn, and the nurses report that his oral intake has declined considerably. On examination, he has some suprapubic tenderness and a few bibasal crepitations. His observations are all within normal range and bloods are unremarkable.

Of the options below, which is the most likely cause for his delirium?