30th April 2024

A 63-year-old man presents with a 6-month history of altered bowel habits, including increased frequency and occasional rectal bleeding.

A 63-year-old man presents with a 6-month history of altered bowel habits, including increased frequency and occasional rectal bleeding. He has lost 5 kg in weight over this period without trying. His family history is significant for colorectal cancer in his brother at the age of 58. On examination, his abdomen is soft with no palpable masses, but there is mild tenderness in the lower abdomen. His digital rectal examination is unremarkable.

Which investigation is most likely to confirm the diagnosis?