A 48 year old man has intermittent left sided lower abdominal pain and feels generally unwell. He has lost his appetite and has lost weight. Temp=38.3C and he has BP=190/100mmHg. What is the single investigation most likely to lead to diagnosis?

The key is E. US abdomen. This is wrong key. Correct key is A. Colonoscopy. [Probable diagnosis is diverticulitis and preferred investigation from given list is colonoscopy. Colonoscopy: It views the colon's interior to see the inflamed, infected pouches. Ultrasound images lack the detail of CT images and cannot evaluate the intestines as well as CT].