ABSTRACT
The choice of treatment and the prognosis of colorectal cancer mainly hinges on early diagnosis and accurate staging of the disease. Staging of colorectal cancer is based on two principles. The first is to determine the factors that influence prognosis, and these have been historically described by TNM classification. The second is to determine a relevant anatomical roadmap in order to aid surgery and radiotherapy. Diagnosis of colorectal cancer is mainly made on colonoscopy and biopsy, which provides the histological proof of the diagnosis. However, CT colonography (CTC) or virtual colonoscopy is a reliable alternative to optical colonoscopy, especially in the elderly and the frail who are unfit to undergo optical colonoscopy. CTC is the radiological investigation of choice for detection of colorectal neoplasia and adenomatous polyps. CTC is a low dose CT scan obtained after adequate bowel preparation, faecal tagging and colonic distension. Bowel is prepared usually by a combination of low residue diet and laxatives.
