Virtual colonoscopy (VC), also known as CT colonography, is a noninvasive imaging method for the examination of the colon. The technique is easy, less labour-intensive than barium enema and conventional colonoscopy and is inherently safer since no adverse event or procedure-related complications have ever been reported. The success rate of VC is approximately 100%, if bowel preparation and distension are optimal and no sedation is required. From the patient's perspective, the major advantages of VC include the very brief time required to perform the examination, the absence of contrast enemas and the potential for same-day colonoscopy when polyps are detected. To date several studies have reported sensitivity and specificity comparable with conventional colonoscopy in the detection of clinically significant polyps. However, the smaller the polyp size, the lower the sensitivity. The currently accepted clinical uses include the evaluation of patients who have undergone unsuccessful or incomplete conventional colonoscopy, patients with obstructing colorectal cancer, and those whose medical problems make them unsuitable for conventional colonoscopy. Current uses generally do not include the screening of asymptomatic persons, although recently published work has demonstrated no statistically significant differences between VC and conventional colonoscopy regardless of polyp size. A practical approach is to consider virtual colonoscopy 'as a currently credible alternative screening method and as a reasonable alternative to the other colorectal cancer screening tests when a patient is unable or unwilling to undergo conventional colonoscopy'.
