Virtual colonoscopy: clinical application

Abstract

Virtual colonoscopy (VC), also known as computed tomography Colonography (CTC), is a non-invasive test for the examination of the colon based on volumetric, thin-collimation CT acquisition of a cleansed and air-distended colon. The technique is easy, less labour-intensive than barium enema and conventional colonoscopy, and is inherently safer. Several studies demonstrate the ability of VC in the detection of colonic neoplastic lesions, not only large carcinomas, but also polyps. Currently, the most widely accepted clinical indication is incomplete or unsuccessful colonoscopy, which may be the result of redundant colon, patient intolerance to the procedure, spasm not resolving even with the use of spasmolytics, obstructing colo-rectal cancer. VC is also used to detect cancer in frail and immobile patients to avoid sedation during colonoscopy or the turning required during barium enema. The use of VC in patients under surveillance following colo-rectal cancer surgery is under investigation. Further studies are necessary in order to assess the cost-effectiveness of this approach. For colo-rectal cancer screening, a practical approach is to consider VC as a currently credible alternative screening method and as a reasonable alternative to the other colo-rectal cancer screening tests when a patient is unable or unwilling to undergo conventional colonoscopy.

Positive predictive value for polyps detected at screening CT colonography

“…Broad consensus among radiologists on the general application of CTC as a clinical tool has been achieved [4,5]. To function as a clinically efficacious and cost-effective screening tool, CTC must not only be sensitive for lesion detection, but also demonstrate a reasonably low false-positive rate [6][7][8]. In contrast to validation trials where OC is performed in all subjects [1,3], including those with negative CTC results, the sensitivity and specificity of CTC (relative to OC) cannot be measured in clinical practice.…”

CT colonography with reduced bowel preparation after incomplete colonoscopy in the elderly

“…Further studies should address such a major issue. As has previously been well assessed, CTC is clearly indicated as a second examination for those patients with incomplete conventional colonoscopy [31][32][33][34].…”

Comparing hyoscine and drotaverine effects on colon in CT colonography

“…One of the main requirements for quality CT colonography is the achievement of optimal distension of the colon [1,2]. Drugs causing relaxation of the colonic wall are administered for better distension [3].…”