Value and utility of virtual colonscopy (colonography)

Colonoscopy is recommended as a screening tool for all men and women 50 years or older. However the colonoscopy has never been accepted fully by the community and the compliance with colonoscopy screening has been low. This is because colonoscopy is a very unpleasant procedure and most of the healthy adult would conveniently postpone their first colonoscopy.

For those who hate colonoscopy, now there is an alternative it is called colonography or virtual colonography. This is an imaging technique similar to CT scan, and involves helical computed tomography to take pictures of your colon to create a high resolution virtual two-dimensional and three-dimensional colonoscopy image of the inner surface of the colon using computer software. In comparison to the regular colonoscopy this procedure does not require sedation analgesia or intervention, and is faster to. If someone is found to have an abnormality in virtual colonoscopy they should be subjected to the conventional colonoscopy.

Disadvantages are that the conventional bowel preparation program is still needed and that the insufflation (blowing gas into the colon to enlarge the area) is uncomfortable. The following study examined the utility of virtual colonoscopy.

A total of 120 patients were recruited for this study. The patients who were included had an increased risk of colorectal abnormalities, due to; suspected polyps, rectal bleeding, blood in the stool, history of prior polyps, or a family or personal history of colorectal cancer. These patients received virtual colonoscopy followed by a traditional colonoscopy on the same day.

The study showed that for both virtual colonoscopy and traditional colonoscopy, patients' thoughts after the procedure were more favorable than what was expected. Patients expressed more favorable thoughts about colonoscopy for pain and embarrassment with most responses being "none" to "a little" for both exams. Overall appraisals of the tests were favorable and similar between colonoscopy and virtual colonoscopy. Patients mainly expressed "not unpleasant" to "a little unpleasant." Overall appraisal of the bowel preparation was the most negative.

Reference: Ristvedt, SL, McFarland EG, et al. "Patient Preferences for CT Colonography, Conventional Colonoscopy, and Bowel Preparation." The American Journal of Gastroenterology. Vol. 98, No. 3. 2003.

In a group of patients who were found to have many polyps, radiologists were in agreement that virtual colonoscopy and traditional colonoscopy identified the same problems.
The evaluation of computed virtual colonoscopy as a non-invasive examination of the colon continues to face new challenges. Early estimates of the diagnostic performance of virtual colonoscopy have been promising but variable.

The purpose of this ader agreement by a radiologist for colorectal polyp detection in a group of patients who had many polyps. This group of patients, who were suspected of having polyps, was first examined with virtual colonoscopy and then traditional colonoscopy the same day. The images were analyzed independently by four experienced radiologists.

A total of 157 colorectal lesions ranging from 4 millimeters to 30 millimeters were found at colonoscopy and correlated with virtual colonoscopy findings. Overall analysis demonstrated a 75 percent agreement among the four readers.

Reference: McFarland EG, Pilgram TK, et al. "CT Colonography: Multiobserver Diagnostic Performance." Radiology. Vol. 225, 2002.

Cancer terms:
Bone scan: Obtaining a picture of the bone using radioactive materials. A radioactive substance is injected in to the blood stream, and a picture of the bone is obtained using sensors that sense radioactivity. This technique is often used to find out the presence of bone metastasis from cancer. See section on medical imaging techniques for details. See cancer terms for more cancer related terms.