During the exam
You'll wear a gown, but likely no other clothes. Sedation usually isn't necessary, but you may be given medication to relax your colon.
You'll begin the exam lying on your side on the exam table, usually with your knees drawn toward your chest. The doctor will place a small tube (catheter) inside your rectum to fill your colon with air or carbon dioxide. The air or gas helps create clear images and may cause a feeling of pressure in your abdomen.
For the next part of the exam, you'll lie on your back. The exam table will be moved into the CT machine, and your body will be scanned. Then you'll turn over to lie on your abdomen or your side, and your body will be scanned again.
You may be asked to turn and hold various other positions, as well as hold your breath at times. If necessary, a contrast agent may be given through a vein in your arm to help create clearer images.
A virtual colonoscopy typically takes about 10 to 15 minutes.
In a multicenter study of people who had virtual colonoscopy to screen for colon cancer, nearly 93 percent of participants labeled their overall experience "excellent" or "good," and 93 percent indicated they would choose the procedure for their next screening.
After the exam
Most of the air or gas will be removed from your colon through the catheter in your rectum. You may feel bloated or pass gas for a few hours after the exam as you clear the remaining air or gas from your colon. Walking may help relieve any discomfort, and you can return to your usual diet and activities right away.
June 09, 2014
- AskMayoExpert. What is computed tomography (CT) colonography? Rochester, Minn.: Mayo Foundation for Medical Education and Research; 2013.
- Kruskal JB, et al. Computed tomographic colonography. http://www.uptodate.com/home. Accessed Feb. 20, 2014.
- Yee J, et al. The time has arrived for national reimbursement of screening CT colonography. AJR. American Journal of Roentgenology. 2013;201:73.
- Pickhardt PJ, et al. Colorectal cancer: CT colonography and colonoscopy for detection — Systematic review and meta-analysis. Radiology. 2011;259:393.
- Sakamoto T, et al. Detection of flat colorectal polyps at CT screening colonography in comparison with conventional polypoid lesions. Acta Radiologica. 2012;53;714.
- Johnson CD, et al. The national CT colonography trial: Assessment of accuracy in participants 65 years of age and older. Radiology. 2012;263:421.
- Virtual colonoscopy. National Institute of Diabetes and Digestive and Kidney Diseases. http://digestive.niddk.6.gov/ddiseases/pubs/virtualcolonoscopy. Accessed Feb. 20, 2014.
- Pooler BD, et al. Screening CT colonography: Multicenter survey of patient experience, preference, and potential impact on adherence. AJR. American Journal of Roentgenology 2012;198:1361.