primary differences between virtual colonoscopy, also referred to as computed tomographic colonography (CTC), and optical colonoscopy.
Technologic advances over the past few years have allowed CTC to evolve into the premiere radiologic method to investigate colonic neoplasia, surpassing double-contrast barium enema. However, optical colonoscopy continues to be the primary tool used for colorectal cancer screening. There are several inherent differences between these two modalities, and each has its own advantages and disadvantages. Although it is necessary for physicians to be cognizant of the unique features of both CTC and optical colonoscopy, the most important fact is that they are equivalent in their ability to detect colorectal cancer and large polyps (> 10 mm).
Virtual Colonoscopy versus Optical Colonoscopy
|Virtual Colonoscopy (CTC)||Optical Colonoscopy|
|Safety profile||Less complications, including lower rate of bowel perforation||More frequent incidence of bowel perforation|
Less well tolerated than CTC
|Complete colonic wall visualization||Better complete colonic wall visualization (4% for CTC versus 7% for optical colonoscopy in one large series of direct comparison*)||Higher rate of incomplete examination|
|Bowel prep||Potential for no bowel prep (laxative-free CTC) with use of fecal tagging||Required|
|Radiation exposure||Uses ionizing radiation, although dose to the patient is not significantly different from that of a routine abdominal CT scan||None|
|Ability to perform procedures||Unable to perform interventions||Able to perform procedure (biopsy or polypectomy) at same time lesions are identified|
|Extracolonic findings||Ability to visualize the colon wall, in addition to detect incidental findings of the abdomen and pelvis||Can only visualize colonic lumen|
CTC, Computed tomographic colonography.
Halligan S, Taylor SA. CT colonography: results and limitations. Eur J Radiol. 2007 Mar;61(3):400-8.