Polyp detection

Preliminary results indicated that the accuracy of CT virtual colonoscopy for polyp detection exceeded barium enema and approached conventional colonoscopy. Recent published studies from Boston Medical Center (BMC), the Mayo clinic and the University of California in San Francisco reported results on relatively large patient populations .

	1- axial CT image at lung window setting shows a 1 cm polyp in the transverse colon. click on picture to see full resolution images
	2- Virtual endoscopy showing the same polyp click on picture to see full resolution images
	3- 3D reconstruction of the colon simulating double contrast barium enema showing the exact location of the polyp. click on picture to see full resolution images

Occlusive cancer

Another application of virtual colonoscopy, is the preoperative assessment of the colon proximal to an occlusive cancer (defined as a tumor that cannot be traversed endoscopically) was recently reported by Fenlon et al from Boston Medical Center. In 29 patients with occlusive carcinomas, virtual colonoscopy identified all 29 occlusive cancers and demonstrated two cancers and 24 polyps in the proximal colon. Both of the synchronous cancers were confirmed intraoperatively and resected. Virtual colonoscopy successfully demonstrated the proximal colon in 26 of 29 patients studied compared with preoperative barium enema which failed to adequately demonstrate the proximal colon in any patient studied.

	1- axial CT image at lung window setting shows an large tumor in the sigmoid colon. Colonoscopy could not assess the colon proximal to the lesion click on picture to see full resolution images
	2- axial CT image at lung window setting shows a large 1.8 cm polyp in the distal transverse colon. click on picture to see full resolution images
	3- 3D reconstruction of the colon simulating double contrast barium enema showing the exact location of the polyp, prior to surgery. click on picture to see full resolution images

Incomplete colonoscopy: Colonoscopy fails to visualize the entire colon in a variable number of patients. The completion rate is usually excellent, in the 95% range, but some patient may have very tortuous, redundant colons, post-surgical adhesions with a fixed difficult to intubate colon, or adverse reaction to sedation, making it impossible to complete a colonoscopy. More than half of adenomatous polyps are localized proximal to the sigmoid colon. In 25% of people found to have adenomas, the adenomas were found only in the proximal colon. This emphasizes the importance of a screening method being able to view the entirety of the colon. In the past, patients were referred for a barium enema following an incomplete colonoscopy, today the availability of virtual colonoscopy makes it immensely easier for patients and doctors to complete the test, usually the same day of the incomplete colonoscopy.


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