Virtual Colonoscopy Detects Large Polyps Found with Visual Colonoscopy

Virtual Colonoscopy Detects Large Polyps Found with Visual Colonoscopy

A recent study published in the American Journal of Roentgenology reports that individual colon polyps or lesions larger than 6mm that are detected by CT colonoscopy (CTC) significantly correlate with a matching polyp that is found by optical colonoscopy.

Colonoscopy is a procedure in which a colonoscope is passed through the rectum, into the colon and into the lower end of the small intestine. The procedure is performed to visually examine the lower portion of the gastrointestinal tract for early signs of cancer, ulcers, inflamed tissue or bleeding. Pictures and biopsies may be taken for further evaluation by the physician. However, patient compliance with screening utilizing colonoscopy is low, so researchers have been evaluating less invasive methods in the hopes that more patients will undergo screening of colorectal cancer. Virtual colonoscopy or CT colonoscopy uses x-rays and computers, versus a colonoscope, to produce 2- or 3-dimensional images of the rectum, colon and the lower end of the small intestine. Clinical studies are ongoing to determine the true effectiveness of CT colonoscopy as compared to standard colonoscopy.

In this recent study, researchers sought to determine if polyps or lesions seen by the CT colonoscopy correlated with the findings of visual colonoscopy. The study included 1,339 asymptomatic adults who were each examined by CTC and visual colonoscopy on the same day. Each polyp or lesion that was detected was given a confidence-based grade based on a three-point scale indicating diagnostic confidence (1= least certain; 2=intermediate; and 3=most certain).

Results of the study found that polyps or lesions with a confidence grade of 1 corresponded to matched lesions on visual colonoscopy in 33% of cases; grade 2 lesions correlated in 50% of the cases; and grade 3 lesions correlated in 66% of the cases. When evaluated by size, similar matching trends were found and the match rate was as high as 82% when the lesion was a grade 3 and 10mm or larger in size. Further analysis found that when grade 3 lesions measured larger than 8mm by CTC, they were frequently found to be malignant on optical colonoscopy.

Researchers concluded polyps or lesions found by CTC that have a high diagnostic confidence significantly correlate with the findings of optical colonoscopy. In addition, higher-grade lesions significantly increased the possibility of the lesions being cancerous. These conclusions could help physicians decide to use CTC for continued surveillance rather than conventional colonoscopy. Patients are encouraged to speak to their physician regarding screening options for their situation.

Reference: Pickhardt P, Choi J, Nugent P, et al. The Effect of Diagnostic Confidence on the Probability of Optical Colonoscopic Confirmation of Potential Polyps Detected on CT Colonography: Prospective Assessment in 1,339 Asymptomatic Adults. American Journal of Roentgenology. 2004; 183: 1661-1665.

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