Colorectal Polyps Missed with Optical Colonoscopy Despite Previous Detection and Localization with CT Colonography

To retrospectively evaluate and characterize nondiminutive colorectal polyps prospectively detected by using computed tomographic (CT) colonography but not confirmed with subsequent nonblinded optical colonoscopy (OC).

This study was institutional review board approved; the need for signed informed consent was waived. Over 113 months, 9336 adults (mean age, 57.1 years) underwent CT colonography, which yielded 2606 nondiminutive (≥6 mm) polyps. Of 1731 polyps that underwent subsequent nonblinded OC (ie, endoscopists provided advanced knowledge of specific polyp size, location, and morphologic appearance at CT colonography), 181 (10%) were not confirmed with initial endoscopy (ie, discordant), of which 37 were excluded (awaiting or lost to follow-up). After discordant polyp review, 66 of the 144 lesions were categorized as likely CT colonography false-positive findings (no further action) and 78 were categorized as potential OC false-negative (FN) findings.

Thirty-one of 144 (21.5%) of all discordant lesions were confirmed as FN findings at OC, including 40% (31 of 78) of those with OC and/or CT colonography follow-up. OC FN lesions were an average of 8.5 mm ± 3.3 in diameter and were identified with higher confidence at prospective CT colonography (on a 3-point confidence scale: mean, 2.8 vs 2.3; P = .001). OC FN findings were more likely than concordant polyps to be located in the right colon (respectively, 71% [22 of 31] vs 47% [723 of 1535]; P = .010). Most (81% [21 of 26]) OC FN lesions that were ultimately resected were neoplastic (adenomas or serrated lesions), of which 43% (nine of 21) were characterized as advanced lesions, and 89% (eight of nine) of advanced lesions occurred in the right colon.

In clinical practice, polyps prospectively identified with CT colonography but not confirmed with subsequent nonblinded (ie, despite a priori knowledge of the CT colonography findings) OC require additional review because a substantial proportion may be FN findings. Most FN findings found with OC demonstrated clinically significant histopathologic results, and a majority of advanced lesions occurred in the right colon.