For years, instrument manufacturers have tried to develop colonoscopes that afford a better, clearer, or new method of casting light on the mucosal surface (eg, narrow-band imaging) to enhance the ability to detect adenomas. The problem of missed lesions was demonstrated by Pickhardt and coworkers, who performed a computed tomographic colonography (CTC) evaluation of over 1,200 individuals who underwent same-day CTC and colonoscopy. With segmental unblinding during a colonoscopic examination that followed CTC, 10% of polyps were missed by colo- noscopy. Of the missed neoplasms found on the second- look colonoscopy after segmental unblinding, 17 were tubular adenomas, 3 were tubulovillous adenomas, and 1 was a small adenocarcinoma (range in size, 6—17 mm). The majority of these neoplasms were located on the edge or on the proximal aspect of a fold.
A more recent paper on CTC simulation reconstructions using a 90-degree imaging field of view corroborated a previous report that showed that 23.4% of the colonic surface is not visualized by direct, straight, end-on examinations. This report by East and associates repeated the type of scan performed by Pickhardt and colleagues but varied the simulated fields of view to 90, 120, 140, and 170 degrees to match the angle of view of various colonoscopes. In this study, the percentage of visualized colonic surface increased with each increasing angle-of-view increment. The total number of missed areas was approximately the same for the fields of view of 90—140 degrees but decreased when the field of view was 170 degrees. Only approximately 85% of the colonic surface was visualized using a 140-degree angle of view, and this percentage increased when the examination was repeated using a 170-degree angle of view comparable to the Olympus 180 series colonoscopes (Olympus Medical Instruments), signifying that more of the surface is seen when the angle of view increases. According to the optical colonoscopy simulation performed by CTC software, approximately 13% of the colonic surface is not seen with the commonly available 140-degree angle of view of most colonoscopes. Simulation of a colonoscope with a 170-degree field of view resulted in an almost 6% reduction in the percentage of surface missed. cialis super active