Up to this time, there have been 5 published reports on the TER. The first report was a feasibility study using colon models implanted with 40 simulated polyps, 27 of which were attached to the proximal aspect of folds and 13 of which were placed in obvious locations readily seen by the straight forward-viewing colonoscope. Six gastrointestinal endoscopists examined these models with either a straightforward colonoscope or the same instru­ment using the TER during withdrawal. The round, brightly colored, simulated polyps were 3 mm in diam­eter and 1.5 mm in height. Twelve percent of the polyps located on the proximal aspect of folds were detected with the straight-viewing colonoscope, and 81% were seen with the first-generation auxiliary retrograde-viewing device. This marked ability to detect polyps hidden from straightforward-viewing stimulated further interest in the development of the device. In the first human pilot study, the TER was associated with an 11.8% increase in polyp detection compared to the straight end-on colonoscope. During this study, a total of 38 polyps were identified in 29 patients as the colonoscope and TER were withdrawn together from the cecum. Thirty of the polyps were seen with the colonoscope, 4 were visualized by both endo­scopes, and an additional 4 were seen only with the TER, as they were located on the proximal aspect of folds. The polyps found only by the TER measured 0.3 cm, 0.3 cm, 0.2 cm, and 0.7 cm in size. All of these polyps were subsequently located by the colonoscope and removed. Histopathologic examination of the tissue showed that 3 were hyperplastic and the largest was a tubular adenoma. The mean time for the total examination was 22 minutes, which included the time for removal of the polyps and the replacement of the device.

The early research regarding the development of the device and its specifications was published in 2009 and described the increase in mucosal visualization provided by the device. A multicenter prospective study was performed in 249 patients in 8 locations. During this investigation, an attempt was made to determine whether detected polyps were identified first by the colonoscope or by the TER. This report revealed an additional 13.2% increase in polyp detection, with an 11.0% increase in adenoma detection (Figure 3). Nine adenomas measur­ing over 10 mm in diameter were seen with the standard forward-viewing colonoscope; 3 additional adenomas of that size were seen with the TER but not the forward- viewing colonoscope, representing a 33% increase in adenoma yield. Most of the 257 polyps seen and removed during this study were visualized simultaneously by both the forward-viewing colonoscope and the TER. The 8 investigators and their study coordinators were instructed to specifically exclude from the TER discovery set lesions that were initially seen with the TER but were readily apparent on the forward view of the colonoscope. These lesions were not considered “additional polyps detected by TER.” The final result was that 34 of257 polyps were first seen by the TER. Among adenomas, 15 of a total of 136 were first seen by the TER. In this group of adenomas, 8 of a total of 40 adenomas greater than 6 mm in diameter were first seen by the TER (20% yield) and 3 of 12 were larger than 10 mm.
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Figure 3. The forward view

Figure 3. The forward view of the colonoscope, looking toward the Third Eye Retroscope, is obscured by the fold (A). However, in the retrograde view, the retroscope is examining the area behind that fold (B) and reveals an adenoma hidden deep behind the fold. This polyp was not visualized by the colonoscope.

It should be noted that the TER is pointed backward and examines folds after they, and the space behind them, have been seen and already cleared by the forward-viewing colonoscope as it is being withdrawn. The mean size of all polyps detected with the TER was 4.6 mm compared to 4.2 mm for those detected with the colonoscope alone. The mean size of adenomas detected with the TER was 5.2 mm compared to 4.4 mm for those detected with the colonoscope. Of the 34 polyps detected with the TER, 10 were over 6 mm and 4 were greater than 10 mm in diameter. The withdrawal phase of both endoscopes took 10.9 minutes during this investigation. This time did not include the actual time required for polyp removal, as all polyps seen by either device were removed immediately. The ability of a retrograde-viewing device to find addi­tional polyps highlights the inability of forward-viewing colonoscopy to locate all of the polyps in the colon. Colo­noscopy is the most effective imaging modality currently available for the large bowel, though it may be an imper­fect tool against colorectal cancer. As recent guidelines for colorectal cancer screening and surveillance depend upon whether polyps are found on colonoscopy and upon their size, the need to identify all of the neoplasia in the colon has assumed greater importance. levitra 10 mg

Another major study examined the impact of experi­ence with the device on adenoma detection rates. This multicenter prospective study demonstrated that the learning curve for using the TER is relatively short and confirms the increase in polyp detection with the device. This study was designed to determine how much experi­ence was required for a previously untrained individual to acquire the necessary skills to find polyps and become proficient in its use. The endoscopists participating in this study had no previous experience with the TER. The protocol required each endoscopist to complete 20 procedures. During this study, when a polyp was seen, the endoscopist indicated whether it could have been seen using a routine withdrawal technique or whether it could only have been detected with the TER. If the polyp was seen with both endoscopes, it was credited as being found by the colonoscope. All polyps seen with the colonoscope or the TER were subsequently found with the colono­scope and removed. In these 298 subjects, 182 polyps were detected with the colonoscope, and an additional 27 polyps were detected with the TER, representing a 14% increase. The 20 subjects who were assigned to each endoscopist were examined in groups of 5 as the study progressed. The learning curve was evaluated by compar­ing results among each group examined by an individual physician. For all polyps, the additional detection rate for the TER was 17.8% in the first group and 17% in the fourth group to be examined. For adenomas, the addi­tional detection for the TER increased from 15.4% in the first group to be examined to 25% in the fourth group. The mean size of all polyps detected with the TER was 6.5 mm, compared to 5.5 mm for those detected with the colonoscope alone. The mean size of adenomas detected with the TER was 6.8 mm compared to 6.5 mm for those found with the colonoscope. Nineteen percent of additional adenomas with a size of 10 mm or larger were detected with the TER compared to the colonoscope. This study suggests that there is a trend toward improvement of adenoma detection with increasing experience and that the basic mechanical skills are acquired rapidly, though varying amounts of experience are required to develop optimal technique.