What if we examine the right colon four, five, or even more times?

I enjoyed reading the study by Lee at al. [1], which showed the significant incremental benefit of examining the right colon with colonoscope retroflexion after two consecutive forward-view inspections of this colonic segment.

At a glance, the study results are scary. After two examinations, 10 % of the adenomas were missed in the right colon. A spontaneous question arises from this observation: “Would more adenomas have been detected after a fourth, fifth, sixth, etc. pass?”

I prefer to interpret the results in a different way, and my pivotal question would be: “What went wrong during the first forward-view examination of the right colon?”

In this study, the proportion of adenomas detected during the first pass was lower than those reported in the four studies discussed in the manuscript (76.8 % vs. 81.4 % – 94.9 %) [2] [3] [4] [5], and significantly lower (P < 0.001) than those in three of them [2] [3] [5].

Therefore, the impressive (and scary, at the same time) study results could be attributed to the study design, at least partially. As each endoscopist acted as their own control during the three passes, endoscopists might have subconsciously (even consciously) introduced a bias to demonstrate the incremental benefit of the third retroflexion examination [6]. In an attempt to evaluate this possible interpretation of these results, an examination of the individual colonoscopist performance during the first pass of the study might prove of value.

• References

• 1 Lee HS, Jeon SW, Park HY. et al. Improved detection of right colon adenomas with additional retroflexion following two forward-view examinations: a prospective study. Endoscopy 2017; 49: 334-341
• 2 Hewett DG, Rex DK. Miss rate of right-sided colon examination during colonoscopy defined by retroflexion: an observational study. Gastrointest Endosc 2011; 74: 246-252
• 3 Chandran S, Parker F, Vaughan R. et al. Right-sided adenoma detection with retroflexion versus forward-view colonoscopy. Gastrointest Endosc 2015; 81: 608-613
• 4 Kushnir VM, Oh YS, Hollander T. et al. Impact of retroflexion vs. second forward view examination of the right colon on adenoma detection: a comparison study. Am J Gastroenterol 2015; 110: 415-422
• 5 Triantafyllou K, Tziatzios G, Sioulas AD. et al. Diagnostic yield of scope retroflexion in the right colon: a prospective cohort study. Dig Liver Dis 2016; 48: 176-181
• 6 Van den Broek FJC, Kuiper T, Dekker E. et al. Study designs to compare new colonoscopic techniques: clinical considerations, data analysis, and sample size calculations. Endoscopy 2013; 45: 922-927