Review for 10.1186/s12876-021-01877-4 (2021)

Reviewer’s report
Title: 
Cecal Retroflexion is Infrequently Performed in Routine Practice and the
Retroflexed View is of Poor Quality
Version: 
2 
Date: 
03 Feb 2021
Reviewer's report:
Summary: This manuscript discusses the frequency and quality of cecum
retroflexion during screening and surveillance colonoscopies. The study is a 6
week prospective single center observational study from 2016. The study
incorporates video recording technology to review the extent, duration, and
regularity that 17 endoscopists used cecal retroflexion to do a second look at the
right colon. The manuscript finds that cecal retroflexion is used infrequently and,
when performed, is often inadequate. 
Major Comments: 
Comment 1: 
In the current study, 3 polyps were identified in the RV (polyp
detection rate of 8.1%) and all were found before forward-view examination.
However, recent studies of retroflexion in the right colon report higher polyp
detection rate at the right colon (Please see the 3 publications below). For
example, RV detected additional 15.4% of polyps after forward view
examination in Miyamoto et al study. Please discuss why the polyp detection rate
of right colon in this study seems lower than other studies and why RV is of poor
quality here. 
(1) Michopoulos S, Axiaris G, Baxevanis P, Stoupaki M, Gkagkari V,
Leonidakis G, Zampeli E, Sotiropoulou M, Petraki K. Retroflexion, a costless
endoscopic maneuver, increases adenoma detection rate in the ascending colon.
Ann Gastroenterol. 2021;34(1):53-60. doi: 10.20524/aog.2020.0549. Epub 2020
Oct 12. PMID: 33414622; PMCID: PMC7774652.
(2) Miyamoto H, Naoe H, Oda Y, Shono T, Narita R, Oyama S, Hashigo S,
Okuda A, Hasuda K, Tanaka M, Sakurai K, Murakami Y, Sasaki Y. Impact of
retroflexion in the right colon after repeated forward-view examinations. JGH
Open. 2018 Sep 10;2(6):282-287. doi: 10.1002/jgh3.12084. PMID: 30619938;
PMCID: PMC6308076.
(3) Kushnir, Vladimir, Oh, Young, Hollander, Thomas, 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(3):415-422. doi:10.1038/ajg.2015.21.
Comment 2: What is the range of ADR of the endoscopists involved in the
study? If these endoscopists have a very high ADR despite poor quality RV,
then good RV is probably not important as they are able to detect polyps with
forward view. If they have low ADR, then the low quality RV may reflect low
quality colonoscopy exams. 
Comment 3: Methods Section: The manuscript mentions that the endoscopists
were aware of the recorders and that they had provided informed consent. Were
the endoscopists aware that you were studying retroflexion in the cecum and
right colon? Concern being that perhaps the two endoscopists who retroflexed
every time were aware of the studies aims whereas the others were not. 
Comment 4: Methods Section: Paragraph 1: Please comment on whether any of
the 6 gastroenterologists evaluating the videos were also one of the 17
endoscopists who performed the procedures and were videotaped. If there was
overlap this would introduce bias.
Comment 5: Results, Right Colon Examination section, 2nd paragraph: Of the
two endoscopists who performed CR for every colonoscopy, how often was their
examination full RV to the hepatic flexure? Specifically interested in the rate of
full RV among the practitioners who frequently used CR. Did the majority of full
RV from the entire study come from just the two endoscopists who did CR every
time? 
Comment 6: It has been shown that examination of right colon with either
forward view or retroflexed view yield similar ADR. Please discuss why
infrequent and low quality CR and RV in this study is important.
Minor Comments:
Comment 1: Results Section: Last sentence of first paragraph: "Seven videos per
colonoscopist (119 videos total) were randomly selected for manually review."
Consider changing "manually review" to "manual review:. 
Comment 2: Discussion Section: 2nd paragraph: "Furthermore, when a RV was
obtained via CR, it was often a brief evaluation of the ascending colon with a
careful examination to the level of the hepatic flexure" - Instead of "with a
careful examination" did you mean to say "without a careful examination?"
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Is the study design appropriate to answer the research question (including the use
of appropriate controls), and are the conclusions supported by the evidence
presented?
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from apparent manipulation?
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