Review for 10.1186/s12876-021-01652-5 (2021)

Title: Impact of obesity in colorectal endoscopic submucosal dissection: single-center
retrospective cohort study
Version: 2 Date: 28 Dec 2020
Reviewer's report:
Thank you for reviewing the paper submitted to BMC Gastroenterology. In the present study,
the authors presented “Impact of obesity in colorectal endoscopic submucosal dissection: single-
center retrospective cohort study ". This is the first retrospective study about relationships
between obesity and outcomes of colorectal ESD. The contents are interesting and also useful
for clinical medicine. However, there are some problems.
1, The author mentioned the short-term outcomes of colorectal ESD in obese patients in this
study, and in previous reports, when there is abundant fat tissue in the submucosal layer, it would
be resulted difficulty in ESD. I think you should show, in results section, the relationship of the
degree of fat tissue in submucosal layer during ESD between the obesity group and the non-
obesity group for proof of the above description.
2, I think that there are two types of obese patients: those with high visceral fat and those with
high muscle mass. For example, have you analyzed the amount of visceral fat using CT?
3, In Definitions and Outcome Measurements section, you defined a “prolonged procedure” as
one that required more than 60 min, which was twice the median time. Moreover, in the results
section and in table 3, the ratio of longer procedure time was over 20%. In previous reports, long
procedure time was defined as 90 min or 120 min [1-3]. I think you should change the definition
of “prolonged procedure time”. What do you think about it?
#1, Yamasaki Y, Takeuchi Y, Uedo N, et al. Efficacy of traction-assisted colorectal endoscopic
submucosal dissection using a clip-and-thread technique: A prospective randomized study. Dig
Endosc. 2018;30:467-476.
#2, Yamashina T, Takeuchi Y, Nagai K, et al. Scissor-type knife significantly improves self-
completion rate of colorectal endoscopic submucosal dissection: Single-center prospective
randomized trial. Dig Endosc. 2017;29:322-329.
#3, Yoshida M, Takizawa K, Nonaka S, et al. Conventional versus traction-assisted endoscopic
submucosal dissection for large esophageal cancers: a multicenter, randomized controlled trial
(with video). Gastrointest Endosc. 2020;91:55-65.e2.
4, How many times have experts took over the procedure from the trainees? And, what are the
specific conditions of the replacement of operators? Please clarify it.
5, In Discussion section, you mentioned the risk factors for hypoxemia associated with sedation
during endoscopy were the total pethidine dose and obesity and so on. I think you should clarify
the amount of pethidine in result section and/or table.
6, In Histopathological Assessment section, there were no assessments of budding grade
according the JSCCR guideline. Please mention it. Moreover, the most recent version of JSCCR
guideline is 2019.
7, In Results (Clinical Outcomes) section, the resection rate, in especially curative resection rate,
were very high! Amazing and excellent. In general, the rate is a bit lower. What are the inclusion
criteria for colorectal ESD at your institution?
8, In Results (Clinical Outcomes) section, what did you treat for adverse events in this
study? Were they all resolved with conservative treatment? What was the rate of endoscopic
hemostasis? Please clarify it in detail.
9, In ESD Procedures section,”…, and the submucosal dissection was performed primarily in
Effect I mode and sometimes in swift coagulation mode….” What is “Effect I”? I think it would
be “End-cut I”. Please correct it (P5, L7).