Review for 10.1186/s12876-019-1053-6 (2019)

Reviewer’s report
Title:  Classification of the Cystic Duct Patterns and Endoscopic Transpapillary Cannulation of the
Gallbladder to Prevent Post-ERCP Cholecystitis
Version: 0 Date: 20 Dec 2018
Reviewer: Gianpiero Manes
Reviewer's report:
The  paper  evaluates  the  possible  role  of cystic duct  anatomy on the  success  rate of cystic duct
cannulation during  ERCP performed to treat or prevent acute cholecystitis.
The study refers to a retrospective series of 226 patients undergoing ERCP in a single center in 14
months. Gallbladder cannulation was performed for most of them with the intent of preventing the
development of PEC.
The paper is interesting mainly because deals with a subject that is somehow neglected in the literature:
usefulness of draining gallbladder to prevent the development of cholecystitis during ERCP is still a
matter  of  debate;  similarly,  it  is  not  clear  whether  transcystic  drainage  may represent  a  reliable
therapeutic option to treat acute cholecystitis in old, morbid patients unfit for surgery.
The conclusion of the authors is that defining the anatomy of the cystic duct may lead the endoscopist
in selecting different techniques and devices with the aim of maximizing the success rate. Actually, I
dot not believe that the results of the study may support such a statement.  In the different sections of
the paper classification of the cystic duct patterns has merely a descriptive intent and does not seem to
help in guiding endoscopic cystic cannulation. Only in the discussion authors try to describe the
different techniques performed according to the cystic duct anatomy.
Several other problems arise from the study:
In the last part of the introduction authors report some data regarding their case series; this part should
be removed and replaced by a clear definition of the aim of the study.
Authors report that the 226 patient undergoing gallbladder drainage were at high risk of developing
PEC:  I  think  they  should  describe  in  a  table  the  patients'  characteristics,  the  different  factors
determining the high risk of PEC, as well as the indication to perform ERCP.
Authors state that gallbladder cannulation was performed according to the cystic duct pattern;  I think
that they should explain how the cannulation technique was different according to the morphology, and
how recognizing the cystic duct pattern may influence the way the endoscopic perform the procedure,
i.e. the position of the scope, the devices that are used, possible tricks to cannulate the cystic duct.
According to the results, type I and III patterns are easier to be cannulated (about 85% success rate),
while  type  II  is  more  difficult  with  a  success  rate  of  75%,  without  any  statistically  significant
differences  according  to  the  types  and  subtypes  morphology.   This  is,  of  course,  an  important
information but accordingly  my question is: if morphology of the cystic duct does not significantly
influence the rate of success cannulation why should we classificate it? Are there any other factors
different than cystic  duct  morphology able to influence the rate of success  in the present series
(stenosis, impacted stones, morphology of the common bile duct, etc.)?
In general, I would suggest to rewrite completely the paper focusing mainly of the following question:
Has the classification in so many types and subtypes really a clinical impact? Would not it be better to
simplify it and try to identify the factors that really request different cannulation techniques? 
Try to describe exactly the endoscopic technique needed to cannulate the cystic duct according to each
single pattern; this description should be placed in the methods section and not in the discussion.
A real discussion is lacking. Authors should try to discuss on the few data available in the literature on
the endoscopic gallbladder drainage; do their data really provide useful information to improve the
cannulation technique? 
Are the methods appropriate and well described?
If not, please specify what is required in your comments to the authors.
No
Does the work include the necessary controls?
If not, please specify which controls are required in your comments to the authors.
No
Are the conclusions drawn adequately supported by the data shown?
If not, please explain in your comments to the authors.
No
Are you able to assess any statistics in the manuscript or would you recommend an additional
statistical review?
If  an  additional  statistical  review  is  recommended,  please  specify  what  aspects  require  further
assessment in your comments to the editors.
I am able to assess the statistics
Quality of written English
Please indicate the quality of language in the manuscript:
Not suitable for publication unless extensively edited
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