Review for 10.1186/s12876-020-01455-0 (2020)

Reviewer’ s report
Title: Duodenal major papilla morphology can affect biliary cannulation and complications during
ERCP, an observational study
Version: 0Date: 10 Jul 2020
Reviewer's report:
I read with interest the article by Po-Han Chen and colleagues. It is a retrospective study
evaluating the association between the morphology of the papilla and the ERCP cannulation andcomplication rates, evaluating also associated risk factors. The conclusions of the study were thatsmall and protruding papillas were associated with greater failure rates.
There are several issue that need to be clarified by the Authors:
-First of all, the aim of the study is not clear and should be clearly defined. In the methods section,it is stated: "The main outcome of this study was cannulation failure". Clearly this cannot be theaim of the study!-Similarly the secondary outcome should be clearly defined. In general the "Outcome and factors"section of the methods should be rewritten and report more specifically the outcomes andinvestigated factors.-One of the main limitations of the study is the classification the authors used in the first place todefine the morphology of the papilla. Indeed, the classification proposed by Haraldsson showed a0.6 (moderate-substantial) interobserver agreement. Unfortunately, the authors did not perform aninterobserver agreement evaluation, that might have possibly been even lower.-The conclusions need to be checked as a few sentences are incomplete.-The authors report that age was a risk factor for cannulation failure. However, it is not defined
what the authors considered as age cut-off.
-Similarly, the authors do not define in the methods what they consider as "platelets", "PT","bilirubin", etc. in the table 2 and 3 and the associated statistical analyses.-In the "complications" paragraph of the discussion, it is stated: "none of the post-ERCPcomplications were found to be significant risk factors…". What do the authors mean with thissentence? How can a complication be a risk factor?-Patients characteristics and procedure complications should be reported in separate tables.
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YesAre 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.
YesAre the conclusions drawn adequately supported by the data shown?
If not, please explain in your comments to the authors.
YesAre 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 furtherassessment 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:
Needs some language corrections before being publishedDeclaration of competing interests
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