Review for 10.1186/s12876-020-01341-9 (2020)

Reviewer ’s report  
 
Title: CO2 or air cholangiography reduces the risk of po st-ERCP cholangitis in patients with 
Bismuth type IV hilar biliary obstruction  
 
Version: 2 Date: 17 May 2020  
 
Reviewer's report:  
 
The manuscript is much improved. Only 2 points are concerned.  
 
1. Page 12, line 54. "The use of CO2 for cholangiography ... is strongly recommended". Since 
this study did not show any inferiority of air t o CO2 especially in case of air embolism in both 
groups, It'd be better if the author could tone down the degree of recommendation.  
 
2. Table 2. It'd be better if the author could change "functional success" to "clinical success" in 
relevant to the main text.   
 
Are the methods appropriate and well described?  
If not, please specify what is requir ed in your comments to the authors.  
 
Yes 
 
Does the work include the necessary controls?  
If not, please specify which controls are required in your comments to the authors.  
 
Yes 
 
Are the conclusions drawn adequately supported by the data shown?  
If not, please e xplain in your comments to the authors.  
 
Yes 
 
Are you able to assess any statistics in the manus cript or would you recommend an 
additional statistical review?  
If an additional statistical review is recommended, please speci fy what aspects require further 
assessment in your comments to the editors.  
 
I recommend additional statistical review  
 
Quality of written English  
Please indicate the quality of language in the manuscript:  
 
Acceptable  
 
 
 
Declaration of competing interes ts 
Please complete a declaration of competing interests, considering the following questions:  
 
1. Have you in the past five years received reimbursements, f ees, funding, or salary from an 
organisation that may in any way gain or lose financially from the pu blication of this 
manuscript, either now or in the future?  
2. Do you hold any stocks or shares in an organisation t hat may in any way gain or lose 
financially from the publication of this manuscript, either now or in the future?  
3. Do you hold or are you c urrently applying for any patents  relating to the content of the 
manuscript?  
4. Have you received reimbursements, fees, funding, or salary from an organization that 
holds or has applied for patents relating to the content of the manuscript?  
5. Do you have any other financial competing interests?  
6. Do you have any non -financial competing interests in relation to this paper?  
 
If you can answer no to all of the above, write 'I declare that I have  no competing interests' 
below. If your reply is y es to any, please give details below.  
 
I declare that I have no competing interests.  
 
Reviewer Publication Consent. I agree for my report to be made available un der an Open 
Access Creative Commons CC -BY License ( http://creativecommons.org/licenses/by/4.0 ) if this 
manuscript is accepted for publication. Any comments that I do not wish to be included in the 
published report have been included as confidential comment s to the editor, which will not be 
published.  If you are not happy for us to publish this report, please contact the edi torial office 
before completing the review.  If you wish, you can include your name in your publish ed report. 
Please note you must decide w hether to include your name at the start of the process and  confirm 
this decision whenever prompted. If you change your decision later, we will not be able to 
publish your name.  
 
I agree to the terms of the CC -BY 4.0 license; please do not publish my name w ith my report.  
(default)