Review for 10.1186/s12876-020-01316-w (2020)

Reviewer ’s report  
 
Title: Percutaneous stent placement for malignant hilar biliary obstruction: side -by-side versus  
stent -in-stent technique  
 
Version: 2 Date: 15 Mar 2020  
 
Reviewer: John Leeds  
 
Reviewer's report:  
 
The authors describe a retrospective comparative study of diff erent methods for inserting self 
expanding metal stents (SEMS) in patients with hilar biliary obstruction. They show some 
differences between the two techniques but recognise the limitations and issues with their study 
design. The main issue as they say is  that it is retrospective and therefore there is no 
randomisation between the groups or stratification for different tumour types and distributions. 
There are a few grammatical errors in the manuscript and a few spelling errors e.g. in the tables 
"Kaplane"  rather than "Kaplan".  
 
Are the methods appropriate and well described?  
If not, please s pecify what is required 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 explain in your comments to the authors.  
 
Yes 
 
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:  
 
Acceptable  
 
Declaration of competing interests  
Please complete a declaration of competing interests, considering the following questions:  
 
1. Have you in the past five years received reimbursements, fees, funding, or salary from an 
organisation that may in any way gain or lose financially from the publication of this  
manuscript, either now or in the future?  
 
2. Do you hold any stocks or shares in an organisation that may in any way gain or lose  
financially from the publication of t his manuscript, either now or in the future?  
 
3. Do you hold or are you currently 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 applie d 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 yes to any, please give details below.  
 
I declare that I have no competing interests.  
 
I agree to the open peer review policy of the journal. I understand that my name will be included  
on my report to the authors and, if the manuscript is accepted for publication, my named report  
including any attachments I upload will be posted on the website along with the authors'  
responses. I agree for my report to be made available under an Open Acc ess Creative Commons  
CC-BY license ( http://creativecommons.org/licenses/by/4.0/ ). I understand that any comments  
which I do not wish to be included in my named report can be included as confidential comments  
to the editors, which will not be published.  
 
I agree to the open peer review policy of the journal