Review for 10.1186/s12876-015-0381-4 (2015)

Reviewer ’s report  
 
Title: Wire -guided cannulation over a pancreatic stent versus double guidewire technique in  
patients with difficult biliary cannulation  
 
Version: 0 Date: 02 Sep 2015  
 
Reviewer: Renumathy Dhanasekaran  
 
Reviewer's report:  
 
Yang et al report a large study where they have compared outcomes between two techniques - 
double guidewire technique (DGT) or wire -guided cannulation over a pancreatic stent (WGC -
PS) in patients with difficult b iliary cannulation. Although this is a retrospective study, it is well 
written and involves a large cohort of patients making this interesting. But several important 
questions remain to be answered before the study can be published:  
 
1. The authors report i n the results section that in Feb 2012 they switched to using the DGT 
technique from the WGC -PS technique but do not explain a rationale for picking this 
specific time point. Was this an institutional protocol; did all ERCP operators decide to 
switch at th e same time?  
 
2. They mention that a switch was made from DGT to WGC -PS if cannulation was 
unsuccessful in 5 mins. And that difficult biliary cannulation was defined as unsuccessful 
cannulation within 10 min of attempting the conventional method.  Since thi s is a 
retrospective study how did they assess for the timing of these interventions. Especially 
given that time is not mentioned as a procedure related variable collected.  
 
3. Since the patients underwent WGC -PS before 2012 I think the authors should first  report 
on this intervention before DGT. And the sequence has to be maintained throughout the 
manuscript so there is no confusion.  
 
4. The main conclusion in the study is that "There were no significant differences in the 
initial and overall biliary cannula tion rates between the two groups. The rate of successful 
biliary cannulation without NKF was significantly higher in the DGT group than in the 
WGC -PS group (86.2% vs.66.7%, P = 0.003)". But this study is not a head -to-head 
comparison of the two techniques  since they are separated by time variables and also by 
overlapping of the techniques in one subgroup. So I think the conclusion is too strong and 
these results have to be worded differently.  
 
5. Also, another conclusion is "In addition, a stepwise approach  using DGT and WGC -PS 
sequentially facilitated successful biliary cannulation and reduced the need for the 
needle -knife precut technique". But the reverse order of performing the interventions was 
not attempted so I think this conclusion is too strong and has to be worded differently.  
 
 
Are the methods appropriate and well described?  
If not, please specify 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.  
 
No 
 
Are you able to assess any statistics in the manuscript or would you recommend an  
additional statistical review?  
If an additiona l 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 gai n 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 this manuscript, either now or in the fu ture?  
 
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 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 yes to any, please give details below.  
 
I declare that I have no competing interests  
 
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