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: 26 Aug 2015  
 
Reviewer : James Tabibian  
 
Reviewer's report:  
 
In this retrospective study, the authors queried the outcomes of DGT and compared them to 
WGC -PS among patients with difficult biliary cannulation. This is a relatively large and well -
written study, and the effort by the others is laudable; nevertheless, there are issues with the 
methods, paucity of exploration of the results, and insufficient discussion of limitation which 
hamper enthusiasm.  
 
Specific points that should be considered, the majority of wh ich are minor, are as follows:  
 
Title:  
- The title suggests that this was a comparative study.  It seems more like a report of an 
additional/novel cannulation technique (DGT) and the results of WGC -PS when said 
technique fails.  WGC -PS is used as a point of  reference, but it's not really a head to head 
or concurrent comparison (they were separated in time, authors may have gained 
experience with cannulation during WGC -PS years that may have contributed to higher 
success rates with DGT).  
 
Abstract:  
- The metho dology should be explained somewhat further; e.g. what was the primary 
outcome?  What were the secondary outcomes?  Were any covariables 
considered/adjusted for?  
 
- As a general stylistic point, it's helpful for the reader if order is kept consistent; e.g. i f 
WGC -PS was conducted first chronologically, it's results should be mentioned first, such 
as in the sentence "The rate of initial successful cannulation was 70.1% (61/87) in the 
DGT group and 66.7% (60/90) in the WGC -PS group (P = 0.632)."  
 
- Consider clari fying the phrase "stepwise approach using DGT and WGC -PS" to 
"stepwise approach using DGT followed by WGC -PS as needed" since the reverse order 
was not study.  
 
Background:  
- In the first sentence, would add other variables that determine success, e.g. procedural 
complexity/anatomy.  
 
- The authors may consider modifying wording as it remains unknown if the needle -knife 
precut technique independently increases the risk for PEP or  if this association is driven 
by the preceding events (e.g. repeated cannulation attempts) and underlying difficult 
anatomy.  
 
Methods:  
- Why the sharp transition from WGC -PS to DGT?  
 
- Regarding the definition of difficult cannulation, was it 10 minutes from  procedure start 
time or 10 minutes from the point of visualizing the papilla (or…?)?  
 
- Is "midazolam, propofol, and meperidine" correctly considered as "conscious sedation"?  
 
- The authors might reconsider the wording of "Wire -guided cannulation of the bile duct 
was attempted over the pancreatic wire" to something more similar to the Figure 1 legend 
or alternatively "Wire -guided cannulation of the bile duct was attempted alongside the 
pancreatic wire" since "over the wire" tends to suggest a different/uninten ded meaning.  
 
- The authors state "the pancreatic wire was removed from the PD with or without 
pancreatic stenting  at the discretion of the endoscopist."; was there a different in PEP rate 
or other outcomes in patients who received a PD stent vs. did not?  
 
- It would be helpful to eliminate confounding if the authors could perform a multivariate 
analysis, at least for their primary outcome of interest.  
 
Results:  
- The authors excluded "176 ERCPs in which the needle -knife precut technique was 
attempted immediatel y after initial failure of the standard cannulation technique".  
Excluded patients and criteria should probably be mentioned in the methods section.  
Perhaps more importantly, why would some patients go directly to needle -knife rather 
than WGC -PSC or DGT?  Who are the patients in which these techniques are skipped?  It 
would be important to know this to better define the study population.  
 
- As shown in Table 2, the rate of PEP was substantially higher in the DGT group.  The 
authors should perform a post -hoc sensitivity/power analysis as DGT could well be 
associated with significantly more PEP, but the p value may not have reached <0.05 due 
to underpowering.  If this is the case, what advantage does DGT have over WGC -PS?   
 
Figures:  
- An arrow/symbols to help denote the two different wires might be helpful.  
 
- Figure C in both figure 1 and 2 is probably not adding much.  
 
- A figure to highlight the most important finding of this study should be considered.  
 
 
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.  
 
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 recommend additional statistical review  
 
Quality of written English  
Please indicate the qualit y 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 f rom 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 this 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 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  
 
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 Access C reative 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