Review for 10.1186/s12876-015-0233-2 (2015)

Reviewer's report
Title:Endoscopic Inside stent placement is suitable as a bridging treatment for
preoperative biliary tract cancer
Version:3Date:25 July 2014
Reviewer: Hirotoshi Ishiwatari
Reviewer's report:
Major Compulsory Revisions
(1) There were several reports about inside stent for malignant biliary obstruction
(Pedersen et al. Gastrointest Endosc.1998;48:574-579, Uchida et al. J
Gastroenterol. 2005;40:291-296, Ishiwatari et al. Digest Endosc.2013;25:94-99).
They have shown conflicting results. Therefore, now, retrospective comparative
study cannot verify the effectiveness of inside stent, namely, it reduces the
quality of the study. Prospective study is desirable, however, if it is impossible to
do so, the retrospective comparative study using the propensity score-matching
method may have more meaningful result.
(2) The allocation method was not showed clearly in the method section. Authors
should specify how to assign inside stent or conventional stent in the method
section. This is a very important item, therefore only citation of a reference article
is insufficient.
(3) Inside stent for the common bile duct obstruction did not show clinical benefit
in previous prospective randomized study (Pedersen et al. Gastrointest
Endosc.1998;48:574-579). Therefore, authors should explain clearly why the
same kind of patients (2/3 of the participants had the common bile duct
obstruction) was enrolled in the study in the introduction section.
(4) What was conventional type stent? Authors should display the detailed profile
of the stent, such as manufacturer and materials. Why did authors use two types
of stent for inside stent? Using various types of stent lowered the quality of the
study.
(5) Although authors mentioned that EST is a risk factor of reflux cholangitis in
the method section, why was EST performed prior to insertion of 10Fr inside
stent? If authors use inside stent technique for preservation of the function of the
oddi sphincter, only the patients who did not underwent EST should be included.
(6) Why did authors exclude the patients who needed percutaneous biliary
drainage after endoscopic treatment? It is important point whether percutaneous
drainage is needed or not after endoscopic treatment.
(7) Why did authors exclude intrahepatic cholangiocarcinoma (ICC) cases? It is
not necessary to exclude ICC cases, because ICC often causes biliary
obstruction, especially in hilar bile duct.
(8) What was the percentage of the patients who underwent ENBD before
placement of internal stenting in each group? What was the decompression
period? The decompression period did not defined in the method section.
However, the study cannot clarify this subject because the participants included
the patients who was performed ENBD before insertion of conventional or inside
stent.
(9) Were there any patients who underwent preoperative portal vein embolization
(PVE) in this study? PVE may influence the outcome of internal stenting.
(10) Authors should define the stent obstruction in the method section.
(11) In this study, the percentage of the patients who underwent
pancreaticoduodenectomy (PD) was about 60%. I think the rate was very high,
because the distance from stricture to the papilla is less than 2cm in most cases
who undergo PD.
(12) Authors should show the evaluation method about postsurgical infectious
complication in the method section. In the result section, severe liver abscess
occurred in 5 patients, however, readers cannot understand why these cases
were severe?
Minor Essential Revisions
(1) Table 1 and 2 are not necessary. It is no need of detailed data of patient
profile.
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Needs some language corrections before being
published
Statistical review: No, the manuscript does not need to be seen by a statistician.
Declaration of competing interests:
I declare that I have no competing interests.