Review for 10.1186/s12876-020-01429-2 (2020)

Reviewer’ s report
Title: Usefulness of peroral cholangioscopy in the differential diagnosis of IgG4-related sclerosing
cholangitis and extrahepatic cholangiocarcinoma: a single-center retrospective study
Version: 0Date: 14 Apr 2020
Reviewer's report:
The authors conduct a retrospective study to elucidate the usefulness of peroral cholangioscopy
(POCS) in the differential diagnosis of IgG4-related sclerosing cholangitis (IgG4-SC) andextrahepatic cholangiocarcinoma (ECC). In this study, the authors evaluated POCS finding in 17IgG4-SC patients (19 stricture sites) and 53 ECC patients (53 stricture site). They comparedmucosal surface, easily bleeding and dilated vessel morphology (tortuosity, caliber alteration anddisruption) between these two groups. The results showed mucosal irregularity, easily bleeding,vessel caliber alteration and disruption were observed more frequently in ECC than IgG4-SC (p <0.001). In IgG4-SC group, extrapancreatic duct stricture showed more dilated vessel than intra-pancreatic ducts stricture. Authors concluded that these POCS findings is useful for distinguishingbetween IgG4-SC and ECC.
Followings are my comments:
1.The background of this study is well-written and author has a good introduction.2.In this study, all POCS was performed by using dual-operator mother-baby scope. Theendoscopy image quality is good to observe mucosa and vascular structure. Currently, digitalsingle-operator cholangioscope (Boston company, Sypglass) was more popular and mostendoscopic units don't have dual operator cholangioscope system. Author should mention aboutthis in discussion.
3.In this study, authors try to use image impression to differentiate IgG4-SC from ECC and
cholangioscopy-guided bile duct biopsy didn't have good diagnostic accuracy as other studies. Theresult of this study may not have great clinical impact. A comprehensive systemic review(diagnostic performance of different cholangioscopes in patients with biliary stricture) waspublished this year (Endoscopy 2020; 52:174). I suggest authors cite this publication and addmore description about this weak point. Recent studies show high diagnostic accuracy inindeterminate biliary stricture.4.Since the aim of this study is to differentiate IgG4-SC and ECC, the result and discussion section"Relation between POCS findings and location of stricture in patients with IgG4-SC) could beomitted.5.In image A and D of Figure 3, authors described this cholangiography showed intrapancreaticduct stricture in image D. However, the location of stricture site seems similar between these twoimages. Dose the stricture site (image D) locate in the intrapancreatic bile duct?6.The limitations of this study are still small sample size and retrospective. The biopsy diagnosisaccuracy in both groups is lower than other studies.
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.
YesAre 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 furtherassessment in your comments to the editors.
I am able to assess the statisticsQuality of written English
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AcceptableDeclaration of competing interests
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