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: 26 Apr 2020
Reviewer's report:
General comment:
Since immunoglobulin G4 related sclerosing cholangitis (IgG4-SC) sometimes may be mis-diagnosed as extrahepatic cholangiocarcinoma (ECC), the differentiation between these twodiseases is clinically important to prevent unnecessary major surgery with the risk of morbidity ormortality. This single center retrospective study aimed to elucidate the usefulness of peroralcholangioscopy (POCS) for the differential diagnosis between IgG4-SC and ECC. They found thecharacteristic findings of IgG4-SC were smooth mucosal surface with dilated vessels withoutcaliber alteration, disruption, and easy bleeding in POCS. Although this is an impressive studyabout POCS findings in patients with IgG4-SC, some issues need to be addressed.
Specific comment:
1.We suggest add a new table or revise table 3. Based on the site of the stricture (extra-pancreaticvs. intra-pancreatic), two groups were compared to see the difference in terms of mucosal surface,dilated vessel, AIP, pancreatic enlargement, and enlargement of pancreatic head.2.Another POSC study about IgG4-SC by Dr. Itoi showed that there is some difference in vascularpattern between hilum cholangiocarcinoma and distal cholangiocarcinoma. Is there a similarfinding in patients with cholangiocarcinoma of this study population?3.We suggest to separate this study population to two groups based on the site of the stricture
(extra-pancreatic vs. intra-pancreatic). Subgroup analysis was performed to compare the difference
on POSC between IgG4-SC and ECC patients.4.The clinical implication based on these data should be mentioned in the section of discussion5.Please describe whether all the patients in this study received biopsy examination during POCS?6.Whether IgG4 stain was performed in 17 patients with IgG4-SC if biopsy results were available?7.In page 20, the meaning of this sentence "The dilated and tortuous vessels were less likely to beassociated with abrupt caliber alteration and disruption" seemed unclear. Please check it or revise.
Are the methods appropriate and well described?
If not, please specify what is required in your comments to the authors.
YesDoes 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.
YesAre 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 statistics
Quality of written English
Please indicate the quality of language in the manuscript:
AcceptableDeclaration of competing interests
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