Review for 10.1186/s12876-021-01616-9 (2021)

Reviewer’s report
Title: 
Clinical and endoscopic features of aorto-duodenal fistula resulting in its
definitive diagnosis: an observational study
Version: 
2 
Date: 
21 Dec 2020
Reviewer's report:
I want to thank the authors for the excellent revision they performed on their
paper, which is now much better organized and easy to read. 
I only suggest few minor changes:
- The first part of methods section is a little too much detailed (lines 57 to 61). I
suggest to modify the section as it follows: "The present study examined
patients' baseline clinical and laboratory data, past medical history, endoscopic
and CT scan findings, number of blood transfusions received, definitive
treatment and outcome. Type of scope used during endoscopy, the use of tip
attachments and of marking clips were also collected").
- The definition of shock provided (line 61) is not typical, is it the standard
definition you use in your institution? Usually, hemorrhagic shock is defined in
literature as the combination of systolic blood pressure < 100 mmHg and heart
rate > 100 beats per minute
- Line 66: the sentence "Even then, we did not find any abnormalities" should be
a hypothetical sentence: "If no abnormalities were found even using a tip
attachment, then we changed to pediatric colonoscope PCF-PQ260L…". 
- Specify if the described endoscopic strategy (lines 63-67) is the standard
strategy you follow in your institution for all suspected AUGIB or is specific for
patients with suspected bleeding from deep duodenum (such as patients with
history of aortic pathology)
- Line 68: reference is missing
- I suggest to put baseline characteristics of the patients (lines 104 to 113) at the
beginning of the result section
- Line 99: add the case number in brackets for the patient who died during
endoscopy
- When mentioning that all patients underwent aortic treatment in the past, report
also the mean timing of the intervention with the range (7 months to 13 years
prior). I think it is interesting that ADF could develop after so much different
periods of time (you could also briefly discuss it in the discussion)
- Line 140: reference is missing
- Discussion section should be a little enlarged and reorganized: I suggest to start
discussion with a short sentence about the importance of a prompt diagnosis in
ADF in order to increase chance of definitive treatment and survival; then
discuss the herald bleeding, that can mimic a "normal upper GI bleeding, and the
importance of patient's history of aortic or para-aortic treatments that should
increase the suspicion of ADF even for small, transient bleeding. Then discuss
the difficulty of definitive diagnosis and the frequent need for combined
radiology/endoscopy. 
- In the discussion, you should mention the missing information about timing of
endoscopy as a limitation of the present study. 
- Line 159: reference is missing
- I suggest to modify as follows the first sentence of conclusions: "In a patient
presenting with upper gastrointestinal bleeding, a history of intervention
involving the aorta should increase the suspicion of ADF. A combination of
endoscopy and CT scan is usually necessary to achieve a definitive diagnosis.
- Table 2: change commercial name "loxonin" to loxoprofen
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