Review for 10.1186/s12876-022-02418-3 (2022)

Reviewer’s report
Title: 
Segmental reversal of the distal small intestine in a short bowel syndrome
model in piglets showed detrimental effect on weight gain
Version: 
1 
Date: 
11 Mar 2022
Reviewer's report:
Dear authors,
Thank you for your manuscript. This is a well-conducted study and a well-
written manuscript. I believe this paper is suited for publication after some
revisions and I have following comments for you:
1. Methods: Why did you choose to resect 70% of the bowel? It was previously
shown that 75% intestinal resection is less suitable as an SBS model, as animals
tend to recover remarkably (check and cite PMID: 26375577 and PMID:
24081112). As a short-term animal model the 70% bowel resection could be not
optimal to test investigate the effects of a reversed segment of the distal small
intestine to improve weight gain. The provided concerns of the local Animal
Experiments Inspector to remove more than 70 % of the small intestine in
present study is opposed to literature. Please discuss this. 
2. Methods: Why did you chose to reverse the distal 25 cm of the remnant
jejunum, why not shorter or longer and why at this part of the bowel? Is this
length and location adequate for your purpose, please discuss and possibly
provide the available literature at the section you state: "Reversal of a 25 cm
segment was chosen taking the available literature". This seems important as you
report "The findings with lower villus height, lesser crypt depth and lower GIP-
levels in the intervention group might indicate, that the reversed segment was too
extensive, and may have caused subileus with related histological changes." but,
as you cite "Grave et al.(21) found no significant difference in weight by
reversing 20 cm in an almost identical SBS model"
3. Methods: Every pig potentially has different bowel length. By resecting 70%
of the present bowel potentially leads to different remnant intestinal lengths from
pig to pig. This might bias the evaluation. A possible optimized approach could
have been to leave an equal length of bowel in each pig in order to standardize
the SBS model (check and cite PMID: 26375577). Please discuss this point as a
limitation of your study. 
4. Results: You report: "No significant difference in GLP-2 and GIP-levels was
found in the intervention group measured at day 0 and day 28, whereas levels for
both hormones increased significantly in the control group. GIP-levels were
significantly lower in the intervention group at day 28, compared with the
control-group at day 28. (Fig2)." And provide a visually helpful figure 2. Could
you discuss how GLP-2 and GIP changes can be explained?
5. Discussion: Please discuss more in depth the implications of your results for
the daily routine are and which other surgical alternatives are available (check
and cite PMID: 23932625, PMID: 24074666 PMID: 26220675, PMID:
27086890, PMID: 30471736 and similar articles). 
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Is the study design appropriate to answer the research question (including the use
of appropriate controls), and are the conclusions supported by the evidence
presented?
Yes
Are the methods sufficiently described to allow the study to be repeated?
Yes
Is the use of statistics and treatment of uncertainties appropriate?
Yes
Is the presentation of the work clear?
Yes
Are the images in this manuscript (including electrophoretic gels and blots) free
from apparent manipulation?
Yes