Title: Factors associated with patency of self-expandable metal stents in malignant biliary
obstruction
Version: 2 Date: 23 Apr 2023
Reviewer's report:
General Comments
This is potentially a valuable contribution to the literature concerning some aspects of the
problems associated with metal stents used for maIignant biliary obstruction but conclusions
are limited by its retrospective design and inherently biased stent type selection.  Additionally,
some details of the procedures and findings are missing from the report which would help
interpretation of the findings.
Specific Comments
1  Introduction: it is misleading to state that there are no data defining the advantages of one
metal stent type over another and no mention is made of the removability of fully-covered SEMS
2  M&M Patients: how was 'unresectable malignant biliary obstruction' defined
3  It was only in the Results section that the patients were mentioned as naiive to stent placement.
This should be defined in the selection criteria.
4  Outcomes and Definitions: The primary outcome cannot be defined as 'factors affecting stent
patency'.  It is patency that is the primary outcome.
5  How was stent dysfunction recognized - was this purely on clinical criteria (regular visits
or symptomatic visits) or were patients followed at defined intervals after stent placement by
regular lab monitoring?
6  For the stent placement ERCPs, how was the length of stent chosen, was a sphincterotomy
always performed, were all stents 10 mm in diameter, were antibiotics used, was the position of
the cystic duct taken into account since all patients had a gallbladder in situ and was bile duct
clearance of stones/sludge undertaken in all cases prior to stent placement?
7  Results: what does the one p value represent in referring to stent dysfunction?
8  Results: The timing of complications  is not clear and presumably many patients suffered
more than one complication.  Are the 37 with stent dysfunction the same 37 with complications?
9  Table 1: please clarify 'bacterial contamination/infections'
10 Table 1: were there no cases of cholecystitis?
11  Figure 2: was statistical comparison of the different causes of stent dysfunction in each stent
type not possible because of small numbers?  This should be stated.
12  Discussion: this report suffers from the issue of inherent bias by being a retrospective analysis
of successful stent cases based on selection by the endoscopist at the time of the initial procedure
without defined selection criteria.  Inevitably, the numbers of the three types of metal stent
are not equally distributed and objective comparisons cannot therefore be made concerning the
causes of stent dysfunction which cannot be assumed to be the same for all metal stent types.
13  Conclusion: this section is probably not needed.
Title: Factors associated with patency of self-expandable metal stents in malignant biliary
obstruction
Version: 2 Date: 23 Apr 2023
Reviewer's report:
General Comments
This is potentially a valuable contribution to the literature concerning some aspects of the
problems associated with metal stents used for maIignant biliary obstruction but conclusions
are limited by its retrospective design and inherently biased stent type selection.  Additionally,
some details of the procedures and findings are missing from the report which would help
interpretation of the findings.
Specific Comments
1  Introduction: it is misleading to state that there are no data defining the advantages of one
metal stent type over another and no mention is made of the removability of fully-covered SEMS
2  M&M Patients: how was 'unresectable malignant biliary obstruction' defined
3  It was only in the Results section that the patients were mentioned as naiive to stent placement.
This should be defined in the selection criteria.
4  Outcomes and Definitions: The primary outcome cannot be defined as 'factors affecting stent
patency'.  It is patency that is the primary outcome.
5  How was stent dysfunction recognized - was this purely on clinical criteria (regular visits
or symptomatic visits) or were patients followed at defined intervals after stent placement by
regular lab monitoring?
6  For the stent placement ERCPs, how was the length of stent chosen, was a sphincterotomy
always performed, were all stents 10 mm in diameter, were antibiotics used, was the position of
the cystic duct taken into account since all patients had a gallbladder in situ and was bile duct
clearance of stones/sludge undertaken in all cases prior to stent placement?
7  Results: what does the one p value represent in referring to stent dysfunction?
8  Results: The timing of complications  is not clear and presumably many patients suffered
more than one complication.  Are the 37 with stent dysfunction the same 37 with complications?
9  Table 1: please clarify 'bacterial contamination/infections'
10 Table 1: were there no cases of cholecystitis?
11  Figure 2: was statistical comparison of the different causes of stent dysfunction in each stent
type not possible because of small numbers?  This should be stated.
12  Discussion: this report suffers from the issue of inherent bias by being a retrospective analysis
of successful stent cases based on selection by the endoscopist at the time of the initial procedure
without defined selection criteria.  Inevitably, the numbers of the three types of metal stent
are not equally distributed and objective comparisons cannot therefore be made concerning the
causes of stent dysfunction which cannot be assumed to be the same for all metal stent types.
13  Conclusion: this section is probably not needed.
Please review this paper.
user
Title: Factors associated with patency of self-expandable metal stents in malignant biliary
obstruction
Version: 2 Date: 23 Apr 2023
Reviewer's report:
General Comments
This is potentially a valuable contribution to the literature concerning some aspects of the
problems associated with metal stents used for maIignant biliary obstruction but conclusions
are limited by its retrospective design and inherently biased stent type selection.  Additionally,
some details of the procedures and findings are missing from the report which would help
interpretation of the findings.
Specific Comments
1  Introduction: it is misleading to state that there are no data defining the advantages of one
metal stent type over another and no mention is made of the removability of fully-covered SEMS
2  M&M Patients: how was 'unresectable malignant biliary obstruction' defined
3  It was only in the Results section that the patients were mentioned as naiive to stent placement.
This should be defined in the selection criteria.
4  Outcomes and Definitions: The primary outcome cannot be defined as 'factors affecting stent
patency'.  It is patency that is the primary outcome.
5  How was stent dysfunction recognized - was this purely on clinical criteria (regular visits
or symptomatic visits) or were patients followed at defined intervals after stent placement by
regular lab monitoring?
6  For the stent placement ERCPs, how was the length of stent chosen, was a sphincterotomy
always performed, were all stents 10 mm in diameter, were antibiotics used, was the position of
the cystic duct taken into account since all patients had a gallbladder in situ and was bile duct
clearance of stones/sludge undertaken in all cases prior to stent placement?
7  Results: what does the one p value represent in referring to stent dysfunction?
8  Results: The timing of complications  is not clear and presumably many patients suffered
more than one complication.  Are the 37 with stent dysfunction the same 37 with complications?
9  Table 1: please clarify 'bacterial contamination/infections'
10 Table 1: were there no cases of cholecystitis?
11  Figure 2: was statistical comparison of the different causes of stent dysfunction in each stent
type not possible because of small numbers?  This should be stated.
12  Discussion: this report suffers from the issue of inherent bias by being a retrospective analysis
of successful stent cases based on selection by the endoscopist at the time of the initial procedure
without defined selection criteria.  Inevitably, the numbers of the three types of metal stent
are not equally distributed and objective comparisons cannot therefore be made concerning the
causes of stent dysfunction which cannot be assumed to be the same for all metal stent types.
13  Conclusion: this section is probably not needed.
assistant