Ferrante 2017.

Study characteristics
Methods	Retrospective cohort. Enrolment period: 2006 to 2016
Participants	Country: Belgium. UC patients who underwent colectomy. Patients who were treated with investigational products and who were anticipated to have a permant ileostomy were excluded
Interventions	1. Preoperative mesalamine (n= 97) 2. Preoperative thiopurine/methotrexate (n= 38) 3. Preoperative steroids (n= 32) 4. Preoperative anti‐TNF medications within 8 weeks of surgery (n= 60) 5. Preoperative vedolizumab within 16 weeks of surgery (n= 34) 6. No preoperative mesalamine (n= 73) 7. No preoperative thiopurine/methotrexate (n= 132) 8. No preoperative steroids (n= 138) 9. No preoperative anti‐TNF medications (n= 110) 10. No preoperative vedolizumab (n= 136)
Outcomes	Pouch specific infectious complications, surgical site infections, non‐surgical site infections within 30 days of surgery
Notes	NOS very high risk of bias overall Unadjusted ORs for preoperative mesalamine, thiopurine/methotrexate, steroids, anti‐TNF therapy, and vedolizumab were obtained from univariate regre ssion models.
Risk of bias
Bias	Authors' judgement	Support for judgement
Representativeness of the exposed cohort	Low risk	All UC patients who underwent colectomy from 2006 to 2016
Selection of the non exposed cohort	Low risk	Both groups obtained from the same hospitals and time period
Ascertainment of exposure	Low risk	Patient charts reviewed
Demonstration that outcome of interest was not present at start of study	Unclear risk	No information provided
Comparability of cohorts (Controlled for critical factor/other medications)	High risk	Did not adjust for other medications
Comparability of cohorts (Controlled for additional factor)	High risk	Did not adjust for additional factors
Assessment of outcome	Low risk	Patient charts reviewed
Was follow‐up long enough for outcomes to occur	Low risk	30 days
Adequacy of follow up of cohorts	Unclear risk	No information provided