Uchino 2010.

Study characteristics
Methods	Retrospective cohort. Study period: 2006 to 2008
Participants	Country: Japan. UC patients who underwent laparotomy. Patients who had subtotal colectomy with mucous fistula before IPAA or ileostomy closure were excluded.
Interventions	1. Preoperative immunosuppressants (n= 20) 2. No preoperative immunosuppressants (n= 172)
Outcomes	Superficial incisional, deep incisional, and organ space surgical site infection within 30 days of surgery
Notes	NOS very high risk of bias overall
Risk of bias
Bias	Authors' judgement	Support for judgement
Representativeness of the exposed cohort	Low risk	UC patients who underwent laparotomy from 2006 to 2008
Selection of the non exposed cohort	Low risk	Both groups obtained from the same hospital and time period
Ascertainment of exposure	Unclear risk	Information not provided
Demonstration that outcome of interest was not present at start of study	Unclear risk	Information not provided
Comparability of cohorts (Controlled for critical factor/other medications)	High risk	Univariate analysis
Comparability of cohorts (Controlled for additional factor)	High risk	Univerariate analysis
Assessment of outcome	Unclear risk	Information not provided
Was follow‐up long enough for outcomes to occur	Low risk	30 days
Adequacy of follow up of cohorts	Unclear risk	Information not provided