Coelho 1992a.

Methods	Single‐centre trial. Generation of allocation: adequate, by cards. (aleatoriamente = randomised). Allocation concealment: unclear. Blinding: not performed. Follow‐up: unclear. Drop‐outs: none mentioned. Intention‐to‐treat: not mentioned. Sample size calculations: no.
Participants	Patients admitted for cholecystectomy. In‐ and exclusion criteria: not very well described. Comparability groups: well matched.
Interventions	SIC versus OC. Both procedures not further specified. Antibiotic prophylaxis: not mentioned. Intra‐operative cholangiography: routinely performed in both groups.
Outcomes	Primary and secondary outcome: not described. Outcome measures: clinical results. Duration of follow‐up: hospital stay.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation?	Low risk
Allocation concealment?	Unclear risk	B ‐ Unclear
Blinding? All outcomes	High risk
Free of selective reporting?	High risk