Morris 1980 C.

Methods	Randomised controlled trial. Randomisation by a list of random numbers. Double‐blinded. Unclear blinding of outcome‐assessor.
Participants	340 eligble patients. 69 excluded after randomisation. 271 patients enrolled in the study. The study has 4 subgroups (see Morris 1980 A & B). In Morris 1980 C 133 patients enrolled in the study. All patients above 14 years. Patients with diabetes or who recieved antibacterial or steroid treatment or had severe peritonitis requiring antibacterial therapy or had allergy to cephalosporin, were excluded before randomisation.
Interventions	Treatment group: Metronidazole 1 g suppositorium and Cefazolin 500 mg i.v / i.m preoperatively and eight‐hourly to a total of four doses. Placebo group: Supp. and injection i.v / i.m preoperatively and eight‐hourly to a total of four doses.
Outcomes	Wound infection (Presence of pus in the wounds).
Notes	No comments on drain treatment. Wrote to author to specify subgrouping on drop‐outs.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment?	Low risk	A ‐ Adequate