Surgical-site infection , recurrent intraabdominal infection , or death occurred in 56 of 257 patients in the experimental group ( 21.8 % ) , as compared with 58 of 260 patients in the control group ( 22.3 % ) ( absolute difference , -0.5 percentage point ; 95 % confidence interval [ CI ] , -7.0 to 8.0 ; P = 0.92 ) .