The diagnostic value of IL–6 and TNF alpha levels in day 3 can be noted (i) to sustain the diagnostic of peritonitis with systemic inflammatory response syndrome, with or without septic complications on that day, and also (ii) the prognostic value of IL–6 and TNF alpha, determined in day 1 (preoperatively), to predict the unfavorable evolution of patients (in all cases, P<0,001). This evidence concerns the gene IL6 and systemic inflammatory response syndrome.