Discussion Investigator's working site will conduct internal retrospective study dealing with SSI in patients with appendicitis and stomach ulcer perforation. 180-200 acute appendectomies will be performed every year with SSI frequency 2.5 - 18.5% according to contamination. Group of patient with stomach ulcer perforation will be evaluated similarly (n=42) with SSI 14.3%, total morbidity 35% and mortality 11.9%. All of those data correlate with results from the world literature however it is possible that after retrospective assessment correct monitoring of ATB prophylaxis (40% compliance) and patient stratification will reduce the frequency of complications.