Morbidity which ranges from 15 to 20%, investigators consider 10% as clinically significant reduction. Minimal extent of each collection is 118 when considering 5% level of significance for single sided test and test power 70%; minimal extent of each collection for portion of nosocomial infection 6-10% is 234 in case of clinically significant decrease by 5%. Estimates of numbers required for detection of clinical difference of two days (standard deviation estimate 2.6 for appendicitis respectively 3.2 for perforation and 2.3 for ileus of small bowel) lead to values 36, 47 a 25 people in each group. Total number for each set is 250 people and it fulfills the above mention criteria and ranges 175, 50 and 25 in each subgroup are sufficient. Group homogeneity will be compared based on descriptive statistical methods; risk factors will be evaluated using regression analysis and multivariant analysis. When comparing basic factors p<0.05 will be considered as clinically significant in case of above given test power.