Inclusion criteria  Adult patients undergoing an elective open or laparoscopic primary tumor resection within GI tract (stomach, small intestine, large intestine , colon and rectum. Age ≥ 18 years ASA ≤ III Written informed consent  Exclusion criteria  ASA ≥IV Emergency operations Peritonitis Surgical interventions in the pancreas, oesophagus Patients with traumatic perforations Pregnant and/or breast-feeding women Patients who had received chemotherapy within the last 4 weeks or radiotherapy on the treated region within the last 2 weeks Patients who were receiving immunosuppressant therapy