Inclusion Criteria:
A. Inclusion criteria for patients with peritonitis (all should be present):
* Age ≥18
* Patient with suspected or confirmed complicated intra-abdominal infection for which a surgical procedure is planned and during which at least one of the following is confirmed:
* Gross peritoneal inflammation with purulent exudates (ie, peritonitis).
* Intra-abdominal abscess.
* Macroscopic intestinal perforation with localized or diffuse peritonitis. e.g. due to intestinal perforation (stomach, bowel, gallbladder, appendicitis, traumatic, postoperatively) or intestinal arterial occlusion or bowel obstruction/ileus.
* Presence of acute organ dysfunction caused by the infection determined by deviation in at least one of the following organ systems:
* Respiration: PaO2/Fio2 ≤ 300 mm Hg
* Coagulation: Platelets ≤ 100x103/μl
* Liver: Bilirubin ≥ 2 mg/dl
* Cardiovascular: Vasopressors required (dopamine, dobutamine, epinephrine or norepinephrine: any dose)
* Central nervous system: Glasgow coma scale score ≤ 12
* Renal: Creatinine \> 2 mg/dl
* Written informed consent from the patient or his/her legal representative.
B. Inclusion criteria for elective surgery patients:
* Age ≥18
* Patient should be scheduled for elective major gastrointestinal surgery
* Written informed consent
Exclusion Criteria:
A. Exclusion criteria for patients with peritonitis:
* Age \< 18 years
* Pregnancy
* Known HIV, Hepatitis B or C
* Clinically significant coagulopathy as assessed by the investigator
* Use of immunosuppressant treatment or in chronic high doses (high-dose therapy exceeding 2 weeks of treatment) of steroids equivalent to prednisone/prednisolone 0.5 mg/kg/day, including solid organ transplant patients. Patients with septic shock treated with hydrocortisone can be included
* Acute liver disease (determined by the treating physician) or chronic liver disease (child pugh A,B,C)
* Chronic insulin dependent diabetes mellitus
* No informed consent obtained
B. Exclusion criteria for elective surgery patients:
* Age \< 18 years
* Pregnancy
* Known HIV, Hepatitis B or C
* Clinically significant coagulopathy as assessed by the investigator
* Use of immunosuppressant treatment or in chronic high doses (high-dose therapy exceeding 2 weeks of treatment) of steroids equivalent to prednisone/prednisolone 0.5 mg/kg/day, including solid organ transplant patients
* Acute or chronic liver disease, diabetes mellitus, dyslipidemia, liver steatosis (macroscopically diagnosed during surgery)
* Signs or symptoms of infection as assessed by the investigator
* Chronic insulin dependent diabetes mellitus
* No informed consent obtained
