With this study, the investigators want to determine whether a fast identification of microorganisms causing intra-abdominal infections in patients with suspected hollow organ perforation or peritonitis is possible using a multiplex PCR system (Unyvero A50), a method that allows rapid detection of predefined bacterial and fungal targets directly from clinical samples. Therefore, intra-abdominal peritoneal fluid samples collected during surgery will be analyzed by multiplex PCR and by conventional microbiological culture. The investigators want to determine whether multiplex PCR diagnostics could provide results faster than conventional microbiological methods and deliver additional information on pathogen detection.