Another previous study showed that frailty (defined with the Groningen Frailty Index, sarcopenia (determined by measuring the skeletal muscle mass at L3 level at the CT-scan) and malnutrition (assessed with Short Nutritional Assessment Questionnaire (SNAQ) en Malnutrition Universal Screening Tool (MUST)) is associated with the occurrence of sepsis and mortality in 273 patients. In a pilot study with 90 patients, preoperative I-FABP plasma levels and postoperative inflammatory plasma concentration (C-reactive protein & calprotectin) were identified as predictive markers for anastomotic leakage after elective colorectal surgery. In addition, composition of volatile organic compounds (VOCs) in exhaled breath varies depending on health status. Various metabolic processes within the body produce volatile products that are released into the blood and will be passed on to the airway once the blood reaches the lungs. Moreover, the occurrence of chronic inflammation and/or oxidative stress can result in the excretion of volatile compounds that generate unique VOC patterns. In this study, we will measure the total amount of VOCs in exhaled air, to see if this is an eligible tool for early clinical diagnosis of anastomotic leakage.