Study design: Prospective observational study Study population: Adult colorectal cancer patients undergoing elective surgery. Main study parameters/endpoints: Primary endpoint: AL within 30 days postoperatively Secondary endpoints: Intestinal microbiome in fecal sample, I-FABP, SM22, Calprotectin, C-reactive protein(CRP), Citrullin, complement factors in blood, VOCs in exhaled air, COX-2 & MBL polymorphisms in buccal smear, L3-index & atherosclerosis measurements on CT-scans, SNAQ & MUST scores