Postoperative ileus (POI) is a common clinical condition after abdominal surgical procedure, leading to increased patient morbidity and prolonged hospitalisation.The mechanism of POI is not very clear until now. At the end of the 20th century, the inflammatory-mediated ileus hypothesis was introduced. But the initial trigger of the inflammatory cascade is unclear.Previous study demonstrate a clear association between colonic transit time, gut microbiota composition and urinary metabolic phenotype. Here the investigators suggest that the perioperative gut microbiota may contribute to POI.

Postoperative ileus (POI) is a common clinical condition after abdominal surgical procedure, leading to increased patient morbidity and prolonged hospitalisation.

The clinical manifestations include abdominal distension, nausea, vomiting and the inability to pass stools or tolerate a solid diet. In addition to the discomfort experienced by patients, postoperative ileus is also an important risk factor for complications such as wound dehiscence and pulmonary and thromboembolic complications. Ileus was found to be an important predictor of extended postoperative hospital stays and costs in patients undergoing colectomy.

The mechanism of POI is not very clear until now. At the end of the 20th century, the inflammatory-mediated ileus hypothesis was introduced. But the initial trigger of the inflammatory cascade is unclear The innate immune system recognises two large classes of macromolecules: first, those related to pathogens or pathogen-associated molecular patterns (PAMPs), and secondly, molecules released in response to cell damage or damage-associated molecular patterns (DAMPs). The prototype of PAMPs is lipopolysaccharide (LPS), a constituent of the Gram-negative bacterial cell wall. Translocation of microbial products into the intestinal tissue is a well-documented feature in POI. Previous study demonstrate a clear association between colonic transit time, gut microbiota composition and urinary metabolic phenotype. Here the investigators suggest that the perioperative microbiome may contribute to POI. This study apply NGS(next generation sequencing) technique to analyse the composition of the perioperative gut microbiota of CRC(colorectal cancer) patients, then analysis the relationship between the dynamic variation of gut microbiota and POI.

Inclusion Criteria:

• Requirements of informed consent and assent of participant, parent or legal guardian as applicable
• Patients with colorectal cancer scheduled for radical coloproctectomy and between the age of 35 and 80 years old without considering sex.
• Patients with BMI= 18.5-23.9

Exclusion Criteria:

• Patients with colorectal cancer with distant metastasis
• Chronic renal diseases and hepatic cirrhosis
• Chronic ischemic heart disease with unstable angina, chronic heart failure at class III or IV and acute myocardial infarction in the last 6 months
• Individuals with a history of Chronic diarrhea
• Individuals with a history of Diabetes mellitus
• Individuals with a history of Hypertension
• Individuals with a history of autoimmune diseases
• Use of antibiotics and probiotics 3 mouth before samples collection
• Individuals with a history of abdominal operation due to any reason
• Individuals with any history of cancer other than colorectal cancer
• Individuals with Inflammatory bowel disease

Study participants are patients need undergo an exhaustive colorectal cancer surgical resection in the First Affiliated Hospital of Harbin Medical University from May 1, 2018 to Dec 31, 2019.