Diverting Ileostomy and Anal Functional Outcomes After Anus Preservation Surgery

Inclusion Criteria: Necessary conditions: meet one of the following conditions 1. Difficult pelvis: narrow pelvis (diameter of ischial tuberosity \<10 cm, diameter of ischial spine \<12 cm) 13 or BMI≥30kg/m2 or tumor diameter≥5cm2. 2. To receive treatment before surgery: preoperative neoadjuvant radiotherapy or concurrent chemoradiation or ESD 3. The anastomosis is below the level of the levator ani muscle: such as ISR, TaTME surgery, etc. Other conditions: 1. Age: 18 to 75 years old, male or female; 2. Preoperative biopsy pathological diagnosis of rectal adenocarcinoma; 3. Received MRI evaluation before surgery, and the distance between the lower edge of the tumor and the anal edge is no more than 10cm; 4. The clinical stage is T1-3N0-2M0; 5. Undertake elective laparoscopic TME for colon-rectal or colon-anal anastomosis 6. ECOG score 0-2; 7. Heart, lung, liver, and kidney functions can tolerate surgery; 8. Patients and their families can understand and are willing to participate in this clinical study, and sign informed consent. Exclusion Criteria: 1. Past history of malignant colorectal tumors or recent diagnosis combined with other malignant tumors; 2. Patients with intestinal obstruction, intestinal perforation, intestinal bleeding, etc. who need emergency surgery; 3. Neighboring organs need to be combined with organ removal 4. ASA grade ≥ grade IV and/or ECOG physical status score\> 2 points; 5. Those who have severe liver and kidney function, cardiopulmonary function, blood coagulation dysfunction, or combined with serious underlying diseases that cannot tolerate surgery; 6. Have a history of severe mental illness; 7. Pregnant or lactating women; 8. Those with a history of taking hormone drugs; 9. Patients with other clinical and laboratory conditions considered by the investigator should not participate in the trial.