Effectiveness and Safety Study on Different Timing of Preventive Ileostomy Closure After Surgery for Rectal Cancer

Inclusion Criteria: * sign the informed consent * postoperative pathology is rectal adenocarcinoma * primary middle and low rectal cancer patients (tumor distance from the anal margin is less than 10 cm) * underwent total mesorectal excision for rectal cancer with preventive loop ileostomy Exclusion Criteria: * postoperative pathology is not rectal adenocarcinoma (rectal neuroendocrine tumor, lymphoma, etc.) * postoperative pathologic staging of rectal cancer is I phase, II phase * underwent total mesorectal excision for rectal cancer without preventive loop ileostomy * emergency operation for rectal cancer * disease progression (local recurrence or distant metastasis, etc.) * anastomotic stenosis * serious system disease, including heart dysfunction, respiratory insufficiency, liver and kidney dysfunction, serious blood diseases * participate in other clinical trial * pregnancy or perinatal woman * combined with other malignant tumor * with a history of neurological and psychiatric disorders * patients with abnormal bone marrow suppression after chemotherapy