Comparison of Postoperative Anal Function Between Parks and Bacon Techniques in Low Rectal Cancer

Inclusion Criteria: Men or women, aged between 18 and 75 years; Pathological diagnosis of rectal cancer before operation, with the distance from the lower edge of the tumor to the dentate line ≤ 3cm by MR imaging; No local complications (including complete/ incomplete obstruction, active bleeding, local invasion of sphincter or levator ani, etc.) before operation; Suitable for anal preservation surgery discussed by MDT; Adequate bone marrow, liver, renal and cardiac function meeting the requirements of surgery and anesthesia; R0 resection is expected technically; Provision of written informed consent. Exclusion Criteria: Previous history of malignant colorectal tumors; Complications such as obstruction and gastrointestinal bleeding that need an emergency operation; Unachievable R0 resection due to invasion of adjacent organs by primary tumor; Multiple primary tumors; History of other malignancy; Participation in other clinical trials within the previous 4 weeks of enrollment; ASA physical status score ≥ IV level and/or ECOG performance status ≥ 2; Intolerance of surgery due to liver, renal, cardiopulmonary or coagulation dysfunction, or underlying diseases; History of serious mental disorders; Women in pregnancy or lactation period; Uncontrolled infection before operation; Unsuitable to be included due to other clinical and laboratory conditions by the judgement of investigators.