Clinical Research Directory

Inclusion Criteria: 1. Preoperative pathology confirmed adenocarcinoma. 2. Preoperative MRI or digital examination of tectum confirmed that the distances from the lower edge of the tumors to the anus were less than 5 cm. 3. The mass is not fixed. 4. Preoperative MRI and rectal EUS indicated that the tumor only invaded muscular layer (T2). 5. No suspicious lymphatic metastasis or distant metastasis was found on preoperative high-resolution CT and MRI. 6. American Society of Anesthesiologists(ASA) grade I-III. 7. Informed consent. 8. No history of familial adenomatous polyposis, ulcerative colitis or Crohn's disease. Exclusion Criteria: 1. Age\<18, or\>75. 2. Have other cancer history. 3. The pathology of rectal tumors is non-adenocarcinoma. 4. Multiple primary colorectal tumors. 5. Preoperative CT and MR showed that lymphatic metastasis and distant metastasis could be positive. 6. Pregnant or lactating women. 7. Patients with severe mental disorders. 8. ASA score \> 3. 9. Receive other cancer treatments (radiotherapy, chemotherapy). 10. Complication with other intestinal diseases (FAP, HNPCC, active ulcerative colitis or Crohn's disease). 11. The general situation is poor and there are other uncontrollable diseases. 12. Preoperative tumor stage was not T2N0M0.