The goal of this clinical trial is to learn about whether it is safe to omit dissection of the No.253 lymph nodes in mid and low rectal cancer surgery. The main question it aims to answer is that if it is possible to achieve the same long-term survival with and without the dissection of the No.253 lymph node in mid and low rectal cancer surgery. Participants will underwent laparoscopic rectal radical resection with or without the dissection of the No.253 lymph node.

The No.253 lymph node, as the third station in the inferior mesenteric artery lymphatic system, plays a significant role in the lymphatic circulation of the descending colon, sigmoid colon, and rectum. They act as the last barrier for tumor metastasis from the regional to distant areas. However, there is still controversy regarding whether rectal cancer patients universally require dissection of the No.253 lymph node. The rate of metastasis to the No.253 lymph node in rectal cancer patients is extremely low, and dissection may not bring survival benefits. Additionally, postoperative urinary and sexual functions may be impaired due to damage to the sympathetic nerves. However, current prospective randomized controlled trials on the safety of omitting the dissection of the No.253 lymph node have small sample sizes and lack sufficient test power. Further confirmation is needed from large-sample prospective randomized controlled studies. Based on this, the investigator plans to collaborate with Peking Union Medical College Hospital, China-Japan Friendship Hospital, Chinese People's Liberation Army General Hospital, Shanghai Ruijin Hospital, Fudan Cancer Hospital, and West China Hospital of Sichuan University, totaling eight medical centers, to conduct a prospective randomized controlled study. This study aims to confirm the safety of mid and low rectal surgery without dissection of the No.253 lymph node, providing high-level evidence-based medical evidence for the implementation of this surgical technique.

Inclusion Criteria:

1. Patient age between 18-75 years.
2. Colonic biopsy pathology confirms adenocarcinoma.
3. At initial treatment, colonoscopy and imaging diagnose the tumor's lower edge as less than or equal to 7cm from the anus.
4. At initial treatment, imaging diagnoses the tumor T stage as less than or equal to 3.
5. At initial treatment, imaging diagnoses no enlarged lymph nodes at the root of the inferior mesenteric artery.
6. At initial treatment, imaging diagnoses the number of mesenteric metastatic lymph nodes as less than or equal to three.
7. Strong willingness for surgery and signed informed consent.

Exclusion Criteria:

1. Previous history of malignant colorectal tumors.
2. Colonic biopsy pathology reveals mucinous adenocarcinoma or signet ring cell carcinoma.
3. Imaging diagnosis of distant metastasis.
4. Patients who have undergone multiple abdominal-pelvic surgeries or have extensive abdominal adhesions.
5. Patients with complications such as intestinal obstruction, intestinal perforation, or intestinal bleeding requiring emergency surgery.
6. Extensive lesions not amenable to R0 resection.
7. Diagnosed with other malignancies within the past five years.
8. ASA (American Society of Anesthesiologists) classification ≥ IV and/or ECOG (Eastern Cooperative Oncology Group) performance status score ≥ 2.
9. Patients with severe liver, kidney, cardiac, pulmonary, coagulation dysfunctions, or serious underlying diseases that cannot tolerate surgery.
10. History of severe mental illness.
11. Pregnant or breastfeeding women.