Safety of Mid and Low Rectal Cancer Surgery Without Dissection of the No.253 Lymph Node (S-M-O-O-T-H)

Inclusion Criteria:

1. Patient age between 18-75 years.
2. Colonic biopsy pathology confirms adenocarcinoma.
3. The inferior margin of the primary tumor is ≤ 7 cm from the anal verge, as confirmed by colonoscopy and baseline imaging at initial diagnosis.
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.