Study on the No.253 Lymph Node Metastasis Patterns in Left-Sided Colon and Rectal Cancer

Inclusion Criteria:

1. Age: 18-75 years;
2. Underwent laparoscopic left hemicolectomy, sigmoid colectomy, or rectal cancer radical surgery.
3. Postoperative pathology confirmed as adenocarcinoma.
4. No evidence of distant metastasis.

Exclusion Criteria:

1. Previous history of malignant colorectal tumors.
2. Patients who have undergone multiple abdominal-pelvic surgeries.
3. Patients undergoing emergency surgery due to complications such as intestinal obstruction, intestinal perforation, or intestinal bleeding.
4. Surgery did not achieve R0 resection.
5. Patients with concurrent other malignant tumors or multiple primary colorectal cancers.
6. Patients unwilling to sign an informed consent or follow the study protocol for follow-up.