Local Methylene Blue Injection for Prevention of Anastomotic Leakage and Permanent Stoma After Low Anterior Resection for Rectal Cancer

Inclusion Criteria: 1. Adults aged 18 years or older with histologically confirmed rectal adenocarcinoma. 2. Patients with mid or low rectal cancer (tumor located within 10 cm from the anal verge) who are scheduled to undergo curative low anterior resection with a temporary diverting ileostomy. 3. Patients with one or more risk factors associated with postoperative stoma non-closure or anastomotic complications, including male sex, narrow pelvis, neoadjuvant chemoradiotherapy, prolonged operative time, or increased intraoperative bleeding risk. 4. Patients who are considered suitable candidates for surgery and postoperative follow-up according to the investigator's assessment. 5. Patients who are willing to provide written informed consent. Exclusion Criteria: 1. Patients with emergency surgical conditions, including intestinal obstruction, bowel perforation, or acute abdominal infection before surgery. 2. Patients undergoing abdominoperineal resection, local excision, or other surgical procedures without colorectal anastomosis and diverting ileostomy. 3. Patients with other active malignancies or recurrent rectal cancer. Patients who are unable to tolerate the planned surgery or follow-up procedures. 4. Patients with contraindications or known hypersensitivity to methylene blue injection. 5. Patients with severe medical conditions or laboratory abnormalities that may increase study-related risks or interfere with study outcome evaluation.