Betacyanin for Early Diagnosis and Recovery of Anastomotic Leakage After Rectal Cancer Surgery: A Single-Center, Prospective, Controlled Trial

Inclusion Criteria: 1. Pathologically confirmed rectal adenocarcinoma prior to surgery. 2. Undergoing laparoscopic anterior resection for rectal cancer. 3. No prophylactic diverting ileostomy. 4. American Society of Anesthesiologists (ASA) Physical Status Classification ≤ 3. 5. No prior history of malignant tumors, and no evidence of other malignancies on preoperative examination. 6. Written informed consent obtained from the patient or a legally authorized representative. Exclusion Criteria: 1. Prior abdominal surgery with severe intra-abdominal adhesions. 2. Currently participating in, or having participated within the past 6 months in, another clinical study related to rectal cancer surgery. 3. Preoperative complications requiring emergency surgery, including bleeding, perforation, or obstruction. 4. History of prior malignancy. 5. Undergoing Parks procedure with anastomosis at the anal verge, or Miles procedure, or Hartmann's procedure. 6. Preoperative neoadjuvant chemoradiotherapy, or presence of other high-risk factors for anastomotic leakage requiring a prophylactic diverting ileostomy. 7. ASA Physical Status Classification \> 3. 8. Patient withdrawal of consent.