This clinical study is a prospective, single-arm, single-center trial aimed at assessing the safety and efficacy of tributyrin (TB) as dietary supplements in the treatment of chronic radiation-induced rectal injury (RRI). We hypothesize that these supplements will help improve rectal bleeding symptoms and elevate the quality of life for patients. The study will test whether the supplements can lower the LENT-SOMA scales of rectal bleeding and enhance overall patient health. Efficacy will be evaluated through blood tests and other non-invasive methods, ensuring patient safety and comfort throughout the study.

Inclusion Criteria:

• Age 18-75 years
• At least 3 months since the completion of pelvic radiotherapy
• No evidence of tumor recurrence or metastasis
• Rectal bleeding with grade 1-2 by LENT-SOMA scales

Exclusion Criteria:

• Acute or chronic infectious diseases
• Serious systemic diseases
• Known allergies to any components of the study medication
• Colonoscopy indicating rectal ulceration (>1cm2), fistula, stricture, or necrosis
• Late complications related to pelvic radiation injury
• Other hemorrhagic or coagulation disorders
• Previous rectal resection
• Bowel obstruction or perforation that require surgery
• Cognitive or psychological disorder