Radiation enteritis is one of the most feared complications after abdominal or pelvic radiation therapy.The gut microbiota is considered to constitute a "microbial organ" which has pivotal roles in the intestinal diseases and body metabolism. Evidence from animal studies demonstrated the link between intestinal bacteria and radiation enteritis. This clinical trial aims to evaluate the efficacy and safety of fecal microbiota transplantation (FMT) for radiation enteritis.

The present clinical trial aims to re-establish a gut functionality state of intestinal microbiota through fecal microbiota transplantation (FMT) for radiation enteritis (RE). FMT is the whole profile of fecal microbiota transplantation. At enrollment, "Shared Decision Making" intervention was applied to support patient involvement in making health decisions. Patients have opportunity to choose fecal microbiota transplantation (FMT). Patients will receive follow-up for at least 12 weeks. Blood test, endoscopy and questionnaire will be used to access participants at study start and at study completion. Fecal microbiota compositions, blood and urinary metabolic profiles of patients will be analyzed to assess associated microbial changes.

Inclusion Criteria:

1. age ≥18 years old;
2. Radiation enteritis diagnosed by colonoscopy after finishing radiotherapy.

Exclusion Criteria:

1. Patients who were pregnant or nursing;
2. Patients who were unable or unwilling to undergo a gastroscopy;
3. Patients who had gastrointestinal infection;
4. Patients with cardiopulmonary failure.