- 1.corresponding to diagnosis standards of CKD-5:eGFR≤15ml/min/1.73m2; 2. did not receive kidney replacement therapy; 3. no gastrointestinal diseases (including ulcerative colitis, irritable bowel syndrome, inflammation, cancer, infection, bleeding, etc.) in the past 1 year; 4.not associated with rectal-related disorders (hemorrhoids, anal fistula, rectal cancer, cancer, infection, bleeding, etc.); 5.Sign informed consent.