I. Enteritis with clear causes 1. infectious colitis (bacterial, viral, parasitic and other infections): intestinal tuberculosis, bacterial dysentery, intestinal amebiasis, Yersinia colitis; 2. physical irritation: radioactive colitis, traumatic enteritis, mucosal prolapse enteritis; 3. pharmacological: pseudomembranous enteritis; 4. vascular: ischemic colitis; 5. concomitant systemic diseases: diabetic colitis, Uremic colitis, lupus erythematosus ulcer. The cause of enteritis is unclear: 1. ulcerative colitis; 2. Crohn’s disease; 3. leukoaraiosis; 4. isolated ulcers; 5. chronic colitis: a collective term for non-ulcerative chronic inflammatory diseases of undefined etiology. Benign: hyperplastic polyps, inflammatory polyps, adenomas, juvenile polyps, mesenchymal tumors, lipomas, fibromas, lymphangioleiomas, etc.; malignant: colorectal cancer, carcinoid tumors, malignant lymphomas; functional diseases of the colon: no organic lesions of the colon, but exhibit a series of single or multiple symptoms of dysfunction of the colon: constipation, diarrhea, abdominal pain, abdominal distension, etc.