Terminal ileitis, as the name implies, is an inflammatory disease of the terminal ileum. Clinically, terminal ileitis is mainly seen in the following three diseases: 1. It usually develops in the summer and autumn, when acute gastroenteritis caused by eating unclean food is complicated by bacterial infection of the terminal ileum. This is usually treated with antibiotics, such as quinolones, and can usually be cured. 2. Terminal ileitis is usually seen in cases where a tumor of the ascending colon causes intestinal obstruction and fecal reflux, and usually requires radical resection surgery for colon cancer. 3. Autoimmune enteropathy, such as ulcerative colitis or Crohn’s disease, is needed to be on high alert for terminal ileitis secondary to ulcerative colitis. Further colonoscopy and treatment with mesalazine are usually required.