Ulcerative colitis is a type of inflammatory bowel disease whose etiology is not yet clear, and the lesions are superficial, nonspecific inflammatory lesions located in the large intestine, with the sigmoid colon being the most obviously involved, with a continuous diffuse distribution. The clinical symptoms are mainly mucopurulent stools, abdominal pain, diarrhea or urgency. There is a regular pattern of abdominal pain and relief after a bowel movement. Pressure pain in the left lower abdomen, if there are signs of peritoneal irritation, one should be alert to toxic megacolon and intestinal perforation. Main complications: 1, toxic megacolon:one of the most serious complications, mostly occurring in fulminant or seriously ill patients. 2.Carcinoma: occurs in heavy patients with long disease duration. 3.Other: haemorrhage, intestinal perforation, intestinal obstruction. Ancillary tests: 1. Blood tests: decreased hemoglobin. Active phase markers: accelerated blood sedimentation, increased C-reactive protein. Severe signs: decreased serum albumin, prolonged prothrombin time. 2.Fecal examination: red blood cells and pus cells can be seen. 3.Colonoscopy: It is the most important tool for diagnosis and differential diagnosis of the disease. The lesion starts from the rectum at the anal end and spreads retrograde upward in a continuous distribution. 4, barium enema examination (severe or fulminant cases are generally not suitable for this examination): Ⅰ multiple shallow ulcers; Ⅱ mucosal disorder or fine granular changes; Ⅲ lead tubular.