1, toxic intestinal dilatation: this is a serious complication of the disease, mostly occurs in patients with total colitis, mortality rate can be as high as 44%, clinical manifestations for the rapid deterioration of the disease, toxic symptoms are obvious, accompanied by diarrhea, abdominal pressure and rebound pain, intestinal sounds weakened or disappeared, increased white blood cell count, easy to complicate intestinal perforation. 2, intestinal stenosis: mostly occurs in cases with extensive lesions, the duration of the disease lasts up to 5-25 years or more, its location is mostly seen in the left hemicolectomy, sigmoid colon or rectum, clinically generally asymptomatic, in serious cases can cause intestinal obstruction, in this disease appears intestinal stenosis, be alert to the tumor, identify benign malignant. 3, intestinal perforation: mostly a complication of toxic intestinal dilatation, can also appear severe type, mostly occurs in the left hemicolectomy, the application of corticosteroids is considered a risk factor for intestinal perforation. 4, intestinal polyps, colon cancer: colitis more than five years, intestinal ulcer surface in the long-term stimulation of inflammation is prone to abnormal hyperplasia, leading to intestinal polyps, more than one centimeter intestinal polyps cancer rate is very high; In addition, about 5% of cases of enteritis can be cancerous, mostly seen in the lesions involving the whole colon, early childhood onset and history of more than 10 years.