At present, the etiology of rectal cancer is not clear, generally speaking, it is related to the following factors: 1, a major cause of rectal cancer in chronic rectal inflammation, such as chronic ulcerative colitis and granuloma formed by chronic schistosomiasis, which is directly related to the occurrence of colorectal cancer. 2. Canceration of rectal adenoma is the direct cause of rectal cancer. 3, diet, meat, protein, fat intake increased, the incidence rate increased significantly. 4. Genetic factors: more than three family members have colorectal cancer, and two of them are of the same generation; At least two generations of similar people have the disease; At least one person was diagnosed with colorectal cancer over the age of 50.