Rectal cancer is cancer between the dentate line and the junction of the rectosigmoid colon, and is one of the most common malignant tumors of the gastrointestinal tract. The location of rectal cancer is low, so it can be easily diagnosed by rectal finger diagnosis and sigmoidoscopy. However, because of its location deep into the pelvic cavity and complex anatomical relationship, surgery is not easy to be complete and the recurrence rate after surgery is high. The proximity of lower and middle rectal cancer to the anal sphincter makes it difficult to preserve the anus and its function during surgery, which is a difficult problem in surgery and is also the most debated disease in terms of surgical methods. The median age of rectal cancer incidence in China is around 45 years old. There is a trend of increasing incidence in young people. The cause of rectal cancer is still not very clear, and its development is related to social environment, dietary habits, genetic factors, etc. Rectal polyps are also a high risk factor for rectal cancer. It is basically recognized that high intake of animal fat and protein and insufficient intake of dietary fiber are the high-risk factors for rectal cancer. In order to detect, diagnose and treat rectal cancer as early as possible, it is also very important to understand the clinical manifestations of rectal cancer! 1.Most of the early rectal cancers have no symptoms. 2. When rectal cancer grows to a certain extent, change in bowel habit, bloody stool, pus-blood stool, urgency, constipation, diarrhea, etc. will appear. 3.The stool will gradually become thinner, and in the advanced stage, there will be obstruction of defecation, emaciation and even cachexia. 4.Tumor invades the bladder, urethra, vagina and other peripheral organs, and then it shows symptoms of urinary tract irritation, vaginal discharge of fecal fluid, pain in the sacral and perineal areas, and edema of the lower limbs.