Rectal cancer, including cancer between the dentate line and the sigmoid junction, is one of the most common malignant tumors of the gastrointestinal tract, second only to stomach and esophageal cancer in incidence, and is the most common part of colorectal cancer (accounting for about 60%). The vast majority of patients are over 40 years old, and about 15% are under 30 years old. Rectal cancer is low in location, easily detected by rectal diagnosis and sigmoidoscopy, and easily diagnosed. However, because of its deep pelvic cavity, it is difficult to operate and has high local recurrence rate after surgery. Etiology 1.Diet and carcinogenic substances: high fat, high protein food, less fiber food, increased methylcholanthrene substances, etc. 2.Chronic inflammation of rectum: ulcerative colitis, schistosomiasis, etc. 3, precancerous lesions: rectal adenoma, especially choroidal adenoma 4.Genetic factors: family history of rectal cancer. Clinical symptoms There are no symptoms in the early stage, but after development, there are the following symptoms: 1. rectal irritation symptoms: frequent bowel movements, urgency, lower abdominal pain, anal drop feeling, etc. 2.Symptoms of intestinal stricture: deformation and thinning of stool, abdominal pain, abdominal distension, etc. 3.Symptoms of cancer infection: blood in stool and mucus, pus and blood in stool. 4.Other symptoms: frequent urination, painful urination, hematuria, anemia, emaciation, swelling, etc. Ancillary tests: fecal occult blood test, rectal finger examination, proctoscopy, colonoscopy, barium enema, ultrasound, CT examination, tumor marker (CEA) measurement, etc. Treatment Surgical radical resection is still the main treatment method for rectal cancer. Pre-operative and post-operative adjuvant radiotherapy, chemotherapy and immunotherapy can improve the therapeutic effect. It is recommended that rectal cancer is one of the more common malignant tumors in clinical practice, and change in bowel habits is its main feature. Therefore, abnormal bowel movements (including regularity and nature) should be given great attention. For those “dysentery” that cannot be cured for a long time, rectal examination or fiberoptic sigmoidoscopy should be done. Generally, the treatment plan should be decided by a specialist after consultation and treatment according to the patient’s actual condition.