At the beginning, the tumor appears as small hard nodes on rectal mucosa or anal skin, and there are no obvious symptoms, but after further development of the disease, the following symptoms may appear: 1. 2.Blood in stool: This is also one of the early symptoms of rectal cancer. It appears as bright red or dark red blood, and the amount is not much. It is often mistaken for hemorrhoids or dysentery and is sought for medical treatment. After further development of the disease, the symptoms will gradually intensify, the number of stools will be more than ten times, the amount of bleeding will increase, the anal swelling will worsen, accompanied by the feeling of urgency or incomplete defecation, and there will be pus, blood and mucus in the stool, with special foul odor. Due to secondary infection around the anus, it may be accompanied by perianal abscess or anal fistula. 3.Deformation of stool: In the late stage of cancer, rectal stenosis of anal canal gradually forms, less stool, thin and flattened stool shape or sheep stool shape, and symptoms of bowel obstruction such as abdominal distension, abdominal pain and intestinal tinnitus. 4.Metastasis signs: If the advanced cancer metastasizes to the liver, hepatomegaly and jaundice will appear. If it invades the sacral plexus, there will be severe pain in the rectum or sacrum, and it will radiate to the lower abdomen, lumbar region or lower limbs. When invading the bladder and urethra, there is dyspareunia and painful sensation. In addition, the patient loses appetite and shows signs of cachexia such as general debilitation, anemia and wasting. Diagnosis 1. Anorectal finger examination: About 80% of rectal cancers are located in areas that can be touched by fingers, therefore, rectal finger examination is extremely important for early diagnosis of rectal cancer. During finger examination, hard nodular masses or ulcerated cauliflower-like masses on the intestinal wall can be touched, and the intestinal cavity is often narrowed, with pus, blood and mucus stained on the finger sleeve. 2.Proctoscopy: This is an important step in the diagnosis of rectal cancer, which can not only see the extent of cancerous lesions, but also take small biopsies for pathological examination to identify cancerous or inflammatory masses. If no rectal lesion is found on finger examination, but symptoms are obvious, sigmoidoscopy or barium enema should be performed to see stricture or barium shadow stump for clear diagnosis. Early increased number of bowel movements or blood in the stool should be differentiated from dysentery, enteritis, and bleeding internal hemorrhoids. When a mass is palpated by rectal palpation, it should be differentiated from inflammatory masses. Cancerous ulcers of the anal canal should be distinguished from anal fistula and warts. Biopsy is a more reliable method of differentiation.