Rectal cancer is often asymptomatic or non-specific in the early stage, so it often does not attract the attention of patients and primary care physicians. Most of the patients may have change in bowel habit and blood in stool in early stage, presenting frequent stool and incomplete feeling of defecation. Frequent stool is different from diarrhea, because the former is only more frequent than normal, but the stool is normal or not much changed in nature; the feeling of incomplete defecation is that soon after defecation, the patient feels the urge to defecate again, but no stool is discharged or only a small amount of stool is discharged with a small amount of mucus and blood; therefore, the patient often does not take it seriously. Most of the blood in the stool of cancer patients is small in volume and bright red in color; it can be unmixed with stool and is often mistaken as hemorrhoids and ignored by patients and physicians. When the cancer grows and infiltrates the intestinal cavity for a week, constipation may occur, with difficulty in defecation, thin stool, and chronic obstructive symptoms such as lower abdominal distension and discomfort, while some patients may show alternating diarrhea and constipation before that. In men, when the cancer penetrates the intestinal wall and infiltrates the prostate or bladder, they may experience frequent urination, urgent urination, painful urination, hematuria, impaired urination or incomplete urination, etc. If the cancer penetrates the bladder, a recto-vesical fistula may be formed, and gas and fecal matter may appear in the urine. In women, cancer of the anterior rectal wall may infiltrate the posterior vaginal wall after penetrating the intestinal wall, causing increased leucorrhea; if it penetrates the posterior vaginal wall, it may form a rectovaginal fistula, and fecal matter and bloody secretion may appear in the vagina. The cancer of the posterior lateral wall of the rectum penetrates the intestinal wall and then infiltrates the pelvic wall, sacrum and sacral plexus. It causes pain in the caudal-sacral region and a feeling of swelling. These symptoms are all late manifestations, and patients are often accompanied by systemic symptoms such as weakness, emaciation, anemia and weight loss. When the cancer involves the anal canal or perianal area, patients often complain of anal pain and lumps protruding from the anal opening, in addition to blood in the stool. Most of the patients have frequent and incomplete bowel movements. When the cancer invades the anal sphincter, fecal incontinence may occur. Since the lymphatic drainage from the anal canal can first reach the inguinal lymph nodes, when lymphatic metastasis occurs, enlarged, hard lymph nodes can appear in the inguinal region and then fuse into a mass. In addition, lymphatic drainage from the anal canal may also follow the middle rectal vessels to the internal iliac and paravalvular lymph nodes in the foramen ovale. When lymph node metastasis infiltrates the foramen ovale nerve, the patient may develop intractable perineal pain radiating to the inner thigh. These are the advanced manifestations of cancer. 1.Changes in bowel habits, bloody stools, pus-blood stools, urgency, constipation, diarrhea, etc. 2.Progressive thinning of stool, and in advanced stage, there is obstruction of defecation, emaciation and even malignant matter. Rectal finger examination: It is a necessary examination step for diagnosis of rectal cancer, about 80% of rectal cancer patients can be found by natural rectal finger examination, and hard and uneven masses can be palpated; in advanced stage, narrowed intestinal cavity masses can be palpated and fixed finger sleeve can see dirty pus and blood containing feces. 4.Proctoscopy: the size and shape of the tumor can be seen and the interventional tissue can be taken directly for pathological examination. The diagnosis of rectal cancer is mainly based on 1.change in bowel habit and nature. 2, rectal finger examination and proctoscopy are well-known to find hard and irregular masses in the rectum, which can be confirmed by taking tissue for in-depth pathological examination. It is possible to reduce the incidence of cancer itch by 30%-60% by consuming beneficial foods to prevent cancer. It is very important to include alkaline foods such as fruits, vegetables and whole grains in your daily diet. The diagnosis of this disease is not very difficult, and more than 75% of patients can detect the lesion only by simple rectal examination. However, the misdiagnosis rate of rectal cancer is very high, and the main reason is that doctors neglect rectal examination. Based on the fact that rectal cancer is a common gastrointestinal malignancy, but it is very easy to be misdiagnosed, clinicians should routinely perform rectal finger examination and sigmoidoscopy for every patient with blood in stool, rectal irritation symptoms or change in stool habit, so as to detect the lesion at an early stage.