Clinical manifestations: change in bowel habits, bloody stools, purulent stools, shortness of breath, constipation, diarrhea, etc. In advanced stage, the stool gradually becomes thinner, and then there is bowel obstruction, emaciation and even malignant. Rectal finger examination: It is a necessary examination step for the diagnosis of rectal cancer, about 80% of rectal cancer patients can be found through natural rectal finger examination, and hard and uneven masses can be palpated; in advanced stage, narrowed intestinal cavity masses can be palpated, and the finger sleeve can see dirty pus and blood containing feces. Proctoscopy: the size and shape of the tumor can be visualized and the intervening tissue can be taken directly for pathological examination. Obstruction symptoms are obstruction of the rectum by the cancer, with difficulty in defecation, less stool, abdominal pain and abdominal distension. In some cases, bowel pattern and hyperactive bowel sounds can be seen. In general, patients with bleeding stools should be highly alert clinically, and should not be rashly diagnosed as “dysentery”, “internal hemorrhoids”, etc. Further examination is necessary to exclude the possibility of cancer. For the early diagnosis of rectal cancer, we must pay attention to the application of rectal finger examination, proctoscopy or sigmoidoscopy and other examination methods. About 90% of rectal cancer, especially lower rectal cancer, can be detected by finger examination alone. However, there are still some physicians who do not perform this routine examination for patients with suspected rectal cancer, thus delaying the diagnosis and treatment. In fact, this diagnostic method is simple and feasible, and the size and degree of infiltration of the lumps can be determined through rectal finger examination, whether they are fixed or not, and whether there are implanted lumps outside the intestinal wall or in the pelvic cavity, etc. 2.Proctoscopy or sigmoidoscopy should be performed after rectal finger examination to assist diagnosis under direct vision, to observe the shape, upper and lower edges and distance from the anal edge of the mass, and to take tissue of the mass for pathological section to determine the nature of the mass and its differentiation degree. If the cancer is located in the middle or upper rectum and cannot be touched by fingers, sigmoidoscopy is a better method. 3.Barium enema and fiber colonoscopy do not help much in the diagnosis of rectal cancer, so they are not included in the routine examination, and are only used to exclude multiple tumors of the colon and rectum. What examinations should be done for rectal cancer? Rectal finger examination: It is a necessary examination step for the diagnosis of rectal cancer, about 70%-79% of rectal cancer patients can be found through rectal finger examination to have a hard and bumpy mass; in advanced stage, a narrowed intestinal cavity mass can be palpated and a fixed finger sleeve can be seen to contain fecal filthy pus and blood. 2. Rectal microscopy: The size and shape of tumor can be seen and tissues can be taken directly for pathological examination. 3.Pathological examination: it is the main basis of rectal cancer diagnosis. Since rectal cancer surgery often involves rerouting, which affects the survival quality of patients, in order to avoid misdiagnosis and mistreatment, the results of pathological examination must be obtained before or during surgery to guide treatment. Absolutely do not easily excavate the anus. 4.Carcinoembryonic antigen determination: carcinoembryonic antigen (CEA) determination has been commonly carried out and is generally considered valuable for evaluating treatment effects and prognosis, and continuous determination of serum CEA can be used to observe the effects of surgery or chemotherapy. A significant decrease in CEA after surgery or chemotherapy indicates a good therapeutic effect. If surgery is incomplete or chemotherapy is ineffective, serum CEA is often maintained at high levels. If CEA decreases to normal and increases again after surgery, it often indicates tumor recurrence. 5.Gas-barium enema contrast imaging: It helps to understand and exclude multiple cancer foci in the large intestine. The imaging manifestations of rectal cancer are: ①Nodular filling defect, mostly in the medial wall of the rectum, round and smooth or mildly lobulated, with local intestinal wall stiffness and concavity. ② cauliflower-shaped mass, larger, with uneven surface, obvious lobulation, its base is wide, and the bowel wall is stiff. (iii) Irregular circumferential stenosis with stiff walls, interrupted mucosa, and truncated demarcation. ④Irregular intraluminal niche shadow, triangular, long, etc., shallow, with uneven width of the surrounding ring dike. ⑤ Complete intestinal obstruction, or signs of intussusception, obstruction of the proximal segment is sometimes difficult to show. It should be noted that the X-ray examination of barium enema sometimes cannot show rectal lesions, and it is easy for people to have the illusion of no lesions. 6.B ultrasound examination: For cases of rectal tumor, rectal luminal ultrasound can be further performed. This is a non-invasive examination developed in recent years. Its advantage is that it can determine the depth and extent of rectal cancer infiltration, and also has some value on whether there is metastasis in lymph nodes. Ultrasound of the liver is especially important to prevent leakage of liver metastasis of rectal cancer. 7. Telomerase activity test: Telomerase activity can be used as a test for the development of colorectal tumor. If the cell division of colorectal tumor is faster, the activity of telomerase will be high; while the activity of telomerase will be low in tumor tissues with slower cell division. A complex mechanism exists in normal humans to inhibit unlimited cell proliferation: one is cell cycle control; the other is apoptosis or programmed cell death caused by progressive telomere shortening that occurs with each cell division. The strength of telomerase activity is positively correlated with the survival time of colorectal tumor cells in the effusion. Telomerase activity is an important indicator for the early diagnosis and prognosis of colorectal cancer. The detection of telomerase activity from stool exfoliated cells can be used as a non-invasive early diagnosis method for colorectal cancer. Telomerase activity can be detected by polymerase chain telomere repeat amplification (PCRTRAP) silver staining technology in the Fourth Hospital of Xingtai City. 8.CT test for rectal cancer: CT scan is not a necessary test for rectal cancer diagnosis, and the confirmation of rectal cancer diagnosis does not require CT examination, although it is expensive. However, in some cases, CT examination of colorectal cancer has its unique role, especially CT scan diagnoses the invasion of lesions into the intestinal wall, the extent of outward spread, the presence of metastasis of surrounding organs and lymph nodes, etc., which is important for the staging of colorectal cancer. Pre-operative CT is mainly used for staging of advanced stage patients in order to adopt appropriate treatment plan and avoid unnecessary surgery; post-operative CT plays an important role in monitoring local recurrence and distant metastasis.