For early and timely detection of retreatable recurrent and metastatic lesions, for early detection of heterochronous multiple primary colorectal cancer for timely treatment, and for dealing with a series of gastrointestinal symptoms and other complications after surgery, patients should be regularly reviewed and followed up for life after surgery. It is generally believed that patients with colorectal cancer treated by surgery are very prone to local recurrence after surgery, with 80%-90% of recurrence cases occurring within 2-3 years after surgery, and only about 2% of recurrence cases occurring after 5 years after surgery. Most scholars believe that local recurrence will be symptomatic, and when symptoms appear clinically, the tumor has mostly developed to advanced stage and lost the chance of reoperation. Therefore, regular examination is of great significance, hoping to detect recurrence at an earlier stage, thus increasing the success rate of reoperation. It is recommended to review once every 3 months within 2 years after colorectal cancer surgery, and once every 6 months afterwards. 1. Physical examination Medical history inquiry and physical examination once every 3 months, including detailed questioning of recent medical history. For patients with smooth postoperative recovery, if there is again unexplained weight loss, change in bowel habits again, pelvic pain or perineal inner thigh pain, unexplained irritating cough, abdominal distension and intestinal bleeding, etc., there is a possibility of recurrence. Comprehensive physical examination, check the axillary, supraclavicular and cervical lymph nodes, abdomen mainly check the liver and spleen, whether there are abdominal masses, anal examination can timely find the recurrent foci in the rectum or pelvis, these physical examination results have certain reference significance for treatment. Although there is still disagreement about the specificity of CEA and whether it can be used as a marker for early diagnosis of recurrence, most scholars believe that elevated CEA in patients with progressive stage and its failure to return to normal level after surgery often indicates poor prognosis, and the elevation of CEA often precedes the clinical symptoms of recurrence by 4-5 months. can not only monitor local recurrence, but also indicate distant metastases in the liver and lungs. Ideally, baseline CEA levels should be obtained prior to the first surgery and CEA levels should return to normal within 2 months after radical surgery is performed. If the CEA level does not drop to normal, it predicts residual tumor. Once the CEA level returns to normal baseline, it should be checked every 3 months. CEA also has some significance in monitoring the efficacy after surgery. If a patient with high CEA value has a decrease in serum CEA value after chemotherapy, it indicates that the tumor is sensitive to chemotherapy drugs. If the serum CEA value continues to remain at a high level, it indicates that chemotherapy is ineffective. The determination of serum CEA should be measured every 4-6 weeks within 2 years after surgery and every 6 months after 2 years. 3.CT or ultrasound examination of abdominal and pelvic cavity CT examination or ultrasound examination of colorectal cancer is used to understand the local recurrence and metastases of distant organs (liver, lung, etc.) and lymph node metastasis of abdominal and pelvic cavity with high accuracy after surgery, which is now generally accepted. Under normal circumstances, CT examination should be performed once a year and ultrasound examination once every 6 months. Patients who are eligible should have a CT scan within 4-6 weeks after surgery as a control for later review. The sensitivity of CT to detect pelvic or distant metastases is as high as 88%, but a definitive diagnosis can only be made when the lesion is larger than 1-2 cm. Of course, smaller lesions can be detected by comparison with CT films reviewed early after surgery. 4. Chest X-ray Regular postoperative chest X-ray is necessary. If a suspicious lesion is found, a CT scan of the chest has some value. If the medical history and physical examination suggest the possibility of bone metastasis, bone scan should be performed. 5.Colonoscopy or 3D CT examination of colon can not only detect recurrent anastomosis or heterochronic colorectal adenoma or colorectal cancer, but also help to detect adenoma cancer in time. Sigmoidoscopy can be used for the examination of low anastomosis. 3D CT of the colon can be used in cases of failed colonoscopy. The advantages of postoperative fiberoptic colonoscopy for colorectal cancer are: ① the correct diagnosis rate can reach 90%-97%, and the positive detection rate is higher than other examination methods; ② biopsy can be performed to determine the diagnosis, which is better than X-ray examination; ③ for postoperative anastomotic stenosis, fiberoptic colonoscopy can determine whether it is benign scar or tumor recurrence; ④ colorectal polyps can be removed by fiberoptic colonoscopy. Colonoscopy has special value for observing the anastomotic condition and should be performed once or more times a year. In summary, the postoperative follow-up program for colorectal cancer patients can be summarized as follows. It should be emphasized that this plan is only a general guideline recommendation, and individualized plan should be formulated according to the patient’s specific condition in clinical application. Physical examination: every 3 months for 2 years after surgery; every 6 months for 3-5 years CEA/CA199: if diagnosed or abnormally elevated before surgery, review every 3 months for 2 years and annually for 3-5 years Abdominal/pelvic CT: 4-6 weeks after surgery as a control; annually for the next 3 years. Revisit at any time if clinically indicated abnormalities. Ultrasound: every 6 months for 3 years after surgery; intraluminal ultrasound annually after surgery Chest X-ray: every 6 months for 2 years after surgery; annually thereafter Colonoscopy: annually for 2 years after surgery; if both are negative, annually thereafter; annually if polyps are found