History and symptoms: Changes in bowel habits or stool characteristics, mostly in the form of more frequent, unformed or loose stools, blood and mucus in the stool. Sometimes constipation or diarrhea alternates with constipation, and stools become thin. Pain in the middle and lower abdomen, varying in severity, mostly vague or distending pain. Patients with right hemi-colon cancer often find abdominal masses. Pay attention to the presence of systemic symptoms such as blood craving, emaciation, weakness, edema, hypoproteinemia, etc. In case of tumor necrosis or secondary infection, patients often have fever. Physical examination: abdominal masses can be found in the abdomen or in the finger intestine, and they are hard with pressure pain and irregular in shape. Anemia, emaciation, and cachexia. For those with lymphatic metastasis, compression of venous return may cause ascites, edema of lower limbs, jaundice, etc. Colon cancer is mostly seen in middle-aged and elderly people, with the majority of them aged 30-69, and more men than women. Early symptoms are not obvious, but common symptoms in middle and late stage patients include abdominal pain and GI irritation, abdominal mass, change in bowel habit and stool properties, anemia and symptoms caused by chronic toxin absorption, intestinal obstruction and intestinal perforation, etc. Symptoms (1) abdominal pain and GI irritation symptoms: Most patients have different degrees of abdominal pain and abdominal discomfort, such as vague abdominal pain, right abdominal fullness, nausea, vomiting and loss of appetite. The symptoms often worsen after eating, sometimes accompanied by intermittent diarrhea or constipation, and are easily confused with chronic appendicitis, ileocecal tuberculosis, ileocecal segmental enteritis or lymphoma, which are common in the right lower abdomen. Colorectal hepatic flexure cancer may present as paroxysmal colic in the right upper abdomen, similar to chronic cholecystitis. It is generally believed that the pain of right hemicolectomy is often reflected to the upper part of the umbilicus; the pain of left hemicolectomy is often reflected to the lower part of the umbilicus. If the cancer penetrates the intestinal wall and causes local inflammatory adhesions, or if a local abscess is formed after chronic perforation, the pain site is the site where the cancer is located. (2) Abdominal masses: generally irregular in shape, hard in texture and nodular in surface. Transverse colon and sigmoid colon cancers have certain degree of activity and light pressure pain in early stage. If ascending or descending colon cancer has penetrated the intestinal wall and adhered to the surrounding organs, chronic perforation and formation of abscess or penetration of adjacent organs and formation of internal fistula, the masses are mostly fixed and immobile, with unclear edges and obvious pressure pain. (3) Change in defecation habit and stool characteristics: It is the result of necrosis of cancer and formation of ulcer and secondary infection. The change of defecation habit due to toxin stimulation of the colon, increase or decrease in the number of bowel movements, sometimes alternating between diarrhea and constipation, and abdominal cramps before defecation, which are relieved after defecation. If the cancer is located low or in the rectum, there may be rectal irritation symptoms such as anal cramping, poor defecation or shortness of breath. The stool is often unformed, mixed with mucus and pus and blood, and sometimes the amount of blood is often misdiagnosed as dysentery, enteritis, hemorrhoid bleeding, etc. (4) Anemia and chronic toxin absorption symptoms: the surface necrosis and ulceration of cancer may have continuous small amount of blood leakage, and blood mixed with feces is not easy to attract patients’ attention. However, chronic blood loss, toxin absorption and malnutrition may lead to anemia, emaciation, weakness and weight loss. In advanced stage, patients may have edema, hepatomegaly, ascites, hypoproteinemia, cachexia and other phenomena. If the cancer penetrates the stomach and bladder to form internal fistula, corresponding symptoms may also appear. (5) Intestinal obstruction and intestinal perforation: caused by intestinal mass filling, strangulation of the intestinal canal itself or adhesions and compression outside the intestinal cavity. Most of them are incomplete intestinal obstruction with slow progress. Patients in the early stage of obstruction may have chronic abdominal pain with abdominal distension and constipation, but they can still eat, and the symptoms are heavier after eating. The symptoms can be relieved after treatment with laxatives, bowel cleansing and Chinese medicine. After a long period of recurrent attacks, the obstruction gradually tends to be complete. Some patients present as acute intestinal obstruction, and about half of the acute colonic obstruction in the elderly is caused by colon cancer. When complete obstruction occurs in the colon, closed-collar intestinal obstruction is formed because the ileocecal valve blocks the backflow of the colon contents into the ileum. The colon from the cecum to the obstruction site can be extremely distended, and the pressure in the intestinal cavity increases continuously, which rapidly develops into strangulated intestinal obstruction and even intestinal necrosis and perforation, causing secondary peritonitis. Cancer in cecum, transverse colon and sigmoid colon can lead to intestinal loop when intestinal peristalsis is intense. Patients with colon cancer do not necessarily have the above-mentioned typical symptoms, and their clinical manifestations are related to the location of the cancer, pathological type and duration of the disease. The left and right halves of the colon can be divided by the splenic flexure of the colon, and the two halves differ in embryonic origin, blood supply, anatomical and physiological functions, intestinal contents and common cancer types, so there are obvious differences in clinical manifestations, diagnostic methods, surgical methods and prognosis. The embryonic origin of the right hemicolectomy is from the midgut, the intestinal lumen is large, the intestinal contents are in liquid state, and one of the main functions is to absorb water; the carcinoma is mostly of mass type or ulcer type, the surface is easy to bleed, and the toxins from secondary infection are easily absorbed. The three main symptoms commonly seen are right-sided anterior abdominal and GI irritation symptoms, abdominal mass, anemia and chronic toxin absorption after the manifestation, while the chance of intestinal obstruction is less. The left hemicolectomy originates from the hindgut, the intestinal lumen is thin, the intestinal contents are solid, the main function is to store and excrete feces, and the cancer is mostly of infiltrative type which easily causes the loop strangulation of the intestinal lumen. The three main symptoms are change in bowel habit, bloody stool and intestinal obstruction. Bowel obstruction may appear as an acute complete obstruction with sudden onset, but most of them are chronic incomplete obstruction with obvious abdominal distension, thin stool shaped like a pencil, and progressive worsening of symptoms eventually developing into complete obstruction. Of course, this distinction is not absolute, and sometimes there are only 1 or 2 clinical manifestations. 2.Signs Physical examination may vary depending on the course of the disease. In early stage patients, there may be no positive signs; in those with longer disease duration, a mass may be palpated in the abdomen, and there may be signs of emaciation, anemia and intestinal obstruction. If a patient intermittently develops an abdominal “air string-like” mass, accompanied by colic and hyperactive bowel sounds, the possibility of colon cancer causing intussusception in adults should be considered. If left supraclavicular lymph node enlargement, hepatomegaly, ascites, jaundice or pelvic masses are found, they are mostly in advanced stage. Metastases of liver, lung and bone have localized pressure pain. Rectal palpation is a non-negligible examination method, which can generally understand whether there are polyps, masses and ulcers within 8 cm from the anus. Low sigmoid colon cancer can be palpated through the abdomen and rectal double diagnosis. The presence of metastatic masses in the pelvis should also be noted. For female patients, triple diagnosis of abdomen, rectum and vagina is feasible. The basic prerequisite for colon cancer treatment is a comprehensive and correct tumor diagnosis. The diagnosis of tumor is a conclusion based on comprehensive medical history, physical examination and relevant instrumentation examination, and the general preoperative diagnosis mainly includes tumor condition and other conditions of the whole body. (1) Localization diagnosis of tumor: to clarify the location of tumor, to understand the relationship between tumor and adjacent tissues and organs, and whether there is distant metastasis. (1) Anatomical site of tumor: clinically, to clarify the anatomical site of tumor, we can use the following localization techniques to determine: A. Physical examination to clarify the site of mass is a simple and effective method, but we should pay attention to some transverse colon and sigmoid colon tumors with large free degree may not be in the regular position, which may cause errors in judgment. B. Ultrasound, CT, MRI can determine the existence of mass and the site of mass. C. The localization function of fiberoptic colonoscopy is unreliable except in rectum, mainly because of the non-linear relationship between colonoscopy and intestinal canal, which can be stretched or overlapped, and the huge difference between colonoscopic localization and surgical findings can often be seen in clinical practice, which makes surgery difficult. The method is barium enema examination, which can give us the most visual and accurate tumor site, and also the length and looseness of intestinal canal, which can help us determine the surgical incision selection and the scope of resected intestinal segment. The relationship between tumor and surrounding tissues: besides clarifying the anatomical site of tumor, it is very important to understand the relationship between tumor and surrounding tissues and organs, especially the relationship with important organs and large blood vessels, the relationship between general colon and surrounding tissues is not too close, only when the tumor is large can it invade other organs, the main ones are huge ileocecal tumor invading iliac vessels and ureter; colon liver cancer invading duodenum and pancreatic head; descending colon cancer invading The main ones are giant ileocecal tumor invading iliac vessels and ureter; colon and liver cancer invading duodenum and pancreatic head; descending sigmoid cancer invading ureter, etc. Preoperative understanding of the relationship between tumor and surrounding tissues is of definite value for the judgment of preoperative resection and for the notification of patients and family members. ③Distant metastasis of tumor: For malignant tumor, besides the condition of primary tumor is very important, the condition of metastasis is more important because with metastasis, the whole treatment plan will be changed significantly, therefore, preoperative careful examination of possible metastasis is a routine check before surgery. For colon cancer, pelvic floor implant metastasis, retroperitoneal lymph nodes, liver, and lung are common sites of metastasis and should be routinely examined. For the rare bone, brain and adrenal gland, the decision of whether to perform brain CT and bone scan is mostly based on clinical symptoms. (2) Qualitative diagnosis of tumor: Qualitative diagnosis of disease is required to clarify the following issues: ① whether the disease is a tumor; ② whether it is a malignant tumor or benign tumor; ③ which type and type of malignant tumor. The first two determine whether to operate and the scope of surgery; while the latter will determine the way of surgery. Although physical examination, ultrasound, CT, MRI and endoscopy can make preliminary qualitative diagnosis, the qualitative diagnosis of colon cancer finally relies on histopathological diagnosis. It should be noted that malignant tumors that can be basically diagnosed clinically are sometimes not necessarily malignant on pathological examination. Some authors have reported cases of preoperative pathological examination of colorectal cancer repeatedly 8 times (including fiberoptic colonoscopy, sigmoidoscopy and dilated anal biopsy) before diagnosis. This is related to the tissue biopsy site and the size of the biopsy tissue block. Therefore, when clinical suspicion of malignant tumor is raised, repeated examinations must be performed, and the diagnosis and treatment of the disease must not be delayed by abandoning the examination at will. In the clinical management of colon cancer, there are the following requirements for preoperative pathology: for colon cancer and colon cancer that can definitely preserve the anus, the current pathology can be uncertain, but there must be a clear lesion and reach a certain size; for rectal cancer that cannot clearly preserve the anus, there must be a pathological diagnosis before surgery. (3) Quantitative diagnosis of tumor: quantitative diagnosis of tumor can be broadly divided into 2 aspects: ① size of tumor. There are 2 ways to express it: the maximum vertical diameter of tumor and the circumference of tumor invading intestinal canal. The former is mostly used for larger tumors, generally multiplied by the maximum diameter of tumor and its maximum vertical diameter, expressed in centimeters; the latter is mostly used for small and medium-sized tumors, which are still limited to the intestinal canal, clinically expressed by the circumference of the intestinal canal occupied by the tumor, such as 1/2 circle; ② volume or weight of tumor, the volume and weight of tumor are less used in intestinal cancer, this method is mostly used for larger solid tumors, such as soft tissue tumors. (4) Preoperative staging of tumor: Preoperative staging of colon cancer, like other tumors, has the problem of accuracy of staging. Generally, a preoperative staging can be given based on the above tumor localization, characterization and quantification, and this staging often differs greatly from the postoperative staging. The current study has shown that for preoperative staging of colon cancer, the clinical guidance is of little significance, but for WHO stage II or III, i.e., middle and lower rectal cancer that has invaded the intestinal wall or has metastatic lymph nodes, preoperative staging is of great significance and can guide neoadjuvant radiotherapy. 2.Diagnosis and treatment of systemic non-tumor diseases When dealing with tumor diseases, the understanding and treatment of the health status of other tissues and organs of the body is also an important basis for formulating treatment plans. (1) Examination of body status: Tumor is a disease that increases with age, and most patients are older than 50 years old. Most of them have some chronic diseases, such as cardiovascular diseases, respiratory system diseases, liver and kidney system diseases, diabetes, etc. Shi Yingqiang reported a group of elderly colon cancer patients, 66% of whom had various types of chronic diseases in combination. The authors emphasized that a comprehensive physical examination should be performed for any tumor patient, including: routine electrocardiogram, chest X-ray, liver and kidney function, blood routine, blood clotting function, infectious diseases, and diabetes-related examinations. For those who have symptoms or whose examinations are suggestive, further examinations such as echocardiography, cardiac function, pulmonary function, electroencephalogram, and examination of bone marrow function should be performed. (2) Examination of diabetes mellitus: diabetes mellitus is closely related to colon cancer. The incidence rate of diabetes mellitus is 42.7% in the general population over 60 years old. Since diabetes and colon cancer have the same pathogenic factors, such as high protein, high fat, high calorie, low fiber and less exercise, the combination of diabetes in colon cancer patients is significantly higher than that in the general population. The study of colon cancer and gastric cancer admitted from 1993 to 1994 by Mo Shanzhen showed that the detection rate of diabetes in colon cancer was 17.6%, while that in gastric cancer was only 6.3% (P<0.025), which was also significantly higher than that of the general population. Due to the disorder of glucose metabolism in diabetes and the stress response in the surgical state, it can delay the healing of the anastomosis and decrease the resistance to infection, which increases the post-surgical complications. Therefore it is very important to detect diabetic patients before surgery. Most hospitals use diabetic history and fasting glucose to check for diabetes, but Mo Shanjian's study suggests that only 14.3% of patients can be detected by diabetic history; 37.1% of patients can be detected by fasting glucose; glucose tolerance test is the most reliable detection method, and it is best to perform routine glucose tolerance test before surgery with anastomosis. In doing the glucose tolerance test, some patients have the following 1 or 2 points of abnormality although they cannot be diagnosed as diabetes, but it also suggests that the patient has abnormal glucose metabolism, and it is also necessary to pay attention to detect or apply insulin to control blood glucose in the case of surgical stress. ①WHO diagnostic criteria for diabetes mellitus (1998): A. Symptoms of diabetic metabolic disorder + random blood glucose ≥ 11.1 mmol/L; B. Fasting blood glucose ≥ 7.0 mmol/L; C. OGTT of 2h postprandial blood glucose ≥ 11.1 mmol/L. ②Fasting blood glucose ≥ 6.1 to < 7.0 mmol/L, or 2h postprandial blood glucose ≥ 7.8 to < 11.0 mmol /L as hypoglycemic tolerance. (iii) Those with atypical symptoms need to be confirmed again on another day. For asymptomatic patients, there must be 2 abnormal blood glucose to be diagnosed.