Colorectal cancer

　　1. Environmental factors
　　Research has proven that among various environmental factors, dietary factors are the most important. The incidence of colorectal cancer is positively correlated with the consumption of high-fat foods in the diet. In addition, it may also be related to a lack of trace elements and changes in lifestyle.

　　2. Genetic factors
　　There are reports of 'familial colorectal cancer' in China and abroad. The number of relatives of colorectal cancer patients who die of the disease is significantly higher than that of the general population. Some colonic adenomas, such as familial adenomatous polyposis, are an autosomal dominant genetic disease, with a prevalence of up to 50% in the family. If not treated, there is a possibility of developing colorectal cancer after the age of 10. Some researchers have studied the relationship between tumor suppressor genes and the occurrence of colorectal cancer, finding that the susceptibility and pathogenesis of colorectal cancer are related to genetic factors.

　　3. Colonic adenoma
　　Research on post-mortem materials from various regions has found that the incidence of colonic adenomas is consistent with that of colorectal cancer. Some statistics show that the incidence of colorectal cancer in patients with one adenoma is 5 times higher than that in patients without adenoma, and that in patients with multiple adenomas is twice as high as that in patients with a single adenoma.

　　4. Chronic colonic inflammation
　　It is reported that the prevalence of colorectal cancer is positively correlated with the prevalence of schistosomiasis. It is generally believed that schistosomiasis can cause inflammatory changes in the intestines, among which a part may undergo carcinogenesis. Other chronic inflammatory diseases of the intestines also have the potential to become cancerous, such as ulcerative colitis, with an incidence of 3% to 5%. According to traditional Chinese medicine, the onset of colorectal cancer is related to intestinal deficiency and coldness, irregular diet, and external pathogenic factors invade internally.

　　Tumor obstruction
　　With the enlargement of the tumor and the increase of cancer cells, when they reach a certain volume, they can cause narrowing of the intestinal tract, reduction of the intestinal lumen, and obstruction of the passage of intestinal contents, leading to intestinal distension, fluid loss, electrolyte disorder, infection, and sepsis.

　　Intestinal perforation
　　According to clinical observations, colorectal cancer patients often suffer from intestinal perforation. Generally, it will cause patients to present with typical acute abdominal symptoms, such as muscle tension, tenderness, and rebound pain. X-ray films show crescent-shaped free air under the diaphragm, which can lead to an initial diagnosis.

　　Intestinal obstruction
　　Because of the gradual enlargement of the tumor, colorectal cancer can easily lead to narrowing of the intestinal lumen, which will form an obstacle to the passage of intestinal contents, resulting in mechanical intestinal obstruction. However, in clinical practice, tumor-related acute intestinal obstruction is not necessarily caused by complete obstruction of the intestinal lumen by tumor growth. In many cases, it is induced by local inflammatory edema, food blockage, or administration of mannitol during intestinal preparation on the basis of severe narrowing caused by the tumor.

　　Early symptoms of colorectal cancer are not obvious. As the tumor progresses, symptoms become more apparent, manifested as changes in bowel habits, hematochezia, abdominal pain, abdominal mass, fever, anemia, and weight loss, among other systemic toxic symptoms. The infiltration and metastasis of the tumor can cause changes in the corresponding organs. Colorectal cancer presents different clinical signs and symptoms depending on the primary site.

　　1. It is important to develop good eating habits in daily life
　　The occurrence of colorectal cancer is closely related to diet. Therefore, people can arrange their diet properly, such as eating more fresh fruits and vegetables that are rich in carbohydrates and coarse fibers, and appropriately increasing the proportion of coarse grains and mixed grains in staple foods, which is very beneficial for the prevention of colorectal cancer;

　　2. Active Prevention and Treatment of Intestinal Diseases
　　This is also a common preventive measure for colorectal cancer. Through long-term clinical observation, it has been found that chronic enteritis, chronic dysentery, and other intestinal diseases can also easily induce colorectal cancer. Therefore, early treatment should be given to these intestinal diseases.

　　3. Timely Treatment of Adenomas
　　When adenomas in the large intestine are found, treatment should be carried out, the adenoma should be removed, and a pathological examination should be performed to prevent the occurrence of the disease;

　　4. Regular Check-ups
　　In real life, if you belong to a high-risk population for this disease, such as men over 40, patients with familial multiple intestinal polyps, patients with ulcerative colitis, chronic schistosomiasis patients, and those with a family history of colorectal cancer, regular checks should be performed.

　　1. Laboratory Examination
　　In addition to blood routine tests that can understand whether the patient has anemia, other various laboratory tests can be performed according to the need for diagnosis and differential diagnosis. The occult blood in stool test during the examination and the detection of colorectal cancer biomarkers are of positive significance for the early diagnosis of colorectal cancer.

　　1. Occult Blood in Stool Test
　　Since colorectal cancer often presents with varying degrees of bleeding due to mucosal erosion and ulcers, it is possible to use simple and convenient occult blood in stool tests to monitor colorectal cancer. Early occult blood in stool tests were chemical coloring methods, commonly using reagents such as benzidine or guaiacum. In recent years, they have gradually been replaced by immunocryptographic reagents with higher specificity. However, since the occult blood in stool test cannot distinguish between cancerous and non-cancerous bleeding, it is currently mostly used as an initial screening method for large-scale population-based colorectal cancer surveys, but a few early cancers can also present false negative results leading to missed diagnoses.

　　2. Rectal Mucus T Antigen Test
　　Also known as the lactose oxidase test, it is a simple method for detecting specific markers of colorectal cancer and precancerous lesions. By simply applying the liquid from a rectal glove to a special paper membrane or slide, and then undergoing lactose oxidase reaction and Schiff's reagent staining, it can be determined whether the patient's intestinal mucosa expresses T antigen. Clinically and through general surveys, this method has been verified to have high sensitivity and specificity for detecting colorectal cancer. When used in general surveys, it has a complementary effect with the immunocryptographic test for screening colorectal cancer, but there is also a certain rate of false positives and false negatives.

　　3. Detection of serum CEA
　　The serum CEA level of most colorectal cancer patients is often elevated, but the specificity of this test is not strong. In some non-gastrointestinal tumors and benign lesions, the serum level can also be elevated. CEA has poor sensitivity to early colon cancer and adenomatous polyps, so its use in the detection of early colorectal cancer is not very effective.

　　Second, endoscopic examination
　　It has been widely applied in clinical practice. For experienced endoscopists, routine X-ray examination can often be performed, and for highly suspicious patients with colorectal cancer, it is especially advocated to perform a full colonoscopy to avoid missed diagnosis. Due to the safety and reliability of fiberoptic colonoscopy, it not only can inspect the size, shape, location, and mobility of the tumor, but also can perform resection of polyps or early microscopic cancer foci. It can also guide the collection of tissue for biopsy from suspicious lesions. Therefore, it is currently the most effective means of diagnosing colorectal cancer, and it is often used as the gold standard for evaluating the effectiveness of various initial screening methods in colorectal cancer screening.

　　Third, X-ray examination
　　It can detect lesions that cannot be seen by rectoscopy or sigmoidoscopy, which is an effective means of diagnosing colorectal cancer. Generally, barium enema examination is performed, with main signs such as local deformation of the mucosa, abnormal peristalsis, narrowing of the intestinal lumen, and defects in filling. It is often difficult to show smaller lesions, especially those with a diameter less than 2cm. The use of barium double contrast imaging can help in the detection of early cancer.

　　Fourth, biopsy and desquamated cell examination
　　Biopsy is of decisive significance for determining colorectal cancer, especially early cancer and polyp malignancy, as well as for differential diagnosis of lesions. It not only can clearly define the nature, histological type, and degree of malignancy of the tumor, but also can judge the prognosis and guide clinical treatment. Although cytology has high accuracy, the sampling process is cumbersome, and it is not easy to obtain satisfactory specimens. Experienced cytological doctors are needed for observation, so its clinical application is relatively rare. Currently, it is mostly replaced by cytological diagnosis through direct brushing and smearing under endoscopy.

　　Patients with colon and rectal cancer often have recurrent diarrhea that does not heal, with weak digestion. Therefore, easy-to-digest and absorbable foods should be provided.
　　Patients with colorectal cancer often have blood in their stool. Advanced patients often have a large amount of hematochezia and should avoid or reduce the intake of刺激性 and spicy foods.
　　Patients often have symptoms such as anorexia, nausea, and even vomiting. Therefore, it is advisable to take light and bland foods and avoid greasy foods.
　　Patients with advanced colorectal cancer often suffer from prolonged diarrhea, hematochezia, and fever, leading to the loss of a large amount of nutrients and water, resulting in weight loss, emaciation, and deficiency of both Qi and blood. Therefore, it is advisable to drink more water or liquid, and the main food can be semi-liquid foods such as congee and noodles.
　　After colorectal cancer surgery, some patients often feel poor appetite or abdominal distension and other gastrointestinal discomfort. Drinking yogurt after surgery can alleviate these discomforts. Because after colorectal cancer surgery, the balance of beneficial bacteria in the intestines is disrupted, and drinking yogurt in moderation can help restore the normal flora of the intestines.
　

　　1. Surgical Treatment
　　(1) The treatment plan for colon cancer is a comprehensive treatment plan with surgery as the mainstay. For stage I, II, and III patients, radical resection plus regional lymph node dissection is commonly used, and the scope of radical resection and the surgical method are determined according to the location of the tumor. For stage IV patients with intestinal obstruction or severe intestinal bleeding, radical surgery is not performed temporarily, and palliative resection can be performed to alleviate symptoms and improve the quality of life of patients.
　　(2) The fundamental basis for radical treatment of rectal cancer is surgery. Rectal surgery is more difficult than colonic surgery. Common surgical methods include: anal resection (extremely early near the anal margin), total mesorectal excision, low anterior resection, and abdominoperineal resection. For stage II and III rectal cancer, it is recommended to undergo radiotherapy and chemotherapy before surgery to reduce the tumor size and lower the local tumor stage, followed by radical surgery.

　　2. Comprehensive Treatment
　　(1) The regimen of oxaliplatin combined with 5-fluorouracil is the standard treatment for stage III colorectal cancer and some patients with high-risk factors, with a treatment duration of 6 months. It is suitable for patients with rectal cancer who have not received neoadjuvant radiotherapy before surgery. Patients who need adjuvant radiotherapy after surgery should also follow this regimen.
　　(2) The treatment for stage IV colorectal cancer mainly includes a comprehensive treatment plan with chemotherapy as the mainstay. Chemotherapy drugs include 5-fluorouracil, capecitabine, oxaliplatin, irinotecan, bevacizumab, cetuximab, panitumumab, and other drugs. Common chemotherapy regimens include FOLFOX, XELOX, FOLFIRI, etc., and targeted drug therapy (bevacizumab, cetuximab, panitumumab) can be combined with chemotherapy as appropriate.

　　3. Radiotherapy
　　Currently, comprehensive treatments including surgery and radiotherapy are more effective and extensively researched. These include preoperative radiotherapy, intraoperative radiotherapy, postoperative radiotherapy, and 'sandwich' radiotherapy, each with its own characteristics. For patients with advanced rectal cancer, locally invasive tumors, or those with surgical contraindications, palliative radiotherapy is used to alleviate symptoms and reduce pain.