1.What is colorectal cancer
Colorectal cancer refers to malignant tumors occurring in the colon and rectum. The so-called malignant tumor refers to the local mass with abnormal structure and function formed by the pathological overgrowth of human local tissue cells. In clinical practice, most colorectal cancers grow in the left half of the colon, namely the descending colon, sigmoid colon and rectum. Malignant tumors growing in the transverse colon and the right ascending node are relatively rare. With the development of society, the improvement of people’s living standard and the change of traditional diet structure, the incidence of colorectal cancer is increasing.
2.What are the causes of colorectal cancer?
The exact cause of cancer in colon is still unclear, but after years of observation and research, some factors are found to be closely related to the occurrence of colorectal cancer. In summary, there are several factors as follows.
(1) Dietary factors: For example, people with high fat and low fiber diet are prone to colorectal cancer. Moldy and pickled foods also have such a role.
(2) Genetic factors: Some colorectal cancers have obvious genetic tendency.
(3) Chronic inflammation of the intestine: Patients with ulcerative colitis, clonorchiasis and intestinal schistosomiasis, for example, have a high incidence of colorectal cancer.
(4) Environmental factors and radiation damage.
(5) Colorectal polyp carcinoma: At present, it is believed that colorectal polyp is a pre-cancerous lesion.
3.What kind of diet structure is likely to cause colorectal cancer?
Scientific research has confirmed that high-fat, high-protein, low-fiber diet is positively correlated with the occurrence of colorectal cancer, that is, people with this diet structure are prone to colorectal cancer. When people consume too much fat, the secretion of bile will increase because bile is used to digest fat. Bile salts and fatty acids in bile, under the action of anaerobic bacteria in the intestine, produce a large amount of neutral cholesterol degradation products of polycyclic hydrocarbons, which have carcinogenic and adjuvant carcinogenic effects. High protein, mainly animal protein food in the cooking process, will produce a strong mutagenic heterocyclic amine compounds, which have obvious carcinogenic effects. At present, it is basically clear that saturated fat, especially trans fat, is the main culprit of colorectal cancer.
4.What are saturated fats and trans fats?
Fats are composed of various fatty acids. It is customary to call fats in liquid form at room temperature as oil, and those in solid form at room temperature as fat. Whether a fat is liquid or solid at room temperature is determined by its degree of saturation. In terms of chemical structure, fatty acids are chain-like carboxylic acids, which contain mostly even number of carbon atoms. Those with no double bonds in the carbon chain are saturated fatty acids, which are solid at room temperature; those with double bonds in the carbon chain are unsaturated fatty acids, which are liquid at room temperature. Unsaturated fatty acids are very beneficial to the human body, but some unsaturated fatty acids cannot be synthesized by themselves and must be taken from food, these unsaturated fatty acids necessary for the human body but cannot be synthesized by themselves are called essential fatty acids. Too much saturated fat intake, blood triglycerides, mainly LDL, will rise, which promotes atherosclerosis and aging, and has certain carcinogenic effects. Trans fats, also called hydrogenated fats, are made by chemically adding hydrogen atoms to both sides of the carbon chain of unsaturated fatty acids during the processing of edible oils. This oil is stable and has a long storage time, and the food cooked with it is bright, beautiful and has a long shelf life. Margarine, refined oil, etc. are all trans fats. A research study in the United States shows that saturated fat and trans fat are one of the predisposing factors for breast cancer, colorectal cancer, and cardiovascular disease.
5.How do harmful fats contribute to the development of cancer?
Saturated fats and trans fats are harmful fats, which are carcinogenic factors or called genetic mutagens. They can damage deoxyribonucleic acid (DNA), the material basis of normal cell genetics, and induce structural changes to certain genes in the long chain of DNA, causing errors in DNA replication or translation, turning certain normal cells into “latent cancer cells”. When this “latent cancer cell” encounters opportunities suitable for its development, such as lowered immune surveillance function and reduced immune function, it will rapidly divide and generate tumors.
6.What are the foods that contain more trans fat?
(1) Vegetable oil containing trans fat: refined vegetable oil, margarine, chocolate, vegetable cream, ice cream, etc.
(2) fried food: even if you use vegetable oil without trans fat frying food, the oil will be heated at high temperature for a long time, the molecules will be mutated and become trans fat. Therefore, a variety of fried foods also contain more trans fats.
(3) a variety of baked goods, such as bread, cookies, pastries, etc.
(4) some seasonings, condiments: such as peanut butter. As long as the packaging labeled “vegetable fats”, “refined vegetable oil” and other words contain a large amount of trans fat.
7.Does a high-fat diet always lead to colorectal tumors?
Epidemiological research results show that the diets of countries and regions with high incidence of colorectal cancer are characterized by refined rice, refined noodles, high fat, high animal protein and low fiber, and the fat content accounts for 40% of the total calories in the diet; while the fat content in the diets of countries and regions with low incidence of colorectal cancer is very low. In Japan, fat calories only account for about 12% of the total calories in the diet, and the incidence of colorectal tumors is very low. Of course, people who eat a high-fat diet only have a much higher chance of developing colorectal tumors than those who eat a low-fat diet, but not necessarily. The high-fat diet is only an external factor to develop colorectal tumor, but whether and when to develop colorectal tumor depends on the internal aspects of the cell phone body. In other words, whether or not to suffer from colorectal tumor, the internal factors of the body play a decisive role, and the external factors are only a condition to promote the development.
8.What are the intrinsic factors to decide whether to suffer from colorectal cancer?
Whether a person has cancer, what kind of cancer, when to get cancer, whether and when to metastasize after getting cancer, etc. are not determined by cancer-causing factors, but by the sensitivity of our chromosomes to cancer-causing substances. As the saying goes, “ten fingers are not all the same”, not all of our 46 chromosomes are equally healthy, and individual chromosomes are weak by nature, just like some people are born strong and some people are born thin. When these weaker chromosomes are attacked by strong carcinogenic substances, they will show susceptibility to damage, such as breakage, and the genes they carry will mutate and become cancer cells. It is important to note that such weaker chromosomes can be inherited, which explains why certain families are at high risk for certain types of cancer. All we can do is try to avoid cancer-causing factors so that we are as cancer-free as possible. It is not clear which chromosome damage will cause colorectal cancer in humans.
9. What other dietary factors are associated with colorectal cancer?
It has been reported in the literature that chloroform and other halides used to disinfect tap water may also be a carcinogenic factor for colon cancer. The incidence of colorectal cancer in well water drinkers is significantly lower than that in river and pond water drinkers, probably because well water is clean water filtered through sand and gravel, while river and pond water have been seriously polluted. Researchers have also found that a substance called S-adenosylmethionine has the effect of inhibiting colorectal cancer by affecting DNA, and the substance is significantly reduced in alcoholics, so alcoholism should also be one of the cancer-causing factors of colorectal cancer. In addition, pickled and moldy foods also contain a lot of carcinogens, which also need to be noticed. As for whether there is a clear relationship between smoking and the incidence of colorectal cancer, there is no definite conclusion yet.
10.What are the other factors related to colorectal cancer?
(1) Radiation often irradiates the colon can lead to colorectal cancer: when some gynecological cancers receive radiotherapy, a local intestinal canal also receives a lot of radiation, the tissue is damaged and the cells mutate to become colorectal cancer.
(2) Tumors in other parts of the body: If you have a history of cancer, it is also one of the risk factors of colorectal cancer. Cancer in other parts of the body can also lead to colorectal cancer through certain transmission routes.
(3) Malignant transformation of benign masses in the colon: Many clinical studies have proved that benign polyps in the colon can become malignant and become colorectal cancer (such as hyperplastic polyps, inflammatory polyps, adenomas, etc. The more the number of polyps and the larger they are, the higher the rate of malignant transformation. Relevant information shows that: the cancer rate of colon polyps with a diameter of less than 1 cm is about 5%; the cancer rate of those with a diameter of 1-2 cm is about 13%; the cancer rate of those with a diameter of more than 2 cm is as high as 41%. Therefore, there is a consensus that benign colorectal tumors are precancerous lesions. Colorectal cancer follows a pattern of development from normal mucosa to polyps to cancer.
(4) Long-term chronic constipation is closely related to colorectal cancer: due to long-term constipation, some toxins and carcinogens in the body cannot be discharged from the body through stool in time, so that these harmful substances stimulate intestinal mucosa for a long time in the colon, leading to chronic inflammation and hyperplasia of mucosa and eventually becoming cancer.
(5) Some trace elements are related to colorectal cancer: Studies have shown that the soil in areas with high incidence of colon cancer lacks trace elements selenium and molybdenum, and selenium supplementation can inhibit the occurrence of colorectal cancer, which indicates that the content of certain trace elements has a direct relationship with the occurrence of colorectal cancer, the specific mechanism of which is still under study, and it is speculated that trace elements may act through enzymes.
11.How is the heredity of colorectal cancer?
When it comes to heredity, people often have the misconception that if one parent suffers from colorectal cancer, it will be passed on to the next generation and the children must also suffer from colorectal cancer. In fact, colorectal cancer itself is not hereditary. The hereditary nature of colorectal cancer refers to two types of autosomal dominant diseases – familial polyposis or familial adenomatous polyposis and hereditary non-polyposis colorectal cancer. Familial adenomatous polyposis usually begins after puberty and manifests as hundreds or thousands of growths in the large intestine, often with multiple cancerous lesions. Hereditary nonpolyposis colorectal cancer often occurs in the right colon and presents with multiple villous adenomas in the intestine, which are not as numerous as in patients with familial pulsatile polyposis. The molecular biology of these two chromosomal dominant disorders differs in that patients with familial adenomatous polyposis have mutations in genes on the long arm of chromosome 5, whereas hereditary nonpolyposis colorectal cancer is mainly a DNA pairing error repair gene mutation. As for sporadic colorectal cancer, although a higher percentage of its family members develop colorectal cancer than the rest of the population, it is currently thought to be due to the environment in which they live together. In other words, there is no clear answer in science whether the colorectal cancer we generally suffer from is hereditary.
12.Which chronic inflammatory diseases of the intestine can become cancerous?
As we have mentioned in the relevant section, chronic ulcerative colitis is prone to cancer, characterized by the younger the age and the longer the course of the disease, the higher the cancer rate, which is about 5%, such as 25 years of ulcerative colitis, the risk of cancer is 42%-45%. Crohn’s disease can also become cancerous, but the risk of cancer is lower than that of ulcerative colitis, with a cancer rate of about 2.8% for those who have had the disease for more than 20 years. In addition, patients with intestinal schistosomiasis can develop cancerous tissues due to the deposition of schistosome eggs on the intestinal mucosa. Other intestinal inflammatory diseases such as bacteriophageal dysentery and amebic dysentery can become cancerous through granulomas, so various chronic inflammatory diseases of the intestine must be actively treated.
13.Where do colorectal polyps come from?
Colon polyp is a tumor growing on the mucosa of the large intestine. It is a kind of abnormal, with the surrounding tissue is not coordinated with the new tissue, is due to the colon mucosa cells in the role of various stimulating factors (such as the intestinal decomposition from the food of polycyclic hydrocarbons and heterocyclic amines, etc.) proliferation, and once this abnormal proliferation, even if the stimulating factors stop stimulating, the proliferation still continue, resulting in polyps. The kind of proliferating cells with mature differentiation and slow growth rate become benign tumors of the colon, while the kind of proliferating cells with immature differentiation and fast growth rate become malignant tumors of the colon.
14.Is the cancer of polyps of different nature the same?
In terms of histology, polyps are divided into tumor polyps and non-tumor polyps. Neoplastic polyps are divided into tubular adenoma, villous adenoma and villous tubular adenoma according to their histology. An analysis of the factors associated with adenoma tissue type and carcinoma has been done and found that the rate of carcinoma varies by tissue type. The cancer rate for tubular adenomas is approximately 8.6%, for villous tubular adenomas is approximately 22%, and for choroidal adenomas is approximately 62.5%. In addition, studies have also shown that the more severe the atypical hyperplasia of polyp gland epithelium, the greater the risk of carcinogenesis. More than 80% of patients with colorectal adenomas aged over 50 years develop cancer. Whether non-neoplastic polyps, such as inflammatory polyps, are cancerous is still debated. If you have a non-neoplastic polyp, you should monitor it closely, and if necessary, it should be removed surgically.
15.How many types of colorectal cancer are there in histology?
Whenever there is a mass on the large intestine, the doctor has to remove a small piece of it and send it to the pathology department to observe its histological structure under the microscope to make a clear diagnosis.
(1) Adenocarcinoma: Most colorectal cancers belong to adenocarcinoma, because the colon is an organ with adenoid structure. Microscopically, cancer cells are irregularly arranged in the form of glandular ducts. According to the degree of differentiation of cancer cells, it can be classified as grade I-IV.
(2) Mucinous adenocarcinoma: The intestinal gland can secrete mucus, and after the growth of tumor, the intestinal adenocarcinoma often secretes a lot of mucus, which makes the cancer cells look like translucent capsules, so it is called mucinous adenocarcinoma. Under the microscope, the nucleus is squeezed to one side by the mucus, just like a ring, so it is also called indolent cell carcinoma, which has high malignancy.
(3) Undifferentiated carcinoma, squamous carcinoma and adenosquamous carcinoma: undifferentiated carcinoma is very heterogeneous in cell morphology, so it has the highest malignancy and the worst prognosis; squamous carcinoma and adenosquamous carcinoma are caused by squamous epithelial metaplasia in intestinal tissues. These types of intestinal cancers are rare.
16.How is colorectal adenocarcinoma staged?
In order to better explain the degree of cancer development and formulate corresponding treatment countermeasures, the clinical staging of malignant tumors was carried out. 1978 Hangzhou colorectal cancer conference formulated a modified Dukes staging trial program.
Stage I 0: lesions are confined to the mucosal layer (including carcinoma in situ and focal carcinoma) and can be locally resected.
Stage I 1: The lesion invades only the submucosal layer (early invasive carcinoma).
Stage I2: The lesion invades the muscular layer.
Stage II: The lesion invades the intestinal wall or invades the surrounding tissues and organs, but radical resection is still possible.
Stage III 1: with lymph node metastasis near the cancer foci (referring to the lymph nodes adjacent to the intestinal wall and marginal vessels).
Stage 2: with lymph node metastasis near the perivascular and mesenteric margins, but radical resection can be done.
Stage IV 1: with distant organ metastases.
Stage IV 2: with distant lymph node metastases or extensive metastases in the lymph nodes supplying the root of the vessels that cannot be completely resected (anterior or para-aortic and internal iliac vessel lymph nodes, etc.).
Stage IV 3: with extensive peritoneal spread, which cannot be removed in its entirety.
Stage IV4: The lesion has extensively infiltrated the adjacent organs and cannot be resected, but the original can be palliatively resected if the systemic condition allows.
17.What is the incidence of colorectal cancer?
In terms of gender, there is no gender difference in the incidence rate of colon cancer, while the incidence rate of rectal cancer is higher in men than in women. Geographically, the incidence rate in developed countries such as Western Europe and North America is higher, reaching 25–35 per 100,000 population. The incidence rate in less developed countries is relatively low, and the incidence rate in developing countries such as Asia and Africa is about 0.6 – 5.0 per 100,000 population, which is significantly lower than that in western countries.
China is a developing country, and the incidence rate of colorectal cancer in the middle of the last century was still below 10 persons/100,000 population. Twenty years ago, the incidence rate of colorectal cancer in China ranked after lung, liver and stomach cancer for men, and after breast, cervical, lung and stomach cancer for women. In recent years, the incidence rate of colorectal cancer in China has been increasing year by year, reaching 24 per 100,000 population at the beginning of this century. A recent research result on malignant tumor epidemiology, which just won the second prize of National Science and Technology Progress Award in 2006, reveals that by 2010, the top three cancer incidences in China are lung cancer, liver cancer and colorectal cancer in men, and breast cancer, lung cancer and colorectal cancer in women. Northeast, north and southeast coast of China are the high incidence areas of colorectal cancer. In addition, the incidence of colorectal cancer in China in recent years is also characterized by a tendency to be younger, with the incidence rate of young and middle-aged people under 40 years old being higher than that of European and American countries.
18.Which section of the intestinal canal is the most common site of colorectal cancer? Why?
The entire colon is divided into five parts: ascending colon (including the ileocecal part, transverse colon, descending colon, sigmoid colon and rectum), from the right side of the ileocecal part to the left side up to the rectum. Since benign masses such as intestinal polyps are precancerous lesions, the good site of colorectal polyps is also the good site of colorectal cancer. A large number of clinical observations have shown that 50% of cancers occur in the rectum, 25% in the sigmoid colon (mainly at the junction of the rectum and the b), which means that 75% of colorectal cancers are on the left side, followed by the right side of the ileocecal region. The reason why this is the case is related to the function of the large intestine. The main function of the large intestine is to absorb water from food residues, so that they can be gradually formed into feces and excreted from the body. In the process of travel, the water of food residues is gradually absorbed, and feces is formed in the sigmoid colon, and the harmful substances and carcinogens in feces are highly concentrated at this time. In the process of repairing the damage, some genes of intestinal epithelial cells may be mutated, defective and lose normal function, resulting in intestinal epithelial atypical hyperplasia, tumor-like hyperplasia and finally malignant transformation and become colorectal cancer.
19.What are the main clinical symptoms of colorectal cancer?
The clinical symptoms of colorectal cancer vary depending on the location of the tumor in the large intestine. Tumor growth in the rectum is called rectal cancer. The most common symptoms of rectal cancer are: an increase in the number of stools, but the volume of each bowel movement is not much or even very little; there is a sense of urgency and incomplete defecation, similar to dysentery, medically known as rectal irritation signs. There is also blood in the stool, which is slightly dark red in color, and patients often think they are bleeding hemorrhoids. As the disease progresses, the enlargement of the cancer will lead to rectal stenosis and obstruction, which may lead to constipation, thinning of the stool, abdominal distension and pain.
No matter where the tumor grows in the colon, it is called colon cancer. The most common symptom of colon cancer is blood in the stool, which is often unformed and mixed with dirty dark red blood. As the tumor continues to grow, abdominal pain and abdominal masses may appear, and the location of abdominal pain and abdominal masses may vary depending on the growth site of the tumor. If the tumor continues to develop, cachexia, anemia, fever, emaciation and other signs of cachexia may appear.
In addition, it should be noted that if rectal cancer infiltrates into anal canal, symptoms such as hardening of anal canal and persistent anal pain will appear.
As mentioned above, the most common and earliest symptoms of colorectal cancer are blood in stool and loose stool, which are also the most easily misdiagnosed at this time, so it is necessary to go to the anorectal department of hospital for examination and clear diagnosis.
20.What are the common complications of colorectal cancer?
There are three common complications of colorectal cancer.
(1) Intestinal obstruction: colorectal cancer mainly occurs in the left side of the large intestine, which is anatomically narrower than the right side of the colon, especially the sigmoid colon lumen is the narrowest and forms an acute angle with the rectum; in addition, the tumors in the left side of the large intestine are mostly infiltrative cancers that can cause circular narrowing of the intestinal lumen. The above determines that the site of obstruction in colorectal cancer is mostly on the left side, which is a kind of progressive obstruction, and patients gradually experience more and more difficulties in defecation, abdominal pain gradually increases, and nausea and vomiting may occur. Because the right colon cavity is relatively wide and the stool is liquid in the right inverted colon, and the right colon tumor is mostly myxomatous, so the right colon cancer is not easy to occur obstruction, and if it causes intestinal obstruction, the tumor must be quite large.
(2) Intestinal bleeding: this is the most common symptom of colorectal cancer and is often the main complaint of patients with intestinal cancer, the amount of bleeding can be large or small, dirty and dark, which needs to be distinguished from hemorrhoids, anal fissure, ulcerative colitis and other diseases.
(3) Intestinal perforation: colorectal cancer combined with intestinal perforation and peritonitis, manifested as continuous severe abdominal pain, high fever, nausea, vomiting, sweating, mouth in, abdominal pressure pain and rebound pain. Emergency treatment is needed, if necessary, caesarean section.
21.What are the advantages and disadvantages of fecal occult blood test?
The fecal occult blood test is a test that uses the redox reaction to check for red blood cells in the stool and to infer whether there is bleeding in the intestine. The advantage of this method is that it is cheap, convenient and easy to do, painless and easy to accept; the disadvantage is that the test is easily interfered by some foods and drugs, and it is easy to have false positive and false negative test results.
There is also a method of checking fecal occult blood called immunoassay, which uses anti-hemoglobin antibodies to check whether human hemoglobin is present in the stool, and its specificity is higher.
Therefore, fecal occult blood test is suitable for preliminary screening and should not be used when the signs of colorectal cancer are obvious. This method is also not used when there is blood in the feces with the naked eye.
22.What are the advantages and disadvantages of carcinoembryonic antigen test?
The CEA test is a recent method to detect or monitor cancer. When adenocarcinoma occurs in the human body, the cancer cells will release a glycoprotein, which can be detected from the serum by chemiluminescence, and this is the carcinoembryonic antigen test.
The advantages of the CEA test are that it is simple, painless and moderate in cost, which is fully affordable for the general public. In addition, CEA can be elevated in some normal people, for example, the serum CEA of smokers is higher than that of non-smokers, so when CEA is elevated, it does not mean that we have colorectal cancer, but this test is meaningful as cancer screening and monitoring whether colorectal cancer recurs after treatment. However, this test is very meaningful as a screening test for cancer and monitoring whether it recurs after treatment.
23.What are the advantages and disadvantages of barium enema examination for colorectal cancer?
Barium enema is one of the important methods to detect colorectal tumor. Before the examination, fasting and intestinal cleansing are performed, and then barium with high concentration, low viscosity and fine particles is instilled into the large intestine, and the movement of the barium in the large intestine is tracked under X-ray fluoroscopy to see if there are abnormalities such as stenosis, dilatation, unevenness and filling defects. Its advantages are that it is less painful, relatively inexpensive, and can observe the mucosal structures in the intestinal cavity and on the surface of the intestinal wall more clearly; the disadvantages are that the preparation stage is more troublesome, the radiation is exposed for a long time about 20 minutes, which is harmful to the body, and the diagnosis may be missed when the x-ray signs are not obvious for early cancer, and it cannot observe the situation inside and outside the intestinal wall, etc. Therefore, at present, barium enema enucleation examination is rarely done except in special cases. Therefore, except for special cases, barium enema is rarely done.
24.What are the advantages and disadvantages of CT and MRI of the colon?
The advantage of CT is that it can clearly display the intestinal cavity, intestinal wall, external intestinal wall and adjacent tissues and organs, so that the shape of the cancer in the intestinal cavity, the extent of involvement of the intestinal wall and adjacent tissues and organs outside the intestine can be clearly seen, etc. The disadvantage of CT is that the resolution of soft tissues is poor, and sometimes a contrast agent needs to be injected, so there is a certain risk. X-rays can also be harmful to the body.
The principle of magnetic resonance imaging (MRI) is as follows: There are a large number of hydrogen nuclei in human tissues and organs, which we call protons. Since the density of each tissue and organ in the human body is different (called proton density), the time required for resonance of different proton densities varies greatly, and the computer can process these differences into images, which is called magnetic resonance examination.
The advantages of resonance examinations with CT are: first, there is no ionizing radiation damage to the body. Second, unlike CT, artifacts can appear, so the image quality is good. Third, the resolution of soft tissue is higher than that of CT. The disadvantages of MRI are: first, the price1 is expensive. Second, the spatial resolution is poor. Third, those who have metal foreign bodies (such as pacemakers) in their bodies cannot be examined.
25.What are the advantages and disadvantages of colonoscopy?
There are three types of colonoscopy: proctoscopy, sigmoidoscopy and fiberoptic colonoscopy. No matter which colonoscopy is used, it can make a clear observation of the intestine visually, and theoretically the diagnosis rate is 100%.
A proctoscope is made of metal, straight and 15 cm long. Proctoscopy does not require intestinal preparation, is basically painless, easy to perform, and inexpensive, and is very suitable for rectal cancer screening; the disadvantage is that it is limited to rectal examination only.
Sigmoidoscopy is also rectal in shape and 25-30 cm long. Since most intestinal cancers occur in the intestinal segment within 30 cm from the anus, the advantages of doing sigmoidoscopy are also obvious, namely, low cost and low pain, but it cannot examine tumors above the descending colon.
Fiberoptic colonoscopy can be an intuitive visual inspection of the entire large intestine; the disadvantage is that the prep is troublesome, expensive and painful, and one-third of the patients stop halfway due to poor tolerance, and patients with serious cardiovascular disease cannot do this examination.
26.How to selectively conduct colorectal cancer examination?
There are many methods to examine colorectal cancer, each with its own advantages and disadvantages. It is not necessary to check each one of them when you suspect bowel cancer, and you can selectively do some of them according to your situation.
If there are changes in stool properties, blood in stool especially dark blood, symptoms of anemia, weight loss and abdominal discomfort, and especially if a lump can be felt in the abdomen, you should undergo examination for colorectal cancer.
(1) The basic steps of doctor’s examination are as follows.
①Get a detailed medical history.
②Check the body and do anal finger diagnosis.
③If the lower rectal lesion is ruled out by anorectal examination and the patient’s physical condition allows, he/she can directly prepare for fiberoptic colonoscopy, and those with poor physical condition can do sigmoidoscopy first.
④If it is necessary to take venous blood to test certain items, carcinoembryonic antigen test can be added.
⑤ When colonoscopy reveals a long tumor, biopsies should be taken for pathological examination. CT or MRI can also be done to further understand the degree of tumor infiltration to the surrounding tissues and organs.
(2) During routine physical examination: If we just conduct physical examination to screen for colorectal cancer, then we only need to conduct anal finger diagnosis, check fecal occult blood (preferably 3 times continuously) and carcinoembryonic antigen. Sigmoidoscopy should also be done if available. Routine physical examination should preferably be performed once a year.
(3) Post-operative colorectal cancer: To monitor whether there is recurrence, the carcinoembryonic antigen should be rechecked once every quarter within 3 years after surgery, once every six months within 5 years after 3 years, and once every year after 5 years, and the colonoscopy should be rechecked once a year if possible.
27.How is the morphology of colorectal cancer under endoscopy?
The morphology of colorectal cancer seen under endoscopy is roughly divided into the following categories, which are often referred to as microscopic staging.
(1) Ulcerated disease type: the most common type, most commonly found in the left colon and rectum. It is bulging around and depressed in the middle, especially like a crater, and septic blood and filthy secretion can be seen on the ulcerated surface.
(2) Proliferative type: Cauliflower-like proliferation, the swelling protrudes into the lumen of the large intestine, the surface is not smooth, brittle, bleeding when touched, dark blood color, can be seen on the swelling with erosion surface and necrosis.
(3) Infiltrative type: This type is usually found in the left colon, especially in the junction of rectum and sigmoid colon and rectum. The tumor tissue grows infiltrating along the intestinal wall, and there is extensive connective tissue hyperplasia. Microscopically, the lesion is seen to be narrowed, or even in a circular narrowing, and the intestinal wall becomes hardened and loses its softness and elasticity, which is very likely to cause intestinal obstruction.
(4) Mass type: It is usually found in the right colon and ileocecal region. The masses are spherical or hemispherical in shape growing into the intestinal lumen, with ulcers on the surface and easy bleeding. This type is less infiltrative and has less metastasis, so the prognosis is generally good.
28.What diseases should be differentiated from colorectal cancer?
Colorectal cancer includes colon cancer and rectal cancer. Colon cancer should be distinguished from ulcerative colitis, clonorchiasis, intestinal tuberculosis, schistosomiasis granuloma, amebic granuloma, etc. Rectal cancer should be distinguished from hemorrhoids, bacillary dysentery, amebic dysentery, schistosomiasis, etc.
(1) Ulcerative colitis: Ulcerative colitis is referred to as ulcerative node, which has been described in the relevant section. The main characteristic manifestations are abdominal pain, diarrhea, mucopurulent stools, and sigmoidoscopy or fiberoptic colonoscopy can distinguish it from colon and rectal cancer.
(2) Clonorchiasis: Almost all clonorchiasis is initially misdiagnosed as appendicitis, and the main symptoms of clonorchiasis are abdominal pain, diarrhea, fever and abdominal mass. Performing fiberoptic colonoscopy is the best means of differentiation. The main microscopic manifestations of Crohn’s disease are large, deep fissure ulcers, pebble signs, and total wall inflammation of the intestinal segments.
(3) Intestinal tuberculosis: Intestinal tuberculosis mainly manifests as abdominal pain, loose stools, abdominal masses, low fever, night sweats and other symptoms of tuberculosis systemic toxicity. There are also constipation-based cases of proliferative intestinal tuberculosis. Patients with intestinal tuberculosis mostly come from pulmonary tuberculosis, and it is not difficult to distinguish them from colorectal cancer by checking blood sedimentation, positive tuberculin test and barium x-ray imaging.
(4) schistosomiasis and its granuloma: patients with a history of living in Gangnam should pay attention to the differentiation of schistosomiasis. The intestinal lesions of schistosomiasis are mainly in the left colon, with abdominal pain, diarrhea and blood in the stool as the main symptoms; colonoscopy can be distinguished, and biopsy of the granuloma must be taken.
(5) Amoebic dysentery and its granuloma: Amoeba is a human intestinal parasite that lives in the wall of the large intestine by feeding on intestinal mucosal fragments and red blood cells, causing amoebic dysentery. The symptoms are similar to those of colorectal cancer, but the stool is fishy and jam-like, and the amoeba trophozoites or cysts can be found in its stool, which can be distinguished; colonoscopy can take its granulomas for tissue biopsy, which can also be distinguished.
(6) Hemorrhoids: Blood in stool is the main symptom of intestinal cancer and hemorrhoids, especially in the early stage of both, it can be the only symptom of each, so there are many cases of misdiagnosis of intestinal cancer as hemorrhoids. Although both of them have blood in stool, there are still differences between them. Hemorrhoids have bright red blood, and blood and stool are not mixed (i.e. blood is blood, is stool); cancer bleeding, dark red, and blood and stool are mixed. Through finger diagnosis and colonoscopy, it is easy to distinguish the two.
(7) Chronic bacillary dysentery: The main symptoms of chronic bacillary dysentery are left lower abdominal pain, diarrhea, urgency and mucus-purulent stools, which are quite similar to intestinal cancer, and those who are over 40 years old must pay attention to these symptoms and seek specialist to do anal finger examination and stool bacterial culture for identification. If the stool culture is positive for Bacillus dysenteriae, it is chronic bacillary dysentery, otherwise, further examination should be done to avoid missing the diagnosis of intestinal cancer.
29.Why is colorectal cancer easily misdiagnosed?
According to the statistics, the misdiagnosis rate of colon cancer is 40%, and the misdiagnosis rate of rectal cancer is 60%-70%. Then why is colorectal cancer so easy to misdiagnosis, according to the author’s experience, the reasons for misdiagnosis are summarized as follows.
(1) Patients do not pay enough attention to their thoughts and have fluke psychology: many male patients do not care about small disasters and diseases, thinking that they are physically well; they will pass after resisting, and it is not manly to go to see a doctor by themselves, and they also have fluke psychology, thinking that the so-called big diseases will not fall on their heads, which results in a big disaster and it is too late to regret.
(2) shyness: many women are in this category, as soon as the doctor is male, turn away, or find a charlatan doctor blindly treat without examination eventually harmed themselves.
(3) Think it’s a relapse of an old disease, and delayed: many patients with previous hemorrhoids or chronic enteritis belong to this category. As the disease has been repeated for more than 10 years, they know what medicine to use to treat it, so they relax their vigilance and do not have regular checkups.
(4) Complex condition and atypical clinical symptoms: The length of large intestine is about 1.3-1.5 meters, and tumor can grow in any part of it. The best time for surgery is missed because of “tiredness”, “cold”, “dietary discomfort”, “chronic appendicitis” and so on. For cancers growing in the descending colon, sigmoid colon and rectum, abdominal pain, abdominal distension, constipation and blood in the stool are common symptoms, which are often misdiagnosed as “habitual constipation” and “hemorrhoids”.
The only way to reduce the rate of misdiagnosis is to “pay attention”. For every clinical symptom that appears without obvious effect after 3-5 days of treatment, it is necessary to go to a regular national hospital for examination.
30.What are the ways of metastasis of colorectal cancer?
There are three main metastasis pathways or called three transmission methods for colorectal cancer.
(1) Direct spread: cancer tissue infiltrates from intestinal mucosa to submucosa and muscle layer until it spreads to adjacent tissues and organs, such as bladder, uterus, intestinal lining, etc.
(2) Lymphatic metastasis: the lymphatic metastasis of rectal cancer is more complicated, it can metastasize upward, downward, and also to both sides. The most common site of upward metastasis is the lymph node next to the superior rectal artery, downward metastasis can be to the anal sphincter and perianal skin, and to the internal iliac vessel lymph nodes and lateral ligament lymph nodes on both sides, but most rectal cancer metastasizes upward. Colon cancer can metastasize to lymph nodes in the paracolon, around mesenteric vessels and the root of mesentery through lymph. Advanced colon cancer may metastasize to inguinal lymph nodes and supraclavicular lymph nodes.
(3) Hematogenous dissemination: after invasion of small local veins, cancer thrombus can be transferred to liver via portal vein with venous blood to cause secondary liver cancer, which is the most distant metastasis site of intestinal cancer; followed by lung metastasis of intestinal cancer; intestinal cancer can also be metastasized to kidney and adrenal gland, brain, bone, skin and so on.
In addition, cancer cells shed from colorectal cancer may fall on the large omentum, abdominal cavity or internal organs, which may occur so-called “implantation metastasis”. This type of metastasis is generally classified as direct spread.