Anatomical structure of the large intestine.
The large intestine is the lower end of the digestive tube, and its total length is about 1.5 m. As shown in the figure, the large intestine includes the appendix, cecum, colon, rectum and anal canal, among which the colon can be divided into ascending colon, transverse colon, descending colon and sigmoid colon. Clinically, the colon is often divided into the left and right halves, which are divided at the junction of the left 1/3 and right 2/3 of the transverse colon.
Introduction of colorectal cancer.
Colorectal cancer is a malignant tumor of mucosal epithelial origin in the large intestine, and it is one of the most common malignant tumors of the gastrointestinal tract. According to statistics, the average age of colorectal cancer patients is 60-65 years old, and the most occurring sites are rectum, accounting for 56%-70%, sigmoid colon 12%-14%, descending colon 3%, splenic flexure 0.6%-3%, transverse colon 2%-4%, hepatic flexure 0.7%-3%, ascending colon 2%-3%, and cecum 4%-6%.
Colorectal cancer in China has the following characteristics.
1. The age of onset is significantly earlier.
2. Low-grade colorectal cancer is common.
3. Combined schistosomiasis is common.
Etiology of colorectal cancer.
1.Dietary factors: It is generally believed that high animal protein p high fat and low fiber diet are the factors of high incidence of colorectal cancer.
Genetic factors: The risk of colorectal cancer is 2-6 times higher for family members with family history of colorectal cancer than for the general population.
3, ulcerative colitis p polyposis p adenoma, etc., are precancerous lesions of the colon, and their pre-cancerous course is 5-20 years.
4.Parasitic diseases: Our data show that some advanced schistosomiasis is also complicated by colorectal cancer.
Other factors: lack of molybdenum, frequent exposure to asbestos, constipation, low stool volume, increased number of anaerobic bacteria in the intestinal cavity may also be related to the occurrence of colorectal cancer.
Pathology of colorectal cancer.
In terms of tissue type, colorectal cancer can be divided into.
1. glandular epithelial carcinoma, including
(1) papillary adenocarcinoma: all or most of the tumor tissues are papillary in structure, the incidence is 0.8% to 18.2%.
(2) tubular adenocarcinoma: the tumor tissue forms a duct-like structure, with an incidence of 66.9% to 82.1%.
(3) Mucinous adenocarcinoma: the cancer cells secrete a lot of mucus and form a “mucus lake”.
(4) Indolent cell carcinoma: The tumor is composed of indolent cells without glandular structure.
(5) Undifferentiated carcinoma: The cancer cells grow in diffuse patches or masses, without forming glandular ducts or other tissue structures.
(6) Adenosquamous carcinoma: also known as adenosquamous cell carcinoma, adenocarcinoma and squamous carcinoma components in these tumor cells are mixed and intermingled.
2.Squamous cell carcinoma: squamous cells are the main component of the carcinoma.
3.Carcinoid tumor: originated from neuroendocrine cells of neural ridge origin, and may also be derived from adenosquamous epithelium.
Dissemination and metastasis pathways of colorectal cancer.
1.Local spread: firstly, the cancer spreads within the intestinal wall, it takes about 2 years for the cancer to grow around the intestinal wall for a week, and it is easy to have hematogenous metastasis after the cancer infiltrates to the muscle layer. The cancer can also invade the whole intestinal wall and the organs around the intestine (such as bladder, prostate, uterus, small intestine, liver, stomach, pancreas, etc.).
2.Lymphatic metastasis: accounting for 60%. Colon cancer cells cross the intestinal wall through submucosal lymphatic network → intestinal wall surface lymph nodes → paracolon lymph nodes → intermediate lymph nodes → central lymph nodes (main lymph nodes) → para-aortic lymph nodes → supraclavicular lymph nodes.
Rectal cancer cells along the lymphatic tract of intestinal wall → paracolic lymph nodes → superior rectal artery or sigmoid artery paracolic lymph nodes → inferior mesenteric artery lymph nodes → abdominal aorta paracolic lymph nodes → supraclavicular lymph nodes.
3, blood metastasis: 34%, mostly to the liver, followed by the lung, and again to the bone, brain and ovary. It rarely metastasizes to adrenal gland or kidney.
4.Plantation metastasis: cancer cells are shed and planted in the abdominal pelvic peritoneum to form nodes.
Clinical manifestations of colorectal cancer.
Symptoms.
1.Blood in stool, mucus stool or pus stool Early colorectal cancer may be asymptomatic, but when the tumor grows to a certain extent, blood in stool, mucus stool or pus stool will appear, and the blood color is mostly light and dark, adhering to the surface of stool. The color of bleeding in colorectal cancer is mostly dark red, and the closer the location is to the anus, the brighter the color is. The amount of bleeding is not proportional to the size of the cancer.
2.Change of defecation habit. Some patients may have change of defecation habit.
3.Abdominal pain and distension. Abdominal pain and abdominal distension are other common clinical manifestations of colorectal cancer patients. Among them, the incidence of abdominal pain is higher than that of abdominal distension. The nature of pain can be vague, dull pain and colic.
Physical signs.
1, anemia and wasting with the progression of the disease, the patient may develop chronic wasting symptoms, such as anemia, wasting, weakness and fever, and even cachexia.
2.Abdominal mass is one of the main manifestations of colorectal tumor. Its incidence rate is 47% to 80%. It is the most common symptom of right hemicolectomy cancer, accounting for about 80% of patients; left hemicolectomy cancer accounts for about 20%-40%.
3, rectal tumor can be in the rectal cavity and the surface is not smooth, brittle and easy to bleed masses or ulcers, finger sleeve with dark brown blood stain.
Special manifestations of tumors in different parts.
1.Right hemi colon cancer right hemi colon cancer often shows symptoms such as abdominal mass, anemia, abdominal pain, general weakness and emaciation. Abdominal pain is also one of the main symptoms for patients with right hemicolectomy cancer. Blood in stool and anemia are the more common symptoms of right hemicolectomy cancer. Anemia is the third common symptom of right hemicolectomy cancer, and the same stool occult blood test is often positive, which can appear as the first symptom.
Blood in stool is the most common symptom of left hemicolectomy cancer, accounting for about 75%. It is often manifested as dark red blood on the surface of stool, which is easily detected by patients and attracts attention. Mucus stool or mucus-purulent stool may also appear.
The main clinical manifestation of rectal cancer is blood in stool and change of bowel habit. Blood in stool is the most common symptom of rectal cancer patients, mostly in the form of fresh blood or dark red blood, which is not confused with stool, while massive bleeding is rare. Sometimes the blood in stool contains blood clots and detached necrotic tissue. Change in bowel habit is also one of the main clinical symptoms of rectal cancer patients. The main symptom is the increase of stool frequency, from several to ten times a day, or even dozens of times a day, with only a small amount of blood and mucus in each stool, accompanied by persistent anal swelling and the feeling of incomplete defecation. The stool often becomes thin and deformed, and there is even difficulty in defecation and constipation.
4.Bleeding and pain are the main manifestations of anal canal cancer and anal cancer. In early stage, the tumor of anal cancer can invade the nerve and cause pain, especially when defecating, the pain is obviously intensified, so patients are afraid of defecation and cause constipation.
Common complications of colorectal cancer.
1.Intestinal obstruction can cause narrowing of intestinal lumen and obstruction of intestinal contents, resulting in mechanical intestinal obstruction.
2.Intestinal perforation has typical clinical manifestations of acute abdomen, abdominal muscle tension, pressure pain and rebound pain, and X-ray film shows crescentic free gas under the septum, etc., which can make the preliminary diagnosis.
3.Bleeding acute haemorrhage is a rare complication of colorectal cancer.
Diagnosis of colorectal cancer.
1.History and physical examination: detailed medical history and physical examination, when rectal and anal canal cancer is suspected, the importance of rectal finger diagnosis is emphasized, because about 85% of rectal cancer can be detected during finger diagnosis.
2.Blood routine p fecal occult blood test: there may be anemia and positive fecal occult blood.
3.Serological examination: serum immunological examination can check CEA, CA19-9, CA24-2, etc. These indicators can be used as the basis for supporting the diagnosis and also as indicators for follow-up.
4.Imaging diagnosis.
(1) X-ray barium enema: it can observe intestinal peristalsis, morphology of colon pouch, whether there is narrowing or dilatation of intestinal cavity, and whether there is mass in intestinal cavity, etc. In the diagnosis of rectal cancer, double contrast imaging of gas-barium enema helps to understand and exclude multiple primary cancers.
(2) Ultrasound: Intraluminal ultrasound can check the degree of tumor infiltration to the intestinal wall and the invasion outside the intestine.
(3) CT and MRI examination: it can check the relationship between tumor and adjacent organs and clarify the situation of retroperitoneum and abdominal lymph nodes.
5.Colonoscopy: Patients suspected of having colorectal cancer need to undergo colonoscopy, the main purpose of which is to clarify the location of tumor and clip tumor tissues for pathological examination, when clip tumor tissues, it is recommended to clip and multi-point clip when retracting the mirror.
Treatment of colorectal cancer: The main treatment measure of colorectal cancer is surgery, while emphasizing and attaching importance to surgical smelting treatment, radiotherapy, chemotherapy and Chinese medicine also play an extremely important role in the treatment of colorectal cancer.
1.Surgical treatment: Any tumor that can be surgically removed should be surgically removed as long as the patient can tolerate the surgery. The main purposes of surgical treatment are
(1) Radical resection of tumor.
(2) clearing the lymph nodes that may be involved.
(3) To reduce the tumor load.
(4) To obtain pathological tissue to clarify the degree of tumor infiltration and lymph node metastasis.
Patients with T1 without lymph node metastasis can have local tumor resection, patients with T2-3 can have radical surgery, patients with T3 can consider preoperative radiotherapy, patients with locally advanced stage can have radiotherapy first or combine chemotherapy at the same time, and then have surgery after the opportunity of surgery.
2.Radiotherapy: radiotherapy is mostly used for anal canal cancer, rectal cancer and sigmoid colon cancer, and also for tumors of liver flexure and splenic flexure of colon, and its indications for radiotherapy are
(1) Patients with clinical stage of T3N0-2M0 can be treated with preoperative radiotherapy.
(2) If the tumor is close to the anus (less than or equal to 5CM) and the surgeon thinks that the anus cannot be preserved, preoperative radiation therapy can be routinely divided into 45-50Gy and then rested for 4-6 weeks, and then operated after the tumor shrinks, and some patients can preserve the anus.
(3) Preoperative radiotherapy is necessary for locally advanced rectal cancer, the dose of which is 50Gy after whole pelvic radiotherapy, then consider local supplementation according to the tumor regression, and operate after 4-6 weeks of rest; if combined with intestinal obstruction, radiotherapy can be performed after surgery to release the obstruction.
(4) Radiotherapy can be considered after local resection of tumor in T1 and T2.
(5) The indications for radiotherapy after radical surgery are T3 or patients with lymph node metastasis, and the dose of radiotherapy is conventional splitting 50Gy.
(6) Some patients with advanced stage can also do palliative radiotherapy.
Since the use of 5-fluorouracil and its analogues at the time of radiotherapy can improve the local control rate and survival rate of postoperative radiotherapy and improve the efficacy of local advanced radiotherapy for tumors, it is recommended to add 5-fluorouracil and its analogues at the time of radiotherapy.
3.Chemotherapy: chemotherapy needs to be considered when the tumor invades the muscle layer to reach the extra-plasma membrane or the parietal intestinal tissue, and when there are lymph node metastasis or distant metastasis.
(1) Single drug therapy: 5-Fu is the basis of standard chemotherapy for colorectal cancer. 5-Fu efficacy is related to the site of lesion, in terms of efficiency, 32% for abdominal lesion, 25% for lymph node metastasis, 24% for liver metastasis, 16% for skin and subcutaneous metastasis, and 8% for other sites, while lung metastasis is the worst, at 6 or 4%.
(2) Combination chemotherapy: Combination chemotherapy has the advantages of improving efficacy, reducing or not increasing toxicity, reducing or delaying the emergence of drug resistance, etc. Many combination chemotherapy regimens have been used for the treatment of colorectal cancer, basically all of them contain 5-Fu.
(3) Adjuvant chemotherapy: adjuvant chemotherapy refers to the use of anti-tumor drugs active against certain tumors to adjuvant radical treatments, and for colorectal cancer, it refers to adjuvant chemotherapy for surgery.
Care of colorectal cancer
In the process of radiotherapy, it is necessary to observe the changes of blood routine, review and treat in time. Meanwhile, keep the perineum clean and perform vaginal douching or antibiotic treatment if necessary. Those with artificial anus need to keep the hygiene of the artificial anus.
Prognosis of colorectal cancer
The prognosis of colorectal cancer is good, the overall five-year survival rate is 58-85%, and the factors affecting the prognosis of colorectal cancer are
1. Clinical factors
(1) Age: The prognosis of young colorectal cancer patients is worse, while young patients have less obvious clinical symptoms and more poorly differentiated mucinous adenocarcinoma.
(2) Tumor site: Many studies found that the prognosis of colon cancer is better than rectal cancer, and the prognosis of colon cancer is significantly better than rectal cancer in Dukes’ C stage patients with lymph node metastasis. The prognosis of rectal cancer is also closely related to the location of the lesion.
(3) Clinical manifestation of tumor: tumor diameter, tumor infiltration fixation and outward invasion can affect the prognosis.
(4) Clinical stage: late stage of disease has poor prognosis.
2.Biological characteristics
(1) Carcinoembryonic antigen: In stage B and C patients, the possibility of recurrence is related to the preoperative CEA concentration, and the content of CEA is inversely proportional to the degree of tumor differentiation.
(2) Ploidy and chromosomes of tumor: the malignancy of cancer cells depends on different degrees of alterations in DNA content, ploidy composition, proliferation and chromosomal aberrations of cancer cells.
Follow-up of colorectal cancer.
1.Regular physical examination, routine blood and biochemical examination, rechecking fecal occult blood, and checking liver ultrasound and chest X-ray.
2.Tumor markers such as CEA positive before treatment can be rechecked during follow-up.
3.CT, MRI and other examinations should be performed when necessary to check the pelvic recurrence.