The adult large intestine is about 1.5m long, including the cecum, ascending colon, transverse colon, descending colon, sigmoid colon and rectum, and is shaped like an M throughout, surrounding the jejunum and ileum. The main function of the large intestine is to absorb water, electrolytes and other substances (such as ammonia, bile acids, etc.), form, store and excrete feces. The large intestine also secretes a small amount of mucus, which protects the intestinal mucosa and lubricates feces, preventing constipation and protecting the intestinal wall from bacterial erosion.
When the colonic mucosa is damaged can occur a variety of diseases, common colorectal diseases are.
1, ulcerative colitis.
Ulcerative colitis is a chronic disease, the cause of which is not well understood. It can occur at any age, but most patients are between the ages of 20-40, and there is little difference between men and women.
Clinical manifestations: The disease is characterized clinically by alternating periods of exacerbation with periods of remission. The main symptoms are diarrhea and pus and blood in the stool, with abdominal pain, accompanied by a feeling of urgency and then heaviness, and in severe cases, fever, anemia, emaciation, loss of appetite and other systemic symptoms, some of which can last more than 10 years, and most of which have intermittent remission periods. Sometimes the disease recurs after mental stimulation and improper diet. In addition, there are symptoms such as abdominal distension, belching, nausea, weight loss and sometimes low fever.
Diagnosis: In addition to routine blood and stool tests, imaging (including abdominal plain film, barium enema, CT, etc.) and e-colonoscopy are often required.
Treatment: There is no cure for the disease, and treatment is still mainly conservative, including general treatment, nutritional support therapy, symptomatic treatment and drug therapy. Drug therapy includes aminosalicylates, such as salazosulfapyridine and mesalazine (5-aminosalicylic acid), glucocorticoids, immunosuppressive drugs and traditional Chinese medicine. When conservative medical treatment is ineffective or accompanied by serious complications (megacolon, perforation, massive blood in the stool, cancer, etc.), surgery can be considered.
2.Colonic polyps.
It is the most common benign tumor in the large intestine, usually found in the colon or sigmoid colon, and can also be widely distributed throughout the colon. Colon polyps can develop at any age, mostly solitary, but also multiple, and even many polyps widely involved in the colon and small intestine, called polyposis. The latter has some family genetic factors and has more chances of malignant transformation.
(1) Adenomatous polyp: It is the most common benign tumor in the large intestine, the cause of which is unknown. Most of them are solitary, or multiple, round or oval, smooth and soft masses, some with tips, and can move. About 50%-70% of them are in the rectum or sigmoid colon, followed by about 25% in the transverse colon. Ulcers can be formed on the polyps, and about 20%-30% can have malignant transformation.
Clinical manifestations: The symptoms are mainly diarrhea, blood and mucus in the stool, abdominal pain, anemia and other symptoms.
Diagnosis: The accuracy of barium enema examination in diagnosing polyps is about 90%. It shows that after the barium is filled or slightly compressed, there can be round filling defect area in the intestinal lumen, and large polyps often have a lobulated shape. After the barium is discharged, a layer of barium adheres around the polyp and shows a ring-shaped shadow. Polyps with long tips can move within the intestinal lumen. The polyp can be observed under direct vision by e-colonoscopy, and a biopsy can be taken to clarify the diagnosis or endoscopic resection.
Treatment: endoscopic resection is the main focus, and laparoscopic surgery is feasible for those with malignant changes.
(2) Familial polyposis: there are many intestinal polyps in this disease, most often found in the rectum and the left half of the colon, usually the whole colon, but the end of the ileum is rarely involved. The disease is autosomal dominant and 2/3 of patients have a family history of colonic polyposis or cancer. The polyps in this disease are adenomatous polyps, and colonic polyp carcinoma usually occurs about 15 years after the polyps are found.
The clinical manifestations are: vague abdominal pain, diarrhea, bloody stools, and weight loss. It can be complicated by intussusception and intestinal obstruction.
Diagnosis: X-ray shows an almost equal sized, multiple, non-tipped, round filling defect on the whole colon. It is more clearly shown by air-barium double imaging. After carcinoma, it appears as a myxoid filling defect.
Treatment: Because of the high rate of malignant transformation, surgical excision is the main treatment.
Appendix: Indications of malignant polyp
(1) The size of the diameter of more than 25px, malignant possibility; diameter of more than 75px is almost all malignant.
(2) Growth rate multiplication time greater than 3 years, only 1-2% for malignant; multiplication time of 300 days-3 years, only 19%-29% for malignant; multiplication time of less than 300 days 35% for malignant.
(3) X-ray pattern.
(1) polyps with tip length over 50px are mostly benign.
(2) When polyps with tips are cancerous, they mostly occur in the cervical segment, and lymph node metastasis rarely occurs in polyps with tips.
③When the cut marks appear on the base of the intestinal wall of broad-based polyps, it often indicates that the polyps have become cancerous.
④It is also important to observe the surface morphology of polyps, when the surface is irregular, it often indicates that the polyp is cancerous.
⑤ When the width of the base of the polyp is larger than the height, it often indicates that the polyp has a higher possibility of malignant transformation.
3.Colon cancer.
Colon cancer is a common malignant tumor of the gastrointestinal tract, its incidence is second only to gastric cancer and esophageal cancer, the cancer is mostly seen in the left half of the colon, mostly occurring in the rectum and sigmoid colon. The right hemicolectomy accounts for about 30%, mostly in the blind and ascending colon. There are more men than women, and the age of prevalence is 50-60 years old.
Factors associated with colorectal cancer.
(1) Dietary factors: high fat, high meat and low fiber diet are closely related to the occurrence of rectal cancer. Especially barbecue, salami, bacon and other diets.
(2) Genetic factors: In the families of rectal cancer patients, about 25% of them have a family history of malignant tumors, half of which are also gastrointestinal tumors.
(3) polyps: the development of rectal cancer is closely related to polyps. In particular, familial polyadenomatous polyposis is now considered precancerous and has a high probability of cancer, followed by papillary adenomatous polyps, which also have a higher chance of cancer.
(4) Chronic inflammatory stimulation: Chronic inflammatory stimulation can easily lead to the occurrence of rectal cancer. Such as amoebic dysentery, ulcerative colitis, chronic bacillary dysentery, etc., all can become cancerous. Patients with ulcerative colitis of more than 10 years duration are prone to cancer, high malignancy, easy metastasis and poor prognosis. According to statistics, the incidence of colorectal cancer with colitis is 8-10 times higher than that without colitis.
(5) In addition, the occurrence of colorectal cancer is also closely related to mental factors, age, endocrine factors, environmental factors, climatic factors, abnormal immune function and viral infection.
Clinical manifestations.
(1) Early symptoms: In the early stage of colorectal cancer, patients have no obvious abnormal changes. Those with the following symptoms need to be alert and need to do rectal examination.
(1) Abnormal stool habit, increased number of bowel movements, along with a small amount of mucus stool or mucus blood stool, recurrent episodes or prolonged treatment.
②Persons with previous history of mucus stool or diarrhea, with sudden worsening of symptoms and changes in the number of bowel movements and the nature of stool.
(③) Constipation and diarrhea with no obvious cause alternating with no improvement after treatment.
(4) Those who have difficulty in defecation and whose stools become thin.
(2) Middle and late stage symptoms: In addition to general symptoms such as loss of appetite, weight loss and anemia, patients with middle and late stage rectal cancer also have symptoms of local irritation of cancer such as increased number of bowel movements, incomplete bowel movements, frequent bowel movements, and shortness of breath. Tumor enlargement may cause narrowing of intestinal cavity and intestinal obstruction. At the advanced stage, rectal cancer often invades the surrounding tissues and organs, such as bladder and prostate and other adjacent tissues, causing urinary frequency, urinary urgency and difficulty in urination. Invasion of the presacral plexus can cause pain in the sacrococcygeal and lumbar areas. Rectal cancer can also metastasize to the liver distantly, causing hepatomegaly, ascites, jaundice, and even malignant fluid and other manifestations.
Rectal cancer is easy to be misdiagnosed, and the early manifestations are mainly vague abdominal pain and discomfort, increased frequency of stool and blood in stool, which are easily misdiagnosed as dysentery, enteritis or hemorrhoids, thus losing the opportunity of early treatment. Therefore, adults who have abnormal bowel movements should be alert and go to a specialist hospital for anal finger examination and, if necessary, e-colonoscopy.
Diagnosis: Blood count shows microcytic anemia and increased sedimentation. X-ray shows barium filling defect, stiffness of the lesioned intestinal wall, reduced or absent peristalsis, irregular colonic pouch, and narrow or dilated intestine. Colonoscopy can clarify the nature of the lesion, size, and some even find early lesions. In addition, serum carcinoembryonic antigen (CEA), ultrasound and abdominal CT examination can also help in diagnosis.
Treatment: Surgery to remove tumor is the first choice for colorectal cancer treatment, supplemented by radiation therapy, chemotherapy and Chinese medicine treatment.