Crohn's disease

　　Crohn's disease is an unexplained granulomatous gastrointestinal inflammatory disease. It is prevalent in young and middle-aged adults. Males are slightly more than females. The onset is insidious, characterized by chronic abdominal pain, diarrhea, abdominal mass, and weight loss. The incidence in China is significantly lower than that in Europe and the United States. In recent years, the incidence of the disease has shown an increasing trend in most parts of the world.

　　This disease can affect the entire gastrointestinal tract from the mouth to the anus, but it is most common in the distal ileum and the right colon, with segmental distribution accompanied by ulcers, granulomas, and scar formation. Non-caseating granulomas are characteristic pathological changes of this disease. The etiology may be related to immunity, infection (bacteria, virus, or mycoplasma), heredity, mental factors, and food allergy or smoking.

　　Complications of Crohn's disease are most commonly intestinal obstruction, followed by abdominal abscess, and occasionally acute perforation or massive hematochezia. Rectal or colonic mucosal involvement may lead to cancer.

　　Intestinal obstruction:The most common clinical symptoms are abdominal pain, vomiting, abdominal distension, and cessation of排气 and defecation. There may also be water, electrolyte, and acid-base balance disorders. In the case of strangulated obstruction or intestinal necrosis, shock, peritonitis, and gastrointestinal bleeding may occur.

　　Abdominal abscess inside:Abdominal abscess: ①Subphrenic abscess: Fever is a common symptom of subphrenic abscess, manifested as persistent high fever, rapid pulse, and thick and greasy tongue coating. Then, general weakness, debility, night sweats, anorexia, and weight loss may begin. Blood tests may show a significant increase in white blood cell count and an increase in the proportion of neutrophils. The site of the abscess may have persistent dull pain, which may worsen with deep breathing. ②Pelvic abscess: The systemic symptoms are relatively mild while the local symptoms are relatively obvious. During the treatment of acute peritonitis, appendiceal perforation, or postoperative patients with colonic or rectal surgery, if the body temperature returns to normal and then rises again, with typical rectal or bladder irritation symptoms such as tenesmus (a feeling that defecation is not complete), frequent and small stools, stools mixed with mucus, frequent urination, urgency, dysuria, and difficulty in urination, etc., it should be considered as a possible pelvic abscess. ③Intercystic abscess: The main manifestation is low fever; localized abdominal pain, mostly dull pain, with abdominal distension and other discomforts. Physical examination may show abdominal tenderness and palpable abdominal mass.

　　Acute intestinal perforation:Abdominal pain often occurs suddenly, presenting as persistent cutting pain, and it worsens during deep breathing and coughing. The extent of pain is related to the extent of peritonitis spread; abdominal breathing is weakened or disappeared, with marked tenderness and rebound pain in the entire abdomen, muscular rigidity, and disappearance of hepatic dullness. There may be mobile dullness, and bowel sounds are weakened or disappeared.

　　The systemic manifestations of Crohn's disease are numerous and prominent, mainly including:

　　1. Fever, one of the common systemic manifestations, is related to intestinal inflammation activity and secondary infection. Intermittent low fever or

　　Moderate fever is common, and a few present with remittent high fever accompanied by sepsis. A few patients have fever as the main symptom, even for a long time without clarification

　　Gastrointestinal symptoms appear after fever.

　　2. Nutritional disorders, caused by chronic diarrhea, decreased appetite, and chronic consumption, mainly manifested as weight loss.

　　Manifestations may include anemia, hypoproteinemia, and vitamin deficiency, etc. Patients before puberty often have delayed growth and development.

　　The extra-intestinal manifestations of this disease are similar to those of ulcerative colitis, but the incidence is higher. Common manifestations include: ①Skin and mucosal manifestations such as nodular erythema, polymorphic erythema, aphthous ulcer, gangrenous pyoderma, etc. ②Ocular damage: conjunctivitis, iridocyclitis, choroiditis, etc. ③Transient migratory joint pain: occasional ankylosing spondylitis. ④Liver disease: fatty liver, chronic active hepatitis, pericholangitis, sclerosing cholangitis, etc. ⑤Blood system manifestations: anemia, thrombotic栓塞现象. ⑥Renal lesions: pyelonephritis and nephrolithiasis occur more frequently in this disease. ⑦Growth and development: children with the disease may be affected.

　　Research shows that smoking is closely related to the onset of Crohn's disease among environmental factors, and the clinical manifestations and prognosis of Crohn's disease patients who smoke are worse than those who do not smoke. Therefore, actively quitting smoking is one of the effective ways to prevent the onset of Crohn's disease.

　　The risk of developing Crohn's disease is increased in users of oral contraceptives, and it is proportional to the duration of use. Therefore, avoiding the use of contraceptives is also a way to prevent the onset of Crohn's disease.

　　Some studies have shown that the occurrence of Crohn's disease is related to Mycobacterium paratuberculosis and measles virus. To prevent bacterial and viral infections, we should advocate the use of communal chopsticks or separate meals, drink milk and dairy products after sterilization, and thoroughly wash fruits and vegetables. The feces of Crohn's disease patients should be disinfected.

　　In terms of immune factors, there is a type of immune cell called T lymphocytes that is closely associated with the onset of Crohn's disease. Therefore, enhancing immunity can also prevent Crohn's disease. In daily life, the simplest and most effective way to enhance immunity is through exercise. One can choose a suitable exercise method according to their own preferences, time, and physical condition, such as running, dancing, swimming, basketball, football, traditional Chinese martial arts, and so on.

　　1. Routine Blood Tests White blood cells are often elevated; red blood cells and hemoglobin are reduced, associated with blood loss, bone marrow suppression, and iron, folic acid, and vitamin B deficiency.₁₂etc., related to reduced absorption. Hematocrit decreases, erythrocyte sedimentation rate increases.

　　2. Stool Examination Red and white blood cells can be seen; the occult blood test can be positive.

　　3. Blood Biochemical Examination Increased mucin, decreased albumin. Serum potassium, sodium, calcium, and magnesium may decrease.

　　4. Intestinal Absorption Function Test For those with extensive intestinal resection due to small intestinal lesions or malabsorption, an intestinal absorption function test can be performed to further understand the function of the small intestine.

　　5. X-ray Examination Barium enema of the intestines can understand the lesions and extent of the terminal ileum or other small intestines. The manifestations include inflammatory lesions of the gastrointestinal tract, such as fissured ulcers, pebble sign, pseudopolyps, solitary or multiple strictures, and fistula formation, with segmental distribution of lesions. Barium enema can help in the diagnosis of colonic lesions, and air-barium double contrast can improve the diagnostic rate. Abdominal X-ray film can show dilatation of the intestinal loops and extraintestinal shadowing.

　　6. Abdominal CT Scan It is valuable for determining whether there are thickened and separated intestinal loops and for differential diagnosis with intra-abdominal abscesses.

　　7. Endoscopy and Biopsy of Living Tissue Endoscopic examination and mucosal biopsy can show different manifestations such as mucosal congestion, edema, ulcers, narrowing of the intestinal lumen, formation of pseudopolyps, and pebble sign. The lesions are distributed in a jumping manner, and non-caseating granulomas can be confirmed pathologically. Ultrasound endoscopy is helpful in determining the extent and depth of the lesions, and detecting abdominal masses or abscesses.

　　How should the diet of Crohn's disease patients be selected? The following is an introduction in detail:

　　1. Food Selection. When selecting food for matching, staple foods should be fine rice and flour, avoiding coarse grains and dried beans to prevent increasing the burden on the gastrointestinal tract and causing damage; side dishes can be selected with lean meat, fish, and other high-quality protein foods as the main source of protein, and greasy foods are prohibited; it is advisable to drink various vegetable and fruit juices to supplement potassium deficiency and anemia in the body; choose foods with high unit nutritional value, which can increase nutrition without increasing the burden on the intestines.

　　2. Cooking Methods. All foods should be cooked soft, with little oil and light in taste, easy to digest. The main cooking methods are stewing, steaming, boiling, and simmering. It is forbidden to eat fried or oil-fried foods, as well as various strongly刺激性 spices, to avoid stimulating the intestinal mucosa and exacerbating symptoms of abdominal pain and diarrhea.

　　3. Eating Habits. It is important to develop good eating habits, adopt the method of eating less and more often to reduce the burden on the intestines, and supplement nutrition gradually. One should not eat too much or too fast to avoid exacerbating the condition. If necessary, elemental diet or parenteral nutrition can be used in the short term, and blood transfusions can be given multiple times in small amounts to improve the overall condition.

　　4. Supplementation of various vitamins: It is particularly worth pointing out that in the past, low-fat and low-residue diet was emphasized, but such a diet for Crohn's disease may affect the appetite of those who have been suffering for a long time; delicious and tasty food can stop weight loss, which is actually more beneficial to physical and mental health, and is not contradictory to the principles of high nutrition, high vitamin content, and easy digestion. It is advisable to supplement a variety of vitamins, folic acid, and minerals such as iron and calcium. Sometimes, zinc, copper, and selenium should also be supplemented, as these substances are components of enzymes and proteins in the body and have a protective effect on cells.

　　The principles of treatment and drug application for Crohn's disease are similar to those for ulcerative colitis, but the specific implementation is different. Western medicine treatment for Crohn's disease is as follows:

　　Aminosalicylate drugs should be selected according to the site of the lesion. The efficacy of aminosalicylates in Crohn's disease is inferior to that in ulcerative colitis. Immunosuppressants, antibiotics, and biological agents are more commonly used in the treatment of Crohn's disease due to the high incidence of patients who are ineffective or dependent on glucocorticoids. A considerable number of Crohn's disease patients eventually require surgical treatment due to complications during the disease process, but the recurrence rate after surgery is high, and there is currently no effective measure to prevent postoperative recurrence. The treatment of Crohn's disease is briefly described as follows:

　　(I) General treatment

　　Smoking must be stopped. Emphasize nutritional support, generally provide high-nutrient, low-residue diet, and appropriately provide various vitamins such as folic acid and vitamin B1. For severe patients, consider using elemental diet or total parenteral nutrition, which not only provides nutritional support but also helps to induce remission. Anticholinergic drugs or antidiarrheal agents can be used as necessary for abdominal pain and diarrhea. For patients with concurrent infection, broad-spectrum antibiotics can be administered via intravenous route.

　　(II) Medication treatment

　　1. Treatment during active phase

　　(1) Aminosalicylic acid preparations: Sulfasalazine is only suitable for mild to moderate patients with lesions limited to the colon. Mesalazine can be localized and released in the distal ileum and colon, suitable for mild ileocolonic and mild to moderate colonic patients.

　　(2) Glucocorticoids: They have a good therapeutic effect on controlling the activity of the disease and are suitable for patients with moderate to severe symptoms of all types, as well as mild to moderate patients who are ineffective to the above-mentioned aminosalicylic acid preparations. It should be noted that a considerable number of patients show no effect or dependence on hormones (relapse after reduction or discontinuation of medication in the short term), and for such patients, immunosuppressants should be considered (see below). Budesonide has few systemic adverse reactions and its efficacy is slightly inferior to that of systemic glucocorticoids. It can be used for mild to moderate jejunoileal or ileocolonic patients under certain conditions, with a dose of 3mg per time, three times a day, taken orally.

　　(3) Immunosuppressants: Azathioprine or mercaptopurine are suitable for patients who are ineffective or dependent on hormone treatment. The use of these drugs can gradually reduce the dosage of hormones or even stop their use. The dosage is 1.5-2.5mg/(kg•d) of azathioprine or 0.75-1.5mg/(kg•d) of mercaptopurine. The effective time of this type of drug is about 3-6 months, and the maintenance medication can last for 3 years or more. It is now believed that the safety of azathioprine or mercaptopurine at the above dose is acceptable. The main adverse reactions are mainly bone marrow suppression, such as leukopenia, and should be monitored closely when used. For those who are intolerant to azathioprine or mercaptopurine, methotrexate can be tried.

　　(4) Antibacterial Drugs: Certain antibacterial drugs such as nitroimidazole and quinolone drugs have certain efficacy in the treatment of this disease. Metronidazole is effective for perianal lesions, and ciprofloxacin is effective for fistulas. The long-term use of these drugs has many adverse reactions, so they are generally used in combination with other drugs for short-term application in clinical practice to enhance efficacy.

　　(5) Biological Agents: Infliximab is a human-mouse chimeric monoclonal antibody against TNF-α, a antagonist of pro-inflammatory cytokines, and clinical trials have proven its efficacy in active Crohn's disease that is refractory to traditional treatment. Repeated treatment can achieve long-term remission, and it has been gradually promoted in clinical use in recent years. Other new biological agents have also been launched or are under clinical research.

　　2. For those who achieve remission with aminosalicylate preparations or corticosteroids during the remission period, aminosalicylate preparations can be used to maintain remission, with the same dose as that used for induction of remission. For those who achieve remission by adding azathioprine or 6-mercaptopurine due to the ineffectiveness or dependence on corticosteroids, remission should be maintained with the same dose of azathioprine or 6-mercaptopurine. For those who achieve remission with infliximab, it is recommended to continue regular use to maintain remission. The duration of maintenance treatment can last for more than 3 years.

　　(3) Surgical Treatment

　　Due to the high recurrence rate after surgery, the indications for surgery are mainly for complications, including complete intestinal obstruction, fistula and peritoneal abscess, acute perforation, or uncontrollable massive bleeding. It should be noted that intestinal obstruction should be distinguished between functional spasm caused by inflammatory activity and mechanical obstruction caused by fibrous stricture; the former can usually be relieved by fasting and active medical treatment without surgery; for fistulas without abscess formation, active conservative medical treatment can sometimes also be closed; fistulas with abscess formation or failure of medical treatment are surgical indications. The main surgical method is the resection of the diseased intestinal segment. The prevention of recurrence after surgery is still a难题. Generally, mesalazine is used; metronidazole may be effective, but long-term use has many adverse reactions; azathioprine or 6-mercaptopurine can be considered for high-risk patients prone to recurrence. It is recommended to start preventive medication 2 weeks after surgery, and the duration should not be less than 3 years.