Pseudomembranous colitis

　　Pseudomembranous colitis is caused by toxins produced by the following two types of bacteria.

　　1. Clostridium difficile
　　Clostridium difficile is an important pathogenic cause of pseudomembranous colitis associated with antibiotics. This bacterium is a resident bacterium in the human body, existing in the normal human intestines. In patients who have not received antibiotic treatment, the number of Clostridium difficile accounts for only 2% to 3% of anaerobic bacteria, and the toxins produced by the bacteria are few, even not producing toxins that are pathogenic to humans. The detection rate of Clostridium difficile in the population is 5% to 13%. Normally, these bacteria mutually restrict each other, cannot reproduce in large numbers, and will not cause disease. Long-term use of a large amount of antibiotics can inhibit the growth of various bacteria in the intestines, and the drug-resistant Clostridium difficile that is not affected by antibiotics will rapidly reproduce. The number of Clostridium difficile in the feces can reach 10% to 20% of anaerobic bacteria, produce a large amount of exotoxins, cause mucosal necrosis, exudative inflammation with pseudomembrane formation, and almost all exotoxins can be found in the feces of pseudomembranous colitis.

　　2. Hemolytic drug-resistant Staphylococcus aureus
　　After the use of a large amount of broad-spectrum antibiotics (such as oxytetracycline, chloramphenicol, tetracycline, ampicillin, cefamycin, and so on), various bacteria in the intestines, including Escherichia coli, are inhibited. The drug-resistant Staphylococcus aureus then reproduce in large numbers, produce exotoxins, and lead to the occurrence of pseudomembranous colitis. Gram staining of the feces of such patients can reveal piles of cocci. Injecting the toxins produced by this bacterium into animals can also cause pseudomembranous colitis.

　　Severe pseudomembranous colitis can complicate irreversible shock, rapid dehydration, and acidosis; or complications such as toxic megacolon, colon perforation, or peritonitis; or complications such as acute intestinal obstruction, hypoproteinemia, and polyarticular arthritis.

　　Pseudomembranous colitis generally occurs during the process of using antibiotics after tumors, chronic consumptive diseases, and major surgeries. Most cases have an abrupt onset and rapid progression, with the earliest onset time being a few hours after starting medication, but it can also occur about 3 weeks after discontinuing medication. About 20% of patients develop symptoms within 2 to 10 days after stopping antibiotics.

　　1, fever
　　10% to 20% of patients have fever and elevated white blood cells. Mild patients often have moderate fever, while severe patients may have high fever.

　　2, diarrhea
　　Diarrhea is an prominent symptom of this disease. Due to mucosal inflammation and the damage to the absorption function of the affected intestinal tract by exotoxins, the absorption of intestinal contents is affected, causing an increase in water and sodium secretion by the intestinal wall into the intestinal lumen, resulting in a large accumulation of intestinal fluid and causing diarrhea. The degree of diarrhea depends on the number of bacteria, the size of their virulence, and the patient's resistance.

　　3, abdominal pain and bloating
　　Under the stimulation of inflammation and intestinal fluid toxins, the intestinal tract presents spastic contractions, causing varying degrees of abdominal pain, which can be very severe in severe cases and accompanied by early hyperactive bowel sounds. After the intestinal peristalsis function is紊乱, it cannot effectively empty the accumulated liquid and gas in the intestines, leading to bloating. Severe cases may have typical symptoms of toxic megacolon.

　　4, toxicosis and shock
　　Late-stage manifestations in severe patients. After absorbing a large amount of toxins, there is a significant decrease in appetite, fever, tachycardia, lassitude, delirium, poor orientation, and consciousness disorders, which eventually lead to liver and kidney dysfunction and irreversible shock.

　　To prevent pseudomembranous colitis, antibiotics should be used strictly according to clinical indications to prevent misuse. The prophylactic use of antibiotics should be strictly controlled. Chloramphenicol is a drug with activity against Staphylococcus aureus and anaerobic Bacteroides fragilis, but it is generally not recommended to use chloramphenicol and lincomycin unless other drugs are ineffective or there are no conditions for their use. Ampicillin is also prone to cause pseudomembranous colitis, and attention should be paid to its clinical use.
　　Clinical workers should closely observe the complications of antibiotic use, identify and diagnose them early to avoid delaying treatment. If patients experience diarrhea, they should discontinue medication and perform stool tests promptly. If necessary, repeat sigmoidoscopy, especially for patients with clinical suspicion of pseudomembranous colitis or patients with unexplained fever after major intestinal surgery.

　　The diagnosis of pseudomembranous colitis depends not only on clinical manifestations but also on laboratory and auxiliary examinations, which are indispensable means. The commonly used examinations are as follows:

　　1. Blood routine and blood biochemical examination
　　Electrolyte disorder can be seen, with common hypokalemia, hyponatremia, etc.; hypoalbuminemia, with serum albumin below 3%; the white blood cell count can be as high as above 20×109/L, and neutrophils are predominant.

　　2. X-ray examination
　　There are no special findings in abdominal X-ray films, which can show intestinal paralysis or intestinal loop expansion, and visible liquid levels. Due to colonic edema, there may be thumbprint marks, and spontaneous megacolon may occur occasionally. Barium X-ray shows no special changes in early or mild patients; in late and severe cases, there may be increased colonic peristalsis, thickening of the mucosa, intestinal spasm, mucosal ulceration, etc. Barium enema often aggravates the condition and is generally not recommended.

　　3. Fecal examination
　　Smear microscopy of feces can be helpful for clinical judgment if Gram-positive bacilli and their spores are found. Subsequent staged bacterial culture can be performed to check for a large number of Gram-positive bacteria.

　　4. Bacteriological examination
　　90% of the cases can be cultured with Clostridium difficile in the feces at the time of onset. In order to reduce contact with air during the inspection, fresh feces in an amount more than the capacity of the container must be taken, along with the container, placed in a sealed wide-mouth bottle with a lid, and sent for inspection within 20 minutes.

　　5. Colonoscopy
　　Pseudomembranous colitis may also invade the colon, especially the sigmoid colon, which can be examined by colonoscopy. The typical manifestations are red and swollen mucosa with plaques or fused pseudomembranes. Biopsy may show acute inflammation of the mucosa, and the pseudomembrane contains necrotic epithelium, fibrin, inflammatory bacteria, etc.

　　6. Ultrasound diagnosis
　　Ultrasound can detect local intestinal wall pseudomembrane, mucosa, and submucosal edema causing severe thickening, narrowing or disappearance of the intestinal lumen. Careful examination may reveal a pseudorenal sign similar to intestinal tuberculosis or tumor in the lower right abdomen. Good-quality ultrasound diagnostic instruments can also more accurately distinguish the layers related to the lesions. In addition, ultrasound diagnosis can detect complications such as ascites associated with the disease.

　　7. CT diagnosis
　　The CT manifestations are not specific, and occasionally, low attenuation and thickened intestinal wall can be found.

　　Patients with mild pseudomembranous colitis can have light diet, consume easily digestible semi-liquid diet, and at the same time, they can consume yogurt containing probiotics. In severe cases or those with severe nausea and vomiting, fasting is required, and parenteral nutrition is provided, and the diet is gradually restored after the symptoms are relieved.

　　The goal of treating pseudomembranous colitis is to eliminate bacteria, eliminate or weaken the effect of bacterial toxins, support the normal intestinal flora, and improve the symptoms of the digestive tract of the whole body and abdomen. The specific treatment methods are as follows:

　　1. Treatment of the etiology
　　is extremely important. The clinical use of drugs should be strictly controlled based on indications, and close observation of changes in the gastrointestinal tract should be made for patients using a large amount of broad-spectrum antibiotics. If the disease is suspected or diagnosed, the use of antibiotics should be discontinued immediately. After discontinuing antibiotics, it is conducive to the growth of other bacteria in the intestines, especially aerobic bacteria, to inhibit the growth of anaerobic bacteria, and to restore the normal intestinal environment.

　　The application of antibiotics
　　Before the results of stool culture and drug sensitivity test are obtained, it is necessary to change to antibiotics in a timely manner, and narrow-spectrum antibiotics with strong specificity can be used.

　　3. Support of normal flora
　　Since the loss of resistance to Clostridium difficile colonization is an important factor in the pathogenesis of pseudomembranous colitis, it is theoretically possible to treat it by reconstructing the normal flora.
　　1. Drug treatment: Lactase, vitamin C, folic acid, vitamin B complex, vitamin B12, glutamic acid, etc., can promote the growth of normal flora in the intestines; lactose, honey, maltose, etc., promote the growth of Escherichia coli.
　　2. Use of healthy human feces: The feces of healthy people containing normal flora are used as donors. The enema treatment of pseudomembranous colitis with feces can achieve good results.

　　4. Symptomatic and systemic supportive treatment
　　1. Treatment of shock and sepsis: replenish blood volume and provide whole blood, plasma, or albumin to enhance resistance and the ability to combat shock. The treatment of sepsis can be applied for a short period of time. Adrenal cortical hormones are expected to alleviate sepsis and are beneficial to correct shock. However, there is no need for large doses or long-term use. Hypotension can be treated with dopamine, metaraminol, and other vasoactive drugs.
　　2. Correction of electrolyte and acid-base imbalance: Diarrhea can lead to dehydration, usually isotonic dehydration, and the lost water and potassium, sodium salts should be supplemented according to biochemical tests and urine output. Alkaline drugs are used to correct acidosis. It is often difficult to replenish blood volume solely by intravenous fluid administration. When the normal mucosa of the intestines can absorb water, glucose and sodium chloride can be supplemented through the oral route, with glucose acting as a carrier to absorb sodium ions at the same time, which is beneficial to replenish the loss of sodium and restore acid-base balance.
　　3. Parenteral Nutrition (PN): Severe diarrhea is present in the treatment of this disease, which affects eating during the course of the disease, has a long course, and is often prone to negative nitrogen balance. Therefore, PN treatment can enhance the body's ability to resist diseases and accelerate tissue repair.
　　4. Treatment of underlying diseases: Pay attention to the treatment of underlying diseases during the treatment process, correct heart failure, improve liver function, etc.

　　5. Surgical Treatment
　　Under active non-surgical treatment, if there is no improvement in the course of the disease, and there is a suspicion of intestinal necrosis, intestinal perforation, or the occurrence of toxic megacolon, active surgical exploration should be performed while correcting acidosis and replenishing blood volume.