Elderly pseudo membranous enterocolitis

　　Pseudo membranous enterocolitis (PMC) is an acute mucosal necrotizing and fibrinous inflammatory disease that mainly invades the colon and can also affect the small intestine. As early as the end of the 19th century, scholars had made a relatively detailed description of PMC, but the etiology was not found. Although various theories such as immunodeficiency, viral infection, and intestinal mucosal circulation disorders had tried to explain the etiology of the disease, none were confirmed. It was not until the 1970s that Clostridium difficile was determined to be the main pathogen of PMC, so the disease is also called Clostridium difficile colitis. This is when the patient's intestinal flora is out of balance (due to low intestinal immune function, excessive use of antibiotics, and severe illness), Clostridium difficile abnormally proliferates, produces toxins, injures the mucosa, and causes inflammation and diarrhea with pseudomembrane formation, which is more common in the elderly.

　　It has been confirmed that the use of antibiotics is the main trigger for PMC. Among them, penicillin antibiotics are most likely to induce the disease, followed by cephalosporins, lincomycin, aminoglycosides, and others. In addition, gastrointestinal surgery, inflammatory bowel disease, uremia, intestinal hemorrhage, and other factors can also trigger PMC, which are all related to decreased immune function (especially low intestinal immune function) in the body. As people age, the body ages, and immune function decreases, making it more susceptible to this disease.

　　Clostridium difficile can produce four toxins: A toxin (enterotoxin), B toxin (cytotoxin), peristalsis factor, and instability factor. A toxin and B toxin are closely related to the pathogenesis of PMC, and they are all macromolecular protein exotoxins. It has been confirmed that the intestinal mucosal tissue of humans is sensitive to both A and B toxins of Clostridium difficile. Among them, A toxin can activate macrophages, mast cells, and neutrophils to release potent inflammatory mediators and cytokines, which cause inflammatory cell infiltration, hemorrhage, and villus damage in the intestinal mucosa. In severe cases, it can lead to extensive necrosis of the intestinal mucosa. B toxin can only exacerbate intestinal mucosal lesions based on A toxin and has no direct effect on the mucosa itself. It has been confirmed that there are specific sugar protein receptors for A toxin on the intestinal mucosa, and A toxin enters the cell by binding to the receptor, causing cell swelling and increased permeability.

　　Severe elderly patients with pseudomembranous colitis can develop various complications of the digestive system, such as toxic megacolon, paralytic ileus, intestinal perforation, intestinal hemorrhagic shock, DIC, and other severe conditions, with a mortality rate as high as 20%.

　　Pseudomembranous colitis can occur in all age groups, but most (over 60%) of the patients are elderly, with a slightly higher proportion of females than males. Patients often have certain underlying diseases, such as intestinal obstruction, inflammatory bowel disease, gastrointestinal surgery, and various critically ill patients, and have a history of short-term, large-scale use of broad-spectrum antibiotics. The onset is abrupt, with rapid development, and the main clinical manifestations include diarrhea, abdominal pain, fever, electrolyte and water imbalance, and acid-base imbalance. Severe cases may develop shock and various complications.
　　1. Diarrhea Patients with pseudomembranous colitis have diarrhea, mostly watery, in large quantities (＞1L/d); severe cases may expel pseudomembranes of varying sizes with watery diarrhea, the largest may be over 10 centimeters long; a small number of patients with severe illness may have paste-like, mucoid, and purulent stools.
　　2. Abdominal pain The site of pain is often located in the perineum, with the nature of dull pain, bloating, or spasmodic pain. The patient's abdomen generally has no obvious tenderness or rebound pain, and occasionally has peritoneal irritation signs.
　　3. Fever Moderate or high fever is common, accompanied by symptoms such as dizziness and fatigue due to toxicosis.
　　4. Disruption of water, electrolyte balance, and acid-base imbalance Severe diarrhea can lead to significant loss of water and salt, if not supplemented in time, it can cause water and electrolyte disorders and acid-base imbalance, and severe cases can lead to shock.

　　Since the use of antibiotics is the main trigger for pseudomembranous enterocolitis, and regardless of the type of antibiotic, dose, and duration of treatment, it can induce the disease. Therefore, elderly patients should try to avoid using antibiotics, especially broad-spectrum antibiotics. Narrow-spectrum antibiotics can be chosen if they must be used. Once suspected of having pseudomembranous enterocolitis, related antibiotics should be discontinued immediately. In addition, the elderly should strengthen their physical exercise to enhance their body's resistance.

　　Patients with critical illness, postoperative, elderly chronic diseases, especially those who receive high-dose antibiotic treatment and suddenly develop diarrhea and abdominal pain should be considered for pseudomembranous enterocolitis. If the stools are watery and accompanied by symptoms such as fever, it should be highly suspected. The final diagnosis depends on pathogenic and histological examinations. Routine examinations are as follows:
　　Firstly, laboratory examinations
　　1. Bacterial culture: Cultured for 24-48 hours in an anaerobic environment at 37℃. If the culture results are positive, toxin identification should also be performed. Since a small number of normal people may carry Clostridium difficile, and this strain does not produce toxins.
　　2. Toxin identification: The gold standard for diagnosing pseudomembranous enterocolitis, mainly using tissue cell culture method, which is the most sensitive and specific method, but difficult to implement in clinical practice. Enzyme-linked immunosorbent assay (ELISA) is not as sensitive as cell culture, but it is rapid, simple, and economical, and has now been applied in clinical practice.
　　3. Antitoxin neutralization test: The mechanism is that the cytotoxic effect of Clostridium difficile toxin can be neutralized by Clostridium difficile antitoxin. The neutralization phenomenon can occur at room temperature or 37℃ after diluting the antitoxin.
　　Secondly, other auxiliary examinations
　　1. Endoscopic examination: A rapid and reliable method for diagnosing pseudomembranous enterocolitis. Under endoscopy, PMC can be divided into 3 types: ① Colitis-like type: visible mucosal congestion and edema, presenting with non-specific colitis-like manifestations, commonly seen in patients with mild disease, early stage of disease course, and timely treatment; ② Mild type: mainly with mucosal congestion and edema, visible pseudomembranes, which are white, spotted, and jump-distributed, with red halos around them. The mucosa between the red halos is normal, commonly seen in the early stage of the disease course; ③ Severe type: many patchy or map-like pseudomembranes can be seen, with pseudomembranes being yellow, light yellow, or brownish yellow, not easy to peel off. Slight peeling or shedding can cause bleeding. The peeled surface resembles the endoscopic manifestations of erosive gastritis, commonly seen in patients with severe disease, late stage of disease course, and untimely treatment.
　　2. X-ray examination: Abdominal X-ray film shows colonic dilation, intestinal cavity effusion, and finger pressure marks. Barium enema double contrast shows colonic mucosal disorder, marginal brush-like edges, and many circular or irregular nodular shadows on the mucosal surface, as well as finger pressure marks and ulcerative signs.

　　The diet of elderly patients with pseudomembranous enterocolitis should be light, with more fresh fruits and vegetables, attention should be paid to reasonable dietary搭配, to ensure adequate nutrition; less greasy, high sugar, high salt food, avoid smoking and drinking, avoid spicy food.

　　Comprehensive measures should be taken for the treatment of elderly pseudomembranous enterocolitis.

　　1. Discontinue related antibiotics

　　Antibiotics-induced pseudomembranous enterocolitis should be discontinued immediately, and narrow-spectrum antibiotics or vancomycin can be used if antibiotics must be used.

　　2. Strengthen symptomatic supportive treatment

　　If the patient needs to be supplemented with water and electrolytes, total parenteral nutrition can be used when necessary, and a small amount of hormones can be used to improve toxic blood symptoms in severe cases.

　　3. Antibacterial treatment

　　Metronidazole is the first-line antibiotic, which is effective for the vast majority of PMC patients. Dosage: oral 0.4g, 4 times/day, or intravenous infusion of 0.5g/8h, course of treatment 7-10 days. If the effect is not ideal or the patient cannot tolerate metronidazole, vancomycin can be used instead. Dosage: oral 125-500mg, 4 times/day, course of treatment 7-14 days.

　　4. Treatment of Clostridium difficile toxin

　　The antitoxin of Clostridium difficile can be used to neutralize the toxin of Clostridium difficile. Dosage: intravenous infusion of 50,000 U, 4 times/day.

　　5. Maintain normal intestinal flora

　　Oral enzymes such as lactic acid bacteria can be taken. In addition, for those few patients with toxic megacolon or intestinal obstruction, surgical treatment should be considered.