Intestinal fistula

　　The common causes of intestinal fistula include surgery, trauma, abdominal infection, malignant tumors, radiation injury, chemotherapy, and intestinal inflammation and infectious diseases.

　　Clinically, intestinal external fistula mainly occurs after abdominal surgery and is a serious postoperative complication. The main cause is postoperative abdominal infection, anastomotic dehiscence, and poor blood supply to the bowel causing anastomotic fistula. Inflammation of the small intestine, tuberculosis, intestinal diverticulitis, malignant tumors, and direct penetration of the intestinal wall by trauma orifice infection, abdominal inflammation, abscess, and other complications can also cause intestinal fistula. Some are complications of inflammatory bowel disease itself, such as internal or external fistula caused by Crohn's disease.

　　According to clinical data analysis, secondary fistula due to abdominal abscess, infection, and postoperative fistula is most common in intestinal fistula, and intestinal fistula is common in malignant tumors. Radiotherapy and chemotherapy can also cause fistula, which is relatively rare.

　　Due to the large daily loss of intestinal fluid, if not supplemented in time, it can quickly lead to dehydration, hypovolemia, peripheral circulatory failure, and shock and other complications.

　　Intestinal fistula can cause gastrointestinal dysfunction, leading to diarrhea or lack of defecation and flatus, weight loss, and toxic symptoms; in severe cases, it can even lead to sepsis, shock, and death. It can also be complicated by stress ulcers, gastrointestinal bleeding, toxic hepatitis, ARDS, renal failure, and other complications.

　　The symptoms of intestinal fistula are relatively complex, and the severity of the condition is influenced by various factors, including the type, cause, physical condition of the patient, and different stages of fistula occurrence. Intestinal inter-fistula may not have obvious symptoms or physiological disorders.

　　In the early stage of intestinal external fistula, it generally manifests as localized or diffuse peritonitis symptoms. Patients may experience fever, abdominal distension, abdominal pain, and local abdominal wall tenderness with rebound pain. In some cases after surgery, it is difficult to distinguish from the symptoms and signs of the underlying disease. Clinical physicians often do not pay enough attention to the patient's complaints of abdominal distension, lack of flatus, and defecation, attributing it to poor intestinal peristalsis and adhesions after surgery, often losing the opportunity for early diagnosis of fistula. After the formation of the fistula and the leakage of intestinal contents outside the body, the main manifestations are: the formation of fistula orifice and leakage of intestinal contents, infection, malnutrition, disorder of water and electrolyte balance and acid-base balance, and multi-organ dysfunction.

　　Malnutrition is caused by the leakage of intestinal contents, especially digestive juices, leading to digestive and absorptive disorders. Added to this are infections, reduced intake of food, and the impact of the underlying disease, resulting in most patients with intestinal fistula experiencing varying degrees of malnutrition, with corresponding clinical manifestations such as hypoproteinemia, edema, and weight loss. The disorder of water and electrolyte balance and acid-base balance varies depending on the location and type of the fistula, and the flow rate, with varying degrees of homeostasis imbalance, which can manifest in various ways, commonly including hypokalemia, hyponatremia, and metabolic acidosis. In the later stage of multi-organ dysfunction due to fistula, if the condition is not controlled, multi-organ dysfunction can occur, making gastrointestinal bleeding, liver damage, and other complications more likely.

　　In addition, intestinal fistula patients may also have some diseases related to the occurrence of fistula, such as gastrointestinal tumors, intestinal adhesions, inflammatory bowel disease, severe pancreatitis, and multiple traumas, and the corresponding clinical manifestations appear.

　　Most intestinal fistulas occur during abdominal surgery. The main reasons include the internal environment of the body, nutritional status, and immune function, etc. In addition to the urgent nature of emergency surgery, adequate preoperative preparation should be made for elective surgery, correcting electrolyte imbalance, improving nutrition, controlling infection, which will effectively reduce the incidence of intestinal fistula.

　　For extensive abdominal adhesion surgery, the operation should be patient and meticulous, reducing the damage to the intestinal wall, repairing the small muscularis mucosae rupture, and for those with larger damage but shorter involved intestinal segments, considering the resection of adhesed intestinal segments can be considered. The indications for surgery for inflammatory intestinal obstruction should be strictly controlled.

　　Anastomotic leakage is one of the main causes of intestinal fistula formation. There are many reasons for anastomotic leakage leading to intestinal fistula, and anastomotic technique is the key. Overly dense suture can lead to local tissue ischemia and poor healing; loosely sutured can cause leakage at the anastomotic site. Effective gastrointestinal decompression after surgery is an effective measure to prevent anastomotic fistula. Controlling intra-abdominal infection is an essential factor to ensure good healing of the anastomosis. Necessary abdominal drainage is also important.

　　The examination of intestinal fistula includes laboratory tests, imaging examinations, especially gastrointestinal and fistula or sinus tract contrast examinations. The specific examination methods are as follows:

　　1. Fistula contrast

　　Through oral dyeing or through inserting a catheter into the fistula or directly using a syringe to inject into the fistula, fistula contrast is performed. After taking diluted bone charcoal powder or methylene blue orally, the fistula opening is observed at regular intervals, and the amount and time of bone charcoal powder or methylene blue excretion are recorded. If dye is discharged through the wound, the diagnosis of intestinal fistula is clear; the location of the fistula can be roughly estimated according to the excretion time; the size of the fistula opening can be preliminarily estimated according to the amount of excretion.

　　2. Abdominal flat film

　　Through abdominal upright and supine flat film examination, determine whether there is intestinal obstruction and whether there is an abdominal space-occupying lesion. Ultrasound can check for abscesses in the abdominal cavity and their distribution, understand the presence of pleural effusion and whether there are space-occupying lesions in the abdominal solid organs, etc., and B-ultrasound guided percutaneous puncture drainage can be performed if necessary.

　　3. Gastrointestinal contrast

　　Including oral contrast enterography and enterography through abdominal wall fistula are effective means for diagnosing intestinal fistula. It can usually clarify whether there is an intestinal fistula, the location and quantity of the fistula, the size of the fistula opening, the distance from the fistula opening to the skin, whether the fistula is accompanied by an abscess cavity, and the drainage condition of the fistula. At the same time, it can also clarify whether the distal and proximal intestinal tubes of the fistula are unobstructed. If it is a lipoma fistula, after clarifying the condition of the proximal intestinal tube of the fistula, contrast medium can be injected into the distal intestinal tube through the fistula for examination. When performing enterography on patients with intestinal fistula, attention should be paid to the selection of contrast medium. Generally, barium is not recommended because it cannot be absorbed or dissolved easily, and it may cause barium to remain in the abdominal cavity and fistula, forming foreign bodies and affecting the spontaneous healing of the intestinal fistula; the inflammatory reaction caused by barium leakage into the abdominal cavity or pleural cavity is also relatively severe.

　　Generally, 60% diatrizoate meglumine is used for early intestinal fistula patients. 60-100ml of 60% diatrizoate meglumine is directly taken orally or injected through a gastric tube, which can usually clearly show the condition of the intestinal fistula. The diatrizoate meglumine in the intestinal lumen and that leaked into the abdominal cavity can be absorbed quickly. There is no need to further dilute the 60% diatrizoate meglumine, otherwise the contrast of the contrast study will be poor, and it will be difficult to clearly identify the fistula and its accompanying conditions. During the contrast study, dynamic observation should be made of the peristalsis of the gastrointestinal tract and the distribution of the contrast agent; attention should be paid to the location, amount, and speed of leakage of the contrast agent, as well as the presence of branch channels and abscess cavities.

　　4. CT scanning

　　CT is an ideal method for clinical diagnosis of intestinal fistula and its complications such as abdominal and pelvic abscesses. Especially through the oral administration of gastrointestinal contrast agents, CT scanning can not only clarify the condition of intestinal patency and fistula, but also assist in preoperative evaluation and help determine the timing of surgery. In CT examination of the intestines with obvious inflammatory adhesions, the manifestation is that the intestines are adhered into a mass, the intestinal wall is thickened, and there is intestinal cavity effusion. At this time, if extensive adhesion separation is performed, it not only cannot completely separate the adhesions, but will also cause more secondary injuries to the intestines, produce more fistulas, and lead to the complete failure of the surgery. Other examinations for small intestinal gallbladder fistula, small intestinal bladder fistula, and other conditions should be performed with bile duct and urinary tract contrast studies.

　　The diet of intestinal fistula patients is an important aspect. Many foods are very detrimental to the recovery of colon fistula patients, so they should be more careful in daily intake to avoid losing balance and causing negative effects on health. The diet should include foods rich in protein, such as lean meat, beef, mushrooms, jujube, sesame, and so on. In addition, there are black fungus, yam, coriander, chive, eggplant, lotus seed, water chestnut, lotus root, fennel, litchi, chicken, lamb, fig, and so on.

　　The main foods that should not be eaten are:

　　Sugar: It is conducive to the rapid proliferation of bacteria in the intestines, especially Escherichia coli, which is easy to form oxalic acid, a cause of rheumatism.

　　Meat: Meat does not contain fiber. If it is not chewed thoroughly, meat is not easy to digest, leading to the proliferation of bacteria in the intestines.

　　Refined flour: It is easy to make the stool hard, especially when there is a lack of fruits and vegetables in the food structure, the condition of the eater will become more serious.

　　Saturated fat: Saturated fat refers to animal fat and artificial fat cream. The accumulation of saturated fat changes the intestinal flora, increasing the content of bacteria that promote the conversion of bile salts into carcinogenic substances.

　　Gluten: Gluten forms a sticky paste-like substance that adheres to the inner wall of the intestines. It slows down the passage of food, easily causes intestinal putrefaction, and interferes with the absorption of the vitamin B group.

　　The Western medical treatment for intestinal fistula first corrects the disturbance of water and electrolyte balance and acid-base balance. Disturbance of water and electrolyte balance and acid-base balance is a serious complication of high-flow intestinal fistula and also the main cause of early death in intestinal fistula.

　　The causes include the large loss of digestive fluid; high catabolic metabolism caused by severe abdominal infection: insulin resistance, glucose utilization disorder, hyperglycemia; difficult to correct acidosis; and inappropriate nutritional support and fluid supplementation during the treatment of intestinal fistulas. Therefore, the electrolyte and acid-base balance disorders caused by intestinal fistulas are relatively complex, with various forms, and贯穿 throughout the entire course of the disease and treatment process. The degree of disorder changes with the change of fistula flow and the degree of infection control.

　　Throughout the treatment process of intestinal fistulas, it is necessary to pay attention to correcting the disorders of water and electrolyte and acid-base balance from beginning to end. The basic measures to maintain water and electrolyte and acid-base balance are to ensure normal water and electrolyte and acid-base supplementation, control the leakage of intestinal fluid, promptly detect and correct electrolyte disorders. For patients with intestinal fistulas, attention should be paid to monitoring 24-hour intake and output, blood electrolytes, blood gas analysis, hematocrit, plasma osmolality, urine volume, urine specific gravity, and urine electrolytes.

　　Special attention should be paid to the presence of hypokalemia, hyponatremia, and metabolic acidosis. During the treatment of intestinal fistulas, both hyperkalemia and hypokalemia can occur, and the patients may not have obvious symptoms. Since the exchange of potassium ions between intracellular and extracellular is slow and requires a certain amount of energy, serum potassium cannot fully represent and reflect the total amount and changes of potassium. During the treatment of intestinal fistulas, as the control of infection improves, the body shifts from catabolism to anabolism, and the demand for potassium ions also increases.

　　When supplementing potassium in clinical practice, it should be monitored more frequently, and it is not advisable to replenish all the missing potassium in a short period of time. Potassium chloride preparations are generally used by adding 10% potassium chloride to the liquid. For patients with concurrent hyperchloremia, potassium glutamate can be used. The route of administration can be peripheral venous, central venous, or through the fistula or oral administration. For patients who need a large amount of potassium supplementation, central venous administration is generally adopted, and electrocardiogram monitoring should be performed to prevent arrhythmias.

　　Part of the intestinal fistulas can heal spontaneously through comprehensive treatment methods such as aspiration, washing, adhesion, blocking, and supplementation, but more than 80% of patients require surgical treatment. Complex intestinal fistulas often require multiple staged surgeries to be successful. In recent times, due to the continuous improvement of complete parenteral nutrition technology, the mortality rate of intestinal fistulas has been greatly reduced, and the cure rate of surgery has been improved.