Duodenal fistula

　　First, etiology

　　The causes of external fistula of the duodenum can be divided into two major categories: systemic and local. From a systemic perspective, there are factors such as severe malnutrition, organ dysfunction, and diabetes. However, it is more important to consider local lesions and trauma factors, such as unsatisfactory suture embedding of the duodenal残端, severe inflammation and edema at the site of duodenal trauma, and inadequate suture repair, all of which can lead to external fistula of the duodenum. The special anatomical position of the duodenum, where a large amount of gastric juice, bile, and pancreatic juice pass through, is also one of the reasons why external fistula of the duodenum is prone to occur.

　　The common diseases that cause external fistula of the duodenum include trauma, abdominal surgery, and pancreatitis. Crohn's disease of the duodenum and intestinal tuberculosis can also cause external fistula of the duodenum. The diseases that cause external fistula of the duodenum can be roughly divided into the following categories:

　　1, Trauma

　　(1) Abdominal closed injury: In abdominal closed injuries, injuries caused by car steering wheel and high-altitude falls are most prone to be accompanied by duodenal trauma, and due to the fact that most of the duodenum is located retroperitoneally, the patient's condition is unstable after injury due to bleeding, shock, and other reasons, and it is easy to ignore the exploration of duodenal trauma. Sometimes, even if duodenal trauma has been found and repair surgery has been performed, there is still a high incidence of postoperative external fistula of the duodenum.

　　(2) Abdominal stab wound: Since the duodenum is located in the middle and upper abdomen, it is also a common site of stab wounds, and it is also very easy to be accompanied by damage to other organs, such as pancreatic trauma and intestinal trauma. If it is not detected in time or the treatment is not satisfactory during the operation, it can lead to the occurrence of an external fistula of the duodenum.

　　2, Surgery

　　(1) subtotal or total gastrectomy: Patients who undergo subtotal or total gastrectomy due to peptic ulcer disease or gastric cancer often need to undergo extensive stripping around the duodenal残端 due to the extensive scope of the lesion and the need for radical resection of gastric cancer. The residual end is prone to ischemia and necrosis, resulting in postoperative fistula of the duodenal残端. Sometimes, there is a degree of obstruction at the distal end of the duodenum, and even if the local treatment is satisfactory, it cannot prevent the occurrence of a fistula.

　　(2) Biliary surgery: The most common biliary surgeries that cause external fistula of the duodenum include cholecystectomy and choledochotomy. In patients with recurrent cholecystitis, the adhesions between the gallbladder and surrounding organs, especially the duodenum, are relatively heavy. It is easy to damage the duodenum during surgical stripping, and if it is not detected in time or handled improperly, it may also lead to an external fistula of the duodenum.

　　Duodenal fistula associated with common bile duct incision and exploration is generally due to stricture at the lower end of the common bile duct. When using different sizes of bile duct probes for exploration, due to excessive force, the probe can further advance and damage the opposite edge of the duodenal papilla when passing through the lower end of the common bile duct into the duodenum, causing duodenal perforation. In more severe cases, it can also damage the transverse colon, causing transverse colon perforation. Since the probe is quickly withdrawn, this kind of injury is often not discovered in time, leading to the occurrence of duodenal fistula, and at the time of discovery, it is often complicated with severe retroperitoneal infection.

　　When performing the Oddi sphincteroplasty through the duodenal incision, due to an excessively large incision range or improper location, and unsuitable suture, it can cause fistula between the lower end of the common bile duct and the duodenum.

　　(3) Duodenal surgery: There may also be duodenal fistula during surgery for duodenal diseases such as duodenal diverticula.

　　(4) Endoscopic examination and duodenal papillotomy: During the duodenoscopy and retrograde cholangiopancreatography (ERCP) examination, especially during the duodenal papilla Oddi sphincterotomy, due to improper force or incorrect location, it is easy to damage the duodenum and cause duodenal fistula.

　　(5) Other surgeries: When operating on organs near the duodenum, such as right hemicolectomy or nephrectomy, there is also a possibility of damaging the duodenum and causing duodenal fistula.

　　3. Disease

　　(1) Severe pancreatitis and pancreatic pseudocyst: Since the pancreas is located inside the duodenal loop, the fourth segment (ascending) of the duodenum is closely adjacent to the middle segment of the pancreas. Acute hemorrhagic necrotic pancreatitis often affects the blood supply of the duodenum, and the extravasated pancreatic juice will digest the surrounding tissue of the duodenum, thus causing duodenal fistula. The incision surgery for pancreatic pseudocyst may also be complicated by duodenal fistula.

　　(2) Crohn's disease: Crohn's disease generally invades the ileocecal region and causes intestinal fistula in that region. However, there have also been reports of Crohn's disease occurring in the duodenum causing duodenal fistula.

　　(3) Intestinal tuberculosis: The duodenum can also be invaded by tuberculosis bacteria and lead to the occurrence of duodenal fistula.

　　Second, pathogenesis

　　1. Pathological classification:There are many classification methods for duodenal fistula. If the internal opening of the intestinal fistula is directly attached to the skin surface, it is called a labial fistula; if there is still a fistula tube between the internal and external openings of the intestinal fistula, it is called a tubular fistula. If the duodenal fistula is discovered early, that is, it has not formed a labial fistula between the skin, nor has it formed a fistula tube between the skin to become a tubular fistula, but rather manifests as a fistula opening inside the free abdominal cavity, that is, an intracavitary fistula. The understanding of 'intracavitary fistula' is the inevitable result of the progress of early diagnosis and early treatment of intestinal fistula. Early detection of intracavitary fistula can be achieved by various methods to promote its spontaneous healing and improve the self-healing rate of duodenal fistula. However, focusing on clinical diagnosis and treatment, duodenal fistula can be classified as follows. This classification method is convenient for clinical doctors to prevent and treat duodenal fistula.

　　(1) Duodenal stump fistula: It mainly occurs in patients who undergo subtotal gastrectomy with Billroth II reconstruction, that is, stomach-jejunum anastomosis, or total gastrectomy. The reasons for subtotal gastrectomy can be gastric ulcer or duodenal bulb ulcer, gastric cancer, or trauma to the stomach and duodenal bulb. The duodenal stump fistula is related to the extensive invasion range of ulcers or tumors, or the extensive range of lesions, and is also related to unsatisfactory suture and embedding of the stump.

　　(2) Duodenal lateral fistula: The fistula is located on the lateral wall of the duodenum, and the gastric juice still passes through it. Such external fistulas are difficult to heal spontaneously.

　　(3) Duodenal end fistula: Due to complete rupture of the duodenum due to trauma or surgery, the fistula can be divided into distal and proximal ends, and such fistulas cannot heal spontaneously.

　　(4) Duodenal anastomotic fistula; the fistula is located at the anastomosis between the stomach and duodenum, the anastomosis between the duodenum and duodenum, or the anastomosis between the duodenum and jejunum. It often occurs in patients who undergo subtotal gastrectomy and have a stomach-duodenum anastomosis, or in patients who undergo jejuno-duodenal anastomosis after duodenal trauma.

　　2. Pathophysiology:Duodenal fistula belongs to high-level intestinal fistula. Due to the large loss of intestinal contents, it is also called a high-output fistula. The most threatening pathophysiological changes to patients include the following aspects.

　　(1) Imbalance of internal environment: The rapid loss of a large amount of digestive fluids can quickly cause dehydration, electrolyte and acid-base imbalance. If it is not corrected in time, it can lead to reduced blood volume, causing circulatory failure, or renal failure, resulting in azotemia.

　　(2) Malnutrition: Due to digestive and absorptive disorders and insufficient energy supplementation, the lost gastrointestinal fluids contain a large amount of protein, which can cause malnutrition and hypoproteinemia, which also reduces immune function.

　　(3) Infection: Infection is a major complication following early disturbances in water and electrolytes. Particularly, intra-abdominal infection causes the body to be in a hypermetabolic state, which can exacerbate the damage to the stability of the internal environment. Infection can not only cause malnutrition but also lead to stress ulcers or diffuse intestinal mucosal hemorrhage, causing shock. Infection can lead to single-organ or multi-organ failure, and it also increases the difficulty of treating intestinal fistulas. The duodenal fluid contains a large amount of digestive enzymes, which has a corrosive and dissolving effect on surrounding tissues, and can cause skin erosion around the fistula, making it difficult for the fistula to heal; it may also cause corrosive rupture of blood vessels, causing massive bleeding that is difficult to control.

　　3. Pathological staging:The pathological process of extra-intestinal fistula can be divided into 4 stages:

　　(1) Peritonitis period: It usually occurs within 3 to 5 days after trauma or surgery.

　　(2) Localized intra-abdominal abscess period: It usually occurs 7 to 10 days after the onset of fistula.

　　(3) Fistula formation and control period: Due to differences in the degree of infection, the location and size of the fistula, etc., it usually takes 10 to 30 days.

　　(4) Fistula healing period: Depending on the control time of infection and the type of fistula, it usually takes about 1 month after the control of systemic infection, with more than half of the patients with fistula recovering spontaneously, and a few recovering within 2 to 3 months.

　　1. Imbalance of internal homeostasis:After the occurrence of external duodenal fistula, a large amount of intestinal fluid is lost, with an excretion volume of more than 1000ml/24h, and in severe cases, it can reach 5000～6000ml per day. At this time, the blood volume is seriously insufficient, and there is a disorder of electrolytes and acid-base balance.

　　2. Hemorrhage:Abdominal hemorrhage is an early complication of intestinal fistula, especially duodenal fistula and high-position jejunal fistula. The bleeding site can be the corroded and digested blood vessels inside the abdomen, or the margin of the fistula or granulation tissue of the fistula tube, or it may be caused by bleeding due to gastrointestinal stress-induced mucosal erosion.

　　3. Infection:Peritoneal infection and systemic infection are the main causes of death in patients with intestinal fistula. Peritoneal infection includes peritonitis, peritoneal abscess, and infection of abdominal internal organs. In the early stage, peritonitis is the main condition, while in the middle and later stages, peritoneal abscess and infection of abdominal internal organs are the main conditions. Some patients' intestinal fistula occurs on the basis of pre-existing peritoneal infection, and the fistula and peritoneal infection coexist, forming a vicious cycle, such as external fistula in severe pancreatitis.

　　4. Malnutrition:Loss of digestive fluid leads to incomplete digestion of food and poor nutrient absorption.

　　It can be roughly divided into two situations: one is the placement of drainage after abdominal surgery; the other is not placing drainage (including elective subtotal gastrectomy or abdominal closed injury, etc.). The former is easier to be detected early; the latter may be misdiagnosed or missed.

　　1. Patients with peritoneal drainage placed:

　　A large amount of mixed bile-like fluid can be observed flowing from the drain or drain tube, but the following characteristics should also be noted.

　　1. The occurrence time of fistula:It generally occurs within 5～8 days after surgery, but there are also cases reported in China that occur 18, 20 days, or even 5, 10 years after surgery.

　　2. The amount of intestinal fluid leakage and the degree of abdominal muscle tension:The amount of intestinal fluid leaking locally mainly depends on the type, location, size of the external duodenal fistula, and the pressure inside the duodenum. For lateral fistulas, the daily loss of intestinal fluid is 500～4000ml, with an average of more than 2000ml. Due to the placement of peritoneal drainage, local abdominal muscle tension may not be significant; in cases where drainage is not smooth or no peritoneal drainage is placed, muscle tension is more obvious.

　　Even though an external duodenal fistula has occurred, the leakage of effusion may not be significant (but not decreasing day by day), or there may be no obvious leakage of bile-like fluid. It is easy to be misdiagnosed as local infection. It is only after the skin is corroded or bile-containing digestive fluid (or containing food residue) is exuded that a diagnosis of external duodenal fistula is made. Therefore, for patients with abdominal trauma or gastric resection surgery, if there is a lot of leakage from the wound, further examination and observation should be carried out to be vigilant for the occurrence of fistula.

　　3. Fever:Generally, the body temperature is between 38～39℃, and for those with unobstructed drainage, the degree of fever is lighter. Fever, like the draining intestinal fluid, is an important symptom.

　　4. Hiccups:Frequent hiccups may occur due to the leakage of intestinal fluid flowing towards the diaphragm, stimulating the diaphragm and causing hiccups. Pay attention to observe for symptoms of hiccups, as this is very helpful for early diagnosis, especially for those who have not had peritoneal drainage. Hiccups can be an important signal in this regard.

　　5. Systemic Symptoms:Early onset of dehydration and electrolyte imbalance, followed by weight loss, malnutrition, and secondary symptoms of infection, such as the formation of an abscess in a certain part of the abdominal cavity (single or multiple locations); it can also spread from localized infection to systemic suppurative infection, such as sepsis, toxic hepatitis, encephalitis, etc., which may be accompanied by the failure of a single important organ function, or even multiple organ failure.

　　II. Without peritoneal drainage

　　The leaked duodenal fluid can flow into any part of the peritoneal cavity and produce atypical abdominal symptoms. These symptoms are often masked by postoperative wound pain, absorption fever, and other discomforts, and are easily overlooked. If attention is paid to observation, most patients will have abdominal pain, belching, fever, and signs of peritonitis to varying degrees.

　　1. Develop good living habits, quit smoking and limit alcohol. Smoking, the World Health Organization predicts that if people stop smoking, the world's cancer rate will decrease by 1/3 in 5 years; secondly, do not drink excessively. Smoking and drinking are extremely acidic acidic substances, and people who smoke and drink for a long time are prone to acidosis.

　　2. Do not eat too much salty and spicy food; do not eat overheated, cold, expired, or deteriorated food; for the elderly, weak, or those with certain genetic diseases, eat some anti-cancer foods and alkaline foods with high alkaline content as appropriate to maintain a good mental state.

　　1. Gastrointestinal Contrast Study

　　For early-stage intestinal fistula patients, 60-100ml of 60% diatrizoate can be taken orally or infused through a gastric tube, which can usually clearly show the situation of the intestinal fistula. Whether it is the diatrizoate in the intestinal lumen or that leaked into the peritoneal cavity, it can be absorbed quickly. During the contrast study, dynamic observation of gastrointestinal motility and contrast agent distribution should be made, and attention should be paid to the location, amount, and speed of contrast agent leakage, as well as the presence of branching pathways and abscess cavities. Since 60% diatrizoate is also a hypertonic liquid, some patients with good intestinal function may experience transient abdominal distension and increased bowel movements after the examination. Patients without intestinal motility can also absorb the contrast agent quickly, and the abdominal distension symptoms will subside quickly.

　　Due to the incomplete obstruction caused by inflammatory intestinal obstruction or intestinal adhesion often accompanied by intestinal fistula, it is not advisable to use barium in clinical practice for gastrointestinal contrast study. Barium contrast study will worsen the degree of gastrointestinal obstruction, causing incomplete obstruction to develop into complete intestinal obstruction.

　　2. Fistulography

　　When the fistula has formed, fistulography can be performed first. Sometimes, gastrointestinal contrast study is not sufficient to meet the diagnostic requirements, and additional contrast studies through the fistula or drain port are needed. The 60% diatrizoate is still used as the contrast agent, which is directly injected into the skin fistula without the need to insert a catheter into the fistula for contrast study. This is to avoid the contrast agent entering the intestinal lumen directly and not showing the situation of the fistula and the surrounding area, such as the bifurcation, abscess cavity, etc. Direct fistulography can better understand the situation of the fistula and the segment of the intestine where the fistula is located. If there is no need to understand the situation of other intestinal loops, such as whether there is obstruction and organic lesions, there is no need to perform a full gastrointestinal contrast study. One fistulography can clearly diagnose the condition and formulate a treatment plan.

　　3. Abdominal puncture

　　Withdrawal of bile-like intestinal fluid, sometimes containing food residue.

　　4. Oral charcoal or methylene blue solution test

　　The colored fluid flowing out of the wound can prove the existence of an intestinal fistula. From the time of flow, the color and amount of the fluid, a rough estimate of the size and location of the fistula orifice can also be made. The amount taken orally should be slightly larger to facilitate observation.

　　5. Abdominal flat film

　　This examination is helpful for the diagnosis of duodenal fistula. If there is a large amount of gas or liquid level in the abdomen, it usually suggests the existence of an intestinal fistula. Through the abdominal flat film, it can also suggest whether there is a combined intestinal obstruction, but this examination cannot make a definite diagnosis.

　　It is an ideal method for clinical diagnosis of intestinal fistula, especially when it is combined with abdominal and pelvic abscesses. It should be performed as soon as possible after the patient has taken oral contrast, and after the gastrointestinal contrast agent is filled, it helps to distinguish from the accumulated fluid outside the abdomen. Occasionally, it can be found that the fistula tube communicates with the fistula orifice of the abscess cavity, and the

　　7. Ultrasound examination

　　Although it can help diagnose the presence of abdominal effusion or abscess, it is inaccurate due to intestinal bloating and is not helpful for diagnosing the existence or specific location of an intestinal fistula.

　　For patients with high-flow fistulas who cannot recover gastrointestinal intake, total parenteral nutrition treatment can be performed by deep venous catheter insertion, with 167-209 KJ (40-50 kcal) of energy supplied per kilogram per day, and 0.2-0.3 grams of nitrogen supplied per kilogram (equivalent to 1.3-1.95 grams of protein per kilogram). Part of the high-level fistulas can have a nasogastric tube inserted into the distal part of the fistula intestine or perform jejunal fistula, or insert a tube through the fistula orifice and send it to the distal part of the fistula for tube feeding or element diet, until it can be taken by mouth.

　　First, treatment

　　The treatment principles for duodenal fistula are: ① As soon as possible to control intra-abdominal infection, effective drainage, prevent the formation of residual abscess; ② Correct dehydration, supplement electrolytes, maintain the stability of the internal environment of the body; ③ Select the best nutritional supplement method according to different stages; ④ Pay attention to the management of the fistula orifice, make it controllable, and promote spontaneous healing; ⑤ Pay attention to the monitoring of important organs and maintain their function; ⑥ For duodenal fistulas that cannot heal spontaneously, choose a favorable opportunity to perform surgical treatment.

　　1. Stage-by-stage treatment plan:The general treatment principle for duodenal fistula is stage-by-stage treatment, and to promote the cure of duodenal fistula at each stage; after the attempt of existing methods, if it still cannot heal spontaneously, and the abdominal adhesions are nearly relaxed, it is generally considered to perform elective definitive surgery, namely the excision of duodenal stump fistula, duodenal fistula repair, or gastrojejunal, duodenal jejunal anastomosis, 6 weeks to 3 months after the occurrence of the intestinal fistula, after the improvement of nutritional status and the control of abdominal infection.

　　It is worth mentioning that the treatment characteristics of intestinal external fistula are comprehensive treatment and stage-by-stage treatment of various methods. It is impossible to expect that one method or one drug can completely cure intestinal fistula. According to the different stages of duodenal external fistula and the complications that occur, the following treatment methods should be selected, and the treatment plan should be adjusted continuously, without sticking to a single treatment method.

　　2. Local fistula treatment:The quality of local fistula treatment can directly or indirectly affect the effectiveness of treatment. Good local fistula treatment can alleviate skin erosion and pain around the fistula; reduce the erosion and bleeding of surrounding tissues, and other complications;有利于控制感染；reduce the loss of intestinal fluid, and benefit the maintenance of homeostasis and the effect of nutritional supply. However, in daily treatment, this point is often overlooked, and it is still treated in the usual way, which not only requires a lot of nursing effort but also cannot achieve good results. Common local fistula treatment methods include:

　　(1) Double-lumen catheter negative pressure drainage: This is the most basic method of fistula treatment, which can timely drain the overflowed intestinal fluid to the outside. In the absence of factors affecting spontaneous healing, 60% to 70% of tubular fistulas can heal after effective drainage. If somatostatin and growth hormone can be used in a timely manner at different stages, the spontaneous healing rate of duodenal external fistulas can be further improved, and the healing time can be shortened.

　　(2) Hydraulic pressure, tube blocking, and bonding glue blocking: After negative pressure drainage, the fistula forms, and double-lumen catheter negative pressure drainage can continue to be used until the fistula heals or surgery is awaited. In some cases, to allow the patient to get out of bed and move around, reduce the workload of nursing care, and resume oral diet, external blocking methods such as hydraulic pressure, tube blocking, and bonding glue blocking can be adopted.

　　The hydraulic pressure method: Generally, a catheter with a diameter similar to that of the fistula is used, with the tip shaped flatly. It is inserted into the fistula, 1 to 1.5 cm from the intestinal wall fistula opening, and the tail end is connected to a sterile saline drip bottle. The bottle is 1.0 meter above the patient, and 1000 ml of isotonic saline is evenly dripped into the intestinal cavity every day without overflowing along the catheter. Due to the high water pressure of up to 1 meter, which exceeds the pressure within the intestinal cavity, the intestinal contents cannot overflow either. The granulation tissue around the fistula gradually grows and eventually heals, and if growth hormone is used at the same time, the fistula can usually heal on its own within about 3 weeks.

　　The tube blocking method: Its basic principle and method are similar to the hydraulic pressure method, but it uses a blind-end tube of the same diameter as the fistula, which is inserted into the fistula. The intestinal fluid cannot overflow, and the fistula gradually heals. The time is also about 3 weeks.

　　The bonding glue blockage: It is an a-cyanoacrylate butyl ester that solidifies rapidly upon contact with water. After being灌入the fistula, the glue forms a solid mass to block the fistula. While the fistula is healing, the glue will gradually be excreted on its own within 2 to 3 weeks. The bonding glue produces high temperatures during its coagulation, which has sterilizing effects and can stimulate the growth of granulation tissue, forming a cast-like coagulum that seals the fistula more tightly.

　　(3) Silicon Sheet Internal Blocking: After negative pressure drainage of the labial fistula, the intestinal mucosa and skin adhere together and cannot heal spontaneously. Since there is no fistula, methods such as water pressure, tube blocking, and adhesion cannot be used. However, the fistula orifice is exposed on the abdominal wall surface, and the method of silicon sheet internal blocking can be adopted. The silicon sheet is thicker in the center (2-3 mm) and very thin around (0.3-0.5 mm), with a diameter of 3.0-9.0 cm (or larger), a specially made circular sheet, rolled into a tube and inserted into the fistula, then allowed to spring up into a tube shape to tightly block the fistula orifice, so that no intestinal contents will leak out, or only a small amount of mucus may leak out. It is sufficient to change the dressing once a day. If the leakage is more, negative pressure aspiration can be added. Patients with good internal blocking effects can resume daily diet and be temporarily discharged to return to the hospital for surgical treatment after the condition improves. The application of this method has enabled many patients with labial fistulas to receive gastrointestinal nutritional support.

　　If it cannot be cured spontaneously after 2 to 3 months, surgery should be considered. There are corresponding treatment principles and stages of treatment at different times.

　　3. Stabilization of Condition and Management of Complications

　　(1) Correction of Homeostasis Imbalance: After the occurrence of duodenal external fistula, due to its high position, it is also mostly a high-flow fistula, which can quickly lead to homeostasis imbalance. Appropriate amounts of fluid and electrolytes should be supplemented via the vein in a timely manner according to the loss of intestinal juice. For those with high flow, the daily fluid requirement can be 7000 to 8000 ml or more, and the loss of intestinal juice alone can reach 5000 to 6000 ml. At this time, it is advisable to use central venous catheterization for fluid infusion, which can ensure the input of fluid and also input a large amount of electrolytes such as potassium chloride.

　　(2) Hemorrhage: Take effective hemostatic measures based on as much understanding as possible of the bleeding site and cause:

　　① Diversion and Inhibition of Intestinal Juice: The leakage of intestinal juice, especially trypsin, etc., which digests and corrodes the intestinal mucosa and surrounding tissues, is an important cause of bleeding. Therefore, inhibiting intestinal juice and diverting gastrointestinal, biliary, and pancreatic juices are one of the methods for preventing and treating intestinal fistula bleeding. A. Use a dripping double-lumen negative pressure suction tube (Li's tube) for active drainage of fluid; B. Administer somatostatin to inhibit the secretion of digestive juices, thereby reducing the drainage of digestive juices through the fistula.

　　② Surgical and Interventional Hemostasis: It is possible to perform reoperation for abdominal exploration and suture the bleeding points, or selective arterial embolization under X-ray fluoroscopy guidance.

　　③ Promoting Coagulation and Vascular Constriction: Systemic use of Ligezhi, local use of thrombin, norepinephrine solution irrigation, and alkalinization of gastric juice.

　　(3) Control of Infection: The early stage of infection associated with duodenal external fistula is mainly peritonitis, while in the middle and late stages, it is mainly abdominal abscess and infection of abdominal visceral organs, such as cellulitis and necrosis caused by duodenal posterior wall fistula, splenic abscess, pancreatic abscess, etc. Some patients develop intestinal fistula on the basis of abdominal infection. The coexistence of intestinal fistula and abdominal infection forms a vicious cycle. Therefore, proper management of abdominal infection is the key to improving the cure rate of patients with intestinal external fistula.

　　① Percutaneous abscess puncture and drainage (PAD): Abdominal infection complicated by intestinal fistula often exists in the form of abscess. PAD technology is the first-line measure for the treatment of abdominal abscess. The key point is to puncture the abscess percutaneously under the guidance of B-ultrasound, X-ray fluoroscopy, or CT, and after confirming the diagnosis, to place a tube for the drainage of pus. It is also possible to inject sterile normal saline through the tube to flush the abscess cavity. It can be used for subdiaphragmatic abscess, abscesses in various spaces of the abdomen, and abscesses in solid organs. PAD technology can cure single-chamber abscesses, and for multi-chamber abscesses, the cure rate can also reach 65％～90％ after repeated punctures at multiple sites. It can temporarily relieve the condition and improve organ function for patients with extremely poor general condition, creating an opportunity for further surgery.

　　② Repeated laparotomy and abdominal lavage: For patients with extremely extensive abdominal infection or unsatisfactory duodenal fistula after puncture and drainage of abscess, a repeat laparotomy is required. The operation removes the source of infection, clears necrotic tissue, and removes pus. During the operation, extensive abdominal lavage is also performed, and drainage tubes are placed after surgery for continuous negative pressure lavage and drainage.

　　In the past, it was believed that abdominal lavage would lead to the spread of infection, so abdominal lavage during surgery was opposed. Now it is believed that abdominal lavage for abdominal infection must be large and thorough. Large means that the amount of abdominal lavage fluid should reach 150-200ml/kg (body weight); thorough means that a wide-range lavage should be performed on all parts of the abdomen, including all potential spaces. After observing the benefits of abdominal lavage, some authors also advocate for multiple planned laparocentesis. However, this method has a significant impact on organ function, especially lung and renal function, and requires a high level of organ support. Due to repeated operations, the patient's catabolism continues, and nutritional support is also difficult to play a good role, so planned multiple laparocentesis is not suitable for widespread promotion and application.

　　Ren Jian'an and others have confirmed through animal experiments that abdominal lavage can significantly reduce the number of bacteria in the abdominal cavity, and has no significant effect on electrolytes. Clinical practice over the past 30 years has also confirmed that abdominal lavage supplemented with continuous negative pressure drainage after surgery is effective, and can usually achieve the purpose of clearing infection.

　　③ Open abdominal therapy: For extremely severe abdominal infections, where it is estimated that a single operation and subsequent drainage cannot resolve the infection, open abdominal therapy can also be used, also known as abdominal ostomy, such as severe pancreatitis or severe multiple injuries complicated by duodenal fistula and severe abdominal infection. Abdominal open therapy is also needed when abdominal compartment syndrome occurs due to increased abdominal pressure caused by severe abdominal infection.

　　The greatest benefit of open abdominal therapy is that it opens the abdominal cavity, relieves the pressure inside the abdomen, and is conducive to the prevention and treatment of respiratory and renal dysfunction. Since the abdomen is in an open state, it is also convenient to remove necrotic tissue at the bedside and to treat bleeding sites under direct vision. The drawback is that the secondary intestinal fistula and the later abdominal wall defect make the later reconstruction surgery very complex. The average waiting time for the final reconstruction surgery is more than 100 days, and the longest can reach more than 8 months. The implementation of this measure in clinical practice requires great caution.

　　To avoid the exposure of the intestinal tract after open therapy leading to external fistula and incisional hernia, temporary abdominal closure techniques can be used. This is to cover the open incision with artificial materials such as polyester fabric and polypropylene mesh while performing open therapy. This can achieve the effect of reducing intraperitoneal pressure and prevent the unrestricted expansion of the wound, preventing the occurrence of abdominal wall defects and external fistula. For patients with external fistula whose abdominal infection quickly subsides after open therapy, the peritoneum can also be temporarily closed for a short period (7-14 days) while ensuring unobstructed drainage, avoiding the shortcomings of continuous open therapy. The latter is also known as temporary open peritoneal therapy.

　　④ Paying attention to the site and method of drainage: Another reason for the persistent infection in patients with external fistula is that the site and method of drainage are not reasonable. Some patients can resolve the problem of abdominal infection simply by changing the method of drainage. It is necessary to emphasize the importance of drainage in patients with abdominal infection.

　　Chinese hospitals at all levels have a variety of drainage materials after abdominal surgery. However, after the occurrence of an external fistula, some drainage methods are insufficient. General rubber and silicone tubes are prone to blockage, causing poor drainage. The smoke tube drainage is difficult to achieve the purpose of drainage from the beginning, causing the accumulation of intestinal fluid and pus in the body, and aggravating the abdominal infection.

　　Li Jieshou and others have effectively treated the abdominal infection associated with an external fistula using a dripping negative pressure suction double tube. The principle is to change passive drainage to active drainage; from simple drainage to dripping flushing drainage, which can prevent the formation of a vacuum locally and the blockage of the catheter.

　　⑤ Rational use of antibiotics: The abdominal infection associated with an external fistula is related to insufficient drainage of residual infection, the use of broad-spectrum antibiotics, acquired infections in intensive care units, and intestinal flora displacement. Therefore, attention should also be paid to the rational use of antibiotics and immunomicroecological nutrition.

　　While treating abdominal infection with surgery, attention should be paid to the rational use of antibiotics. During the initial stage of infection, antibiotics can be empirically used based on the clinical characteristics of the infection, the nature of the pus, and past treatment medications, while conducting relevant body fluid bacterial culture and drug sensitivity tests. Subsequently, antibiotic use can be adjusted based on the treatment response and bacterial culture results. Regular statistical analysis of bacterial culture results should be performed for reference in empirical medication. Under the condition of effective drainage of the infection, there is no need to persistently administer antibiotics to avoid the development of bacterial resistance leading to secondary infection.

　　The abdominal infection associated with external fistula of the duodenum has both commonalities and individual characteristics compared to general abdominal infection. If the abdominal infection associated with an external fistula is not treated in a timely manner, it may be accompanied by complications such as hemorrhage and malnutrition, and it may form a vicious cycle. Removing the source of infection and treating the infection is the key to breaking this vicious cycle. Among various measures, surgical treatment is extremely critical. These infection management methods are also suitable for other severe abdominal infections.

　　4. Promote the spontaneous healing of duodenal fistula:Somatostatin was applied in the treatment of intestinal fistula in the mid-1980s. The Department of General Surgery of the General Hospital of the Nanjing Military Region also reported on it early on. In recent years, Ren Jian'an and others, based on many years of experience in treating intestinal fistula, creatively proposed the combined use of nutritional support, somatostatin, and growth hormone to promote the spontaneous healing of intestinal fistula, taking into account the pathophysiology of intestinal fistula and the characteristics of the action of growth hormone. They further applied growth hormone in various aspects of the treatment of intestinal fistula. After the occurrence of an intestinal fistula, due to the loss of a large amount of intestinal fluid, it can cause water, electrolyte, and acid-base disorders and circulatory failure; the loss of intestinal fluid also causes the gastrointestinal tract to lose the function of absorption, digestion, and nutrition, leading to malnutrition; or the contamination of the abdominal cavity by intestinal fluid can lead to severe abdominal infection and systemic infection, multiple organ dysfunction, or failure. Therefore, in the early stage of an intestinal fistula, while draining the intestinal fluid, the secretion of intestinal fluid should be suppressed to the maximum extent to reduce the loss and contamination of the abdominal cavity, which becomes the key to treatment. The application of somatostatin can achieve this goal.

　　The application of total parenteral nutrition (TPN) for the treatment of intestinal fistula began in the 1970s. Research results show that TPN has the effect of reducing gastrointestinal fluid secretion and improving the nutritional status of patients, which has improved the therapeutic effect of intestinal fistula and changed the treatment strategy. In 1985, somatostatin analogs (octreotide 0.3mg/d) were added on the basis of TPN, which had an additive effect with TPN, could promote the healing of tubular intestinal fistulas, shorten the treatment time of intestinal fistula, and was consistent with foreign literature reports. However, the powerful effect of octreotide (more than 7 days) gradually disappeared. Moreover, in the initial foreign literature reports, there were cases where the fistula healed, but the patients died due to abdominal infection. The General Hospital of the Nanjing Military Region made improvements, believing that controlling infection and correcting homeostasis imbalance is the primary treatment step for intestinal fistula. On the basis of draining the intestinal fluid and controlling infection, somatostatin (6mg/d) was added, and the treatment was successful. The spontaneous healing rate of 60 fistulas reached 78.3%, and there were no cases of infection exacerbation or death in patients.

　　In addition to reducing the amount of intestinal juice, somatostatin can also reduce portal blood flow, and it can be applied to patients with intestinal fistula and intra-abdominal hemorrhage, especially those with stress ulcers.

　　Growth hormone is a protein hormone secreted by the adenohypophysis, consisting of 191 amino acids and having a high specificity to the species. With the advancement of genetic engineering technology, recombinant human growth hormone has been successfully synthesized and officially approved for clinical use, and its role in promoting growth and anabolic metabolism has received increasing attention in clinical practice.

　　Growth hormone mainly exerts its effect through insulin-like growth factor 1 (IGF-1). IGF-1 mainly exists in the form of binding with IGF-binding proteins (IGFBPs). Six types of IGFBPs have been discovered, which are both carrier proteins for IGF-1 and important regulatory factors. Among them, IGFBP-1 is a blocking factor, and IGFBP-3 is an activating factor. Growth hormone mainly acts through the GH-IGF-IGFBPs pathway.

　　Patients with intestinal external fistulas are often in a state of stress due to surgery and infection, and they often need to address issues such as nutrition, wound healing, suppressed protein synthesis under hypermetabolic conditions, and excessive inflammatory reactions. Traditional nutritional support often cannot reverse this state, and people hope to change this abnormal metabolic state through metabolic support and metabolic regulation, reduce catabolism, promote synthesis, and achieve the goal of reducing injury and promoting body repair. Growth hormone can basically meet these requirements.

　　It has been noted that promoting the self-healing of patients with intestinal external fistulas through various treatment methods is the key to reducing complications and mortality, shortening hospital stay, and reducing treatment costs. As mentioned earlier, somatostatin can reduce the secretion of digestive juices and shorten the time for healing of intestinal external fistulas. Subsequently, protein-energy malnutrition has become an important factor affecting the self-healing of patients with intestinal external fistulas. In recent years, it has been found that recombinant human growth hormone and TPN can promote protein synthesis, counteract the catabolic response caused by trauma, preserve and even increase the total lean body mass (LBM), and enhance humoral and cellular immunity. Therefore, it is possible to achieve the suppression of intestinal fluid secretion, promotion of fistula tissue healing, by the sequential use of somatostatin and growth hormone and the combined application of nutritional support.

　　Therefore, some scholars have designed a program to promote the self-healing of intestinal external fistulas. The basis for the treatment plan is that in the early stage of fistula occurrence, by using drainage, total parenteral nutrition, and somatostatin (Stilamin 6mg/d), the secretion and leakage of intestinal fluid are reduced, infection is controlled, and the formation of tubular fistulas is promoted. Subsequently, growth hormone (Sizeng 8U/d) is used to improve protein synthesis and tissue proliferation, promote the shrinkage and closure of the fistula, and ultimately achieve the self-healing of the fistula.

　　The results showed that this method allows the majority of fistulas occurring in the early postoperative period to heal within one week, and for refractory intestinal external fistulas, self-healing can also occur within three weeks. This method not only rapidly promotes the self-healing of intestinal external fistulas but also makes it possible for the self-healing of multifocal and complex fistulas, such as biliary fistulas combined with duodenal external fistulas, and pancreatic fistulas combined with colonic fistulas. It also makes it possible for traditionally considered difficult-to-heal mucosal fistulas and colonic fistulas.

　　5. Surgical treatment:The surgical treatment for patients with duodenal external fistula can be divided into auxiliary surgery and definitive surgery. Auxiliary treatment surgeries such as laparotomy, drainage, and enterostomy can be performed at any time as needed. However, the timing of definitive surgeries such as repairs and resections for the elimination of fistulas depends on the control of peritoneal infection and the improvement of the patient's nutritional status. Generally, these surgeries are performed 3 to 6 months after the fistula occurs. Common surgical methods for duodenal external fistula include:

　　(1) Local wedge resection and suture: This is a commonly used method for the treatment of duodenal external fistula with satisfactory results. However, if no special measures are taken in the early stage after the occurrence of an intestinal fistula, and there is severe infection, the possibility of postoperative leakage is extremely high. In recent years, the application of fibrin glue (fibringlue) has reduced the occurrence of recurrence.

　　(2) Intestinal Loop Serosa Coverage Repair: The principle is to cover the surface of the defect in the injured bowel with the serosal surface of a healthy bowel and suture it in place. The surgical method is: first trim and suture the duodenal fistula, then lift a segment of the proximal jejunum loop, pass it through the incision in the transverse mesocolon, cover one side of the bowel wall of this loop over the sutured site of the duodenal fistula, and perform interrupted seromuscular layer sutures to fix it, which is conducive to the healing of the sutured site of the duodenal fistula. Then, perform a side-to-side anastomosis of the jejunum.

　　It is also possible to use the serosal covering technique of jejunal Y-type anastomosis. During the jejunal serosal covering operation, the bowel used as the covering must have its fat tissue cleared, making the supply blood vessels of the serosal surface clearly visible. The edges of the defect in the covered bowel must be fresh and may need to be trimmed and sutured in full thickness with interrupted sutures if necessary. Then, place the predetermined covering bowel on top and suture the seromuscular layer in a running suture for one week, with a stitch spacing of 3 to 4 mm. When suturing, the sutures must be a certain distance from the edge of the fistula to allow the sutures to pass through healthy, well-perfused duodenal wall tissue, which is conducive to the healing of the fistula.

　　(3) Pedicled Intestinal Seromuscular Layer Coverage Repair: The advantages of this technique are convenient material acquisition, simple construction, good blood supply, strong anti-infection and healing capacity, and the fact that the bowel at the fistula site does not need to be widely mobilized during surgery. Sites for material acquisition include the antrum of the stomach, segments of the large or small intestine, and the round ligament of the liver, among others. Specific operation methods: First, perform a limited dissection and trimming of the bowel at the fistula site, and suture the fistula. If suture is difficult or may lead to stenosis of the bowel lumen, partial suture can be performed. Then, cut a small segment (length depending on the size of the fistula) of pedicled intestinal tissue (jejunum or ileum) with retained mesenteric blood supply and immediately perform end-to-end anastomosis at both ends after cutting. On the opposite side of the mesenteric margin, longitudinally cut the wall of the cut intestinal tube, remove the mucosa, and then place this seromuscular patch on the duodenal fistula site and fix it with fine sutures. It is also possible to use a gastric seromuscular flap with the right gastroepiploic vascular pedicle to repair the duodenal defect. Regardless of the type of pedicled tissue flap used, it should be sufficiently large, with the edge being more than 0.6 cm wider than the duodenal fistula to prevent narrowing of the duodenal lumen when the tissue heals and contracts. Due to the convenience of making the pedicled tissue flap and the few complications associated with the surgery, it has gradually replaced the more complicated jejunal serosa covering repair.

　　(4) Roux-Y Anastomosis of Jejunum and Duodenum: In cases with severe large defects or fistulas in the duodenal wall, there may be twists, stricture, or obstruction in the distal duodenum or jejunum, which can cause high pressure inside the duodenal lumen. For such duodenal fistulas, conventional repair or dressing methods often cannot achieve ideal therapeutic effects. In such cases, Roux-Y anastomosis must be used to fully decompress and drain the duodenal lumen and achieve complete healing of the fistula. Specific operation methods: Incise the jejunum 25 to 30 cm from the Treitz ligament, suture the distal end of the jejunum, and elevate this segment of jejunum through the mesocolon incision, and perform a side-to-side anastomosis with the duodenal fistula. Then, an end-to-side anastomosis is made between the proximal and distal ends of the jejunum. The proximal jejunum loop should not be too long, with the anastomosis being tension-free.

　　(5) Intestinal bypass surgery.

　　The success of external fistula surgery depends not only on the selection of the timing and method of surgery, but also on the postoperative prevention of adhesive intestinal obstruction, abdominal infection, and postoperative nutritional support.

　　The abdominal cavity of external fistula patients has had infection, and there are extensive adhesions in the abdominal cavity. After surgery, there is a large range of pollution and adhesion separation in the abdominal cavity, and the possibility of postoperative adhesive intestinal obstruction and abdominal infection is very high, which are two reasons for the recurrence of fistula after external fistula surgery. At the end of the external fistula surgery, additional enteropexy can be performed to prevent postoperative intestinal obstruction. After the Nobel's operation, there is a gap between the mesentery, which may cause intermesenteric infection. At the same time, after suture and arrangement, the intestine may form a sharp angle at the turn, causing intestinal obstruction. The intestinal intubation arrangement (White method) can avoid these shortcomings. Some scholars believe that inserting an arrangement tube from the residual end of the excised appendix or ileocecal ostomy in reverse can avoid the discomfort symptoms after high-position jejunal ostomy tube insertion and is conducive to the removal of the tube. After observing more than 300 cases, there is no phenomenon of the arrangement tube retreating with peristalsis.

　　At the end of the operation, rinsing the abdominal cavity with a large amount of isotonic saline (150ml/kg) can reduce the number of bacteria in the abdominal lavage fluid to less than 10-100/ml, and then according to the degree and location of abdominal contamination, double套negative pressure drainage tubes are placed. Postoperative drainage for 3-4 days can prevent the occurrence of postoperative abdominal infection.

　　The scope of external fistula surgery is wide, and the trauma is great, and the recovery of intestinal function after surgery requires a long time. Therefore, external nutritional support should still be given for a period of time after surgery until the patient can recover oral diet, which is conducive to the patient's recovery.

　　6. Nutritional support

　　(1) Analysis of nutritional status and selection of nutritional support methods: Nutritional status analysis and nutritional support run through the entire process of duodenal fistula treatment, and have a decisive impact on the treatment of duodenal external fistula. Once diagnosed with a duodenal external fistula, it should be considered to stop eating and prepare for nutritional support.

　　①Analysis of nutritional status: A systematic analysis of the patient's nutritional status should be conducted before nutritional support. Due to the occurrence of fistula in trauma, major surgery, postoperative severe pancreatitis, and postoperative inflammatory bowel disease, patients often have malnutrition or deficiencies in certain nutrients such as phosphorus and zinc. Monitoring of indicators such as body weight, triceps skinfold thickness, and visceral protein should be carried out, and it is also possible to monitor special indicators such as trace elements and energy metabolism. The purpose of nutritional analysis has two points: A. Identify whether the patient has energy-protein malnutrition and/or specific nutrient deficiencies, or has potential risks. B. Observe whether the subsequent nutritional support therapy is reasonable.

　　②Nutritional support methods: Should be determined by the type of external fistula and the treatment requirements at each stage of the external fistula. Due to the long course and high cost of external fistula patients, it is as much as possible to choose enteral nutritional support. However, in the early stage of the occurrence of external fistula and in patients with external fistula complicated with severe abdominal infection, total parenteral nutrition is often adopted. Enteral nutritional support can be carried out in a timely manner when the infection is effectively drained and intestinal function is restored.

　　For patients with intestinal fistula who are expected to self-heal without surgery, general enteral nutritional support should be adopted. Certain special types of parenteral fistula can also achieve self-healing of the fistula through the implementation of enteral nutrition. For patients with intestinal fistula who require definitive surgery, enteral nutritional support should be adopted as much as possible for a period of time before surgery. Long-term enteral nutritional support can also improve intestinal blood supply, increase the thickness of the small intestinal wall, reduce peritoneal adhesions, and the latter's effect may be related to the promotion of intestinal peristalsis by enteral nutrition. For duodenal fistula, enteral nutrition can be implemented early by performing a jejunostomy at the distal end of the fistula.

　　(2) Parenteral nutritional support: In the early stage of duodenal fistula and when combined with severe peritoneal infection, total parenteral nutrition is often the only nutritional support method. It is the application of total parenteral nutrition that has greatly improved the self-healing rate and survival rate of intestinal fistula. Due to the fact that patients with intestinal fistula often have stress from trauma and infection, attention must be paid to the total amount and supply ratio of nutrients. It is best to actually measure the energy consumption of patients with intestinal fistula, such as resting energy expenditure and substrate oxidation rate, and supply non-protein calories according to 1.1 to 1.2 times the REE, and supply protein according to 1.5 to 2.5 g/(kg·d). Or supply carbohydrates, fats, and proteins according to 1.2 to 1.3 times the REE and substrate oxidation rate. For patients with intestinal fistula who cannot be measured in actual practice, non-protein calories can be supplied according to 104.6 to 125.52 kJ/(kg·d), and the sugar-fat ratio can be 6:4 to 4:6. For patients with high stress and insulin resistance, the proportion of fat energy supply should be appropriately increased. The protein supply amount can be 1.0 to 1.5 g/(kg·d).

　　For patients with long-term fasting and severe stress, glutamine should also be provided to provide energy for the intestinal mucosa, skeletal muscle, and immune cells. Since glutamine is more easily decomposed under high temperature and pressure, it is difficult to use glutamine in its completely free form in clinical practice. Glutamine can be provided using pyroglutamic acid or diamide. Considering that short-chain fatty acids are the main energy substances for the colonic mucosa and can promote the proliferation of colonic mucosa, there are literature reports on adding short-chain fatty acids to parenteral nutrition. However, implementing long-term total parenteral nutrition in patients with intestinal fistula is quite challenging. The first challenge is repeated infection complications, mainly catheter infections, followed by cholestasis and liver function damage, and thirdly, various metabolic complications. Especially the first two often make it impossible to continue total parenteral nutritional support.

　　With the understanding of the pathophysiology of intestinal fistula patients and the introduction of various enteral nutritional products, parenteral nutrition is no longer the only nutritional support method for intestinal fistula patients. Some types of patients with parenteral fistula can achieve self-healing when receiving enteral nutrition, and a certain period of enteral nutritional support also creates good conditions for further surgery.

　　(3) Enteral nutritional support: A large number of animal experiments have proven that enteral nutritional support can promote the proliferation of intestinal mucosa, improve the immune status of the intestines, enhance the intestinal barrier, prevent the translocation of intestinal flora, and reduce the incidence of systemic infections in critically ill patients. The tissue-specific nutritional factors, intraluminal nutrition, and microbiota nutrition recently proposed are all in line with the importance of enteral nutrition.

　　The products of enteral nutrition include elemental diet, short peptide, whole molecule pattern, and homogenized diet. For patients who have completely lost digestive fluids, pure monomer forms of elemental diet can be given to achieve the purpose of absorption without digestion. However, some literature also proposes that elemental diet can only meet nutritional needs and is difficult to achieve the purpose of improving the intestinal mucosal barrier and preventing bacterial translocation. Therefore, it is recommended to use short peptide and whole molecule pattern enteral nutrition, especially enteral nutrition fluids containing dietary fiber, as much as possible.

　　Before implementing enteral nutrition, fistula contrast and gastrointestinal barium meal examination should be performed to understand the position of the fistula and whether the gastrointestinal tract is unobstructed. When there is no intestinal obstruction, the fistula can be temporarily sealed by various methods, such as patching, hydrostatic pressure, and adhesive plugs, to restore the continuity of the intestine. After the continuity of the intestine is restored, enteral nutrition support can be implemented through a nasogastric tube. Currently, for most duodenal fistulas, enteral nutrition can be implemented by placing the gastrointestinal tube beyond the fistula with the assistance of gastroscopy. For duodenal stump fistulas, the gastric tube can be changed to be placed in the jejunal output loop to implement enteral nutrition support.

　　If the patient requires long-term nutritional support or the aforementioned methods cannot implement enteral nutrition, it is possible to perform a jejunal ostomy at a site distant from the fistula. The preferred method for jejunal ostomy is the standard Witzel jejunal ostomy or percutaneous jejunal ostomy, which is safe and effective and saves time and effort. In recent years, there have been many reports on the use of percutaneous endoscopic gastrostomy and percutaneous endoscopic jejunostomy, which are worth trying if conditions permit. For tubular fistulas, such patients can often heal spontaneously during enteral nutrition. If it is not possible to temporarily close the fistula, it is also possible to collect intestinal fluid and enteral nutrition fluid together from the proximal end and return them through the distal end. If the proximal end is unobstructed and there are no contraindications, nutritional fluids can also be administered nasally, and then the nutritional digestive fluids collected from the proximal fistula can be returned through the distal end, which is a very labor-intensive method. Generally, gravity infusion can be used to infuse nutritional fluids, and infusion pumps can be used when the nutritional fluid is thick or the infusion rate needs to be controlled.

　　In fact, it is very difficult to provide long-term and effective parenteral nutrition support for patients with extraintestinal fistulas, and it also costs a lot. It is also not easy to carry out complete enteral nutrition support, which is often limited by the motility, digestion, and absorption functions of the small intestine. Conditions for carrying out enteral nutrition support can be actively created according to the methods provided above, and appropriate enteral nutrition products can be selected for enteral nutrition support. When enteral nutrition support cannot meet the patient's energy and protein needs, non-protein calories and protein to be supplemented can be provided through peripheral routes. This not only meets the patient's nutritional needs but also overcomes the respective deficiencies of parenteral and enteral nutrition support. Literature reviews have analyzed clinical nutritional support in the past 10 years and believe that due to the current understanding and vigorous promotion of enteral nutrition, there is concern about insufficient nutrient supply when only enteral nutrition support is used for critically ill patients. Therefore, it is advocated that enteral plus parenteral nutritional support models may be the main mode of nutritional support for patients with extraintestinal fistulas in the coming period.

　　(5) Microecological immunonutrition: For patients with duodenal fistula complicated with severe infection, the concept of immunomicroecological nutrition can be applied during nutritional support to achieve the dual purpose of improving nutritional status and controlling infection. Studies have shown that the large colonization of intestinal bacteria is related to the bacterial culture results of abdominal infection in patients with intestinal fistula. Absence of gastrointestinal drainage of abscess cavities is the main cause of multiple organ failure. The barrier function of the gastrointestinal tract includes: ① Intracavitary barrier: which includes: A. Barrier formed by chemical substances, such as gastric acid, pepsin, bile salts, lactoferrin, lysosomes. B. Barrier formed by mechanical factors, such as movement and mucus. C. Barrier formed by products of normal flora. ② Intestinal mucosal epithelial barrier. ③ Immune barrier: IgA, GAIT, Kupffer cells. ④ Normal flora barrier. In critically ill patients, these barrier functions are damaged to varying degrees, and bacteria can be translocated from the gastrointestinal tract to the blood.

　　Therefore, it is necessary to improve dysbiosis through enteral nutrition, especially through the method of microecological immunonutrition. By means of immunonutrition, such as glutamine and arginine, improve the immune barrier of the intestines and the body's immune function. It should also provide specific energy substances for the colonic mucosa, such as short-chain fatty acids or dietary fiber. Normal bacteria, such as lactobacillus, can be provided when necessary, through microecological nutrition to improve the barrier function of the colon, reduce or eliminate the occurrence of intestinal flora translocation.

　　II. Prognosis

　　Once duodenal fistula occurs, it can cause bleeding, infection, imbalance of internal homeostasis, malnutrition, and multi-organ failure, with a very high mortality rate.