The principles of treatment for patients with severe pancreatitis have changed over the past 50 years, but the complication of extra-intestinal fistula has not been eliminated. The site and timing of the complication of extra-intestinal fistula also vary after treatment according to different principles. Even the current principle of non-surgical treatment followed by surgical management has not reduced the occurrence of extra-intestinal fistula. The literature on the diagnosis and treatment of severe pancreatitis combined with extra-intestinal fistula is scarce. In this regard, the authors present their experience according to the practice of treating severe pancreatitis combined with parenteral fistula in recent years. 1, prevention and treatment of duodenal fistula The causes of severe pancreatitis complicated by duodenal fistula include the following: necrosis of the head of the pancreas and surrounding tissues, open abdominal therapy, early surgical exploration, bile duct incision and exploration of the formation of a pair of penetrating injuries. Open laparotomy, also known as laparotomy pouch therapy, was very popular in China in the early years and is still used in some hospitals at home and abroad to treat severe pancreatitis with severe abdominal infection. However, after the abdominal cavity is opened, the exposed part is mostly the duodenum. If the abdominal cavity is not closed in time, duodenal fistulas in different locations will eventually occur. In patients with severe biliary pancreatitis, the common bile duct often needs to be opened for exploration in order to release the biliary obstruction. Due to inflammatory edema or stone obstruction at the lower end of the common bile duct, it is difficult to complete the exploration successfully. If a bile duct probe is forcibly used to explore the lower end of the common bile duct, due to excessive force, after the bile duct probe passes through the sphincter of Oddi, it still has a certain impulse, and the probe can continue to move forward and injure the intestinal wall corresponding to the sphincter of Oddi, that is, the intestinal canal at the junction of the descending and horizontal part of the duodenum. This injury is mostly instantaneous and is not easily detected by the surgeon, or if it is not treated correctly, an external duodenal fistula can occur after surgery. For severe pancreatitis where duodenal fistula may occur, intraoperative prophylaxis includes gastrostomy and double jejunostomy. A double jejunostomy is a retrograde upward jejunostomy made 15 cm below the flexural ligament of the jejunum, with the tip of the catheter in the duodenum to drain bile, pancreatic and gastric fluids; another jejunostomy is made about 15 cm distal to this jejunostomy, with the tip of the catheter pointing to the distal jejunum, for the purpose of postoperative enteral nutrition to address the long-term nutritional support of these patients. When a duodenal fistula is suspected, the occurrence and location of the fistula can be determined by transdrainage imaging, oral contrast and melanoma[1] . Once a duodenal fistula is identified, drainage should be improved promptly. If necessary, surgery can be performed to improve drainage to prevent the occurrence and aggravation of bleeding and abdominal infection. A gastrostomy and a double jejunostomy are also performed. It is not necessary to repair the fistula urgently, but the use of growth inhibitor (Stanozolol) to reduce the secretion of intestinal fluids after the above measures will help the duodenal fistula to heal on its own[2] . If the drainage is clear, no additional surgical drainage is required. To enhance nutritional support, total parenteral nutritional support can be administered in the early stages of duodenal fistula. After intestinal function is restored, a gastric tube can be placed in the fistula with the aid of a gastroscope so that the tip of the tube is located in the upper jejunum. The implementation of enteral nutrition through this tube can solve the problem of long-term nutritional support without aggravating the leakage of intestinal fluid through the fistula. The prevention and treatment of high jejunal fistula is very similar to the principle of duodenal fistula, as necrosis and drainage of the pancreas and surrounding tissues, open therapy surgery can be complicated by jejunal fistula, especially high jejunal fistula. In addition, jejunostomy failure resulting in jejunostomy fistula is not uncommon. For severe pancreatitis after drainage, whether forced or purposeful opening of the abdominal cavity, attempts should be made to close the abdominal cavity in a timely manner after the symptoms of infection are controlled. If the abdominal cavity cannot be closed for a short period of time, various artificial materials (such as taping) should be used to temporarily close the abdominal cavity to avoid prolonged exposure of the intestinal canal, which may lead to intestinal fistula. Another measure that needs attention is the use of the correct jejunostomy method, i.e., Witzel jejunostomy, which ensures purse-string suturing, tunnel encapsulation, and abdominal wall lifting. The best material for a jejunostomy is a 12 to 14 gauge rubber catheter, not a thicker latex or silicone tube. If the jejunostomy occurs early and abdominal adhesions are not formed, early definitive surgery is feasible along with early drainage surgery[3] . If the patient has a severe abdominal infection, the fistula has occurred for a certain period of time, and the abdominal adhesions are extensive, drainage surgery alone can be performed to promote self-healing first. If self-healing is not possible, intestinal fistula and intestinal anastomosis can be performed after the adhesions are released and the abdominal infection is eliminated. The prevention and treatment of colonic fistulae The main colonic fistulae combined with severe pancreatitis are colonic splenic flexure fistulae (with necrosis of the tail of the pancreas) and transverse colonic or hepatic flexure fistulae (with necrosis of the head and body of the pancreas). The cause of colonic fistula may be related to the digestion of the colon by activated pancreatic enzymes. When drainage surgery is performed for severe pancreatitis, the thinness of the colonic wall is often seen, and the lesions are especially evident where pancreatic fluid accumulates. In recent years, early non-surgical treatment of severe pancreatitis has become more common. Accordingly, the proportion of colonic fistulas is also on the rise. This is related to the accumulation of fluid in the abdominal cavity can not be drained in a timely manner. Another reason for severe pancreatitis combined with colonic fistula may be related to necrosis of the colonic mesenteric vessels due to inflammatory embolism. Therefore, a large amount of peritoneal fluid in the early stage of severe pancreatitis should be drained, such as multi-site puncture drainage. For patients with clear and abdominal infection, the infected necrotic tissue should be cleared promptly to avoid digestion of the surrounding tissues by pancreatic enzymes and further spread of infection. Patients with severe pancreatitis combined with colonic fistulas are difficult to heal on their own, and generally require surgical treatment. The specific treatment plan has two: one is the principle of drainage, waiting, and then surgery; the second is the principle of second-stage surgery. For patients with colonic fistula who have been drained or have no serious abdominal infection, the first method is mostly used. In other words, total parenteral nutritional support should be provided at an early stage while ensuring the patency of drainage, and later on, feeding or enteral nutrition can be resumed by the method of “eating while leaking”[4] . When the infection is controlled, the inflammation subsides, and the nutritional status improves, usually after 3 months, definitive surgery is feasible. The diseased intestinal canal is removed and an intestinal anastomosis is performed. For patients with severe abdominal infection, poor drainage, and fistulae deep in the abdominal cavity without the tendency to form a tubular fistula or labyrinthine fistula (intraluminal fistula), second-stage surgery is feasible. The proximal end of the fistula is dragged out of the stoma, the intestinal tube of the fistula is removed or temporarily left open, and the abdominal cavity is drained. After surgery, the infection can be quickly controlled and enteral nutrition can be restored in time. When the situation improves later, the definitive surgery will be performed again. The most important feature of this method is that it can remove the source of infection in time, control the symptoms of infection, and save money [5]. Severe pancreatitis complicated by parenteral fistula is inevitable for the development of the disease, and is also related to the limitations of the local treatment technology at that time, and the occurrence of surgical malpractice is rare after all. Surgeons should be familiar with the rules of the evolution of severe pancreatitis and take preventive measures in time to minimize the incidence of this complication. They should also communicate with the patient’s family in a timely manner in order to have appropriate psychological expectations and tolerance for this complication and to reduce unnecessary misunderstandings and disputes.