Pancreatic fistula is a common complication of pancreatic surgery that has not been eradicated to date, nor has a fully accepted standard and management been achieved, for which discussion is still necessary. Traditional concept and classification of pancreatic fistula Broadly speaking, pancreatic fistula refers to the communication of pancreatic fluid with the outside world through a non-physiological route after rupture of the pancreatic duct, usually due to pancreatic inflammation, injury (such as trauma, pancreatic surgery or medically induced injury to the pancreas). Kirschner’s Surgery defines a pancreatic fistula as a rupture of the pancreatic duct from various causes and leakage of pancreatic fluid from the pancreatic duct for more than 7 days. The most clinically relevant is the postoperative pancreatic fistula caused by various pancreatic surgeries. Pancreatic fistulas can be divided into various types: for example, according to the route of pancreatic fluid outflow: external and internal pancreatic fistulas. According to the composition of the drainage fluid: simple (pancreatic fluid) and mixed (pancreatic fluid, bile, intestinal fluid, etc.). According to the amount of pancreatic fluid leakage: divided into high-flow fistula and low-flow fistula. According to the time of occurrence of pancreatic fistula: early fistula (within one week after surgery) and late fistula (more than one week after surgery). In addition, special types of pancreatic fistulas are: pancreatic pseudocysts (pancreatic fluid flows into the abdominal cavity and is encapsulated by surrounding organs and fibrous tissue, which is essentially an intrapancreatic fistula), pancreatic duct venous fistulas and pancreatic duct portal fistulas (small pancreatic ducts communicating with veins can produce persistent hyperamylasemia). Modern definition of pancreatic fistula Although pancreatic surgery techniques are becoming more sophisticated and the associated mortality rate has decreased to less than 5%, postoperative complications can still be as high as 30%-50%. Among them, pancreatic fistula is the most common complication and the initiating factor of the “triad” of postoperative pancreatic surgery (pancreatic fistula, abdominal infection and hemorrhage), which can cause death in severe cases. The Institute of Pancreatic Diseases, Fudan University, combined with the clinical exploration of a large number of pancreatic surgery cases (>200 cases/year), believes that the diagnosis of pancreatic fistula should take into account the following three factors: 1. the time point of postoperative amylase detection of drainage fluid, it is recommended to detect postoperative d1, d3, d5 and d7, and observe the development trend. d3 postoperative amylase value as one of the diagnostic criteria stipulated by ISGPF is questionable. Elevated amylase values within 3 days after surgery are mostly caused by leakage from the pancreatic section, peritoneal injury or leakage from the staple eye, which usually closes on its own 3-5 d after surgery. The real pancreatic fistula is caused by leakage of pancreatic fluid from the main pancreatic duct through the anastomotic fissure (including tearing of the pancreatic tissue, tearing of the pancreatic-enteric anastomosis, poor healing of the anastomosis due to excessive pancreatic-enteric anastomotic gap, local bleeding inflammation, etc.), and often this type of fistula will last for a long time. According to our experience, postoperative d5 drainage fluid amylase has decreased to normal values in most patients, so we suggest using postoperative d5 drainage fluid amylase values as the time point for judging the criteria. 2. Drainage flow: we suggest using >50ml/d as the standard. Pancreatic surgery is traumatic and extensive, especially for those with extensive posterior peritoneal lymph node dissection, postoperative trauma exudate will naturally increase, so the standard of 10ml/d of drainage fluid is obviously too low. In our clinical practice, we found that the amount of drainage fluid on the 5th postoperative day has generally decreased to below 50ml/d, so it is more appropriate to take >50ml/d5. 3, amylase value: According to our recent clinical study, on the 5th day after surgery, most patients’ drainage fluid amylase has dropped to less than 3 times the blood value. Therefore, it is more appropriate for the amylase value to exceed 3 times the upper limit of the plasma amylase value. Since the amylase value decreases when the amylase is diluted when there is more exudate, or the amylase value increases due to the concentration of the drainage fluid, to compensate for this, we suggest that the total amylase value of the drainage fluid on postoperative day 5 should be used as a criterion for determining pancreatic fistula (Td5=V×C, that is, the total amylase value d5=drainage volume L×amylase value IU/L, which should be within a relatively constant interval). This pancreatic fistula criterion takes into account three factors: amylase value, drainage volume and drainage time. Information on related studies will be presented separately. Risk factors for pancreatic fistula There are many studies on the risk factors for pancreatic fistula, which are summarized in the following aspects. Individual patient factors: such as age, jaundice, nutritional status of the body, hypoproteinemia, co-morbidities (such as diabetes), etc. Pancreatic factors: texture of the pancreas (high incidence of pancreatic fistula in “soft pancreas”), location of the pancreatic section (poor blood supply within the left 2 cm of the neck of the pancreas), pathological type of the pancreas, diameter of the main pancreatic duct (high incidence of pancreatic fistula <3 mm), etc. Operative-related factors Operators' experience and technique are the most important human factors causing pancreatic fistula: such as technical defects in pancreatic-intestinal anastomosis, too close or too sparse sutures, rough treatment of the wound surface, poor hemostasis, excessive use of electrocautery, improper selection of sutures; residual hooks, improper treatment of the main pancreatic duct after distal pancreatectomy, or omission of stenosis or obstruction at the proximal end of the main pancreatic duct; improper disposal of the distance between the pancreatic-intestinal and biliary-intestinal anastomoses (too close with tension, which can lead to anastomotic avulsion during intestinal peristalsis). In fact, the experience of the surgeon directly affects the incidence of pancreatic fistula, and some studies have reported a significant reduction in the incidence of pancreatic fistula in experienced medical centers (>20 pancreatic surgeries/year). In view of this, the Shanghai Municipal Health Bureau commissioned the Municipal Medical Association to organize an accreditation meeting for pancreatic surgery qualification, and established that only units with >20 cases/year of pancreaticoduodenectomy in the calendar year can be qualified for pancreatic surgery according to the surgical grading management system. Prevention of postoperative pancreatic fistula 1. improve the patient’s systemic status including preoperative correction of hypoproteinemia, improvement of liver and kidney function, effective yellowing reduction, control of acute inflammation, and postoperative strengthening of nutritional support. For the prevention and treatment of pancreatic fistula, the current research is more focused on intraoperative management and improvement of surgical techniques. Pancreatic-jejunal anastomosis: There are various anastomoses for pancreatic-jejunal anastomosis, but there is a lack of prospective randomized comparative studies. Clinical meta-analyses have concluded that no one anastomosis is yet significantly superior to the others. In recent years, we have made a series of improvements and explorations on the technique of pancreatic-jejunal anastomosis, from the initial “stump closure type pancreatic-jejunal telangiectomy” to “stump closure type embedded pancreatic-jejunal anastomosis”, and recently, we have pioneered another new type of anastomosis. Recently, we have pioneered another new type of anastomosis, namely “pancreatic-jejunal anastomosis with artificial papilla implantation of pancreatic stump”, which has achieved obvious clinical results. This technique is easy to operate, easy to master the suturing technique, eliminates stump bleeding, and basically eliminates the occurrence of pancreatic fistula. The specific method will be described separately. Pancreaticogastric anastomosis: It was first used clinically by Waugh and Clagett in 1946, but the results of a randomized controlled trial showed no significant difference in the incidence of pancreatic fistula compared with the classic pancreatic-enteric anastomosis. In some patients, pancreaticogastric anastomosis can be used as an alternative and complementary to pancreaticojejunostomy. Regarding intraoperative pancreatic drainage, there are advantages and disadvantages of external or internal drainage. Although external drainage reduces the incidence of pancreatic fistula, it affects the patient’s digestive function due to the loss of pancreatic fluid. Although internal drainage has no loss of pancreatic fluid, there is a risk of pancreatic fistula, which can occur due to blockage of the duct, dislodgement of the stent into the bile duct, and reverse into the distal end of the pancreatic conduction and the corresponding symptoms. The use of growth inhibitors Growth inhibitors have a powerful inhibitory function on the endocrine and exocrine functions of the pancreas, and were once considered effective in reducing the secretion of pancreatic fluid and the incidence of pancreatic fistula, and were once widely used. However, some randomized clinical trials in recent years have shown that perioperative growth inhibitor use can neither reduce the incidence of pancreatic fistula nor reduce operative mortality, but can reduce the biochemical detection index of pancreatic fistula and reduce the severity of postoperative related complications. Therefore, the role of growth inhibitors in the prevention and treatment of pancreatic fistula is still controversial and more clinical evidence-based studies are needed. In our opinion, the use of growth inhibitors early after surgery can benefit patients by effectively reducing postoperative pancreatic fluid leakage, but it should be noted that once a pancreatic fistula is formed, it should not be overly dependent on growth inhibitors for management. Management of pancreatic fistula The amount, character and amylase value of drainage fluid should be routinely monitored after pancreatic resection. It was found that drainage fluid amylase >5000 U/L on the first postoperative day is at high risk of pancreatic fistula. Close observation of postoperative clinical symptoms such as fever, abdominal pain and distention, and impaired gastric emptying should be performed. In suspicious patients, imaging examinations (ultrasound, CT, etc.) are feasible. Treatment of drainage tube: It is advisable to choose a drainage tube with good histocompatibility and moderate texture for easy replacement. The tube should be placed close to the anastomosis, placed smoothly, fixed exactly, and with moderate negative pressure. Compression of adjacent organs (blood vessels, intestinal tubes) should be avoided. When withdrawing the tube, the method of rotation and gradual withdrawal can be used. There is no standard plan for the management of pancreatic fistula, and it should be considered according to the different stages of pancreatic fistula, the patient’s general condition and the experience of the operator. The main principles of management include: maintaining water, electrolyte and acid-base balance; adequate drainage and regular flushing if necessary; preventing infection and secondary bleeding; enhancing nutritional support; using acid- and enzyme-suppressing drugs appropriately; and preventing other possible complications. The majority of pancreatic fistulas can be cured by non-surgical treatment. For example, patients with ISGPF clinical grade A and B can be cured by conservative management with a cure rate of >85%. In recent years, with the widespread use of endoscopic technology, the treatment of pancreatic fistula through endoscopy has begun to receive attention, such as endoscopic placement of pancreatic duct stent to promote the healing of pancreatic fistula by decompression.