Pancreatic pseudocyst

　　First, etiology

　　1. Howord and Jorden's classification method This is the most commonly used classification method before, which divides pseudocysts into 5 types, mainly post-inflammatory and post-traumatic pseudocysts, other types are relatively rare.

　　(1) Pseudocyst after inflammation: including acute and chronic pancreatitis. accounting for about 80%, the most common being alcoholic pancreatitis; followed by cholelithiasis, which is most common in China; other causes such as hyperlipidemia, etc.

　　(2) Pseudocyst after trauma: accounting for about 10%, including blunt trauma, penetrating trauma, and surgery.

　　(3) Idiopathic or of unknown cause.

　　(4) Pseudocyst caused by tumor: Caused by obstruction of the pancreatic duct leading to pancreatitis.

　　(5) Parasitic pseudocyst: Such as ascaris and hydatid cysts, caused by parasites leading to local necrosis of the pancreas and forming cysts.

　　2. Acute and chronic classification divides pseudocysts into acute and chronic types, which is helpful in selecting treatment options.

　　(1) Acute pseudocyst: Caused by acute pancreatitis or pancreatic trauma, leading to accumulation of pancreatic juice or exudate, encapsulated by adjacent serosa, mesentery, and peritoneum, etc. The cyst fluid is easily absorbed in the early stage, but becomes difficult to absorb as the cyst wall thickens and becomes fibrotic.

　　(2) Chronic pseudocyst: Occurring after chronic pancreatitis without acute exacerbation of pancreatitis. Caused by obstruction of larger pancreatic ducts leading to dilation of small pancreatic ducts or acinar cells, atrophy of epithelial cells, forming a 'retention' cyst, which gradually increases in size, may exceed the range of the pancreas, and also forms a relatively thick cyst wall, making it difficult for the cyst fluid to be absorbed.

　　However, some people believe that cysts formed after the onset of acute pancreatitis are acute if they are less than 6 weeks old, and chronic if they are more than 6 weeks old.

　　3. Yeo and Sarr's classification Recent clinical research has found that even if the etiology of pseudocysts is the same, the effects of treatment and prognosis reported by different parties are very different. This is mainly due to the difference in pathological types. The traditional concept of pseudocysts is relatively general, and doctors do not distinguish whether the cyst communicates with the pancreatic duct and whether there is necrotic tissue inside the cyst during treatment. Moreover, a large part of the fluid accumulation around the pancreas in acute pancreatitis is also treated as pseudocysts, resulting in different outcomes. Yeo and Sarr propose a classification method based on these issues, which helps to select treatment plans, compare efficacy, and judge prognosis.

　　(1) Pancreatic true-pseudocyst: It refers to cysts formed by the extrusion of pancreatic juice from the rupture of the pancreatic duct due to various reasons. The cyst communicates with the pancreatic duct, and the concentration of pancreatic enzymes and zymogens in the cyst fluid increases.

　　(2) Pancreatic pseudo-pseudocyst: It is caused by inflammatory exudate accumulation due to pancreatic or peripancreatic inflammation and trauma. The cyst does not communicate with the pancreatic duct, and the concentration of pancreatic enzymes and zymogens in the cyst fluid does not increase, and it does not contain necrotic tissue.

　　(3) Pancreatic necrotic cyst (pancreatic haemorrhagic cyst): It is a local cystic change and exudate accumulation after necrosis of the pancreas and peripancreatic tissue due to necrotizing pancreatitis. The cyst contains necrotic pancreas tissue or peripancreatic retroperitoneal fat, which may or may not communicate with the pancreatic duct. The concentration of pancreatic enzymes or zymogens in the cyst fluid may increase or not increase.

　　Second, Pathogenesis

　　In the past, pseudopancreatic pseudocysts were considered as a single cyst and were treated with traditional expectant strategies. With the in-depth study of the occurrence, development, and pathological changes of acute and chronic pseudopancreatic pseudocysts, there have been updates in the principles of treatment.

　　Pancreatic juice containing various digestive enzymes leaks from the necrotic pancreatic tissue to the retroperitoneal space behind the pancreas, causing inflammatory reactions and fibrin deposition. After one to several weeks, a fibrous capsule is formed, and the posterior peritoneum constitutes the anterior wall of the cyst. Alternatively, pancreatic juice can directly seep into the lesser omentum, and the Winslow hole is often sealed due to inflammation, forming a cyst within the lesser omentum. Sometimes, pancreatic juice can enter other parts along the tissue spaces to form cysts in special locations, such as pseudopancreatic cysts in the mediastinum, spleen, kidney, and inguinal region.

　　1. Pseudopancreatic cysts are about 80% solitary, often communicating with the pancreatic duct, and the pancreatic duct can be visualized when contrast medium is injected into the cyst. The cyst fluid contains pancreatic digestive enzymes such as amylase, esterase, protease, chymotrypsin, decarboxylase, and albumin, mucin, cholesterol, inflammatory debris, and sometimes blood. The secretory pressure in the pancreatic duct does not exceed 2.94 kPa (30 cmH2O), and the secretion of pancreatic juice stops when the intracystic pressure is too high. However, due to the high protein content in the cyst fluid, water continuously infiltrates, and the cyst can gradually enlarge. Pseudopancreatic cysts are more common in the body and tail, with a large variation in size, from a small diameter of 4-5 cm to a large one containing thousands of milliliters of fluid. In cysts with a long duration, the activity of pancreatic enzymes in the cyst fluid often disappears.

　　2. Acute pancreatic pseudocysts are also known as acute pancreatic juice retention. During acute pancreatitis, especially acute necrotizing pancreatitis, pancreatic juice exudes outwardly, causing necrosis and liquefaction of the pancreatic itself and peripancreatic tissues due to self-digestion. The accumulated retention around the pancreas is abrupt due to the accumulation of pancreatic juice and inflammatory exudate. After injury, the pancreatic duct ruptures, and the retained fluid contains a large amount of blood. The cyst contents often appear brown-black due to bleeding and tissue necrosis, and the amylase level is generally high. The cyst wall is formed by the inflammatory fibrous tissue hyperplasia generated by the peritoneum and omentum around the stimulated organs, without the covering of pancreatic epithelial cells, without a true capsule, and the cyst wall is actually the surrounding cavity organs and omentum. In view of the above reasons:

　　(1) The maturation of the cyst wall requires a certain amount of time, generally about 6 weeks, only when a relatively firm fibrous wall is formed, can a cysto-gastrointestinal anastomosis be safely performed, otherwise, it is easy to occur anastomotic fistula.

　　(2) It should not be forced to separate the cyst wall during surgery to avoid causing bleeding and gastrointestinal rupture. The cyst contents containing a large amount of digestive enzymes have many hazards locally: ① Secondary infection and easy to destroy the intestinal mucosal barrier, causing endogenous infection; ② Corrosion of adjacent organs causing perforation; ③ Pancreatic enzymes destroy the elastic fibers of the blood vessel wall, causing vessel rupture, triggering massive intracystic hemorrhage; ④ Large cysts compressing surrounding organs can cause obstructive jaundice and gastrointestinal obstruction, etc.; ⑤ Sudden increase in intracystic pressure combined with external force factors can cause rupture, forming acute diffuse peritonitis.

　　3. Chronic pancreatic pseudocysts often occur on the basis of chronic pancreatitis, leading to gradual formation of focal or diffuse fibrosis and necrotic changes in the pancreatic parenchyma, causing pancreatic duct obstruction, poor excretion of pancreatic juice, and ultimately forming pancreatic pseudocysts. They often occur in the pancreatic parenchyma and peripancreatic area, generally smaller, and the cyst contents are mostly pancreatic juice,呈grayish white. Due to the long course of the disease, the cyst wall is gradually formed by the fibrous tissue layer, often thicker, and mostly mature. Once there is intracystic hemorrhage, the cyst will also rapidly expand and increase in size. Chronic pancreatic cysts are often accompanied by clinical manifestations of incomplete exocrine and endocrine function of the pancreas, and the appearance of chronic gastrointestinal symptoms and the occurrence of diabetes mellitus.

　　Complications of pancreatic pseudocysts are more common in acute pancreatic pseudocysts.

　　1. Intracystic hemorrhage

　　Peripancreatic and many coarse blood vessels in the upper abdomen often constitute part of the cyst wall, such as the left gastric artery and vein, the right gastric artery and vein, and the splenic artery and vein, etc. The blood vessel wall is eroded by activated pancreatic enzymes and infection, which can suddenly rupture and cause bleeding. The patient may suddenly develop severe, persistent abdominal pain, the abdominal mass rapidly increases in size, and there are irritative signs, often showing symptoms of internal hemorrhage, and quickly entering a shock state. Ultrasound can find strong echo blood clots inside the cyst. After bleeding, the intracystic pressure suddenly increases, which can cause a gastrointestinal fistula of the cyst, resulting in massive gastrointestinal bleeding. If the patient's general condition allows, percutaneous selective arteriography can be performed to find the bleeding site and block it or perform emergency surgery. After cleaning the intracystic hemorrhage, the bleeding vessel is ligated, and 2 to 3 ligations are performed away from the lesion site. If the patient's condition is extremely poor, to save the life, it is also possible to use long gauze strips to pack the wound, and gradually remove the gauze strips after the bleeding stops for 3 to 4 days.

　　2. Cyst rupture

　　After the rupture of the cyst, the abdominal mass suddenly disappears. If the cyst fluid enters the peritoneal cavity, it can cause persistent severe abdominal pain, leading to acute diffuse peritonitis. Emergency external drainage of the cyst should be performed. If the gastrointestinal tract is pierced, diarrhea often occurs, and a few cases may lead to gastrointestinal bleeding. If the bleeding is not severe, non-surgical treatment can be performed first, and the further treatment plan can be decided after 6 weeks.

　　3. Intra-cystic infection

　　When a cyst becomes infected, symptoms such as abdominal pain, fever, and leukocytosis often occur. It is difficult to distinguish between secondary infection of acute pancreatic pseudocysts and necrotizing pancreatitis with concurrent infection, especially within the first 2 weeks. Immediate drainage should be performed for treatment. For suspected patients, puncture smear examination and bacterial culture under ultrasound or CT guidance can help with diagnosis. Once infection is confirmed, if the cyst is unilocular and the cyst fluid is not thick, puncture and catheter drainage can be chosen. If surgery is required, external drainage should be chosen.

　　4. Compression on the surrounding tissues

　　Large cysts can compress the stomach and duodenum or colon, causing gastrointestinal obstruction. Compression of the common bile duct can lead to obstructive jaundice. Compression of veins or the formation of venous thrombosis can occur, the most common being the splenic vein, followed by the portal vein and superior mesenteric vein, which can lead to high pressure in the stomach-spleen area, extrahepatic portal hypertension, or submucosal varices in the duodenum, resulting in massive upper gastrointestinal bleeding. Compression of the inferior vena cava can cause edema in both lower limbs, and extremely rarely, it can extend to the esophagus or aortic hiatus, rising to the mediastinum and thoracic cavity, compressing the heart and lungs, affecting circulatory and respiratory function. In such cases, immediate drainage and decompression surgery should be performed.

　　Pain is the most common symptom, often located in the upper abdomen, with mild pain, such as dull or bloating pain, occasionally radiating to the back or left rib, often accompanied by decreased appetite, nausea, vomiting, weight loss. Sometimes other symptoms are not obvious, and the upper abdominal mass is the main complaint. In a few patients, the cyst compresses the bile duct, causing jaundice. During physical examination, about 3/4 of the patients can feel the mass, which is mostly located in the upper abdomen, slightly to the left, with a smooth surface. Due to the tension, there is rarely a cystic sensation. Without inflammation, there is usually no significant tenderness. About 10% of patients may have jaundice, and in 30% to 50% of patients, the serum amylase level is elevated.

　　The transition period between spring and summer is a high incidence season for pancreatic cysts. During the change of the third and fourth months, the temperature fluctuates, and the body's immunity decreases. If the body is overfatigued and overeats, it is easy to trigger an attack of acute pancreatitis, followed by the occurrence of a pancreatic cyst. The Pancreatic Swelling Decoction can regulate and enhance the body's resistance, which is conducive to the formation of cysts. Correct and effective treatment of the primary disease (acute and chronic pancreatitis, pancreatic trauma, pancreatic tumors, parasites, etc.) can prevent the formation of cysts due to the rupture of the pancreatic parenchyma or pancreatic duct, leading to the encapsulation of pancreatic juice, blood, and necrotic tissue.

　　About half of the patients show elevated serum amylase and leukocyte count, and bilirubin can increase in cases of biliary obstruction. If the serum amylase in patients with acute pancreatitis remains elevated for more than 3 weeks, about half of the patients may develop pseudocysts, and a small number of patients may have abnormal liver function tests.

　　1. X-ray examination

　　Including abdominal X-ray and gastrointestinal barium meal contrast

　　(1) Abdominal X-ray: The displacement of the stomach and colon bubble shadows can be seen. Due to calcification caused by pancreatitis, patchy calcification spots in the pancreas can be occasionally seen, and the cyst wall is displayed as an arc-shaped dense linear shadow.

　　(2) Gastrointestinal barium meal contrast: Barium meal, barium enema, or a combination of both methods can be used depending on the situation.

　　① Gastro-duodenal type: The cyst is located between the head of the pancreas and the medial side of the duodenum. Larger cysts can cause the duodenal loop to expand into a large circular arc, with the inner edge compressed, the intestinal lumen narrowed, barium passage slow, the prepyloric area of the stomach and the superior part of the duodenal ampulla shifted upward, and the horizontal and ascending parts of the duodenum shifted to the left inferiorly.

　　② Hepatogastric type: The cyst is located between the upper margin of the pancreatic body and the hepatogastric area, causing the lesser curvature of the stomach to shift to the left inferiorly in a long arched shape.

　　③ Retrogastric type: The cyst is located in front of the pancreatic body and behind the corpus of the stomach. In the lateral position, the corpus of the stomach can be seen to shift forward, with an increased distance from the spine. The posterior wall of the stomach shows an arched concave indentation, and the stomach cavity appears as a curved thin strip. The transverse colon shifts downward, and the spleen shifts to the left inferiorly.

　　④ Gastro-colonic type: The cyst is located in the anterior inferior part of the pancreatic neck or body, causing the stomach to shift forward and upward, and the transverse colon to shift downward.

　　⑤ Mesenteric colon type: The cyst is located at the lower margin of the pancreatic body, extending into the transverse mesocolon, causing the transverse colon to shift forward and upward, the descending colon to shift to the left, and the stomach to shift to the upper right.

　　⑥ Gastro-spleen type: The cyst is located between the tail of the pancreas and the spleen, causing the corpus of the stomach to shift to the right anteriorly, with a smooth, arched indentation on the greater curvature of the stomach. The spleen shifts to the left inferiorly, and a large cyst can raise the diaphragm and limit activity.

　　This method is simple and about 77% to 86% of cysts show positive signs, which can display the degree of compression of the stomach and duodenum and the displacement of the aforementioned organs, thus clearly defining the location and relationship of the cyst with the gastrointestinal tract. When combined with other imaging methods, it provides an indispensable basis for the selection of internal drainage methods.

　　2. Ultrasound

　　A well-defined circular or elliptical liquid area can be found around the pancreas, with most being clear internally and a few having scattered echo dots. The posterior wall echo is enhanced, and the normal pancreatic structure is generally invisible at this location. In some cases, part of the pancreatic tissue echo can be seen, and the rest connected to the liquid area can detect the structure of the pancreatic tissue. A few pancreatic pseudocysts have multiple septal lines within the liquid area, indicating a multicystic structure. Some cysts can be detected with strong echoes and shadow, suggesting calcification or pancreatic duct stones. Larger cysts can show signs of compression and displacement of surrounding organs, blood vessels, and bile ducts. True cysts are generally smaller, located within the pancreatic tissue, with normal pancreatic structure surrounding them. Pseudocysts are located para-pancreatic, where there is usually no pancreatic tissue echo, making them easy to differentiate. This method is simple, non-invasive, low-cost, and has an accuracy rate of 95% to 99%. It not only determines the size and location of the cyst but also identifies the nature of the cyst, the thickness of the cyst wall, clarity within the cyst, and the presence of septa. Therefore, it should be the first choice for pancreatic cyst examination, allowing for repeated checks, dynamic observation, to guide treatment and determine the timing and method of surgery.

　　3. CT

　　The pancreatic pseudocyst is close to water-like, with a thin and uniform cyst wall and no enhancement. There are no wall nodules. When there is irregular calcification on the cyst wall or within the cyst, small satellite cysts or papillary nodules can be seen protruding into the cyst cavity on the cyst wall. If wall nodules are found on the enhanced cyst wall, there is a possibility of cystadenocarcinoma. If irregular small bubbles or liquid-gas levels are seen within the cyst, it is a suspicious sign of abscess. When there is bleeding, infection, or necrotic tissue within the cyst, the density within the cyst increases. The differentiation mainly relies on the medical history. This method not only can show the location and size of the cyst, but also can determine its nature, which is helpful for distinguishing between pancreatic pseudocyst, pancreatic abscess, and pancreatic cystic tumor. For patients with more intracystic gas or obesity, especially for those with a diameter

　　4. ERCP

　　It can show the narrowing of the pancreatic duct in chronic pancreatitis and can also find that some cysts are connected with the pancreatic duct, but this examination has the risk of causing infection, and it is not recommended to use it in recent years. Generally, it is only arranged before surgery under the condition of sufficient application of antibiotics, to provide a basis for the selection of surgical methods.

　　5. Selective Arterial Angiography

　　Selective arterial angiography has definite diagnostic value for pseudocysts, can show the location of the lesion, the cystic area shows an avascular area, and there is also displacement and deformation of adjacent blood vessels. This examination can correctly diagnose the invasion of blood vessels, determine whether there is bleeding and the source of bleeding, and judge whether there is a pseudo-aneurysm within the cyst wall. This examination can correctly diagnose the invasion of blood vessels, determine whether there is bleeding and the source of bleeding, and judge whether there is a pseudo-aneurysm within the cyst wall.

　　6. Percutaneous Fine Needle Aspiration Cytology Examination

　　Used to differentiate cystic fluid, there is still disagreement on this examination method, the reasons for the opponents are two,

　　(1) Concern about the implantation of malignant cells into the peritoneum or puncture route;

　　(2) Concern about misdiagnosis leading to inappropriate treatment, therefore, for patients with clearly diagnosed pancreatic pseudocysts, there is no need to perform this examination at all. It is only used for patients with a high suspicion of pancreatic cystadenocarcinoma who are not suitable for surgery for various reasons and need to be diagnosed.

　　After the surgical treatment of pancreatic pseudocyst, a good dietary habit has become an extremely important part. It is mainly necessary to pay attention to some dietary habits in daily life. It is necessary to eat in moderation, and not to overeat, otherwise it is not conducive to the absorption and digestion of the gastrointestinal tract; eat less high-protein foods, such as meat, grains, and seafood should be eaten in moderation, so as to reduce hyperlipidemia and promote blood transportation; it is no longer advisable to drink alcohol, as alcohol contains a large amount of alcohol that can cause damage to the liver, pancreas, and other organs after absorption. Patients should eat more vegetables, as vegetables contain a large amount of vitamins. However, spicy foods should not be eaten, as they are not conducive to digestion and absorption in the human body. Excessive intake of vitamins can enhance the body's resistance. Patients should eat more vegetables, as vegetables contain a large amount of vitamins, and excessive intake of vitamins can enhance the body's resistance. During the treatment process, it is necessary to maintain a good mood, reduce stress, and it is conducive to physical recovery.

　　First, Treatment

　　The treatment of pancreatic pseudocysts has two methods: non-surgical and surgical treatment.

　　1. Selection of Treatment Methods and the Role of ERCP The selection of treatment methods should be based on various factors such as the presence of symptoms and complications, the size of the cyst, and the duration of the condition. For acute pseudocysts, observation should be the first step; chronic pseudocysts with large volume often cannot absorb spontaneously. If symptoms such as persistent abdominal pain and back pain occur, surgery should be performed as soon as possible to reduce the occurrence of severe complications such as cyst rupture. The characteristics of chronic pseudocysts include: no recent episode of pancreatitis, but symptoms of chronic pancreatitis. CT shows oval or spherical cysts within the pancreatic parenchyma, often with calcification; the cyst is clearly demarcated from the surrounding tissue. For both acute and chronic pseudocysts, the following manifestations often suggest a low possibility of spontaneous absorption: the cyst exceeds 12 weeks or is larger than 6 cm; accompanied by chronic pancreatitis; in addition to communication between the pancreatic duct and the cyst, there are other pancreatic duct abnormalities such as stenosis; imaging examination suggests a thicker cyst wall.

　　Clinical studies by Yeo and Sarr et al. show that 60% and 57% of pseudocysts can absorb spontaneously after 6 weeks to 1 year, about 40% of cysts 5 to 6 cm in size can absorb spontaneously, and even 27% of cysts larger than 10 cm can absorb spontaneously, with only 3% and 9% complications. This is significantly different from previous conclusions, which stated that 'most spontaneously absorbable pseudocysts absorb within 6 weeks; after 6 weeks, only a few cysts can absorb spontaneously, almost none at 5 to 6 cm, and the incidence of complications is significantly higher than within 6 weeks'. Therefore, it is believed that about half of the patients with pseudocysts only need to be observed under B-ultrasound or CT without treatment, only a small number of patients (10%) develop severe, life-threatening complications. Although larger cysts are less likely to absorb, it should not be considered an absolute indication for treatment if the cyst exceeds 12 weeks or is larger than 6 cm. Treatment is only necessary when the patient has obvious symptoms and complications related to the cyst, or if the cyst increases in size during the observation period. For true-false pancreatic pseudocysts, if the communication with the pancreatic duct is not blocked, the cyst should be surgically drained, endoscopically drained, or excised according to the situation. If the communication with the pancreatic duct is blocked, the cysts are often absorbed spontaneously and should be observed. For pseudopseudocysts, if there is no secondary infection or other complications, treatment is often not necessary, and the fluid in the cyst can be absorbed as the local inflammation around the pancreas subsides. Although 40% to 60% of pancreatic necrotic cysts can absorb spontaneously, those that cannot often have secondary infection and usually require external drainage or surgical removal of necrotic tissue, and percutaneous needle aspiration drainage is not recommended. If the cyst does not communicate with the pancreatic duct, it can be cured after external drainage. If the cyst communicates with the pancreatic duct, it will form an extrapancreatic fistula. For less severe intraluminal necrosis or when it can be cleared, endoscopic drainage surgery can also be performed.

　　There is controversy about whether an ERCP is necessary before the treatment of pseudocysts. Although retrograde imaging may cause infection, it helps to understand the anatomy of the pancreatic and bile ducts and to select a treatment plan, especially for recurrent cysts, multiple cysts, biliary obstruction related to the cyst, pseudocyst rupture causing pancreatic ascites and pleural effusion, and pseudocysts without a clear cause. Sometimes, contrast material can be seen entering the cyst through the pancreatic duct. If there is obstruction of the pancreatic duct or communication between the pancreatic duct and the cyst, internal drainage should be performed; for ampullary or multiple pancreatic duct strictures, especially when the patient has significant abdominal pain, transduodenal sphincteroplasty or longitudinal pancreaticojejunal anastomosis can be performed; when chronic pancreatitis causes fibrosis of the pancreatic head, leading to stenosis of the common bile duct, biliary-enteric anastomosis can be performed; biliary obstruction caused by cyst compression can usually be relieved after cyst drainage. It should be noted that ERCP cannot be used for cysts with infection or bleeding. If ERCP is performed before surgery, surgery should be performed within 24 hours, and broad-spectrum antibiotics should be used to reduce the possibility of secondary infection of the cyst.

　　2. Non-surgical treatment: For the early stage and small asymptomatic cysts, no special treatment is generally required. It is necessary to control the primary disease first, and antibiotics and other treatments should be given as needed. B-ultrasound or CT should be used for follow-up observation, hoping that the cyst will absorb spontaneously, but complications should be noted. Recent reports suggest that the long-acting somatostatin analog octreotide (Octreotide) may be helpful in the treatment of pseudocysts.

　　(1) Percutaneous catheter drainage (PCD): PCD is suitable for most pseudocysts, especially in the elderly or weak, or when the cyst does not communicate with the pancreatic duct; it can also be used for secondary infected pseudocysts, but not for necrotic pseudocysts of the pancreas. This method involves draining fluid from the cyst to the outside world or into the gastric cavity through a catheter placed through the abdominal cavity, retroperitoneum, stomach, liver, or duodenum, with transgastric catheter drainage being the most commonly used. The catheters usually selected are 7-16F, and gravity is used to drain the cyst fluid. Although some authors have reported that PCD is as effective as surgical drainage, others have found through long-term follow-up that the recurrence rate of PCD is high, and the main reason for failure is that the internal partitions of the cyst and the presence of necrotic tissue in the cyst fluid cause poor drainage. PCD is only used for the following emergencies as temporary treatment: massive cysts causing compression symptoms; the possibility of rupture (sudden increase in cyst size and pain); and concurrent infection.

　　(2) Endoscopic drainage: LO reported a success rate of 90% in 437 cases of endoscopic pancreatic cyst drainage, with complications of 20% and a mortality rate of 0.23%. Beckingham reported that in 34 cases of endoscopic pancreatic cyst drainage, there was a high success rate, with 71% regression, a recurrence rate of 7%, and a mortality rate of 0%. Patients who have recurrences can undergo endoscopic treatment again.

　　When a pseudocyst is adhered to the stomach or duodenum, a fistula can be created between the cyst and the stomach or duodenum under the endoscope using electrocautery or laser, so that the cyst fluid can be drained into the stomach or duodenum; or anastomosis between the cyst and the stomach or duodenum can be performed under the endoscope. In the past, it was believed that this method had a high incidence of complications such as perforation, bleeding, and infection, and a low success rate. Currently, the application of endoscopic ultrasound can clearly define the anatomical relationship between the cyst and the surrounding structures, avoiding large blood vessels; the combined application of a child endoscope and endoscopic ultrasound shortens the operation time, reduces the chance of infection, and expands the indications for surgery; the application of balloon dilation technology and the placement of internal stent tubes during surgery reduces the chance of infection and bleeding. In recent years, some people have drained cysts through the endoscope via the papilla. This method is suitable for those with pancreatic duct rupture, where a catheter is placed directly into the ruptured pancreatic duct to drain the cyst, or the catheter is used as a stent tube. However, inserting a catheter into the pancreatic duct via the papilla can damage the pancreatic duct or lead to acute pancreatitis or infection through the catheter; it can also cause significant pancreatic pain symptoms. Catheter blockage or pancreatic duct stenosis can lead to the recurrence of the cyst. The success rate is 80% regression, the recurrence rate is 9%, the complications rate is 12%, and the mortality rate is 0%. Although both methods of endoscopic drainage are theoretically good methods, as they are all endoscopic and do not require surgery, they have many complications, uncertain effects, and are not the main means of treating pseudocysts at this stage, and further research is needed.

　　Indications for endoscopic drainage:

　　① The cyst has been present for more than 6 weeks, has treatment indications, and has been excluded as a tumor.

　　② CT or endoscopic ultrasound confirms that the cyst is tightly adhered to the stomach or duodenum, and the stomach or duodenum is compressed and intruding under the endoscope, with the distance between the cyst wall and the gastrointestinal wall less than 1 cm.

　　③ The wall of the cyst is less than 1 cm.

　　During the operation, first puncture the most prominent part of the gastrointestinal wall with a double-lumen catheter and quickly insert the guide wire into the cyst. Inject contrast medium to confirm that it is within the cyst, which can also be confirmed by endoscopic ultrasound. Then, dilate the balloon to 3-5 cm, and place 1-2 catheters or pigtail catheters. Generally, this is done for 2-4 months until the ultrasound shows that the cyst has disappeared. If a supporting tube is not placed, the closure rate of the gastrointestinal orifice of the cyst reaches 20%. According to reports, the success rate of endoscopic cyst gastrostomy is 82%-89%, the recurrence rate is 6%-18%, the main complications are bleeding (4%-8%) and perforation (4%-8%), and the mortality rate is 0%.

　　(3) Laparoscopic treatment: In recent years, laparoscopic cystogastrectomy has been performed with the help of laparoscopic ultrasonic knife and balloon catheter, with an average operation time of 90 minutes. On the second day after the operation, liquid food can be consumed, with an average hospital stay of 3 days, and the cysts disappeared completely after a follow-up of 6 months. There are also reports on the safe and effective performance of giant cyst jejunal Rouxen-Y anastomosis and the removal of necrotic tissue. In summary, laparoscopic cyst-enteric anastomosis shows a good application prospect, but the number of reported cases is small, and the operator needs to have a high level of laparoscopic skills, and the clinical effects need to be further confirmed.

　　3. Surgical treatment Surgical treatment is the main method for treating pseudocysts. The purpose is to drain the cyst fluid; relieve symptoms; prevent and treat serious complications such as cyst rupture, hemorrhage, infection, and obstruction. The timing of surgery is very important; if surgery is performed too early, the cyst wall is not mature, and only external drainage surgery can be performed; if surgery is delayed, the incidence of complications is high. The surgical methods include cyst resection, internal drainage, and external drainage. If there is hemorrhage, cystic hemorrhagic artery ligation, splenectomy, or resection of the body and tail of the pancreas should be performed according to the bleeding site; occasionally, emergency resection of the head of the pancreas and duodenum can also be performed; when stricture of the common bile duct pancreatic segment due to chronic pancreatitis causes obstructive jaundice, cystoenteric anastomosis should be performed at the same time. Pathological examination of the cyst wall should be performed simultaneously with all operations to exclude cystic tumors and other cystic lesions. Postoperative blood and urine amylase should be re-examined and compared with preoperative values.

　　(1) Internal drainage operation: Internal drainage operation involves anastomosing the cyst with the jejunum, stomach, or duodenum. As long as the cyst wall is mature and there are no complications, this operation can be performed. The choice of surgical technique is often based on the anatomical location of the cyst, adopting the principle of nearby drainage, such as cystogastrectomy is more suitable for retrogastric cysts. After the operation, gastrojejunal decompression and fasting for about 4 days are given according to the recovery of intestinal peristalsis. Then, start eating with clear liquid or liquid diet, and if infection occurs in the cyst after eating, fasting should be resumed and antibiotics added.

　　① Cyst jejunal anastomosis: It is the most commonly used operation, suitable for almost all cysts, especially when the cyst is large or polycystic. There are two types of anastomosis, one is the cyst jejunal Rouxen-Y anastomosis, which involves cutting the jejunum 15-20 cm away from the treitz ligament, and anastomosing the distal jejunum to the cyst with 3-0 silk thread for full-thickness interrupted suture of the cyst wall and intestinal wall. Then, the distal jejunum 30-40 cm away from this anastomosis is anastomosed to the proximal jejunum. This is currently the most ideal type of internal drainage operation; the other is the cyst jejunal loop anastomosis combined with jejuno-jejunal side-to-side anastomosis, which involves anastomosing the jejunal loop 45 cm away from the treitz ligament to the cyst, and then performing a side-to-side anastomosis of the two jejuna 30 cm away from this anastomosis. It is also possible to seal the proximal jejunum above this anastomosis with a side-to-side anastomosis device to block the entry of intestinal contents into the cyst. The advantages of cyst jejunal anastomosis are that it can be anastomosed with the lower part of the cyst, fully draining the cyst, and also preventing the reflux of intestinal contents into the cyst. The disadvantages are that the operation time is longer, and there is a possibility of anastomotic fistula.

　　② Cysto-gastric anastomosis: This is suitable for cases where the cyst is densely adherent to the posterior wall of the stomach, especially when the wall of the cyst is not fully mature. The method is to first incise the anterior wall of the stomach, anastomose the cyst with the posterior wall of the stomach, and place or not place the tip of the nasogastric tube into the cyst cavity. Finally, suture the anterior wall incision of the stomach to allow the cyst fluid to flow into the gastric cavity. The anastomosis between the cyst and the stomach should first be sutured with a non-absorbable suture (2-0 Dexon suture can be used) for a continuous locking suture around the entire thickness of the posterior wall of the stomach and the cyst wall, and then reinforced with 2-0 Dexon or 3-0 silk suture for间断 to prevent bleeding. For critically ill patients, a simpler surgical method can also be used, such as one-stage cysto-gastric internal and external drainage, which involves placing a rubber tube into the cyst cavity, passing it through the posterior wall of the stomach, the gastric cavity, and the anterior wall of the stomach, and then bringing it out through the abdominal wall to the outside, so that the cyst fluid is first drained outward. The rubber tube can be removed 2 weeks later to allow communication between the cyst cavity and the gastric cavity. The advantages of cysto-gastric anastomosis are that the operation is simple, the operation time is short, and it is safe for draining large cysts as well. Postoperative hemorrhage is the main complication of this operation.

　　③ Duodenal cystojejunal anastomosis: This is only applicable to cysts located in the head of the pancreas or when the first two anastomosis methods are very difficult. It involves anastomosing the lowest part of the cyst with the lateral wall of the duodenum. The operation usually requires a Kocher incision to open the retroperitoneum, free the second segment of the duodenum, and the head of the pancreas. The surgical method for anastomosing the cyst with the duodenum is the same as that for anastomosing the cyst with the stomach, but it uses 3-0 Dexon suture for anastomosis, and horizontal or vertical sutures can be used to close the duodenal incision. Another anastomosis method can also be used, namely, performing a cystojejunal side-to-side anastomosis directly. This operation is the most in line with physiological requirements, but there is a possibility of injury to the common bile duct segment of the pancreas and the gastroduodenal artery, and there may be complications such as duodenal fistula, with a mortality rate of 5%, making it the least commonly used among the three internal drainage operations. After cystojejunal anastomosis, delayed gastric emptying is often present, so the time for placing the gastric tube should be relatively long. When the amount of gastric juice is less than 200ml in 24 hours, the gastric tube can be clamped first, and if there are no obstruction symptoms, the gastric tube can be removed. It is recommended to start with clear liquid food first. If there are symptoms of delayed gastric emptying, there is no need to rush for barium meal examination, as obstruction symptoms often resolve with the subsidence of edema around the duodenum.

　　④ Complications and precautions of internal drainage surgery:

　　A. Upper gastrointestinal bleeding: It is the most common complication, accounting for about 12%, mainly after cyst-gastric anastomosis, with a mortality rate of up to 50%, mostly due to bleeding from the cyst-gastric anastomosis and gastric mucosa. The reasons for bleeding after cyst-gastric anastomosis are: the acidic gastric juice enters the cyst cavity, causing inflammation, erosion, and bleeding of the cyst wall; in addition, food entering the cyst and remaining there can cause infection, necrosis, and bleeding; of course, incomplete hemostasis during surgery is also one of the main reasons for bleeding. The reason for bleeding from the gastric mucosa is mainly that the alkaline cyst fluid flows into the stomach, causing erosion or ulceration of the gastric mucosa. It is rare to see bleeding in patients with cyst jejunal (or duodenal) anastomosis after surgery. Therefore, when performing cyst-gastric anastomosis, the posterior wall of the stomach and the margin of the cyst should be tightly sutured to stop bleeding, and the full-thickness anastomosis between the posterior wall of the stomach and the cyst wall should be carefully performed.

　　B. Cyst recurrence: The recurrence rate of cyst-gastric anastomosis after surgery is 2.5%, and the recurrence rates of cyst-jejunal anastomosis and cyst-jejunal anastomosis are 4.5% and 5%, respectively. The reasons for cyst recurrence include: the cyst is multicystic and was not discovered or treated during surgery; the anastomosis was not performed from the lowest part of the cyst; the anastomosis is too small. Therefore, if the cyst is found to have septa during surgery, the septum should be separated before drainage; the anastomosis should be performed as low as possible in the cyst, and the anastomosis should be large enough, generally 3-4cm, and a part of the cyst wall should be excised in the shape of a spindle or nearly circular. Within one week after a successful internal drainage operation, the cyst will significantly shrink, and it can disappear after 2-3 weeks, and the serum amylase will also be normal. If the blood or urine amylase level remains high, or rises after falling, it indicates a possible recurrence.

　　C. Secondary infection of the cyst: It is often caused by the reflux of gastrointestinal contents into the cyst, so when performing a cyst jejunal anastomosis, the anastomosis or Braun anastomosis of the proximal and distal ends of the jejunum should be more than 30cm from the anastomosis between the cyst and the jejunum. Of course, attention should also be paid to the size and location of the anastomosis.

　　(2) Cystectomy: In theory, this method is the most thorough surgical procedure. However, pseudocysts are often caused by significant inflammation and dense adhesions with surrounding tissues, making the surgery difficult and prone to damage surrounding important structures, thus it is rarely used. To avoid pancreatic fistula, it is generally not advisable to perform simple cystectomy, but rather to perform a cyst and pancreatic resection of the part where the cyst is located. This surgery has a high mortality rate, up to 10%, and is therefore mainly used for small cysts in the tail of the pancreas, especially in cases of small cysts in the tail of the pancreas after trauma, when the head and body of the pancreas are normal. Sometimes, a distal pancreatectomy can be performed for cysts in the body or tail of the pancreas; when the cyst is adherent to the spleen, inflammatory lesions can easily surround and compress the splenic vessels or form venous thrombosis. If separation is difficult, it is advisable to remove the spleen together. After distal pancreatectomy, if there is obstruction of the proximal pancreatic duct, a proximal pancreatic jejunal Rouxen-Y anastomosis can be performed. In cases where the cyst in the head of the pancreas has obvious symptoms accompanied by chronic pancreatitis, it is occasionally possible to perform a pancreaticoduodenectomy or a pylorus-preserving (or duodenal) pancreatic head resection. Cysts in the head of the pancreas are benign lesions, and when accompanied by chronic pancreatitis, the cysts often compress the superior mesenteric vein or portal vein, making surgical resection potentially damage blood vessels and increase the risk of surgery, so angiography should be performed before surgery to understand the situation of vessel compression, and the indications should be strictly controlled. Surgery can be considered in the presence of the following conditions:

　　① Chronic pancreatitis with significant pain.

　　② Multiple cysts.

　　③ Gastrointestinal bleeding caused by pseudo-aneurysm.

　　④ Common bile duct obstruction.

　　⑤ Un-drainable hook cysts.

　　⑥ Duodenal obstruction.

　　(3) External Drainage: This method has a recurrence rate 4 times higher than that of internal drainage, so it is less commonly used and is only used for emergency surgery in cases of cyst rupture, hemorrhage, and infection; if the cyst wall is too thin and widely adherent, internal drainage cannot be performed, this method can also be used; occasionally, external drainage is performed first when it is impossible to perform internal drainage on large cysts. During surgery, a thick drainage tube is placed into the cyst cavity and led out through the abdominal wall, allowing the cyst fluid to flow out of the body through gravity or negative pressure. The amount of drainage after surgery is recorded, and water and electrolytes are appropriately supplemented. The previous external drainage method is also known as bag drainage (or bag surgery), which directly sutures the cyst wall incision to the peritoneum and skin of the abdominal wall incision, forming a bag opening connected to the outside world, and directly draining the contents of the cyst outside the peritoneum. However, pancreatic juice causes significant damage to the local skin, and postoperative management is relatively difficult, so it is now basically not used. In summary, external drainage is often used as a temporary treatment measure. Some patients develop pancreatic fistula after external drainage, and subcutaneous injection of octreotide may help close the pancreatic fistula. Patients with excessive loss of pancreatic juice should be given nutritional support. If the pancreatic fistula has not closed within half a year, it is mostly due to proximal pancreatic duct obstruction, and it should be first performed with pancreatic fistula angiography, and then partial pancreatectomy or fistula jejunostomy should be performed according to the situation.

　　Second, Prognosis

　　The recurrence rate of pseudocyst of the pancreas is 10%, and the recurrence rate of external drainage is relatively higher. Severe postoperative hemorrhage is rare and mainly seen in gastric cyst anastomosis. In summary, the surgical treatment of pseudocyst is effective and complications are rare. Many patients later show chronic pain, mainly due to chronic pancreatitis.