Pancreatic pseudocysts

　　Acute pancreatic pseudocysts refer to cysts formed by the acute accumulation of cyst contents, which often occur secondary to acute pancreatitis and pancreatic injury. The causes of acute pancreatitis vary from country to country and region to region. In China, acute pancreatitis induced by gallstones accounts for the majority, while alcohol-induced cases are fewer; in Western countries, alcohol-induced acute pancreatitis accounts for the majority, and gallstone-induced cases account for only 10%.

　　Chronic pancreatic pseudocysts are caused by pancreatic duct obstruction and rupture on the basis of chronic pancreatitis. The main causes of chronic pancreatitis are gallstones, alcoholism, and injury, which are rarely seen in hyperlipidemia and hypercalcemia due to primary hyperparathyroidism. About 75% of pseudocyst cases are caused by acute pancreatitis, about 20% occur after pancreatic trauma, and 5% are caused by pancreatic cancer. A group of reports on 32 pseudocyst cases showed that 20 cases occurred after acute pancreatitis, 3 after abdominal trauma, 8 with unclear causes, and 1 due to compression by a pancreatic fibroma. Among the 20 cases occurring after acute pancreatitis, the earliest cyst appeared one week after onset, the latest two years after onset, and most were during the 3-4 weeks after onset.

　　Pancreatic juice containing various digestive enzymes exudes from the necrotic pancreatic tissue to the retroperitoneal space around 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. Or the pancreatic juice directly渗入小网膜囊内，Winslow孔often due to inflammation and sealed, the cyst then forms within the lesser omentum. Sometimes the pancreatic juice enters other parts along the tissue spaces to form cysts in special locations, such as pseudocysts in the mediastinum, spleen, kidney, and inguinal region, etc.

　　The recurrence rate of pancreatic pseudocysts is 10%, and the recurrence rate of external drainage surgery is relatively high. Severe postoperative hemorrhage is rare, mainly seen in gastric cyst anastomosis. In summary, the efficacy of surgical treatment for pseudocysts is rapid with few complications. Many patients later develop chronic pain mainly due to chronic pancreatitis. Thirty percent of pancreatic pseudocyst cases are complicated with infection, involving adjacent vessels or viscera, and perforation, as follows:

　　One, Secondary Infection

　　This is the most common and most serious complication of pseudocysts. The patient's condition deteriorates rapidly, leading to severe sepsis. If surgery is not performed in a timely manner, it often rapidly progresses to pancreatic abscess and septicemia, and death is almost inevitable due to this.

　　Two, Pancreatic Ascites

　　Pancreatic juice within the pseudocyst may leak into the peritoneal cavity through fistulas or cracks, stimulating the peritoneum and causing ascites. Ascites can also occur due to obstruction of the lymphatic vessels around the pancreas, leading to lymphatic exudation. Normally, the peritoneum can absorb a large amount of fluid, but in cases of pancreatic ascites, due to the exudation of fibrin, proliferation of fibrous tissue, infiltration of inflammatory cells, and degeneration of elastic fibers, fluid cannot be absorbed in large quantities and accumulates in the peritoneal cavity.

　　Three, Pancreatic Pleural Effusion

　　About 50% of pancreatic pleural effusions coexist with pancreatic pseudocysts. If the pancreatic juice within the cyst diffuses into the pleural cavity through the lymphatic vessels of the diaphragm, stimulating the pleura or forming a fistula between the cyst and the pleural cavity, pleural effusion can occur, which is usually located on the left side.

　　Four, Hemorrhage

　　Bleeding is a rare but most dangerous complication of pseudocysts. Bleeding can occur due to rupture of blood vessels within the pseudocyst; invasion of the gastrointestinal wall by the cyst; esophageal variceal rupture due to portal or splenic vein obstruction; bleeding due to invasion of the biliary tract by the cyst; or rupture of a pseudoaneurysm. When bleeding occurs within the cyst, the cyst rapidly increases in size, and the sound of blood flow can be heard. Therefore, if the cyst suddenly increases in size and signs of systemic hemorrhage are present, immediate arteriography should be performed, and emergency surgery is often required at this time, including cyst removal or ligation of bleeding vessels within the cyst, and cyst drainage.

　　Five, Spleen Involvement

　　Patients with pancreatic pseudocysts may simultaneously have spleen involvement, which may be due to erosion of the spleen by the pseudocyst; digestion of the spleen by the pancreatic juice exuding from the cyst; inflammation of the transplanted pancreatic tissue in the spleen; and the formation of splenic vein thrombosis with liquefaction of the梗死area in the spleen. In such cases, early splenectomy should be performed, and a distal pancreatectomy should be considered as soon as possible.

　　Six, Rupture and Perforation of Cysts

　　Pancreatic pseudocysts can spontaneously perforate or rupture into adjacent organs, often leading to gastrointestinal bleeding. Rupture of a pseudocyst into the stomach, duodenum, or colon may not necessarily present with symptoms, and at this time, it may not be dangerous to the patient, but can provide effective drainage. However, if the cyst ruptures into the peritoneal cavity, the mortality rate is extremely high. In this situation, patients often experience shock, with a mortality rate of 18% to 80%.

　　Seven, Other

　　1. Jaundice: Obstructive jaundice can occur due to compression of the common bile duct by the pseudocyst.

　　2. Diarrhea: Pancreatic pseudocysts can sometimes cause severe diarrhea.

　　The clinical characteristics of pancreatic pseudocysts are mainly based on the stage of acute or chronic pancreatitis. During acute pseudocyst, symptoms include fever, abdominal distension and tenderness in the upper abdomen, mass, abdominal bloating, and gastrointestinal dysfunction, with severe cases potentially leading to various complications. Chronic pancreatic pseudocysts often occur on the basis of chronic recurrent pancreatitis, with symptoms mainly resembling those of chronic pancreatitis, such as pain in the upper abdomen and lower back, dysfunction of fat digestion, and diabetes. Splenomegaly and upper gastrointestinal bleeding are characteristic of this condition.

　　After acute pancreatitis or pancreatic trauma, if there is persistent upper abdominal pain, nausea and vomiting, weight loss, and fever, and a cystic mass is palpated in the abdomen, the possibility of pseudopancreatic cyst formation should be considered first. A few pseudocysts are asymptomatic and are only found during ultrasound examination. Most cases of clinical symptoms are caused by compression of adjacent organs and tissues by the cyst. About 80% to 90% of cases have abdominal pain, most of which are located in the upper abdomen and are related to the location of the cyst, often radiating to the back. The pain is caused by compression of the gastrointestinal tract, retroperitoneum, peritoneal plexus, and inflammation of the cyst and pancreas itself. About 20% to 75% have nausea and vomiting; about 10% to 40% have decreased appetite; weight loss is seen in about 20% to 65% of cases; fever is usually low-grade; diarrhea and jaundice are relatively rare. If the cyst compresses the pylorus, it can lead to pyloric obstruction; if it compresses the duodenum, it can cause duodenal stasis and high intestinal obstruction; if it compresses the common bile duct, it can cause obstructive jaundice; if it compresses the inferior vena cava, it can cause symptoms of inferior vena cava obstruction and lower limb edema; if it compresses the ureter, it can cause renal pelvis hydrops. Pancreatic pseudocysts in the mediastinum can cause symptoms of heart, lung, and esophagus compression, such as chest pain, back pain, difficulty swallowing, and jugular vein distension. If the pseudocyst extends to the left inguinal canal, scrotum, or rectouterine pouch, symptoms of rectal and uterine compression may occur. During physical examination, about 50% to 90% of patients have a mass palpable in the upper abdomen or left hypochondrium, which is spherical, smooth, rarely nodular, but may have a fluctuating sensation, with little mobility and often tenderness.

　　The key to preventing pancreatic pseudocysts is to make an early diagnosis of acute pancreatitis or pancreatic injury and take appropriate treatment measures early. Once diagnosed, surgery should be scheduled.

　　The clinical examination methods for pancreatic pseudocysts mainly include laboratory examination and other auxiliary examinations, as follows:

　　First, laboratory examination

　　About half of the patients show elevated serum amylase and increased white blood cell count, and bilirubin can increase when there is 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.

　　Second, other auxiliary examinations

　　1, X-ray examination: including abdominal plain film and gastrointestinal barium meal. Abdominal plain film shows displacement of gastric and colonic bubble shadows, and patchy calcification spots may occasionally appear in the pancreas due to pancreatitis, with arc-shaped dense linear shadows in the cyst wall. Gastrointestinal barium meal examination can be performed using barium meal, barium enema, or both methods depending on the situation.

　　2, Ultrasound examination: This method has an accuracy rate of 95% to 99%, not only can determine the size and location of the cyst, but also identify the nature of the cyst, the thickness of the cyst wall, the clarity inside the cyst, and whether there is a septum. Therefore, it should be the first choice for the examination of pancreatic cysts, and can be examined multiple times dynamically to guide treatment and determine the timing and method of surgery.

　　3. CT examination: This method not only can show the location and size of the cyst, but also can determine its nature, which is helpful in distinguishing pancreatic pseudocysts from pancreatic abscesses and pancreatic cystic tumors. For patients with more intracystic gas or obesity, especially those with a diameter

　　4. ERCP examination: Can show stenosis and lesions of the pancreatic duct in chronic pancreatitis, and can find that some cysts communicate with the pancreatic duct, but this examination has the risk of triggering infection and is not recommended in recent years. Generally, it is only arranged before surgery, under the full application of antibiotics, to provide a basis for choosing the surgical method.

　　5. Percutaneous fine needle aspiration cytology: Used for distinguishing cystic fluid. There is still some disagreement about this method of examination.

　　During the medical period, food should be light and easy to digest and absorb, without causing a burden on the gastrointestinal tract. At the same time, eat more foods rich in vitamins to enhance the body's resistance. After the condition improves, eat oil-free light liquid diet, such as congee, fruit juice, vegetable soup, and lotus root starch, and gradually change to pure vegetarian semi-liquid diet, soft rice, etc. Strictly prohibit alcohol and absolutely prohibit overeating. Since drinking and overeating can cause excessive secretion of pancreatic juice, obstructed excretion of pancreatic juice,紊乱 of pancreatic blood and decreased trypsin inhibitor, chronic pancreatitis patients should abstain from alcohol and overeating to prevent acute attacks. It is also necessary to have enough vegetables and fruits to supplement vitamins and minerals, and not to eat greasy foods.

　　In clinical practice, early-stage pancreatic pseudocysts should be treated first with conservative medical methods, such as in the case of acute pancreatitis, the pancreas should be kept in a resting state to reduce the exudation of pancreatic juice and control the further development of the cyst. Endoscopic cyst-gastrointestinal anastomosis and endoscopic cyst-jejunal anastomosis can be used for treatment, which is especially suitable for older patients who cannot tolerate surgery. For patients with gastrointestinal compression symptoms, especially those with pancreatic head cysts located next to the duodenum with a diameter greater than 6 centimeters and not suitable for surgery, endoscopic treatment is relatively safe.

　　First, surgical treatment

　　The treatment of pancreatic pseudocysts is mainly surgical. Pseudocysts often communicate with pancreatic duct branches and functional pancreatic tissue, so they often persist and continue to increase. Unless a few small cysts can spontaneously resolve, about 85% of pseudocysts require non-surgical treatment.

　　1. Timing of surgery: Most people believe that delayed surgery is better, so as to have enough time for the cyst wall to form a mature fibrous capsule. Early surgery often fails due to the脆性囊壁, which cannot be effectively sutured, and the postoperative anastomotic rupture is easy to occur. The best plan is to follow up with B-ultrasound during the observation period, observe whether the cyst has disappeared or increased. If the cyst increases or cannot spontaneously disappear after 7 weeks, surgery should be performed.

　　2. Common surgical methods: There are three types of commonly used surgical methods:

　　(1) Cyst resection: This is the most ideal method, but it is mostly suitable for small cysts at the tail of the pancreas, and the operation is more difficult for large cysts.

　　(2) Cyst Drainage: In the past, it was believed that external drainage was the first choice for the treatment of pancreatic pseudocysts, but due to a high incidence of pancreatic fistula after external drainage, most scholars have gradually tended towards internal drainage surgery. The complications after external drainage are numerous, in order of frequency: pancreatic fistula, peritoneal abscess, pancreatitis, cyst recurrence, and hemorrhage. Shatney and Lillehei reviewed the results of surgical treatment for 119 cases of pancreatic pseudocyst and also believed that internal drainage surgery has a low mortality rate and complication rate.

　　The preferred method for internal drainage surgery is cyst-gastric anastomosis, which can dissipate the cyst. For those who are not suitable for cyst-gastric anastomosis, the cyst can be drained into the jejunum or duodenum according to the Roux-en-y method.

　　(3) Pancreaticectomy: Pancreatic resection is often performed when there is severe pancreatic disease or malignant tumor, and can be pancreaticoduodenectomy, pancreatic body and tail resection, or total pancreatectomy.

　　2. Other Drainage Methods

　　During endoscopic drainage, if the pseudocyst is closely adjacent to the gastric wall or chest wall, correctly speaking, if the distance between the cyst wall and the gastrointestinal cavity is not more than 1cm on CT or ultrasound, endoscopic drainage can be performed. The method involves puncturing the gastric or duodenal wall and the cyst wall with a thermal puncture needle or laser under the endoscope, and then inserting a nasogastric tube into the cyst for continuous drainage. Endoscopic duodenal or gastric-cyst anastomosis was performed in 96% and 100% of cases, respectively, with successful drainage and a recurrence rate of only 9% and 19%. Some advocates for the use of the duodenal papilla approach to place the catheter into the pseudocyst through the Vater壶腹.

　　3. Drug Treatment

　　Somatostatin has a significant inhibitory effect on pancreatic exocrine secretion. The synthetic somatostatin analog Sandostatin (sandostatin) has a long half-life in the body and can promote stoma closure in patients with pancreatic fistula. Sandostatin treatment was administered to 4 patients with pancreatic fistula after pseudocyst drainage and 1 patient after pancreatic cancer resection. The initial dose was 50μg, twice a day, gradually increased to 150μg, twice a day, for 2-6 weeks. On the second day after treatment, the average discharge volume of the fistula decreased by 52%, by 70% after 3 days, and all fistulas closed within 7-44 days, with no significant side effects.