Pancreatic Cysts

　　Etiology:

　　1. True Cyst

　　The most common true cysts are retention cysts, which are often caused by extrapancreatic compression, pancreatic duct stones, inflammatory stricture, etc., leading to pancreatic duct obstruction and high pressure. This causes the distal pancreatic duct or acinar cells to undergo cystic dilation, resulting in pancreatic juice retention and the formation of cysts. True cysts may also be caused by congenital maldevelopment of the pancreatic duct, which are also known as congenital cysts. The endothelial cells of true cysts still have certain secretory functions, forming a cyst lined with complete endothelium. When true cysts are complicated with chronic inflammation and infection, the epithelial layer may also be destroyed and disappear. Such cysts vary greatly in size, from microscopic to over 10 centimeters. The inner wall of the cyst is smooth, covered with flat or low columnar epithelium, containing serous fluid, mucus, or occasionally turbid fluid formed due to infection. The cyst does not contain solid tissue components, septa, or similar tumor-like growths. Typically, cysts are classified into solitary cysts and multiple cysts based on the number of cysts. Pancreatic multiple cysts may be associated with fibrotic cystic fibrosis or pancreatic fibrocystic disease, which is a systemic genetic disease that is relatively rare in clinical practice. It often occurs simultaneously with multiple cysts in the kidneys, liver, lungs, or central nervous system.

　　2. Pseudocysts

　　Pseudopancreatic cysts are formed after the trauma or inflammation of the pancreas, when extravasated blood and pancreatic juice enter the peripancreatic tissue, or in rare cases, encapsulate and form cysts in the lesser omental sac. The difference between pseudocysts and true cysts lies in the latter occurring in the pancreatic tissue, with the cyst located within the pancreas, and the inner layer of the cyst composed of acinar or ductal epithelial cells; whereas the former is formed by the peripancreatic tissue such as peritoneum, omentum, or inflammatory fibrous connective tissue, encapsulating the effusion to form a cyst. The wall of the cyst does not have epithelial cells as a衬垫, hence the name pseudocyst, which accounts for more than 80% of all pancreatic cysts.

　　According to the etiology of pseudocyst formation, pancreatic cysts are classified as:

　　(1) Pseudocysts after inflammation: seen in acute and chronic pancreatitis.

　　(2) Pseudocysts after trauma: seen in blunt trauma, penetrating trauma, or surgical trauma.

　　(3) Pseudocysts caused by tumors.

　　(4) Parasitic pseudocysts: caused by Ascaris or cysticercosis.

　　(5) Idiopathic or of unknown cause. About 75% of pseudocyst cases are caused by acute pancreatitis, about 20% occur after pancreatic trauma, and 5% are caused by pancreatic cancer.

　　Due to the necrotic effusion of pancreatitis penetrating the capsule, it enters the lesser omental sac from the pre-renal space and the posterior renal and retroperitoneal spaces, or along the para-aortic space to the side of the spine, and upward to below the diaphragm, even piercing the diaphragm. It can also spread to the abdominal cavity along the mesentery of the small intestine and transverse colon. Therefore, pseudocysts can form at any of the above locations, with the most common being around the pancreas. The wall of the pseudocyst has no epithelium and is composed of granulation tissue and fibrous tissue. The contents of the cyst are necrotic tissue, inflammatory exudate, blood, and a large amount of pancreatic enzymes, so it can be a clear yellow liquid or a chocolate-like thick and turbid liquid, and some even contain cottony necrotic tissue. Animal experiments show that the formation of pseudocyst walls requires 4 weeks, and at least 6 weeks in humans. Pseudopancreatic cysts are about 80% solitary and of varying sizes. Typical pseudocysts communicate with the main pancreatic duct, and this type of pancreatic cyst can continuously expand towards all directions due to the secretion pressure of pancreatic juice inside the cyst, and can persist, with a diameter reaching several centimeters to more than ten centimeters.

　　3, Pancreatic cystic tumors

　　Cystic tumors of the pancreas are a special type of pancreatic tumor, accounting for about 1% of pancreatic tumors and 10-13% of pancreatic cystic lesions. They generally occur more frequently in female patients, with a male-to-female ratio of about 1:4-6. Benign tumors include serous cystadenoma, mucinous cystadenoma, benign or borderline intraductal papillary mucinous neoplasms (IPMNs), and solid pseudopapillary tumors. Malignant tumors include mucinous cystadenocarcinoma and invasive IPMNs.

　　Among them, serous and mucinous cystadenomas are the most common benign tumors among pancreatic cystic tumors, accounting for 32-39% and 10-45% of cystic tumors, respectively. Mucinous cystadenomas have a tendency to become malignant. Literature reports indicate that 80% of mucinous cystadenoma specimens can be found to have atypical hyperplasia or malignant changes locally. It was previously believed that serous tumors had no tendency to become malignant, but recent reports have also described cases of serous cystadenocarcinoma.

　　Intraductal papillary mucinous neoplasms account for about 21-33% of cases, histologically showing cystic dilatation of the pancreatic duct, with both the main and branch pancreatic ducts potentially involved. The tumor tissue in the pancreatic duct grows in papillary form, with varying sizes and can be multicentric or segmental in distribution. The pancreatic duct is often filled with mucus, containing shed tumor cells.

　　Solid pseudopapillary tumors of the pancreas are relatively rare, often occurring in young women. The typical pathological features are pseudopapillary structures and hemorrhagic necrotic foci, which belong to low-grade malignant or borderline tumors.

　　Cystic tumors have a clear boundary with normal pancreatic tissue, most of which have a complete thin film. The amylase in the cyst fluid is normal, and in the cyst fluid of mucinous cystadenoma and cystadenocarcinoma, the cancer embryonic antigen (CEA) can be significantly increased. The cyst cavity is generally not connected with the main pancreatic duct.

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

　　2, Pancreatic ascites pseudocysts may cause ascites due to leakage of pancreatic juice into the peritoneal cavity through fistulas or fissures, which can stimulate the peritoneum. Obstruction of the lymphatic vessels around the pancreas can also lead to ascites. The normal peritoneum can absorb a large amount of fluid, but in pancreatic ascites, due to the exudation of fibrin, proliferation of fibrous tissue, infiltration of inflammatory cells, and degeneration of elastic fibers, the fluid cannot be absorbed in large quantities and accumulates in the peritoneal cavity.

　　4. Pancreatic pleural effusion About 50% of pancreatic pleural effusions coexist with pseudopancreatic cysts. If the pancreatic fluid within the cyst diffuses into the pleural cavity through the diaphragmatic lymphatics, stimulates the pleura, or forms a fistula between the cyst and the pleural cavity, pleural effusion can occur. Pleural effusion is usually on the left side.

　　3. Pancreatic pleural effusion About 50% of pancreatic pleural effusions coexist with pseudopancreatic cysts. If the pancreatic fluid within the cyst diffuses into the pleural cavity through the diaphragmatic lymphatics, stimulates the pleura, or forms a fistula between the cyst and the pleural cavity, pleural effusion can occur. Pleural effusion is usually on the left side.

　　4. Bleeding Bleeding is a rare but most dangerous complication of pseudocysts. Bleeding can occur due to: (1) rupture of blood vessels within the pseudocyst; (2) invasion of the gastrointestinal wall by the cyst; (3) esophageal variceal rupture due to portal or splenic vein obstruction; (4) bleeding due to invasion of the biliary tract by the cyst; (5) rupture of a pseudo-aneurysm. When there is intracystic bleeding, the cyst rapidly enlarges and blood flow sounds can be heard. Therefore, if the cyst suddenly enlarges and there are signs of systemic hemorrhage, urgent arteriography should be performed, and emergency surgery, including cystectomy or ligation of the bleeding vessels within the cyst, and cyst drainage, is often required.

　　5. Splenic involvement Patients with pseudopancreatic cysts may also have splenic involvement, which may be due to: (1) erosion of the spleen by the pseudocyst; (2) digestive action of the pancreatic fluid that leaks from the cyst on the spleen; (3) inflammation of pancreatic tissue in the spleen due to displacement; (4) concurrent formation of splenic vein thrombosis and liquefaction of the infarcted area in the spleen. In such cases, early splenectomy should be performed, and it is preferable to perform distal pancreatectomy at the same time.

　　7. Other (1) Jaundice: Obstructive jaundice can be caused by compression of the common bile duct by the pseudocyst. (2) Diarrhea: Pseudopancreatic cysts can sometimes cause severe diarrhea.

　　1. Symptoms

　　There may be dull pain in the upper abdomen, fullness, nausea and vomiting; when the cysts enlarge, there may be compression symptoms; constipation, jaundice, ascites, lower limb edema, etc.; when the cysts rupture into the abdominal cavity, there may be symptoms of acute peritonitis; if they break into the digestive tract, internal fistulas may form, and symptoms such as recurrent high fever, abdominal pain, and even upper gastrointestinal bleeding may occur.

　　2. Signs

　　Most patients can palpate a circular, smooth, cystic mass in the upper abdomen, which may be tender when infected.

　　1. This disease often occurs secondary to acute pancreatitis and pancreatic injury, with about 3/4 of the patients caused by acute pancreatitis, and about 10% of acute pancreatitis cases develop pseudopancreatic cysts.

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

　　3. Take an active part in physical exercise to enhance personal physical fitness. Improve the body's immunity to diseases.

　　1. In a small number of patients, serum amylase and blood glucose levels are elevated, and there are more fat droplets in the stool.

　　2. Barium meal examination shows dilatation of the duodenal bulb, compression and displacement of the stomach, duodenum, and transverse colon.

　　3. B-ultrasound examination shows a spherical, smooth, and clear lesion area with no light spot reflection in the dark area, or shows an internal fistula formed between the cyst and the digestive tract.

　　4. Angiography shows the vessels are compressed in a birdcage-like manner, and the capillaries show a uniform and faint staining feature around the pancreatic cyst, or there may be an internal fistula between the cyst and the blood vessels.

　　5. Pancreatic scan: 75Se-methionine pancreatic scintigraphy shows no aggregation phenomenon.

　　CT shows round, elliptical, and clear low-density shadows with clear edges, and CT values close to the density of water.

　　1. Foods that are good for the body for pancreatic cysts

　　Pay attention to eating light foods, eat rationally, and eat vegetarian meals to prevent the deterioration of the disease. However, long-term restriction of fat should pay attention to the supplementation of fat-soluble vitamins, such as egg yolks, fresh milk, carrots, spinach, tomatoes, etc.

　　2. Foods that are best not to eat for pancreatic cysts

　　Strictly prohibit alcohol and absolutely prohibit overeating and drinking due to the fact that both alcohol and overeating and drinking can cause excessive secretion of pancreatic juice, obstructed excretion of pancreatic juice, disorder of pancreatic blood circulation, and reduced amount of trypsin inhibitor substances. Therefore, patients with chronic pancreatitis should abstain from alcohol and overeating and drinking to prevent acute attacks.

　　Pseudocysts are complications of trauma and acute pancreatitis, with an average formation process of 6 weeks. Their treatment is divided into two categories.

　　1. Emergency Surgery

　　In cases where pseudocysts rupture, bleed, or develop secondary infection, life-threatening conditions, emergency external drainage (incision and drainage or cyst bag suture) should be performed, with attention to the supplementation of water, electrolytes, and systemic treatment. Surgery should be performed again after the fistula forms.

　　2. Elective Surgery

　　After the formation of pseudocysts for 2 to 4 months, surgery is selected according to the degree and scope of the lesion. A pancreatic tail splenectomy can be performed at the tail of the pancreas; cystogastrostomy, cystoduodenostomy, and cystojejunostomy Roux-Y anastomosis can be performed in the head and body of the pancreas. The anastomosis should be large enough to prevent reflux infection. When an internal fistula exists, the intestines should be cleaned before surgery, taking 1g of neomycin, 4 times a day, and 0.2g of metronidazole, 3 times a day. At the same time, vitamin K should be injected intramuscularly.

　　True cysts are generally not tightly adhered to the surrounding tissues, making them easier to peel off. They can also be removed along with a part of the pancreas containing the cyst.