PSEUDOCYST A pseudocyst is a collection of amylase-rich fluid enclosed in a well-defined wall of fibrous or granulation tissue. Pseudocysts typically arise following an attack of mild acute pancreatitis, lie outside the pancreas, and represent an APFC that has not resolved and matured. Formation of a pseudocyst requires 4 weeks or more from the onset of acute pancreatitis. The Term 'pseudocyst' is often used more loosely, to include sterile WON that has failed to resolve, or a collection that has developed in the context of chronic pancreatitis or after pancreatic trauma. If carefully investigated, more than half of these will be found to have a communication with the main pancreatic duct. Pseudocysts are often single but, occasionally, patients will develop multiple pseudocysts. A pseudocyst is usually identified on ultrasound or a CT scan. It is impoant to differentiate a pseudocyst from an APFC; the clinical scenario and the radiological appearances should allow that distinction to be made. Occasionally, a cystic neoplasm may be confused with a chronic pseudocyst. EUS and aspiration of the cyst fluid is very useful in such a situation. The fluid should be sent for measurement of carcinoembryonic antigen (CEA) levels, amylase levels and cytology. Fluid from a pseudocyst typically has a low CEA level, and levels above 400 ng/mL are suggestive of a mucinous neoplasm. Pseudocyst fluid usually has a high amylase level, but that is not diagnostic, as a tumour that communicates with the duct system may yield similar findings. Cytology typically reveals inflammatory cells in pseudocyst fluid. If there is no access to EUS, then percutaneous FNA is acceptable (just aspiration, not percutaneous inseion of a drain). ERCP and MRCP may demonstrate communication of the cyst with the pancreatic duct system, demonstrate ductal anomalies, or diagnose chronic pancreatitis and thus help in planning treatment. Pseudocysts will resolve spontaneously in most instances, but complications can develop. Pseudocysts that are thick-walled or large (over 6 cm in diameter), have lasted for a long time (over 12 weeks), or have arisen in the context of chronic pancreatitis are less likely to resolve spontaneously,but these factors are not specific indications for intervention. Therapeutic interventions are advised only if the pseudocyst causes symptoms, if complications develop, or if a distinction has to be made between a pseudocyst and a tumour. There are three possible approaches to draining a pseudocyst: percutaneous, endoscopic and surgical. Percutaneous drainage to the exterior under radiological guidance should be avoided. It carries a very high likelihood of recurrence. More over, it is not advisable unless one is absolutely ceain that the cyst is not neoplastic and that it has no communication with the pancreatic duct (or else a pancreaticocutaneous fistula will develop). A percutaneous transgastric cystgastrostomy can be done under imaging guidance, and a double-pigtail drain placed with one end in the cyst cavity and the other end in the gastric lumen. This requires specialist expeise but, in experienced hands, the recurrence rates are no more than 15%. Endoscopic drainage usually involves puncture of the cyst through the stomach or duodenal wall under EUS guidance, and placement of a tube drain with one end in the cyst cavity and the other end in the gastric lumen. The success rates depend on operator expeise. Occasionally, ERCP and placement of a pancreatic stent across the ampulla may help to drain a pseudocyst that is in communication with the duct. Surgical drainage involves internally draining the cyst into the gastric or jejunal lumen. Recurrence rates should be no more than 5%, and this still remains the standard against which the evolving radiological and endoscopic approaches are measured. The approach is conventionally through an open incision, but laparoscopic cystgastrostomy is also feasible. Pseudocysts that have developed complications are best managed surgically. There is a small group of patients who, having suffered an attack of necrotising pancreatitis with duct disruption, go on to suffer repeated complications in the form of recurrent fluid collections, pseudocysts, pleural effusions or pancreatic ascites. Very often disruption of the main pancreatic duct in the neck, body or tail is compounded by a stricture or a stone in the head that cannot be treated endoscopically. In such patients, some form of surgical resection and/or a drainage procedure even though it may be technically challenging may be the only way to achieve lasting resolution. Ref: Bailey and love 27th edition Pgno : 1229