Pancreatic pseudocyst
From Medical-Wiki
Pancreatic pseudocysts are the most common cystic lesion of the pancreas. They should be distinguished from pancreatic cysts because their anatomy and origin are totally unrelated.
A pancreatic cyst has an epithelial lining and contains fluid. Examples of pancreatic cysts are congenital cysts and cystic neoplasms, e.g. mucinous cystic tumors or serous cystadenomas.
A pancreatic pseudocyst has a well-defined capsule of fibrous and/or granulation tissue that contains fluid and is associated with acute or chronic pancreatitis, or trauma. A pseudocyst does not possess an epithelial lining.
Both of these must also be distinguished from acute fluid collections. These occur early in the course of acute pancreatitis and are located in proximity to the gland or within it. A fluid collection has neither an epithelial lining nor a fibrous capsule surrounding it.
Contents |
Formation process
The process that results in the formation of a pseudocyst begins with pancreatic inflammation. When the inflammation leads to necrosis of a part of the pancreas, there is ductal disruption and leakage of pancreatic fluids. Pancreatic fluid is rich in amylase, lipase, and enterokinase. This fluid initiates an aggressive inflammatory response that over time leads to the formation of a thick fibrous capsule that surrounds the fluid.
Until the fluid forms the capsule, it is considered a fluid collection. It usually takes 4 weeks for a fibrous capsule to form. Most acute fluid collections associated with acute pancreatitis resolve spontaneously—prior to the formation of a capsule.
The mechanism by which trauma and chronic pancreatitis produce pseudocysts is basically the same—disruption of ductal integrity causing extravasation of pancreatic fluid. [1]
Pseudocysts may be single or multiple. Multiple cysts are seen more frequently in patients with alcoholism. One third of pseudocysts are associated with the head of the gland—two thirds with its tail.
Differential diagnosis
A pseudocyst should be suspected in a patient who has had a recent episode of pancreatitis and has ongoing abdominal pain, anorexia, and weakness. On physical examination, an abdominal mass may be noted. Rarely, patients are jaundiced from obstruction of the common hepatic duct. A pleural effusion is a common finding.
Diagnosis
Radiological findings
Abdominal CT scanning is the imaging technique of choice for pancreatic pseudocysts. It has a sensitivity of 90% to 100%. One complication of a pseudocyst that may be noted by CT scanning is a pseudo-aneurysm of the splenic artery that can potentially bleed into the cyst. [2]
Treatment
Pseudocysts that have persisted for less than 6 weeks and are smaller than 6 cm in diameter may be followed without intervention. Those that exceed 6 weeks in age or 6 cm in diameter will typically require drainage because their rate of spontaneous resolution is low and their continued presence is associated with a high morbidity.
Appropriate disposition of pseudocysts is contingent upon a variety of factors. Chronic pancreatitis is associated with a high degree of narcotic dependence—a problem worsened by the fact that it is a disease also associated with alcoholism. Thus a “definitive” treatment is often sought to reduce one risk factor. However, alcoholism is also associated with a higher incidence of operative morbidity.
All of this must be factored into the decision of how to approach the excision or drainage of a pseudocyst. When there is an unanswered question about the existence of a cancer, open excision is often favored. [3]
