Pancreatic pseudocyst

A pancreatic pseudocyst is a circumscribed collection of fluid rich in amylase and other pancreatic enzymes, blood and necrotic tissue typically located in the lesser sac. It has a non-epithelialised lining made of granulation tissue and hence the name pseudocyst (pseudo - false). By contrast, true cysts have an epithelial lining. This is typically a complication of acute pancreatitis, but may also occur following abdominal trauma. Pancreatic pseudocysts account for approximately 75% of all pancreatic masses.

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Etiopathogenesis

Acute pancreatitis results amongst other things in the disruption of pancreatic parenchyma and the ductal system. This results in extravasation of pancreatic enzymes which in turn digest the adjoining tissues. This results in a collection of fluid containing pancreatic enzymes, hemolysed blood and necrotic debris around the pancreas. The lesser sac being a potential space, the fluid collects here preferentially. This is called an acute pancreatic collection. Some of these collections resolve on their own as the patient recovers from the acute episode. However, others become more organised and get walled-off within a thick wall of granulation tissue and fibrosis. This takes several weeks to occur and results in a pancreatic pseudocyst.

Investigations

The questions that need to be answered are:

• where, how big and how many?
• is there a communication with the pancreatic ductal system? Draining such a pseudocyst carries an increased risk of pancreatic fistula.

The most useful imaging tools are

• Ultrasonography - The role of ultrasonography in imaging the pancreas is limited by patient habitus, operator experience and the fact that the pancreas lies behind the stomach (and so a gas-filled stomach will obscure the pancreas).
• Computerised tomography - This is the gold standard for initial assessment and follow-up
• Magnetic Resonance Cholangio-pancreatography - to establish the relationship of the pseudocyst to the pancreatic ducts

Treatment

A small pseudocyst that is not causing any symptoms may be managed conservatively. However, a large proportion of them will need some form of treatment, The interventions available are:

• Endoscopic trans-gastric drainage
• Imaging guided percutaneous drainage
• Laparoscopic/open cystogastrostomy