Pseudocysts

A pancreatic pseudocyst is a circumscribed collection of fluid rich in pancreatic enzymes, blood, and necrotic tissue, typically located in the lesser sac of the abdomen. Pancreatic pseudocysts are usually complications of pancreatitis, although in children they frequently occur following abdominal trauma. Pancreatic pseudocysts account for approximately 75% of all pancreatic masses.The prefix pseudo- distinguishes them from true cysts, which are lined by epithelium; pseudocysts are lined with granulation tissue.

(Intraoperative Photograph Showing A Large Pseudocyst Compressing The Duodenum.)

Pathophysiology

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).
• Computerized tomography - This is the gold standard for initial assessment and follow-up
• Magnetic resonance cholangiopancreatography (MRCP) - to establish the relationship of the pseudocyst to the pancreatic ducts

(Magnetic Resonance Imaging Of The Abdomen Showing A Pseudocyst Of The Pancreas Compressing The Duodenum.)

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