GI Radiology > Pancreas > Inflammatory > Psuedocysts

Pancreatic Pseudocysts


   Pseudocysts occur most frequently in patients with acute or chronic pancreatitis; other etiologies include pancreatic trauma, pancreatic ductal obstruction, or neoplasm.  Following an episode of pancreatitis, pancreatic enzymes cause local inflammation and tissue distruction.  This process causes exudation of fluid from the pancreas which collects within the pancreatic membrane or the surrounding compartments.  Most of these "acute fluid collections" resolve within 4-6 weeks; if these collection persists, it evolves into a pseudocysts with a fibrotic capsule.  (It should be noted that the capsule of a pancreatic pseudocyst does not have a true epithelial lining, which distinguishes it from a cystic pancreatic neoplasm.)  Most pseudocysts are located in the lesser peritoneal sac, near the pancreas.  Larger pseudocysts can extend into the paracolic gutters, pelvis, and mediastinum.

   Pseudocyst development should be suspected in patients with persistant abdominal pain, mild fevers, and elevated amylase or lipase, following resolution of pancreatitis.  Complications of pseudocysts include infection (most common), obstruction, perforation, hemorrhage (eroding adjacent vessels).

   US and CT can detect pseudocysts as small as 5 mm.  Opacification of the ducts during ERCP may also assist in the visualization of pseudocysts by highlighting secondary signs of ductal obstruction or displacement.  Furthermore, 30-80% of pseudocysts communicate with the pancreatic duct, and become visible during fluoroscopy.  Care must be taken to prevent over distention of the pseudocyst during ERCP, and patients must be monitored for signs of sepsis after the introduction of contrast medium into the cyst.

 

Pseudocyst Findings

Contrast-enhanced CT:
-Low attentuation and homogenous appearence
-Well-defined, nonepithelial, fibrous wall (distinguished this from actue fluid collection)
-Round or ovoid shape

ERCP:
-Communicating pseudocyst filling with contrast.

   The table below distinguished the radiographic findings of pseudocysts and acute fluid collections:
 

Distinguishing Radiographic Features of
Pseudocyst vs. Acute Fluid Collection

Pseudocyst Acute fluid collection
-Round, ovoid, well-defined
-Well-defined, fibrous wall
-Poorly defined shape
-No fibrotic capsule

 

   Weekly U/S are recommended to monitor the evolution of pseudocysts, should one be discovered in the workup of pancreatitis.  A small fluid collection within the first 6 weeks may be tolerated and evaluated for progression.  Pseudocysts > 5cm, growing, or persistent for more than 6 weeks, should be treated regardless of the presence of symptoms.  US or CT guided drainage is advised for such cases; surgical intervention is rarely indicated because of the development of endoscopic and interventional radiological procedures.
 
 

 

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