Pancreatic Pseudocyst


  • A pancreatic pseudocyst is a peripancreatic (or intrapancreatic) fluid collection associated with a history of pancreatitis, that is surrounded by a well-defined inflammatory wall and that has no solid component.
    • The term “pseudocyst” is often incorrectly used to define various types of fluid collections associated with pancreatitis. As a result, medical literature on pseudocysts is not consistent in its descriptions or its findings.
    • An important distinction between “fluid collections” associated with pancreatitis is that some consist of fluid alone, whereas others arise from necrosis of pancreatic parenchyma and/or peripancreatic tissues. The latter type of fluid collection involves a solid component (with variable amounts of fluid), which distinguishes them from pseudocysts.
  • Types of fluid collections:
    • Acute peripancreatic fluid collection (APFC)
      • A fluid collection that develops in the early phase of interstitial edematous acute (typically mild) pancreatitis
      • Lack a well-defined wall on CT scan
      • Not associated with necrotizing pancreatitis
      • Remains sterile and usually resolves without intervention
      • If APFC persists beyond 4 weeks, likely to develop into a pancreatic pseudocyst, although this is considered a rare outcome
    • Pancreatic pseudocyst
      • Refers specifically to a peripancreatic (or less commonly, an intrapancreatic) fluid collection
      • Surrounded by a well-defined inflammatory wall and containing no solid material
      • Pancreatic pseudocysts develop >4 weeks after the onset of interstitial pancreatitis.
    • Acute necrotic collection (ANC)
      • A collection of both variable amounts of fluid and solid (necrotic) material related to pancreatic and/or peripancreatic necrosis
      • Occur within the first 4 weeks of disease and can resemble an APFC in the first few days of acute pancreatitis
      • As necrotizing pancreatitis develops and necrosis evolves, solid component become evident.
      • May be multiple and may involve the pancreatic parenchyma alone, the peripancreatic tissue alone, or most commonly both
      • May be infected or sterile
      • Generally associated with more severe sequelae of acute pancreatitis
    • Walled-off necrosis (WON)
      • Collection of varying amounts of liquid and solid material surrounded by a mature, enhancing wall of reactive tissue
      • Represents a mature, encapsulated ANC
      • Develops no earlier than 4 weeks after episode of necrotizing pancreatitis
      • May be multiple and present at sites distant from the pancreas
      • May be sterile or infected


  • Pseudocysts occur when there is disruption in the pancreatic ductular system, or its intrapancreatic branches, without any evidence of pancreatic or peripancreatic necrosis.
  • This results in the extravasation of pancreatic enzymes evoking an inflammatory response.
  • The inflammatory reaction leads to a fluid collection that is rich in pancreatic enzymes (APFC).
  • If the duration of the fluid collection is >4 weeks, becomes localized (intrapancreatic or extrapancreatic), and develops a fibrin capsule, it becomes a pseudocyst.
  • A pseudocyst does not have a true epithelial lining.
  • If there is communication between the pseudocyst and the pancreatic duct, the enzyme level in the fluid remain elevated; if there is no communication, the enzyme level falls with time.

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