Clinical meaning
A pancreatic pseudocyst is an encapsulated collection of fluid rich in pancreatic enzymes (amylase, lipase, trypsin) that develops as a complication of acute or chronic pancreatitis, pancreatic trauma, or rarely pancreatic duct disruption from malignancy. The term pseudocyst distinguishes it from a true cyst because it lacks an epithelial lining; instead, the wall is composed of fibrous tissue, granulation tissue, and inflammatory debris that organizes over a period of 4-6 weeks following the initial pancreatic insult. The pathogenesis begins with pancreatic ductal disruption, which allows pancreatic juice to leak into the peripancreatic space. In acute pancreatitis, autoactivation of trypsinogen to trypsin within the pancreas initiates a cascade of enzyme activation that causes parenchymal autodigestion, necrosis, and inflammation. Inflammatory mediators (interleukin-1, interleukin-6, tumor necrosis factor alpha) increase vascular permeability, leading to fluid extravasation into the peripancreatic tissues and lesser sac. Over weeks, this fluid collection becomes encapsulated by a wall of reactive fibrous tissue without an epithelial lining, forming the pseudocyst. The fluid within the pseudocyst is rich in pancreatic enzymes (markedly elevated amylase and lipase), and the enzymatic content makes...