Pseudocyst

A pseudocyst is a localized collection of fluid walled off by a non-epithelial lining, typically composed of fibrous or granulation tissue. Unlike true cysts, pseudocysts lack an epithelial lining. The term is most commonly used for pancreatic pseudocysts, which arise after pancreatitis or pancreatic trauma, but pseudocysts can occur in other organs and spaces.

Pancreatic pseudocysts form when pancreatic juice leaks from damaged ducts and collects in the retroperitoneum or peripancreatic tissues. A fibrous capsule gradually develops around the fluid. The fluid content often contains high levels of pancreatic enzymes. Pseudocysts may be asymptomatic or cause early satiety, abdominal pain, or a sense of fullness. Complications include infection, rupture, hemorrhage, and obstruction of nearby structures.

Diagnosis relies on imaging and cyst-fluid analysis. Ultrasound or CT scan typically reveals a well-defined, cystic lesion with a thin wall. MRI can provide detailed anatomy. Endoscopic ultrasound may assist in evaluation and planning drainage. Fluid analysis showing very high amylase levels with low or variable carcinoembryonic antigen (CEA) helps distinguish pseudocysts from mucinous cysts; infection should be considered if the fluid is purulent.

Management depends on symptoms, size, and complications. Asymptomatic and small pseudocysts may be observed with treatment of the underlying pancreatitis. Persistent or symptomatic pseudocysts (often after 4–6 weeks) can be drained endoscopically (transpapillary or transmural drainage), percutaneously, or surgically (cystogastrostomy, cystojejunostomy). Infected or enlarging pseudocysts require prompt drainage and antibiotics. Prognosis is generally favorable with appropriate treatment.