What is a Pancreatic Pseudocyst?
A pancreatic pseudocyst is a collection of pancreatic juice enclosed by a wall of fibrous or granulation tissue that develops as a complication following an attack of acute pancreatitis, requiring at least four weeks from the onset of pancreatitis to form. 1
Anatomic and Pathologic Characteristics
- The defining feature is the organized wall composed of fibrous or granulation tissue, which distinguishes it from acute fluid collections that lack this structured wall 1
- The pseudocyst contains pancreatic juice rather than necrotic tissue or pus 1
- This is a non-necrotic collection, differentiating it from walled-off necrosis which contains non-viable pancreatic parenchyma 2
- The four-week minimum timeframe from pancreatitis onset is critical for diagnosis—collections occurring earlier are classified as acute peripancreatic fluid collections, not pseudocysts 1, 3
Clinical Context and Epidemiology
- Pancreatic pseudocysts occur as complications of both acute and chronic pancreatitis, with higher incidence in chronic pancreatitis 4, 5
- The clinical presentation is often nonspecific, with abdominal pain being the most common symptom 6
- More than half of acute fluid collections resolve spontaneously without intervention 1
Diagnostic Approach
- CT scanning is the most commonly used diagnostic tool, though it cannot reliably distinguish pseudocyst from other peripancreatic collections alone 1
- Ultrasound or MRI should be obtained to confirm the presence of fluid (as opposed to necrotic tissue) before definitively diagnosing a pseudocyst 1
- Endoscopic ultrasound with fine needle aspiration has become the preferred test to distinguish pseudocyst from other cystic lesions of the pancreas when diagnostic uncertainty exists 7, 6
Important Distinctions from Other Pancreatic Collections
- Acute peripancreatic fluid collections: Occur early in pancreatitis and always lack a wall of granulation or fibrous tissue 1, 3
- Pancreatic abscess: Contains pus with little or no pancreatic necrosis 1, 3
- Infected necrosis: Involves non-viable pancreatic parenchyma with infection, tripling mortality risk 1, 3
- Walled-off necrosis: A chronic necrotic collection (>4 weeks) containing non-viable pancreatic tissue 2
Complications Requiring Recognition
- Hemorrhage: CT attenuation values >50 HU suggest blood content 1
- Infection: Indicated by sudden high fever, though low-grade fever is common in necrotizing pancreatitis without necessarily indicating infection 1
- Rupture: Free gas in retroperitoneum on plain films is a late sign of infection with gas-forming organisms 1
- Biliary or gastric outlet obstruction: Epigastric mass with vomiting suggests persistent fluid collection causing obstruction 1