Contrast-enhanced CT in a 50-year-old with acute pancreatitis shows pancreatic parenchymal necrosis (no enhancement in 40% of gland) along with a well-defined, thick-walled, homogeneous fluid collection adjacent to the pancreatic tail at 5 weeks from onset. According to the revised Atlanta Classification, this collection is classified as:

• A Acute peripancreatic fluid collection (APFC)
• B Pancreatic pseudocyst
• C Walled-off necrosis (WON) ✓
• D Acute necrotic collection (ANC)

Explanation

In necrotising pancreatitis, collections evolving beyond 4 weeks that contain necrotic debris (solid or semi-solid) within a well-defined wall constitute walled-off necrosis (WON) per the revised Atlanta Classification. Pancreatic pseudocyst occurs in interstitial oedematous pancreatitis (no necrosis) after 4 weeks and contains only fluid. Acute necrotic collection (ANC) is the early (< 4 weeks) form. APFC is an early fluid collection (< 4 weeks) without a defined wall in interstitial pancreatitis.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.