Acute necrotic collection

Acute necrotic collections (ANCs) are an early, local complication of necrotizing pancreatitis.

Terminology

The following are the latest terms according to the updated Atlanta classification to describe fluid collections associated with acute pancreatitis ^1,2:

• fluid collections in interstitial edematous pancreatitis
  • acute peripancreatic fluid collections (APFC): in the first 4 weeks: non-encapsulated peripancreatic fluid collections
  • pseudocysts: develop after 4 weeks; encapsulated peripancreatic or remote fluid collections
• fluid collections in necrotizing pancreatitis
  • acute necrotic collections (ANCs): in the first 4 weeks; non-encapsulated heterogeneous non-liquefied material
  • walled-off necrosis (WON or WOPN): develop after 4 weeks; encapsulated heterogeneous non-liquefied material  

Pathology

Acute necrotic collections develop within the first four weeks and contain a variable amount of fluid/non-liquid necrotic material. They may be pancreatic or peripancreatic in location and can be sterile or infected. 

Radiographic features

CT

On contrast-enhanced CT the following features are seen:

• heterogeneous, non-liquid density collection within the pancreas and/or peripancreatic tissues
• no defined capsule
• no peripheral enhancement

Differential diagnosis

• acute peripancreatic fluid collections (APFC): within the first week, differentiation between acute necrotic collections (ANC) and APFC may prove impossible