Acute peripancreatic fluid collection

Acute peripancreatic fluid collections (APFC) are an early complication of acute pancreatitis that usually develop in the first four weeks. After four weeks, the term pseudocysts is used. The absence of necrosis differentiates APFCs from acute necrotic collections (ANC), that is, APFCs occur in interstitial edematous pancreatitis, not in necrotizing pancreatitis.

Terminology

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

• 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

APFCs result from pancreatic/peripancreatic inflammation and/or rupture of one of the small pancreatic side ducts .

Radiographic features

CT

Homogeneous peripancreatic fluid collection that is non-encapsulated and bound by the retroperitoneum .

Treatment and prognosis

Most acute peripancreatic fluid collections resolve spontaneously in the first few weeks. They very rarely become infected. Drainage (surgical/percutaneous) is not recommended .

Differential diagnosis

• acute necrotic collection (ANC): radiographic differentiation between it and an acute peripancreatic fluid collection in the first week may prove impossible
• pancreatic necrosis: fluid collections can accumulate within the pancreas (acute peripancreatic fluid collection are always peripancreatic, as their name implies)