Pancreatic pseudocyst: The past, the present, and the future

Table 1 Definitions of pancreatic fluid collections according to the 2012 Atlanta classification[1]

Collection type	Definitions
Acute peripancreatic fluid collection	Peripancreatic fluid seen within the first 4 wk after onset of interstitial edematous pancreatitis, with no associated peripancreatic necrosis or features of a pseudocyst
Pancreatic pseudocyst	An encapsulated collection of fluid with a well-defined inflammatory wall usually outside the pancreas with minimal or no necrosis. It usually takes more than 4 wk for it to mature after the onset of interstitial edematous pancreatitis and contains amylase-rich fluid with no solid debris
Acute necrotic collection	A collection containing variable amounts of both fluid and necrosis associated with necrotizing pancreatitis within the first 4 wk. The necrosis can involve the pancreatic parenchyma and/or the peripancreatic tissues
Walled-off necrosis	A mature, encapsulated collection of pancreatic and/or peripancreatic necrosis with a well-defined inflammatory wall. It usually matures 4 wk after the onset of necrotizing pancreatitis