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

Table 2 Classification by Nealon and Walser[30]

Classification	Description
Type I	Normal duct, no communication between duct and pseudocyst
Type II	Normal duct, with communication between duct and pseudocyst
Type III	Otherwise, normal duct with stricture and no communication between duct and pseudocyst
Type IV	Otherwise, normal duct with stricture and communication between duct and pseudocyst
Type V	Otherwise, normal duct with presence of complete cut-off along its course
Type VI	Chronic pancreatitis, no communication between duct and pseudocyst
Type VII	Chronic pancreatitis, with communication between duct and pseudocyst