Walled off pancreatic necrosis and pseudocysts occur 4 weeks after a bout of pancreatitis. They may be symptomatic due to a gastric outlet or biliary obstruction. Before this time they are termed "acute necrotic collections" or "acute peripancreatic fluid collections", respectively.

One form of treatment is a through drainage into the stomach (cyst gastrotomy) or less commonly percutaneously.