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Recovery from acute pancreatitis is now expected, with mortality less than 10%, which reflects improvements in the treatment of complications and intensive care management.1 A third of patients with acute pancreatitis develop complications and a quarter of these will die of them. These complications can be local, regional, or systemic. Most regional and systemic complications occur in association with severe acute pancreatitis. The most important determinants of severity in acute pancreatitis are infected local complications and multiple organ dysfunction.2 These regional and systemic complications provide the basis for defining four categories of severity (Table 55-1).3 This chapter will focus on the diagnosis and management of the important complications of acute pancreatitis.
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Severe acute pancreatitis is associated with fluid collections and tissue necrosis in and around the pancreas.4 These local complications of acute pancreatitis were defined by the Atlanta Symposium in 1992 as pancreatic necrosis, pseudocyst, and abscess. These terms, however, have proven to be confusing and new terminology has been introduced in an attempt to reflect current understanding of the pathophysiology and morphology of the disease.5,6 In the revised Atlanta Classification, fluid collections less than 4 weeks after disease onset are termed either an acute fluid collection or a postnecrotic pancreatic or peripancreatic fluid collection.7 Over time changes in the morphology of the lesion occur, in particular the reaction of the surrounding tissue to the enzyme-rich fluid produces a wall, and this is usually well defined on CT scan after 4 weeks. A pancreatic pseudocyst is the term that has traditionally been applied to this lesion, but it is now appreciated that the contents may be anywhere on a continuum from entirely solid to entirely fluid.8 When a fluid collection has developed in association with pancreatic necrosis, the revised Atlanta Classification has suggested that this is termed “walled off necrosis” (WON). In addition to this variation in content (solid to fluid) local complications can also be sterile or infected, with the latter having significant prognostic significance.
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Acute Fluid Collections
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