Persistent organ failure continues to be the main determinant of severity in the late phase; however, local and systemic complications have important implications for management and are characterized by imaging. Imaging plays a major role in the late phase for assessing severity (including identifying the presence and extent of necrotizing pancreatitis and its complications), guiding interventional, endoscopic, or surgical treatment, and monitoring treatment response. Although leukocytosis and fever are clinical hallmarks of infection, imaging is also important for the evaluation of superimposed infection. It is imperative to identify superimposed infection, as the presence of infection within areas of necrosis is associated with an extremely high mortality [3]. The presence and extent of pancreatic and peripancreatic necrosis increases the likelihood of infection and infection within areas of pancreatic necrosis portends an increased risk of death, which is exacerbated by persistent organ failure. By comparison, infected necrosis without persistent organ failure has a lower mortality rate than infected necrosis with persistent organ failure [3,21]. In the absence of infection, patients with peripancreatic (extrapancreatic) necrosis without concomitant pancreatic parenchymal necrosis have a better prognosis than patients with pancreatic parenchymal necrosis. It has been suggested that, given the improved prognosis, extrapancreatic necrosis should be considered a separate clinical entity in AP [25]. In the presence of infection; however, the rates of complication and mortality for patients with only extrapancreatic necrosis are similar to those for patients with pancreatic parenchymal necrosis with or without extrapancreatic necrosis [25].
Acute Pancreatitis. Persistent organ failure continues to be the main determinant of severity in the late phase; however, local and systemic complications have important implications for management and are characterized by imaging. Imaging plays a major role in the late phase for assessing severity (including identifying the presence and extent of necrotizing pancreatitis and its complications), guiding interventional, endoscopic, or surgical treatment, and monitoring treatment response. Although leukocytosis and fever are clinical hallmarks of infection, imaging is also important for the evaluation of superimposed infection. It is imperative to identify superimposed infection, as the presence of infection within areas of necrosis is associated with an extremely high mortality [3]. The presence and extent of pancreatic and peripancreatic necrosis increases the likelihood of infection and infection within areas of pancreatic necrosis portends an increased risk of death, which is exacerbated by persistent organ failure. By comparison, infected necrosis without persistent organ failure has a lower mortality rate than infected necrosis with persistent organ failure [3,21]. In the absence of infection, patients with peripancreatic (extrapancreatic) necrosis without concomitant pancreatic parenchymal necrosis have a better prognosis than patients with pancreatic parenchymal necrosis. It has been suggested that, given the improved prognosis, extrapancreatic necrosis should be considered a separate clinical entity in AP [25]. In the presence of infection; however, the rates of complication and mortality for patients with only extrapancreatic necrosis are similar to those for patients with pancreatic parenchymal necrosis with or without extrapancreatic necrosis [25].