In the late phase (after the first week) of moderately severe or severe pancreatitis, local complications fully develop, and it is important to characterize these complications, as they may require different interventions to avoid increased morbidity or mortality. Imaging plays a major role in identifying the presence and extent of pancreatic and peripancreatic necrosis and characterizing local complications in the late phase. CT Abdomen and Pelvis In the acute phase, it may not be possible to differentiate an acute peripancreatic fluid collection from an acute necrotic collection, as they both appear as fluid density on CT. However, after the first week in the late phase, it is easier to distinguish whether a collection is associated with pancreatic or peripancreatic necrosis. Pancreatic necrosis on CT abdomen and pelvis with IV contrast is characterized by single or multiple areas of nonenhancing pancreatic parenchyma, whereas peripancreatic fat necrosis usually appears as a low attenuation collection. False- positive results for pancreatic necrosis using enhancement on CT are due to reversible reduced perfusion and edema or fluid in the pancreatic parenchyma [21]. Infected pancreatic necrosis usually arises in the second to third week, and signs of infection on CT include gas within areas of necrosis or fluid collections. Acute Pancreatitis CT abdomen and pelvis with IV contrast is the most commonly obtained imaging test to detect the presence of peripancreatic collections [26]. Acute peripancreatic fluid collections do not have a solid component and have a density of 0 to 30 HU on CT. They also lack a discrete wall, are usually sterile, and rarely become infected. Although the majority of acute peripancreatic fluid collections are peripancreatic in the lesser sac or anterior pararenal space, some may track down into the pelvis or superiorly into the mediastinum. Therefore, CT of both the abdomen and pelvis may be warranted.
Acute Pancreatitis. In the late phase (after the first week) of moderately severe or severe pancreatitis, local complications fully develop, and it is important to characterize these complications, as they may require different interventions to avoid increased morbidity or mortality. Imaging plays a major role in identifying the presence and extent of pancreatic and peripancreatic necrosis and characterizing local complications in the late phase. CT Abdomen and Pelvis In the acute phase, it may not be possible to differentiate an acute peripancreatic fluid collection from an acute necrotic collection, as they both appear as fluid density on CT. However, after the first week in the late phase, it is easier to distinguish whether a collection is associated with pancreatic or peripancreatic necrosis. Pancreatic necrosis on CT abdomen and pelvis with IV contrast is characterized by single or multiple areas of nonenhancing pancreatic parenchyma, whereas peripancreatic fat necrosis usually appears as a low attenuation collection. False- positive results for pancreatic necrosis using enhancement on CT are due to reversible reduced perfusion and edema or fluid in the pancreatic parenchyma [21]. Infected pancreatic necrosis usually arises in the second to third week, and signs of infection on CT include gas within areas of necrosis or fluid collections. Acute Pancreatitis CT abdomen and pelvis with IV contrast is the most commonly obtained imaging test to detect the presence of peripancreatic collections [26]. Acute peripancreatic fluid collections do not have a solid component and have a density of 0 to 30 HU on CT. They also lack a discrete wall, are usually sterile, and rarely become infected. Although the majority of acute peripancreatic fluid collections are peripancreatic in the lesser sac or anterior pararenal space, some may track down into the pelvis or superiorly into the mediastinum. Therefore, CT of both the abdomen and pelvis may be warranted.