CT abdomen and pelvis with IV contrast to evaluate for pancreatic necrosis, is more reliable when performed 5 to 7 days after presentation, as impaired pancreatic perfusion, edema, and pancreatic necrosis evolve over several days and earlier imaging may underestimate necrosis [2,3]. Similarly, CT abdomen and pelvis with IV contrast is also frequently used for the evaluation of acute peripancreatic fluid collections. Most fluid collections develop in the early phase of pancreatitis and approximately half spontaneously resolve. These acute peripancreatic collections do not have a solid component or a discrete wall and are usually found in the lesser sac and anterior pararenal space. They are usually sterile, rarely become infected, and do not typically necessitate early (if any) intervention [18,21]. Moreover, because patients who undergo early CT for AP are more likely to have repeat CT scans during the same admission [6,8], waiting 5 to 7 days to evaluate the severity and complications of AP with CT abdomen and pelvis with IV contrast is recommended, even in patients with suspected severe AP. In the presence of suspicion for severe disease, the utility of CT abdomen and pelvis without IV contrast is limited to the detection of fluid collections as it cannot assess the presence of pancreatic necrosis. Similarly, adding a noncontrast phase by performing CT abdomen and pelvis without and with IV contrast does not add additional diagnostic information. In a severely ill patient who may not be able to stay still through a fairly long MRI without and with IV contrast with MRCP, an MRI without IV contrast with MRCP may be performed, as a motion-degraded MRI may not add additional diagnostic value. An MRI abdomen without IV contrast with MRCP could detect the presence of pancreatic necrosis. Diffusion-weighted imaging may be used as an alternative to contrast to assess the presence of necrotizing pancreatitis in some cases.
Acute Pancreatitis. CT abdomen and pelvis with IV contrast to evaluate for pancreatic necrosis, is more reliable when performed 5 to 7 days after presentation, as impaired pancreatic perfusion, edema, and pancreatic necrosis evolve over several days and earlier imaging may underestimate necrosis [2,3]. Similarly, CT abdomen and pelvis with IV contrast is also frequently used for the evaluation of acute peripancreatic fluid collections. Most fluid collections develop in the early phase of pancreatitis and approximately half spontaneously resolve. These acute peripancreatic collections do not have a solid component or a discrete wall and are usually found in the lesser sac and anterior pararenal space. They are usually sterile, rarely become infected, and do not typically necessitate early (if any) intervention [18,21]. Moreover, because patients who undergo early CT for AP are more likely to have repeat CT scans during the same admission [6,8], waiting 5 to 7 days to evaluate the severity and complications of AP with CT abdomen and pelvis with IV contrast is recommended, even in patients with suspected severe AP. In the presence of suspicion for severe disease, the utility of CT abdomen and pelvis without IV contrast is limited to the detection of fluid collections as it cannot assess the presence of pancreatic necrosis. Similarly, adding a noncontrast phase by performing CT abdomen and pelvis without and with IV contrast does not add additional diagnostic information. In a severely ill patient who may not be able to stay still through a fairly long MRI without and with IV contrast with MRCP, an MRI without IV contrast with MRCP may be performed, as a motion-degraded MRI may not add additional diagnostic value. An MRI abdomen without IV contrast with MRCP could detect the presence of pancreatic necrosis. Diffusion-weighted imaging may be used as an alternative to contrast to assess the presence of necrotizing pancreatitis in some cases.