Imaging of Acute Pancreatitis and Its Complications Desiree E. Morgan  Clinical Gastroenterology and Hepatology  Volume 6, Issue 10, Pages 1077-1085 (October 2008) DOI: 10.1016/j.cgh.2008.07.012 Copyright © 2008 AGA Institute Terms and Conditions

Figure 1 Mild (nonsevere) acute pancreatitis. A 36-year-old woman presented with acute onset of abdominal pain. Axial CECT image shows a small amount of inflammatory stranding (arrow) extending from the tail of pancreas, consistent with acute peripancreatic fluid collection. Visualized portions of the glandular tissue are enhancing normally. Clinical Gastroenterology and Hepatology 2008 6, 1077-1085DOI: (10.1016/j.cgh.2008.07.012) Copyright © 2008 AGA Institute Terms and Conditions

Figure 2 Severe acute pancreatitis. (A) Axial CECT image through the pancreatic body and tail region shows edema of the tail (arrow), with low attenuation replacing the pancreatic parenchyma (short arrows) anterior to the splenic vein. (B) Slightly more inferiorly, normal enhancement is seen in the pancreatic head region (arrow). There is a large amount of peripancreatic retroperitoneal fluid as well as a small amount of ascites and anasarca. Clinical Gastroenterology and Hepatology 2008 6, 1077-1085DOI: (10.1016/j.cgh.2008.07.012) Copyright © 2008 AGA Institute Terms and Conditions

Figure 3 Subacute severe pancreatitis. A 52-year-old man presented on transfer from an outside hospital approximately 10 days after onset of acute pancreatitis. (A) Axial CECT through the body region of the pancreas demonstrates partial enhancement of the pancreatic neck (arrow), with heterogeneous low density replacing the remainder of the pancreas at this level. (B) Slightly more inferiorly at the uncinate level, there is partial granulation of the wall, with internal septations seen in the complex collection. The inflammatory exudate has also broken through Gerota's fascia and is in the perirenal space bilaterally. This patient has greater than 50% glandular necrosis and fluid collections in 2 regions, resulting in a CTSI of 10. Clinical Gastroenterology and Hepatology 2008 6, 1077-1085DOI: (10.1016/j.cgh.2008.07.012) Copyright © 2008 AGA Institute Terms and Conditions

Figure 4 MRI of acute pancreatitis. T1-weighted intravenous gadolinium-enhanced axial images through the pancreatic body (A) reveal partial replacement of glandular tissue by low signal collection that expands the retrogastric region. (B) T2-weighted fat-suppressed axial image through the collection reveals the complex nature of the fluid (bright) and solid components depicted by the low signal foci (arrows). (C) Same patient's coronal T1-weighted gadolinium-enhanced image demonstrates the relationship of this postnecrotic pancreatic fluid collection to the duodenal (short arrow) and gastric (arrow) walls, important for endoscopic drainage planning. Clinical Gastroenterology and Hepatology 2008 6, 1077-1085DOI: (10.1016/j.cgh.2008.07.012) Copyright © 2008 AGA Institute Terms and Conditions

Figure 5 Acute interstitial edematous pancreatitis. Axial CECT image through the mid pancreas reveals obscuration of the normal fatty interdigitation of the pancreatic parenchyma in the neck and body region (arrow), as well as acute peripancreatic fluid. The gland is hypoperfused but still enhancing, indicating the absence of necrosis. Clinical Gastroenterology and Hepatology 2008 6, 1077-1085DOI: (10.1016/j.cgh.2008.07.012) Copyright © 2008 AGA Institute Terms and Conditions

Figure 6 Acute necrotizing pancreatitis with peripancreatic fat necrosis. Axial CECT image through the pancreatic body region reveals a large amount of peripancreatic fluid extending into the left anterior pararenal space, mesenteric root, and lesser sac. There is enhancement of the pancreatic body (neck and head located on more caudal images). Lower density retroperitoneal fat (arrows) has been incorporated into the collection. Clinical Gastroenterology and Hepatology 2008 6, 1077-1085DOI: (10.1016/j.cgh.2008.07.012) Copyright © 2008 AGA Institute Terms and Conditions

Figure 7 Acute necrotizing pancreatitis with pancreatic glandular and peripancreatic fat necrosis. Axial CECT image through the pancreatic tail reveals a geographic area of diminished enhancement (arrow) surrounded by a peripancreatic inflammatory fluid extending in the anterior pararenal space and transverse mesocolon. Low-density retroperitoneal fat (long arrow) has been incorporated into this postnecrotic pancreatic fluid collection. Clinical Gastroenterology and Hepatology 2008 6, 1077-1085DOI: (10.1016/j.cgh.2008.07.012) Copyright © 2008 AGA Institute Terms and Conditions

Figure 8 Inadequate drainage of postnecrotic pancreatic fluid collection. This 63-year-old man was transferred from an outside hospital after placement of a percutaneous 7F catheter, with failure to improve. (A) Axial CECT image through the pancreatic head region reveals a heterogeneous, air-containing collection in the retroperitoneum. Note 7F drainage catheter (arrow) coursing toward collection from anterior approach. Inflammatory fluid is also seen extending into the right and left anterior pararenal spaces. (B) During endoscopic transgastric drainage of the collection the next day, injection of contrast into the cavity reveals large filling defects (arrows) representing solid necrotic debris that would not pass through the small-bore catheter. (C) Two weeks after placement of transgastric double pigtail catheters and irrigation, noncontrast axial CT through the retroperitoneal cavity reveals near complete evacuation of its contents. The patient underwent noncontrast CT because of renal failure. Clinical Gastroenterology and Hepatology 2008 6, 1077-1085DOI: (10.1016/j.cgh.2008.07.012) Copyright © 2008 AGA Institute Terms and Conditions

Figure 9 Acute peripancreatic fluid collection. A 22-year-old woman had onset of nausea, vomiting, and abdominal pain 24 hours before admission. CECT of the abdomen reveals nonorganized inflammatory fluid extending throughout the left retroperitoneum from the tail of pancreas region. There is no glandular necrosis. Clinical Gastroenterology and Hepatology 2008 6, 1077-1085DOI: (10.1016/j.cgh.2008.07.012) Copyright © 2008 AGA Institute Terms and Conditions

Figure 10 Infected postnecrotic pancreatic fluid collection. Patient presented with acute pancreatitis approximately 3 weeks earlier. CECT through the level of the pancreatic tail reveals multifocal moderately marginated collections surrounding the pancreas and enhancement of the pancreatic body (arrow). Each collection contains dependent air bubbles dispersed through the viscous peripancreatic fluid. The predominantly peripancreatic postnecrotic collection is poorly contained, with gas extending to the periphery (short arrows). The gas is indicative of infection in most cases, although spontaneous fistulization to bowel might give rise to air within postpancreatitis retroperitoneal collections. Clinical Gastroenterology and Hepatology 2008 6, 1077-1085DOI: (10.1016/j.cgh.2008.07.012) Copyright © 2008 AGA Institute Terms and Conditions

Figure 11 WOPN. (A) CECT through the mid-body region of the pancreas reveals enhancing glandular tissue in the head and tail region (arrows), with replacement of the mid-body by a low attenuation collection. The poorly marginated acute inflammatory fluid extends into the transverse mesocolon and bilateral anterior pararenal spaces. The patient was treated in the intensive care unit with supportive measures. (B) Same patient 10 days later. CECT through a similar level once again reveals enhancement of remaining pancreas, with replacement of the central gland by low attenuation. There is partial septation within the collection, and enhancement on the periphery suggests that granulation tissue is beginning to wall off the collection. (C) CECT obtained 5 weeks later shows replacement of the central gland by well-demarcated WOPN. A second collection in the transverse mesocolon is seen more anteriorly. This collection, although homogeneous and low in attenuation, does not reflect a simple pseudocyst because it replaces portions of the gland and arose from necrosis. (D) Same patient 3 months after initially presenting with severe acute pancreatitis. The unenhanced CT demonstrates the walled off collection; a portion of the necrotic pancreas (sequestrum) is visible as a slightly more dense structure (arrows) in the posterior portion of the collection. Clinical Gastroenterology and Hepatology 2008 6, 1077-1085DOI: (10.1016/j.cgh.2008.07.012) Copyright © 2008 AGA Institute Terms and Conditions

Figure 12 Pancreatic pseudocyst. A 45-year-old man with pancreas divisum, 5 weeks after onset of acute pancreatitis. (A) Axial CECT image demonstrates a focal, well-circumscribed low attenuation collection extending anteriorly from the main pancreatic duct (arrow) in the body/tail junction. (B) Same patient's coronal reformatted CT image demonstrates the cyst location in a predominantly extrapancreatic, anterior location. Communication with the main pancreatic duct (demonstrated in A) should be noted because the lesion would be more amenable to successful endoscopic drainage rather than percutaneous approach. Clinical Gastroenterology and Hepatology 2008 6, 1077-1085DOI: (10.1016/j.cgh.2008.07.012) Copyright © 2008 AGA Institute Terms and Conditions

Figure 13 Infected pseudocyst. (A–B) Successively caudal axial CECT images through the inferior pancreatic head region reveal a low attenuation fluid collection, with less well-defined irregular walls. This lesion was drained surgically and contained frankly purulent material. Clinical Gastroenterology and Hepatology 2008 6, 1077-1085DOI: (10.1016/j.cgh.2008.07.012) Copyright © 2008 AGA Institute Terms and Conditions

Figure 14 Relationship of nomenclature: Atlanta Classification vs proposed revisions. Clinical Gastroenterology and Hepatology 2008 6, 1077-1085DOI: (10.1016/j.cgh.2008.07.012) Copyright © 2008 AGA Institute Terms and Conditions