What are the diagnostic criteria and initial imaging studies for necrotizing pancreatitis?

From the Guidelines

Necrotizing pancreatitis is diagnosed based on clinical features, laboratory findings, and imaging studies, with the initial imaging study of choice being contrast-enhanced computed tomography (CECT) performed 72-96 hours after symptom onset. The diagnosis requires evidence of acute pancreatitis (abdominal pain, elevated pancreatic enzymes) plus identification of pancreatic necrosis on imaging. Laboratory markers include elevated serum amylase and lipase (typically >3 times the upper limit of normal), along with inflammatory markers like elevated white blood cell count, C-reactive protein >150 mg/L at 48 hours, and procalcitonin 1. Some key points to consider in the diagnosis and management of necrotizing pancreatitis include:

• The use of the Determinant-Based Classification (DBC) system, which categorizes acute pancreatitis into mild, moderate, severe, and critical based on the presence of organ failure and pancreatic necrosis 1.
• The importance of identifying pancreatic necrosis, which can be detected using CECT, with a sensitivity of close to 100% after 4 days 1.
• The role of the CT severity index in assessing the severity of acute pancreatitis, which evaluates the extent of necrosis and presence of fluid collections 1.
• The potential use of MRI as an alternative to CECT in patients who cannot receive iodinated contrast, although it is less sensitive for detecting gas in fluid collections 1.
• The limited utility of ultrasound for initial diagnosis, but its potential use for monitoring complications 1. Early identification of necrotizing pancreatitis is crucial as these patients require close monitoring, aggressive fluid resuscitation, nutritional support, and vigilance for complications like infected necrosis, which may require antibiotics and possibly intervention 1. The 2019 WSES guidelines for the management of severe acute pancreatitis recommend the use of CECT for diagnosis, staging, and detection of complications, and emphasize the importance of early identification and management of necrotizing pancreatitis to improve outcomes 1. In terms of specific diagnostic criteria, the guidelines recommend the use of the DBC system, which categorizes acute pancreatitis into mild, moderate, severe, and critical based on the presence of organ failure and pancreatic necrosis 1. The guidelines also recommend the use of CECT to detect pancreatic necrosis, with a sensitivity of close to 100% after 4 days 1. Overall, the diagnosis and management of necrotizing pancreatitis require a multidisciplinary approach, with close monitoring and aggressive management to improve outcomes 1.

From the Research

Diagnostic Criteria for Necrotizing Pancreatitis

• The diagnosis of necrotizing pancreatitis is based in large part on imaging findings, particularly computed tomography (CT) and magnetic resonance imaging (MRI) 2.
• The revised Atlanta classification system of 2012 subdivides necrotizing pancreatitis anatomically into parenchymal, peripancreatic, and combined subtypes, and temporally into clinical early (within 1 week of onset) and late (>1 week after onset) phases 2, 3.
• Necrosis due to acute pancreatitis is best assessed on IV contrast-enhanced CT performed 40 seconds after injection 3.

Initial Imaging Studies for Necrotizing Pancreatitis

• CT is used to confirm the diagnosis of acute pancreatitis when the diagnosis is in doubt and to differentiate acute interstitial pancreatitis from necrotizing pancreatitis 3.
• Imaging, primarily CT and MRI, plays an essential role in the diagnosis of necrotizing pancreatitis and the identification of complications, including infection, bowel and biliary obstruction, hemorrhage, pseudoaneurysm formation, and venous thrombosis 2.
• CT-guided percutaneous catheter drainage is an important treatment option for necrotizing pancreatitis, and can be effective whether used alone or as an adjunct to operation 4.

Classification of Fluid Collections in Necrotizing Pancreatitis

• Fluid collections associated with necrotizing pancreatitis are labeled on the basis of age and the presence of a capsule, with collections within 4 weeks of acute pancreatitis onset termed "acute necrotic collections (ANC)" and older collections termed "walled-off necrosis (WON)" if they have a perceptible wall on CT 3, 5.
• ANC and WON can be infected or sterile, but infection is far more likely compared with acute interstitial pancreatitis collections 3.