What is the recommended classification system for acute pancreatitis?

Classification of Acute Pancreatitis

The revised Atlanta classification system (2012) is the recommended standard for classifying acute pancreatitis, which categorizes the disease into mild, moderately severe, and severe based on the presence of organ failure and local/systemic complications. 1, 2

Diagnostic Criteria

• Diagnosis of acute pancreatitis requires at least two of three criteria: (1) abdominal pain consistent with pancreatitis, (2) serum amylase and/or lipase greater than three times the upper limit of normal, and (3) characteristic findings on abdominal imaging 1, 3
• Lipase is preferred over amylase for diagnosis when available due to its superior accuracy 4
• When diagnosis is uncertain, contrast-enhanced CT provides definitive evidence of pancreatitis 4, 1

Severity Classification

The Atlanta classification identifies two phases of acute pancreatitis:

Early Phase (first 1-2 weeks)

• Characterized by systemic inflammatory response syndrome (SIRS) and/or organ failure 2

Late Phase (after 1-2 weeks)

• Characterized by persistence of systemic signs of inflammation or local complications 2

Severity Categories

1. Mild Acute Pancreatitis

   • No organ failure 1
   • No local or systemic complications 1
   • Usually resolves within the first week 1, 2

2. Moderately Severe Acute Pancreatitis

   • Transient organ failure (<48 hours) 1, 2
   • Local complications (fluid collections, necrosis) 1
   • Exacerbation of comorbid disease 1, 2

3. Severe Acute Pancreatitis

   • Persistent organ failure (>48 hours) affecting cardiovascular, respiratory, and/or renal systems 1, 2
   • Highest mortality risk, especially when combined with infected necrosis (up to 35.2%) 1

Local Complications Classification

According to the revised Atlanta classification, local complications are categorized as:

1. Acute Peripancreatic Fluid Collection (APFC)

   • Occurs in interstitial edematous pancreatitis 5, 2
   • Develops within first 4 weeks 2
   • No definable wall 2

2. Pancreatic Pseudocyst

   • Encapsulated collection of fluid with a well-defined wall 2
   • Contains little or no solid material 2
   • Develops >4 weeks after onset of interstitial edematous pancreatitis 5, 2
   • Rare in acute pancreatitis 6

3. Acute Necrotic Collection (ANC)

   • Contains variable amounts of fluid and necrotic material 2
   • Occurs in necrotizing pancreatitis 2
   • No definable wall 2

4. Walled-off Necrosis (WON)

   • Mature, encapsulated collection of pancreatic and/or peripancreatic necrosis 2
   • Develops >4 weeks after onset of necrotizing pancreatitis 2
   • Has a well-defined wall 2

Clinical Application and Validation

• Severity assessment should be performed within 48 hours of admission using established scoring systems 1
• The revised Atlanta classification has been validated and shows statistically significant and clinically relevant differences in outcomes between severity categories 7
• Patients with persistent organ failure should be admitted to an intensive care unit 1
• Monitoring for at least 48 hours is required to distinguish between transient and persistent organ failure 1

Imaging Recommendations

• Ultrasound is recommended on admission to determine biliary etiology 1
• Contrast-enhanced CT (CE-CT) or MRI is recommended for all patients with severe acute pancreatitis 1
• Optimal timing for initial CE-CT assessment is 72-96 hours after symptom onset 1
• A standardized template for reporting CT images has been developed to ensure consistent communication of findings 2

Mortality Risk

• Persistent organ failure is the key determinant of mortality in acute pancreatitis 1
• Mortality should be lower than 10% overall and less than 30% in severe cases 4
• Infected necrosis without organ failure has a much lower mortality rate (approximately 1.4%) compared to sterile necrosis with organ failure (approximately 19.8%) 1