How is pancreatitis diagnosed?

Diagnosing Pancreatitis

The diagnosis of acute pancreatitis should be based on compatible clinical features and elevations in serum lipase levels greater than 3 times the upper limit of normal, with lipase being preferred over amylase due to its higher specificity. 1, 2

Diagnostic Criteria

Acute pancreatitis diagnosis requires at least two of the following three criteria:

1. Characteristic abdominal pain - Typically severe upper abdominal pain often radiating to the back
2. Elevated pancreatic enzymes:
   • Serum lipase >3 times upper limit of normal (preferred)
   • Serum amylase >4 times upper limit of normal (less specific)
3. Imaging findings consistent with pancreatitis

Clinical Presentation

• Epigastric or diffuse abdominal tenderness
• Nausea and vomiting
• Abdominal distension
• Occasionally body wall ecchymoses (Cullen's sign at umbilicus, Grey-Turner's sign in flanks) - indicative of severe disease 1, 2

Laboratory Assessment

• Serum lipase - First-line test with higher sensitivity and longer diagnostic window than amylase 1, 3

  • Remains elevated longer than amylase
  • No other sources of lipase to reach serum, providing higher specificity
  • Levels >3 times upper limit of normal are diagnostic

• Serum amylase - Less specific than lipase 1, 3

  • Levels >4 times upper limit of normal are diagnostic
  • May be elevated in other non-pancreatic conditions
  • Shorter diagnostic window than lipase

• Additional laboratory tests:

  • Liver function tests - to assess for biliary etiology (ALT >3x normal suggests gallstone pancreatitis)
  • Triglyceride levels - to identify hypertriglyceridemia as potential cause
  • Calcium levels - to identify hypercalcemia as potential cause 2

Imaging Studies

• Abdominal ultrasound - Should be performed at admission 1, 2

  • Detects gallstones, biliary duct dilation, free peritoneal fluid
  • Limited visualization of pancreas (25-50% of cases)
  • Not reliable for definitive diagnosis but important for etiology assessment

• Contrast-enhanced CT scan - Gold standard for confirmation 1, 2

  • Not routinely needed if diagnosis is clear from clinical and laboratory findings
  • Should be performed after 72 hours of illness onset if needed (early CT may underestimate necrosis)
  • Indicated when:
    • Diagnostic uncertainty exists
    • Alternative diagnosis needs to be excluded
    • Clinical deterioration occurs
    • Assessment of complications is needed

• MRI - Alternative to CT in specific situations 2

  • Suitable for patients with contrast allergy or renal impairment
  • Better for characterizing fluid collections
  • Superior detection of non-liquefied material (debris/necrotic tissue)

Severity Assessment

Once diagnosis is established, severity assessment is crucial for management decisions:

• APACHE II score - Most comprehensive scoring system 1, 2

  • Score ≥8 indicates severe disease
  • 48-hour score more accurate than admission score

• C-reactive protein (CRP) 1, 2

  • 150 mg/L at 48 hours suggests severe disease

• CT severity index - Combines assessment of inflammation and necrosis 2

  • Scores 0-3: 8% complications, 3% mortality
  • Scores 4-6: 35% complications, 6% mortality
  • Scores 7-10: 92% complications, 17% mortality

Common Pitfalls and Caveats

1. Relying solely on amylase - Lipase is more specific and has a longer diagnostic window 3

2. Ordering both amylase and lipase - Co-ordering has shown little to no increase in diagnostic accuracy and increases costs unnecessarily 3

3. Performing CT too early - CT within 72 hours of onset may underestimate pancreatic necrosis 1, 2

4. Missing non-pancreatic causes of enzyme elevation - Renal failure can cause non-specific elevations in pancreatic enzymes 1

5. Overlooking acute pancreatitis in patients with unexplained multiorgan failure - Acute pancreatitis should be considered in the differential diagnosis of unexplained multiorgan failure or systemic inflammatory response syndrome 1

6. Relying solely on clinical assessment - Clinical assessment alone will misclassify approximately 50% of patients; laboratory and imaging studies are essential 2