What is the diagnostic approach for pancreatitis?

Diagnostic Approach for Pancreatitis

The diagnosis of acute pancreatitis requires at least two of the following three criteria: characteristic abdominal pain, elevated pancreatic enzymes (preferably serum lipase), and imaging findings consistent with pancreatitis. 1

Clinical Presentation

• Characteristic abdominal pain (typically epigastric, radiating to back)
• Abdominal tenderness and distension
• Prolonged ileus
• Occasionally, body wall ecchymoses (Cullen's sign at umbilicus, Grey-Turner's sign in flanks)

Laboratory Testing

First-line Tests

• Serum lipase: Preferred over amylase 2, 1

  • Higher sensitivity (79% vs 72% for amylase) 2
  • Longer diagnostic window (rises within 4-8h, peaks at 24h, remains elevated for 8-14 days) 2
  • Levels >3 times upper limit of normal are diagnostic 1

• Serum amylase: Less specific than lipase 1

  • Rises within 6-24h, peaks at 48h, normalizes within 3-7 days 2
  • Levels >4 times upper limit of normal are diagnostic 1
  • Can be elevated in non-pancreatic conditions (renal disease, appendicitis, cholecystitis, etc.) 2

Additional Laboratory Tests

• Triglyceride levels: Should be measured when no gallstones or significant alcohol history
  • Values >11.3 mmol/L (>1000 mg/dL) indicate hypertriglyceridemia as etiology 2
• Calcium levels: Should be checked to rule out hypercalcemia as cause 2
• Trypsinogen-2 dipstick test: Rapid bedside test with 82% sensitivity and 94% specificity 2

Imaging Studies

Initial Imaging

• Abdominal ultrasound: Should be performed at admission 1
  • Detects gallstones, biliary duct dilation, free peritoneal fluid
  • Helps determine etiology

Advanced Imaging

• Contrast-enhanced CT scan: Gold standard for confirmation 1

  • Not routinely needed if diagnosis is clear from clinical and laboratory findings
  • Should be performed after 72 hours of illness onset if needed
  • CT severity index correlates with morbidity and mortality:
    • Score 0-3: 8% complications, 3% mortality
    • Score 4-6: 35% complications, 6% mortality
    • Score 7-10: 92% complications, 17% mortality

• MRI: Suitable alternative to CT in specific cases 1

  • Patients with contrast allergy or renal impairment
  • Young or pregnant patients
  • Better characterization of fluid collections needed
  • Superior detection of non-liquefied material but less sensitive for gas in collections

• Endoscopic ultrasound (EUS): Accurate alternative for screening cholelithiasis and choledocholithiasis 1

Severity Assessment

• APACHE II score: Most comprehensive scoring system 1

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

• C-reactive protein (CRP):

  • 150 mg/L at 48 hours suggests severe disease 1

  • Peak level >210 mg/L in first four days indicates severity
  • Major drawback: peak levels reached only after 48-72h 2

• Procalcitonin (PCT): Most sensitive laboratory test for detection of pancreatic infection 2, 1

  • Low values are strong negative predictors of infected necrosis

• Urea >20 mg/dL: Independent predictor of mortality 2

Common Pitfalls and Caveats

1. Relying solely on amylase levels: Lipase is more specific and has a longer diagnostic window than amylase 2, 3

2. Ordering both amylase and lipase routinely: Co-ordering has shown little to no increase in diagnostic sensitivity and specificity 3

3. Delayed CT imaging: CT should be performed after 72 hours of illness onset for better assessment of necrosis 1

4. Missing alternative diagnoses: Correct diagnosis should be made within 48 hours to avoid missing other life-threatening intra-abdominal conditions 1

5. Relying solely on clinical assessment: Clinical assessment alone is unreliable and will misclassify approximately 50% of patients 1

6. Using laboratory tests alone for severity prediction: A combined approach using APACHE II, CRP, and CT severity index offers the most comprehensive assessment 1