What is the diagnostic approach for pancreatitis?

Diagnostic Approach for Pancreatitis

The diagnosis of pancreatitis should be established using serum lipase as the preferred diagnostic marker, with a threshold of greater than 3 times the upper limit of normal, due to its higher specificity and longer elevation duration compared to amylase. 1

Clinical Diagnosis

• Patients typically present with upper abdominal pain and vomiting, with features of epigastric or diffuse abdominal tenderness 2
• Body wall ecchymoses such as Cullen's sign (periumbilical) or Grey-Turner's sign (flank) may be evident in severe cases 2

Laboratory Diagnosis

Primary Diagnostic Tests

• Serum lipase is the preferred diagnostic marker for pancreatitis with greater specificity than amylase 2, 1
• Lipase offers a larger diagnostic window than amylase since it remains elevated for 8-14 days versus 3-7 days for amylase 3
• Diagnosis is typically made when lipase is elevated to greater than 2-3 times the upper limit of normal 2, 1
• Serum lipase has a sensitivity of 79% and specificity of 89% for acute pancreatitis according to Cochrane data 3

Secondary Laboratory Tests

• In the absence of gallstones or significant alcohol use history, serum triglyceride should be measured and considered the etiology if >11.3 mmol/l (>1000 mg/dl) 3
• Liver function tests (bilirubin, AST, ALT, alkaline phosphatase) should be obtained to evaluate for biliary obstruction 2
• Serum calcium levels should be checked to identify hypercalcemia as a potential cause 2, 1

Imaging Studies

Initial Imaging

• Abdominal ultrasonography should be performed at admission to look for:
  • Gallstones or bile duct stones (to establish etiology) 2, 1
  • Pancreatic inflammation and free peritoneal fluid 2
  • Note: Ultrasound has limitations with poor visualization of the pancreas in 25-50% of cases 2

Advanced Imaging

• CT scan is indicated when:

  • Clinical and biochemical findings are inconclusive 2
  • Assessment of severity is needed (after 72 hours to avoid underestimating necrosis) 2, 1
  • Patients have predicted severe disease or evidence of organ failure 1

• MRCP or endoscopic ultrasound (EUS) should be used:

  • To screen for occult choledocholithiasis if no other etiology is established 2
  • For unexplained pancreatitis in patients over 40 years to rule out pancreatic malignancy 1

Severity Assessment

• Laboratory markers of severity include:

  • C-reactive protein ≥150 mg/L at 48 hours after onset (considered the gold standard for severity assessment) 3
  • Hematocrit >44% 2
  • Urea >20 mg/dl (independent predictor of mortality) 3
  • Procalcitonin (most sensitive test for detection of pancreatic infection) 3

• The APACHE II scoring system with a cutoff of 8 is recommended to predict severe disease 1

• CT Severity Index combining assessment of pancreatic inflammation and necrosis correlates with increased morbidity and mortality 2

Common Pitfalls and Caveats

• Relying solely on amylase can lead to misdiagnosis as it has lower specificity and a shorter diagnostic window than lipase 3, 4
• Normal amylase doesn't exclude pancreatitis in cases of hyperlipidemia, acute exacerbation of chronic pancreatitis, or delayed presentation 5
• Co-ordering both lipase and amylase provides little to no increase in diagnostic accuracy and increases unnecessary costs 4
• Early CT scanning (within first 72 hours) might underestimate pancreatic necrosis 1
• Once diagnosis is established, daily measurements of pancreatic enzymes have no value in assessing clinical progress or prognosis 5