What is the diagnostic approach for pancreatitis?

Diagnosis of Pancreatitis

Diagnose acute pancreatitis when at least 2 of 3 criteria are met: characteristic upper abdominal pain, serum lipase >3 times the upper limit of normal, and/or imaging evidence of pancreatic inflammation. 1

Laboratory Testing

Serum lipase is the single preferred diagnostic test and should be ordered instead of amylase due to superior specificity (89% vs lower for amylase), longer elevation duration (8-14 days vs 3-7 days), and better sensitivity particularly in alcohol-induced pancreatitis. 2, 3, 4

• The diagnostic threshold is lipase >3 times the upper limit of normal, which is most consistent with acute pancreatitis and should be obtained within 48 hours of admission. 1
• Lipase has a sensitivity of 79% and specificity of 89% for acute pancreatitis. 2
• A threshold of 2-3 times the upper limit of normal is acceptable, but 3 times is preferred for specificity. 2, 3

Additional laboratory tests to determine etiology:

• Liver function tests (bilirubin, AST, ALT, alkaline phosphatase) at admission to evaluate for biliary obstruction as the cause. 2, 5
• Serum triglycerides if no gallstones or alcohol history—consider hypertriglyceridemia the etiology if >1000 mg/dL (>11.3 mmol/L). 2
• Serum calcium to identify hypercalcemia as a potential cause. 2

Imaging Studies

Abdominal ultrasound should be performed at admission to look for gallstones, bile duct stones, pancreatic inflammation, and free peritoneal fluid. 2, 1, 5

Contrast-enhanced CT of the abdomen is indicated when:

• Clinical and biochemical findings are inconclusive for diagnosis. 2, 1
• Assessment of severity is needed in predicted severe disease or evidence of organ failure. 2, 1
• Delay CT until after 72 hours from symptom onset because early scanning underestimates pancreatic necrosis. 2, 1

MRCP or endoscopic ultrasound (EUS) should be used:

• To screen for occult choledocholithiasis when initial ultrasound is negative but gallstone etiology is suspected. 2, 5
• To rule out pancreatic malignancy in unexplained pancreatitis in patients over 40 years old. 2, 1
• MRCP has sensitivity of 97.98% and specificity of 84.4% for choledocholithiasis. 5

Clinical Features to Recognize

• Upper abdominal pain (epigastric or diffuse) with vomiting is the typical presentation. 2, 5
• Cullen's sign (periumbilical ecchymosis) or Grey-Turner's sign (flank ecchymosis) indicate severe necrotizing pancreatitis with retroperitoneal hemorrhage. 2, 5

Severity Assessment

Use APACHE II scoring system with a cutoff of 8 to predict severe disease requiring intensive monitoring. 2, 1

Laboratory markers of severity at 48 hours:

• C-reactive protein ≥150 mg/L at 48 hours after onset. 2, 5
• Hematocrit >44%. 2, 5
• Blood urea nitrogen >20 mg/dL. 2, 5
• Procalcitonin elevation. 2

CT Severity Index (combining pancreatic inflammation and necrosis assessment) correlates with increased morbidity and mortality, but should be performed after 72 hours. 2, 5

Common Pitfalls to Avoid

• Do not order both amylase and lipase—co-ordering provides no diagnostic advantage and wastes resources; lipase alone is sufficient. 4
• Do not use enzyme levels to monitor severity or predict outcomes—neither amylase nor lipase correlates with disease severity once diagnosis is established. 3
• Do not perform CT in the first 72 hours for severity assessment—it will underestimate necrosis and provide falsely reassuring information. 2, 1
• Do not dismiss the diagnosis if lipase is only 2-2.5 times elevated—while 3 times is preferred, 2 times can still indicate pancreatitis in the right clinical context. 2, 3