How do I test for pancreatitis?

How to Test for Pancreatitis

Measure serum lipase as your first-line diagnostic test, with a diagnostic threshold of ≥3 times the upper limit of normal, which is the preferred enzyme marker over amylase due to superior specificity and sensitivity. 1, 2

Initial Laboratory Testing

Serum Lipase (Preferred Test)

• Order serum lipase immediately when pancreatitis is suspected 1, 2
• Diagnostic threshold: ≥3 times the upper limit of normal confirms acute pancreatitis 1, 2, 3
• Lipase is superior to amylase because it:
  • Remains elevated longer (wider diagnostic window) 2, 4
  • Has higher specificity for pancreatic tissue 2, 4
  • Performs better in alcohol-induced pancreatitis 2, 4
  • Is more sensitive in delayed presentations 2

Important Caveat: Elevations <3 times the upper limit have low specificity and are consistent with but not diagnostic of pancreatitis 1

Serum Amylase (Alternative)

• Can be used if lipase is unavailable 1
• Diagnostic threshold: ≥4 times the upper limit of normal 1
• Less reliable than lipase, particularly in alcoholic pancreatitis and delayed presentations 2, 4

Etiologic Workup (Obtain Simultaneously)

Order these tests at admission to identify the underlying cause 1, 2:

• Liver chemistries (bilirubin, AST, ALT, alkaline phosphatase) - to evaluate for gallstone pancreatitis 1, 2
• Serum triglycerides - levels >1000 mg/dL indicate hypertriglyceridemia-induced pancreatitis 1, 2
• Serum calcium - to assess for hypercalcemia as a potential cause 1, 2

Imaging Strategy

Abdominal Ultrasound (Perform at Admission)

• Obtain in all patients with suspected pancreatitis 1, 2
• Detects gallstones, bile duct dilation, and free peritoneal fluid 1, 2
• Early gallstone detection is critical for determining need for urgent ERCP in severe disease 1, 5
• Limitation: The pancreas is poorly visualized in 25-50% of cases, so ultrasound cannot definitively exclude pancreatitis 1, 5

Chest and Abdominal X-rays

• Obtain routinely to exclude other pathology (perforated viscus, intestinal obstruction) and provide baseline assessment 1, 2

Contrast-Enhanced CT (Selective Use)

• Do NOT order routinely - reserve for specific indications 1, 5, 2
• Indications for CT:
  • Diagnostic uncertainty after clinical and biochemical evaluation 1, 2
  • Predicted severe disease (APACHE II score >8) 1, 2
  • Evidence of organ failure during initial 72 hours 1, 2
• Timing: Perform after 72-96 hours from symptom onset, as early CT underestimates pancreatic necrosis 1, 5, 2

Severity Assessment

Clinical Scoring

• Use APACHE II scoring system with cutoff of 8 to predict severe disease 1, 2
• Presence of organ failure (pulmonary, circulatory, or renal insufficiency) indicates severe attack 5

Laboratory Markers for Severity

• C-reactive protein (CRP): >150 mg/L at 48 hours is the best available laboratory marker for severity 1, 2
• Procalcitonin: Most sensitive test for detecting pancreatic infection; low values strongly predict absence of infected necrosis 1, 2

Diagnostic Timeline

Complete diagnosis within 48 hours of admission to avoid missing alternative life-threatening conditions (mesenteric ischemia, perforated viscus, leaking aortic aneurysm) 5, 2

Special Situations

Unexplained Pancreatitis in Patients >40 Years

• Perform CT or endoscopic ultrasound (EUS) to exclude underlying pancreatic malignancy, even after a single episode 1, 2

Recurrent Idiopathic Pancreatitis

• EUS is the preferred test, performed 2-6 weeks after resolution, uncovering etiology in 29-88% of patients 2
• MRCP is a reasonable alternative when EUS expertise is unavailable 5

Common Pitfalls to Avoid

• Don't rely on enzyme levels to assess severity - the degree of elevation does not correlate with disease severity 2
• Don't order daily enzyme measurements - they have no value in monitoring clinical progress or prognosis 1
• Don't order early CT (<72 hours) unless diagnostic uncertainty exists - it underestimates necrosis and rarely changes initial management 5, 2
• Don't accept "idiopathic" diagnosis without obtaining at least two good quality ultrasounds to search for gallstones 1