What are the diagnostic criteria for pancreatitis in adults?

Diagnosis of Acute Pancreatitis

Acute pancreatitis is diagnosed when at least 2 of the following 3 criteria are present: characteristic upper abdominal pain, serum lipase and/or amylase >3 times the upper limit of normal, and characteristic findings on abdominal imaging. 1, 2

Diagnostic Algorithm

Step 1: Clinical Assessment

• Look for epigastric or diffuse upper abdominal pain with associated vomiting and tenderness on examination 3, 1
• Examine for body wall ecchymoses: Cullen's sign (periumbilical) or Grey-Turner's sign (flank discoloration), though these are rare and indicate severe disease 3, 1
• Clinical findings alone are unreliable and should never be used in isolation, as they overlap significantly with other acute abdominal conditions 1

Step 2: Biochemical Testing (Most Critical)

• Serum lipase is the preferred diagnostic marker over amylase due to higher specificity for pancreatic tissue, longer elevation duration (remains elevated beyond 24 hours), and superior diagnostic accuracy 1, 2, 4
• Diagnostic threshold: >3 times the upper limit of normal for either lipase or amylase 1, 2
  • Elevations <3 times the upper limit have low specificity and are consistent with but not diagnostic of acute pancreatitis 1
• If lipase is unavailable, serum amylase ≥4 times above normal is acceptable, though less specific due to elevation from salivary glands, small intestine, and ovaries 3, 1, 2
• Do not order both amylase and lipase together as the combination only marginally improves diagnostic efficiency while increasing costs 4
• Occasionally, urinary amylase may be helpful when serum amylase is equivocal 3

Step 3: Imaging Studies

Initial imaging:

• Abdominal ultrasound should be performed in all patients with suspected acute pancreatitis, primarily to identify gallstones as the etiology 1, 2
• Ultrasound may detect pancreatic swelling and free peritoneal fluid, but the pancreas is poorly visualized in 25-50% of cases due to overlying bowel gas, so it cannot be used for definitive diagnosis 3, 5
• Chest x-ray should be obtained to exclude other pathology (perforated viscus) and assess for pleural effusions or ARDS in severe cases 3

Advanced imaging when needed:

• Contrast-enhanced CT is the preferred confirmatory imaging modality and should be used selectively when: diagnosis is uncertain despite biochemical testing, severe disease is predicted, or organ failure is present 1, 2
• CT is occasionally indicated for diagnostic purposes if clinical and biochemical findings are inconclusive 3, 2
• Plain abdominal x-rays should NOT be used for diagnosis as findings like sentinel loop, colon cut-off, and renal halo sign are unreliable and non-specific 1

Critical Diagnostic Pitfalls

• Never rely on clinical presentation alone as it frequently mimics other acute abdominal conditions, especially in postoperative patients where the picture may be obscured 3, 1
• Failure to visualize the pancreas on ultrasound due to bowel gas does not rule out pancreatitis—if clinical suspicion remains high, proceed directly to contrast-enhanced CT 5
• Document ultrasound limitations when bowel gas prevents adequate visualization, as this may mandate further evaluation 5
• Diagnosis should be established within 48 hours of admission to ensure accurate diagnosis and prevent missing other life-threatening conditions 2

Determining Etiology (Secondary Priority)

Once acute pancreatitis is diagnosed:

• Abdominal ultrasound at admission to identify gallstones (most urgent to determine need for ERCP) 1, 2
• Laboratory tests including bilirubin, ALT, AST, and alkaline phosphatase to distinguish biliary from non-biliary etiology 6
• If no gallstones or alcohol history, check triglycerides and calcium 1