Diagnosis of Acute Pancreatitis
Diagnose acute pancreatitis when at least two of three criteria are present: characteristic abdominal pain, serum lipase (preferred) or amylase greater than three times the upper limit of normal, and/or characteristic findings on contrast-enhanced CT imaging. 1, 2
Diagnostic Criteria
Lipase is the preferred biochemical marker over amylase for diagnosing acute pancreatitis due to superior diagnostic accuracy. 3
The three diagnostic criteria are:
- Abdominal pain: Epigastric pain radiating to the back, consistent with acute pancreatitis 4, 2
- Elevated pancreatic enzymes: Serum lipase and/or amylase >3 times the upper limit of normal 1, 4, 2
- Imaging findings: Characteristic features on contrast-enhanced CT scan 3
Initial Laboratory Assessment
Obtain serum lipase, complete liver function tests (including aminotransferases, bilirubin, alkaline phosphatase, GGT), triglycerides, and calcium immediately at admission. 1, 5
Identifying the Etiology
Early elevation of serum aminotransferases or bilirubin strongly suggests gallstone etiology and requires urgent action. 1, 5, 4
- Gallstones: Elevated liver enzymes (ALT >150 IU/L has 48% sensitivity, 96% specificity for gallstone pancreatitis), hyperbilirubinemia, or GGT >224 IU/L (80.6% sensitivity, 75.3% specificity) 4
- Hypertriglyceridemia: Triglyceride levels >1000 mg/dL (>11.3 mmol/L) can cause acute pancreatitis 6
- Medications: Review all current medications for known pancreatitis-inducing agents 1
Important caveat: Elevated liver function tests have poor positive predictive value (only 15-50%) for common bile duct stones, as the inflammatory process itself elevates liver enzymes without actual biliary obstruction. 4
Imaging Strategy
Perform immediate abdominal ultrasonography at admission to identify gallstones and assess for common bile duct dilation. 1, 5, 4
When to Use CT Imaging
Obtain contrast-enhanced CT scan when:
- Doubt exists about the diagnosis (ultrasonography is often unhelpful for visualizing the pancreas itself) 3
- Severe pancreatitis is present or suspected 1, 4
- Persistent organ failure, signs of sepsis, or clinical deterioration occurs 6-10 days after admission 3
Timing of CT: Perform dynamic CT with non-ionic contrast within 3-10 days of admission in severe cases to assess for pancreatic necrosis and peripancreatic fluid collections. 1, 4
Severity Assessment
Assess severity within the first 24-48 hours of admission using clinical impression, APACHE II score, obesity, or C-reactive protein >150 mg/L at 48 hours, as this determines urgency and intensity of intervention. 3, 1
Defining Severe Pancreatitis
Severe acute pancreatitis is defined by persistent organ failure (cardiovascular, respiratory, and/or renal) beyond 48 hours, with mortality rates of 13-35%. 3, 4
Critical distinction: Organ failure present within the first week that resolves within 48 hours should NOT be considered an indicator of severe pancreatitis. 3
Prognostic Features Predicting Complications
- Clinical impression of severity 3
- Obesity 3
- APACHE II score in the first 24 hours 3
- C-reactive protein >150 mg/L at 48 hours 3
- Glasgow score ≥3 3
- Persisting organ failure after 48 hours in hospital 3
Establishing Diagnosis Timeline
The diagnosis should be established within 48 hours of admission, with etiology identified in at least 80% of cases (no more than 20% should be classified as idiopathic). 3, 1
Critical Pitfalls to Avoid
- Never rely on amylase alone when lipase is available – lipase is the preferred diagnostic test 3
- Never assume elevated liver enzymes alone confirm common bile duct stones – only 15-50% of patients with elevated LFTs in pancreatitis actually have biliary obstruction 4
- Never delay severity assessment – this must occur within 24-48 hours to guide appropriate level of care and prevent mortality 1, 5, 4
- Never skip abdominal ultrasound at admission – this is essential for identifying gallstones and planning definitive management 1, 5, 4