Lipase

Lipase is a pancreatic enzyme that hydrolyzes triglycerides into glycerol and free fatty acids. Serum lipase is the preferred biomarker for the diagnosis of acute pancreatitis in the emergency department, offering superior sensitivity and a wider diagnostic window compared to amylase.

Background

• Lipase is primarily produced by pancreatic acinar cells; smaller amounts are produced by the liver, intestinal mucosa, and other tissues
• Normal reference range is approximately 0-160 U/L (varies by assay and institution)
• Preferred over amylase for diagnosis of acute pancreatitis per ACG, AGA, and IAP guidelines

Diagnostic threshold

• ≥3 times the upper limit of normal (ULN) is the accepted diagnostic cutoff for acute pancreatitis
  • At this threshold: sensitivity 80-100%, specificity 95-99%
• Rises within 3-6 hours of symptom onset
• Peaks at 24-48 hours
• Remains elevated for 7-14 days (longer than amylase, which normalizes within 3-5 days)
• A normal lipase does not completely exclude acute pancreatitis, particularly in recurrent or chronic disease

Interpretation

Lipase ≥3x ULN

• Highly suggestive of acute pancreatitis when combined with compatible clinical presentation
• Diagnosis of acute pancreatitis requires ≥2 of 3 criteria:
  • Characteristic abdominal pain (epigastric, radiating to back)
  • Serum lipase (or amylase) ≥3x ULN
  • Characteristic findings on imaging (CT, MRI, or ultrasound)

Lipase <3x ULN but elevated

• Non-specific; consider both pancreatic and non-pancreatic causes
• Abdominal imaging advised if associated with abdominal pain

Non-pancreatic causes of elevated lipase

• Reduced clearance:
  • Renal failure / AKI (most common non-pancreatic cause; incidence 14-80% in renal failure)
  • Macrolipasemia (lipase-immunoglobulin complexes)
• Intra-abdominal pathology:
  • Cholecystitis, choledocholithiasis
  • Small bowel obstruction
  • Mesenteric ischemia / intestinal infarction
  • Peptic ulcer disease / perforated viscus
  • Appendicitis
  • Inflammatory bowel disease
  • Pancreatic or periampullary malignancy
• Metabolic:
  • Diabetic ketoacidosis (may elevate lipase >3x ULN without pancreatitis)
  • Hypertriglyceridemia
• Other:
  • Sepsis / critical illness
  • Intracranial hemorrhage / neurosurgical pathology
  • Medications (e.g., DPP-4 inhibitors, valproic acid, azathioprine, didanosine)
  • Post-ERCP
  • Trauma
  • HIV infection

Pearls

• Lipase alone is sufficient — co-ordering amylase with lipase does not improve diagnostic accuracy and adds unnecessary cost
• Do not trend lipase — serial monitoring is unnecessary and does not predict severity, complications, or guide management
• Degree of lipase elevation does not correlate with disease severity in adults
• Lipase has a wider diagnostic window than amylase, making it more useful in patients with delayed presentations (>24-48 hours after symptom onset)
• In hypertriglyceridemic pancreatitis, lipase may be falsely normal due to assay interference; if clinical suspicion is high, treat empirically
• Consider non-pancreatic causes when lipase is elevated but clinical features are not consistent with pancreatitis, especially in patients with renal failure or DKA
• If the diagnosis remains uncertain, CT abdomen with IV contrast is recommended ≥72 hours after symptom onset for optimal sensitivity in detecting necrosis

See Also

• Pancreatitis
• Amylase
• Choledocholithiasis
• Diabetic ketoacidosis
• Hypertriglyceridemia
• ERCP

External Links

• ACG Clinical Guideline: Acute Pancreatitis