Lipase

Background

• 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.

• 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