What labs should be ordered for a patient with gastrointestinal (GI) pain consistent with a possible gallbladder attack?

Laboratory Tests for Suspected Gallbladder Attack

For patients with GI pain consistent with a possible gallbladder attack, liver biochemical tests (ALT, AST, bilirubin, ALP, GGT) and abdominal ultrasound should be performed as the initial diagnostic investigations. 1

Initial Laboratory Workup

• Complete liver biochemistry panel including:

  • Total and direct bilirubin
  • ALT (alanine aminotransferase)
  • AST (aspartate aminotransferase)
  • ALP (alkaline phosphatase)
  • GGT (gamma-glutamyl transferase) 1, 2

• Serum amylase and lipase to rule out pancreatic involvement or pancreatitis 3, 4

  • Lipase is preferred over amylase due to greater specificity and longer elevation period (8-14 days) 3
  • Serial measurements of amylase and lipase every 6 hours may be useful if initial values are inconclusive 5

• Complete blood count to assess for leukocytosis (indicating inflammation or infection) 6

• Coagulation studies (INR/PT) especially if endoscopic or surgical intervention might be considered 1

Risk Stratification for Common Bile Duct Stones

Based on laboratory and imaging findings, patients can be stratified for risk of common bile duct stones:

• Very strong predictors:

  • Visualization of common bile duct stone on ultrasound 1

• Strong predictors:

  • Common bile duct dilation on ultrasound
  • Bilirubin level >4 mg/dl 1

• Moderate predictors:

  • Abnormal liver function tests
  • Age >55 years
  • Clinical gallstone pancreatitis 1

Diagnostic Value of Laboratory Tests

• Normal liver biochemical tests have a high negative predictive value (97%) for common bile duct stones, but the positive predictive value of abnormal results is only about 15% 1

• GGT and direct bilirubin have the highest sensitivities (83% and 79% respectively) for detecting common bile duct stones 2

• In biliary colic specifically, total bilirubin has a high positive predictive value (85%) for common bile duct stones 2

• In acute cholecystitis, elevated liver function tests are less reliable predictors of common bile duct stones (positive predictive value <40%) 2

Special Considerations

• For suspected gallstone-related pancreatitis, additional tests should include:

  • Serum amylase or lipase (diagnostic when lipase is greater than twice the upper limit of normal)
  • Triglyceride level
  • Calcium level 3

• In patients with negative initial ultrasound but persistent symptoms, consider repeat testing or additional imaging 3

• If hyperlipidemia is present, amylase levels may be falsely normal even in the presence of pancreatitis 4

Common Pitfalls to Avoid

• Do not rely solely on amylase for diagnosis, as it has low specificity and may be normal in certain conditions like hyperlipidemia-induced pancreatitis or acute exacerbation of chronic pancreatitis 4

• Avoid daily repeated measurements of pancreatic enzymes once diagnosis is established, as they do not correlate with clinical progress or prognosis 4

• Do not dismiss the possibility of gallbladder disease if liver function tests are normal, as they may be normal in up to 15-20% of patients with gallstone disease 6

• Remember that GGT and bilirubin levels, while sensitive, have high false-positive and false-negative rates, especially in patients with acute cholecystitis 2