What laboratory tests should be requested for suspected retained cholelithiasis?

Laboratory Tests for Suspected Retained Cholelithiasis

For suspected retained cholelithiasis, liver biochemical tests including ALT, AST, bilirubin, ALP, and GGT, along with abdominal ultrasound should be performed as the initial diagnostic investigations. 1

Initial Laboratory Workup

• A complete liver biochemistry panel should include:

  • Total and direct bilirubin
  • Alanine aminotransferase (ALT)
  • Aspartate aminotransferase (AST)
  • Alkaline phosphatase (ALP)
  • Gamma-glutamyl transferase (GGT) 2, 1

• Complete blood count (CBC) and coagulation studies (INR/PT) should be performed, especially if endoscopic or surgical intervention is being considered 1

Diagnostic Value and Limitations

• Normal liver biochemical tests have a high negative predictive value of 97% for common bile duct stones, but the positive predictive value of any abnormal liver biochemical test result is only 15% 2, 1

• Liver function tests alone are insufficient to identify patients with choledocholithiasis and further diagnostic tests are needed when clinical suspicion remains high 2

• Elevated alkaline phosphatase and gamma-glutamyl transferase are particularly suggestive of biliary obstruction 3

Risk Stratification for Common Bile Duct Stones

Based on laboratory and imaging findings, patients should be stratified according to risk for choledocholithiasis:

Very Strong Predictors:

• Visualization of common bile duct stone on ultrasound 2, 1

Strong Predictors:

• Common bile duct dilation on ultrasound
• Bilirubin level >4 mg/dl 2, 1

Moderate Predictors:

• Abnormal liver function tests
• Age >55 years
• Clinical gallstone pancreatitis 2, 1

Additional Investigations Based on Risk

• For patients with moderate risk for choledocholithiasis, additional investigations should be performed based on local expertise and availability:

  • Magnetic resonance cholangiopancreatography (MRCP) (sensitivity 93%, specificity 96%) 2
  • Endoscopic ultrasound (EUS) (sensitivity 89.5-95%, specificity 96.5-97%) 2, 3
  • Intraoperative cholangiography (sensitivity 87%, specificity 99%) 2
  • Laparoscopic ultrasound (sensitivity 87%, specificity 100%) 2

• For high-risk patients (those with confirmed common bile duct stones on ultrasound or with strong predictors), preoperative ERCP should be considered 2

Common Pitfalls to Avoid

• Relying solely on liver function tests to rule out common bile duct stones, as patients may have stones despite normal laboratory values 2

• Assuming that common bile duct dilation alone confirms choledocholithiasis, especially in elderly patients where loss of musculature tone may increase the diameter even without stones 2, 4

• Proceeding directly to ERCP without confirming the presence of common bile duct stones, as ERCP carries a 1-2% risk of complications (up to 10% with sphincterotomy) 2, 5

• Overlooking the need for additional imaging in patients with negative ultrasound but persistent clinical suspicion, as ultrasound has limited sensitivity (22.5-75%) for common bile duct stones 4, 6