What laboratory tests should be ordered for a patient with suspected cholecystitis?

Laboratory Tests for Suspected Cholecystitis

For patients with suspected cholecystitis, a combination of inflammatory markers and liver function tests should be ordered, specifically C-reactive protein (CRP) and white blood cell count (WBC) as primary inflammatory markers, along with liver enzymes including ALT, AST, alkaline phosphatase, and bilirubin. 1, 2

Core Laboratory Tests

Inflammatory Markers

• White Blood Cell Count (WBC): Elevated in acute inflammation
  • Neutrophil count is particularly important, showing 70% sensitivity and 65.8% specificity for acute cholecystitis 1
• C-Reactive Protein (CRP): Elevated in acute inflammatory processes
  • Both WBC and CRP are key components in the diagnostic criteria for acute cholecystitis 1, 2

Liver Function Tests

• Alanine Aminotransferase (ALT)
• Aspartate Aminotransferase (AST)
• Alkaline Phosphatase (ALP)
• Total and Direct Bilirubin

Diagnostic Algorithm

1. Initial Laboratory Panel:

   • Complete Blood Count with differential (focus on WBC and neutrophil count)
   • CRP
   • Comprehensive metabolic panel including:
     • ALT, AST
     • ALP
     • Total and direct bilirubin
     • GGT (particularly useful if common bile duct stones are suspected)

2. Interpretation:

   • Elevated WBC and CRP suggest inflammation consistent with cholecystitis
   • Elevated liver enzymes (particularly ALT) may indicate biliary obstruction
   • GGT >224 IU/L has 80.6% sensitivity and 75.3% specificity for common bile duct stones 2

Important Considerations

Limitations of Laboratory Testing

• No single laboratory test has sufficient diagnostic power to establish or exclude the diagnosis of acute cholecystitis 1
• Laboratory findings must be combined with clinical assessment and imaging for diagnosis 1
• Normal laboratory values do not exclude cholecystitis, as demonstrated in case reports of patients with normal WBC counts who were later confirmed to have cholecystitis 3

Common Bile Duct Stones Assessment

• Elevated liver function tests or bilirubin require further evaluation for common bile duct stones 2
• In patients with elevated liver enzymes, particularly ALT (OR: 2; P=0.04), there is an increased likelihood of choledocholithiasis 4

Atypical Presentations

• Some patients may present with only mildly elevated liver enzymes and normal WBC counts despite having acute cholecystitis 3
• In these cases, further imaging studies become crucial for diagnosis

Follow-up Testing

If laboratory tests suggest possible cholecystitis or are inconclusive but clinical suspicion remains high:

1. Imaging studies should be ordered:

   • Abdominal ultrasound as first-line imaging (sensitivity 81%, specificity 83%) 1, 2, 5
   • If ultrasound is inconclusive and clinical suspicion remains high, consider:
     • CT with IV contrast (especially if complications are suspected)
     • HIDA scan (highest sensitivity and specificity for acute cholecystitis)
     • MRI/MRCP (particularly useful in pregnant patients) 1, 2

2. Additional laboratory tests may be considered in specific scenarios:

   • Coagulation studies if hemorrhagic cholecystitis is suspected 6
   • Blood cultures if sepsis is suspected
   • Pancreatic enzymes (amylase, lipase) to rule out concurrent pancreatitis

Remember that the diagnosis of acute cholecystitis requires a combination of clinical findings, laboratory tests, and imaging studies, as no single test is sufficiently diagnostic on its own 1, 2.