What is the diagnostic approach for cholecystitis?

Diagnostic Approach for Cholecystitis

The diagnosis of acute cholecystitis should begin with ultrasound as the first-line imaging modality, followed by HIDA scan if ultrasound is equivocal but clinical suspicion remains high. 1

Clinical Diagnosis

Cholecystitis should be suspected in patients presenting with:

• Right upper quadrant pain and tenderness
• Murphy's sign (pain on inspiration when palpating the right upper quadrant)
• Fever
• Nausea and vomiting, often associated with eating
• Systemic signs of inflammation (elevated white blood cell count, elevated C-reactive protein)

While no single clinical finding can definitively diagnose cholecystitis, the combination of these findings increases diagnostic accuracy 2, 3.

Diagnostic Algorithm

Step 1: Initial Evaluation

• Assess for local signs of inflammation:
  • Murphy's sign
  • Right upper quadrant pain, tenderness, or mass
• Assess for systemic signs of inflammation:
  • Fever
  • Elevated white blood cell count
  • Elevated C-reactive protein

Step 2: Laboratory Testing

• Complete blood count (looking for leukocytosis)
• Liver function tests (may be elevated, particularly in biliary obstruction)
• C-reactive protein

Step 3: Imaging Studies

1. Ultrasound (first-line imaging)

   • Sensitivity: 81-88%, Specificity: 80-83% 1, 2
   • Key findings:
     • Gallstones
     • Gallbladder wall thickening (>3mm)
     • Pericholecystic fluid
     • Sonographic Murphy's sign (pain when probe is pressed against gallbladder)

2. HIDA Scan (if ultrasound equivocal but high clinical suspicion)

   • Gold standard diagnostic test with sensitivity 86.7-89.3% and specificity 66.8-79% 1, 2
   • Non-visualization of gallbladder within 60 minutes indicates cystic duct obstruction
   • Protocol includes:
     • IV injection of radiotracer
     • Imaging up to 60 minutes
     • If gallbladder not visualized, administer morphine (0.04 mg/kg IV)
     • Continue imaging for additional 30 minutes 1

3. CT with IV contrast (if ultrasound equivocal)

   • Better visualizes pericholecystic inflammation
   • Useful for identifying complications (perforation, emphysematous cholecystitis) 1, 4

4. MRCP (preferred in pregnant patients)

   • Accuracy >90% for detecting bile duct stones
   • No radiation exposure
   • Provides clearer picture of surrounding structures 1

Severity Assessment

Tokyo Guidelines classify cholecystitis severity into three grades 5:

1. Grade I (Mild):

   • No organ dysfunction
   • Limited disease in gallbladder

2. Grade II (Moderate):

   • No organ dysfunction
   • Extensive disease in gallbladder
   • Elevated WBC, palpable tender mass in RUQ
   • Disease duration >72 hours
   • Significant inflammatory changes on imaging

3. Grade III (Severe):

   • Presence of organ dysfunction

Common Pitfalls and Caveats

1. Reliance on single clinical findings: No single clinical or laboratory finding has sufficient diagnostic accuracy to rule in or rule out cholecystitis 3. A comprehensive approach using multiple findings is necessary.

2. Missing acalculous cholecystitis: 5-10% of cholecystitis cases occur without gallstones, typically in critically ill patients 2. Maintain high suspicion in appropriate clinical contexts even with absence of stones.

3. Delayed diagnosis: Complications of cholecystitis (gangrenous, emphysematous, perforated) increase with delayed diagnosis 4. Early imaging is crucial when clinical suspicion exists.

4. Overreliance on ultrasound alone: When ultrasound is equivocal but clinical suspicion remains high, proceeding directly to HIDA scan is appropriate rather than dismissing the diagnosis 1.

5. Inadequate risk stratification: Patients should be stratified into risk categories based on clinical presentation, laboratory findings, and initial imaging to guide management decisions 1.

By following this diagnostic approach, clinicians can accurately diagnose cholecystitis and initiate appropriate management to reduce morbidity and mortality associated with this common condition.