What are the diagnostic and treatment approaches for acute cholecystitis?

Diagnosis of Acute Cholecystitis

The diagnosis of acute cholecystitis requires a combination of detailed history, physical examination, laboratory tests, and imaging, with abdominal ultrasound being the recommended first-line imaging modality due to its wide availability, lack of radiation exposure, and good diagnostic accuracy. 1

Clinical Evaluation

Key Clinical Features

• History findings: Right upper quadrant pain, fever, vomiting or food intolerance 1
• Physical examination: Right upper quadrant tenderness, Murphy's sign (pain on inspiration during palpation of the right upper quadrant) 1
• Laboratory tests: Elevated C-reactive protein, elevated white blood cell count 1

Important Diagnostic Principle

No single clinical or laboratory finding has sufficient diagnostic power to establish or exclude the diagnosis of acute cholecystitis, making a combined approach necessary. 1

Imaging Approach

First-Line Imaging: Abdominal Ultrasound

• Recommended as initial imaging by multiple guidelines including the World Society of Emergency Surgery and American College of Radiology 1, 2
• Key ultrasound findings:
  • Gallstones
  • Gallbladder wall thickening
  • Pericholecystic fluid
  • Sonographic Murphy's sign
  • Biliary ductal dilatation (if present) 2
• Diagnostic performance:
  • Sensitivity: 81% (range 50-100%)
  • Specificity: 83% (range 33-100%) 1
  • High negative predictive value (97%) when gallstones are absent 1

Second-Line Imaging Options (when ultrasound is inconclusive)

HIDA Scan

• Highest sensitivity and specificity for acute cholecystitis compared to other imaging modalities 1, 2
• Protocol:
  1. HIDA radiotracer injection with patient supine
  2. Imaging for up to 60 minutes to assess gallbladder visualization
  3. Morphine administration (0.04 mg/kg IV) if gallbladder not visualized by 60 minutes
  4. Additional 30 minutes of imaging post-morphine 2
• Interpretation:
  • Positive for acute cholecystitis: Non-visualization of gallbladder after 90 minutes total
  • Negative: Gallbladder visualizes after morphine administration 2
• Limitations: Time-consuming, requires specific resources, not always readily available 1

CT with IV Contrast

• Recommended when complications of cholecystitis are suspected
• Can identify alternative diagnoses for right upper quadrant pain
• Less accurate than HIDA scan for uncomplicated cholecystitis 2

MRI/MRCP

• Preferred in pregnant patients
• Useful when biliary obstruction is suspected
• Comparable accuracy to ultrasound for cholecystitis 1, 2

Special Considerations

Evaluating for Common Bile Duct Stones

• Warning signs: Elevated bilirubin, transaminitis, biliary dilatation on ultrasound
• Next step: MRCP for detailed evaluation of the biliary tree 2

Potential Complications to Assess

• Hemorrhagic cholecystitis
• Gangrenous cholecystitis
• Emphysematous cholecystitis
• Gallbladder perforation 3

Diagnostic Algorithm

1. Initial evaluation: Clinical assessment + laboratory tests

   • Look for: Right upper quadrant pain, fever, leukocytosis 1

2. First imaging study: Abdominal ultrasound

   • If positive (gallstones + inflammatory signs): Diagnosis confirmed
   • If negative or inconclusive but clinical suspicion remains high: Proceed to step 3

3. Second imaging study (based on availability and clinical context):

   • HIDA scan: Best diagnostic accuracy but resource-intensive 1, 2
   • CT with IV contrast: When complications suspected or alternative diagnoses considered
   • MRI/MRCP: When biliary obstruction suspected or in pregnant patients 2

4. Diagnosis confirmed: Proceed to treatment (early laparoscopic cholecystectomy within 72 hours of diagnosis is recommended for most patients) 1, 4

Common Pitfalls and Caveats

• Relying on a single finding: No single clinical, laboratory, or imaging finding has sufficient diagnostic power 1
• Delayed imaging: Early diagnosis improves outcomes; mortality and morbidity increase with complications 5
• Missing associated conditions: Evaluate for choledocholithiasis, cholangitis, or biliary pancreatitis, especially with elevated liver enzymes 4
• False positives on HIDA scan: Can occur with prolonged fasting, severe liver disease, parenteral nutrition, alcoholism, and chronic cholecystitis 2
• False negatives on HIDA scan: May occur with partial cystic duct obstruction 2

The diagnosis of acute cholecystitis requires a systematic approach combining clinical, laboratory, and imaging findings, with abdominal ultrasound as the cornerstone of initial evaluation, followed by additional imaging when necessary.