What is true regarding acute cholecystitis?

Acute Cholecystitis: Key Facts and Diagnostic Considerations

Acute cholecystitis is primarily associated with gallstones, with approximately 90-95% of cases being calculous cholecystitis, while only a small percentage are acalculous in nature. 1

Pathophysiology and Clinical Features

• Gallstone association:

  • 90-95% of acute cholecystitis cases are associated with gallstones (calculous cholecystitis) 1
  • Only 5-10% of cases occur without stones (acalculous cholecystitis)

• Microbiology:

  • Bacterial infection is a secondary event, not the primary cause
  • Positive bacterial cultures are found in only 20-40% of cases 1
  • Common organisms include E. coli, Klebsiella, Enterococcus, and anaerobes

• Clinical presentation:

  • Right upper quadrant pain or tenderness
  • Fever
  • Nausea and vomiting
  • Murphy's sign (pain on inspiration during palpation of the right upper quadrant)
  • Leukocytosis and elevated inflammatory markers (CRP) 1

Diagnostic Approach

Imaging Studies

1. Ultrasound (US):

   • First-line imaging modality for suspected acute cholecystitis
   • High sensitivity (81%) and specificity (83%) for detecting gallstones 1
   • Key findings: gallstones, gallbladder wall thickening, pericholecystic fluid, sonographic Murphy's sign
   • Advantages: cost-effective, widely available, no radiation exposure 1

2. HIDA scan:

   • Most accurate test for diagnosing acute cholecystitis
   • A normal HIDA scan effectively rules OUT acute cholecystitis
   • Non-visualization of the gallbladder indicates cystic duct obstruction, a hallmark of acute cholecystitis 1
   • Should be used when ultrasound findings are equivocal 1

3. CT scan:

   • Less sensitive than US for gallstones but better for complications
   • Useful for identifying complications such as perforation, emphysematous cholecystitis, or pancreatitis 1

Diagnostic Challenges

• No single clinical or laboratory finding has sufficient diagnostic power to establish or exclude acute cholecystitis 1
• Combination of history, physical examination, laboratory tests, and imaging is recommended 1
• Ultrasound sensitivity varies widely (26-100%) in different studies 1
• Atypical presentations can occur without classic findings such as fever, leukocytosis, or positive Murphy's sign 2

Management Considerations

• Early laparoscopic cholecystectomy (within 72 hours of diagnosis) is the preferred treatment 1, 3
• Medical management before surgery includes:
  • Fasting
  • IV fluid resuscitation
  • Antimicrobial therapy
  • Pain management 3
• For high-risk surgical patients, percutaneous gallbladder drainage may be considered 4

Common Pitfalls to Avoid

1. Relying on a single diagnostic criterion - No single feature has sufficient diagnostic power 1
2. Overlooking atypical presentations - Acute cholecystitis can present without classic symptoms or laboratory findings 2
3. Delaying surgical intervention - Early cholecystectomy results in shorter hospital stays and fewer complications 1, 3
4. Misinterpreting normal HIDA scans - A normal HIDA scan effectively excludes acute cholecystitis; non-visualization of the gallbladder strongly suggests acute cholecystitis 1, 2
5. Assuming bacterial infection is primary - Infection is typically secondary to obstruction, not the primary cause 1

In conclusion, among the options presented in the question, the correct answer is A: 75% associated with stone. This is actually an underestimate, as current guidelines indicate that 90-95% of acute cholecystitis cases are associated with gallstones 1. Options B and C are incorrect, as bacterial cultures are positive in only 20-40% of cases 1, and a normal HIDA scan effectively rules out acute cholecystitis rather than being compatible with it 1, 2.