What is the imaging of choice for hepatic abscess?

Imaging of Choice for Hepatic Abscess

Contrast-enhanced CT scan is the imaging modality of choice for diagnosing hepatic abscess in adults and adolescents due to its high sensitivity (97%) and ability to visualize abscess characteristics regardless of patient factors. 1, 2

Diagnostic Algorithm for Hepatic Abscess

First-Line Imaging

• Adults and adolescents: Contrast-enhanced CT abdomen

  • Provides superior visualization of abscess wall 1
  • Less operator-dependent than ultrasound 1
  • Maintains accuracy despite surgical dressings, stomas, drains, or obesity 1
  • Sensitivity of 97% for hepatic abscess detection 2
  • Typical findings: low attenuation lesions (<20 HU), rim enhancement, single/double-ring signs 3

• Children: Ultrasound (US) as initial imaging modality

  • Avoids radiation exposure 1
  • Eliminates need for sedation 1
  • Reasonable sensitivity (79%) for abscess detection 2

• Pregnant patients: Either US or MRI (knowledge gap exists) 1

  • Both avoid ionizing radiation

Second-Line Imaging (if initial imaging is inconclusive)

• MRI with contrast if CT is contraindicated or unavailable 1
• CT if ultrasound is negative but clinical suspicion remains high 1

Key Imaging Characteristics of Hepatic Abscess

CT Findings

• Low attenuation lesions (<20 HU) 3
• Rim-shaped enhancement of abscess wall (91.7% of cases) 3
• Single or double-ring signs (54.2%) 3
• Honeycomb/grid-like enhancement (75%) 3
• Gas-liquid level (only in 8.3% of cases) 3

Ultrasound Findings

• Anechoic or hypoechoic lesions with posterior acoustic enhancement 1
• May appear as solid-appearing masses in organizing abscesses 4
• Limited sensitivity for small abscesses or those in the dome of the liver 2

Special Considerations

Clinical Pitfalls

• Absence of fever (31% of patients), normal WBC count (23%), or normal liver function tests (13%) does not exclude hepatic abscess 2
• Clinical suspicion should guide imaging decisions despite normal laboratory values

Technical Considerations

• IV contrast significantly improves visualization of abscess wall 1
• Ultrasound is operator-dependent and may yield equivocal results 1
• CT maintains accuracy despite surgical dressings, stomas, or drains 1

Interventional Applications

• Both CT and US can guide percutaneous drainage procedures 1, 5
• Contrast-enhanced US via vessels and surgical drains can improve drainage efficacy (95.56% vs 80.49% with standard US) 5

Patient-Specific Approaches

Immunocompromised Patients

• Lower threshold for CT imaging due to atypical presentations
• Consider fungal etiologies which may have different imaging characteristics

Post-Surgical Patients

• CT preferred due to maintained accuracy despite surgical dressings 1
• Evaluate for biliary communication if bile is present in aspirate 6

In summary, while ultrasound is often used as an initial screening tool due to its accessibility and safety, contrast-enhanced CT is the most reliable imaging modality for definitive diagnosis of hepatic abscess in adults, with MRI serving as an alternative when CT is contraindicated or unavailable.