Liver abscess

Background

Microbiology

• Pyogenic
  • Polymicrobial in 20-50% (more in abscesses from biliary source)
  • Gram-negative bacteria
    • Escherichia coli
    • Klebsiella, especially hypermucoviscous Klebsiella pneumoniae
    • Less common: Pseudomonas aeruginosa, Proteus, Enterobacter, Citrobacter, and Serratia
  • Gram-positive bacteria
    • Streptococcus, especially Streptococcus anginosus group
    • Enterococcus
    • Other Viridans group streptococci
    • Less common Staphylococcus aureus and Streptococcus pyogenes
  • Anaerobes
    • Bacteroides
    • Less common: Fusobacterium, anaerobic streptococci, Clostridium, Lactobacillus
  • Fungi (rare): Candida
• Amebic
  • Entamoeba histolytica

Pathophysiology

• Pyogenic
  • Biliary: most common mechanism, includes ascending cholangitis
  • Hematogenous via hepatic artery: from bacteremia
  • Hematogenous via portal vein: from an infection abdominal organ duch as diverticulitis, pancreatitis, or appendicitis
  • Contiguous spread
  • Trauma: including things like ingested toothpicks
  • Cryptogenic: second most common mechanism is "unknown"
• Amebic: see Entamoeba histolytica

Risk Factors

• Likely more common in diabetes mellitus, cardiopulmonary disease, malignancy, and cirrhosis
• Neutrophil dysfunction, including chronic granulomatous disease
• Hemochromatosis, especially for abscesses involving Yersinia enterocolitica

Clinical Manifestations

• Most common signs are fever, abdominal pain, leukocytosis, and an elevated alkaline phosphatase
  • Often presents with fevers alone, however
• May also have weight loss, diarrhea, RUQ tenderness, and jaundice
• The classic triad is considered to be fever, jaundice, and RUQ tenderness

Investigations

• Blood cultures are about 50% sensitive
• Imaging with ultrasound or CT is important
• Consider Entamoeba histolytica serology to rule out amoebic liver abscess, since the syndromes cannot reliably be distinguished clinically

Management

• Get source control
• Antibiotics should be broad-spectrum, such as piperacillin-tazobactam, ertapenem or meropenem, ceftriaxone plus metronidazole, or ciprofloxacin plus metronidazole
• Treat for 4-6 weeks total, ensuring radiological resolution of abscess
  • Can step down to oral therapy after 2 to 3 weeks if responding appropriately