Liver pyogenic abscess

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Liver pyogenic abscess

1. Cause

A liver bacterial (pyogenic) abscess is a localized collection of pus in the liver caused by bacterial infection, most commonly resulting from:

  • Biliary tract infections (e.g., cholangitis)
  • Portal vein bacteremia (e.g., from intra-abdominal infections like appendicitis or diverticulitis)
  • Hematogenous spread (systemic bacteremia)
  • Direct extension from contiguous infection
  • Post-traumatic or post-surgical infections

2. Etiology

Common bacterial organisms involved:

  • Gram-negative bacteria:
    • Escherichia coli (most common)
    • Klebsiella pneumoniae (especially in diabetics and East Asian populations)
  • Gram-positive bacteria:
    • Streptococcus species
    • Staphylococcus aureus
  • Anaerobes:
    • Bacteroides species
  • Polymicrobial infections are frequent, especially with intra-abdominal sources.

3. Pathophysiology

  • Infection reaches the liver through:
    • Biliary tree (ascending cholangitis)
    • Portal venous system (from gastrointestinal tract infections)
    • Hepatic artery (systemic bacteremia)
    • Direct extension (from adjacent infections)
    • Trauma or surgery (iatrogenic)
  • Once in the liver, the bacteria trigger an inflammatory response leading to:
    • Tissue necrosis
    • Suppuration
    • Formation of a fibrous capsule around the abscess

4. Epidemiology

  • Incidence: ~2.3 cases per 100,000 person-years (varies by region)
  • More common in:
    • Older adults
    • Men > women
    • Patients with diabetes, malignancy, or immunosuppression
    • Developing countries (higher rates due to poor sanitation and endemic parasitic diseases)
  • Rising incidence in some areas due to more widespread use of biliary instrumentation (e.g., ERCP)

5. Clinical Presentation

  • Symptoms:
    • Fever and chills (most common)
    • Right upper quadrant (RUQ) abdominal pain
    • Nausea, vomiting
    • Malaise, anorexia, weight loss
  • Signs:
    • Hepatomegaly
    • RUQ tenderness
    • Jaundice (in ~25% of cases)
    • Sepsis or shock (if advanced)

6. Imaging Features

Ultrasound (initial modality)


  • Hypoechoic or mixed echogenic lesion
  • May have internal debris or septations

CT Scan (gold standard)


  • Hypodense lesion with peripheral rim enhancement ("double target" or "ring" sign)
  • Gas within an abscess may be seen with gas-forming organisms

MRI


  • T1: hypointense
  • T2: hyperintense lesion
  • Enhanced peripheral rim after contrast

7. Treatment

Medical

  • Broad-spectrum intravenous antibiotics tailored to culture results
    • Empirical coverage: third-generation cephalosporin + metronidazole
    • Adjust based on sensitivities

Interventional

  • Percutaneous drainage under imaging guidance (preferred for abscesses >3 cm)
  • Surgical drainage if:
    • Failed percutaneous drainage
    • Multiloculated abscess
    • Ruptured abscess
    • Underlying surgical pathology (e.g., perforated viscus)

8. Prognosis

  • With appropriate treatment, the mortality rate is <10%
  • Factors associated with poor prognosis:
    • Delayed diagnosis
    • Sepsis or shock at presentation
    • Immunocompromised status
    • Multiple or large abscesses
    • Incomplete drainage

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