Liver Abscess 

1. Definition

A liver abscess is a localized collection of pus within the liver parenchyma, resulting from bacterial, amoebic, or (rarely) fungal infection leading to tissue necrosis.


2. Classification

A. Based on Etiology

Type

Common Pathogen

Key Features

Pyogenic Liver Abscess (PLA)

Klebsiella pneumoniae, E. coli, Streptococcus milleri, Enterococcus

Usually polymicrobial; common in diabetics and biliary sepsis

Amoebic Liver Abscess (ALA)

Entamoeba histolytica

Monomicrobial, associated with poor sanitation, fecal-oral spread

Fungal Liver Abscess

Candida spp.

Usually in immunocompromised or critically ill patients


3. Epidemiology

  • Most common type: Amoebic liver abscess in developing countries (India, Africa, Latin America).
  • Pyogenic abscess more common in developed countries.
  • Incidence: 2.3–3.6 per 100,000 population.
  • Mortality:
    • Pyogenic: 6–14%
    • Amoebic: <2% with treatment


4. Pathogenesis

Routes of Infection

  1. Biliary tree (most common) — ascending infection from cholangitis or gallstones.
  2. Portal vein — from intra-abdominal infections (appendicitis, diverticulitis, IBD).
  3. Hematogenous spread — from systemic bacteremia (especially Klebsiella).
  4. Direct extension — from adjacent infections (subphrenic abscess).
  5. Trauma / Post-procedure — following liver biopsy or surgery.


5. Risk Factors

  • Diabetes mellitus
  • Biliary tract disease or manipulation (ERCP)
  • Malignancy
  • Immunosuppression (HIV, steroids, transplant)
  • Chronic alcoholism (esp. amoebic)
  • Poor sanitation or unsafe water (amoebic)


6. Clinical Features

Feature

Pyogenic Liver Abscess

Amoebic Liver Abscess

Onset

Subacute

Acute to subacute

Fever

High-grade with chills, rigors

Moderate, often with sweats

Pain

Right upper quadrant, pleuritic, referred to right shoulder

Dull aching RUQ pain

Hepatomegaly

Tender, enlarged liver

Tender, smooth surface

Jaundice

Present in 30–50%

Rare

Diarrhea

Uncommon

May precede abscess (amoebic dysentery)

Toxic appearance

Marked

Variable

Cough / Pleuritic pain

If subdiaphragmatic spread

Common

Complications

Rupture → peritonitis, empyema, sepsis

Rupture → pleural or pericardial involvement


7. Investigations

A. Laboratory Findings

Parameter

Findings

CBC

Leukocytosis with left shift

LFTs

Mild to moderate ↑ ALP, AST, ALT; hyperbilirubinemia (especially in PLA)

ESR / CRP

Elevated

Blood cultures

Positive in ~50–70% of PLA

Stool microscopy

E. histolytica trophozoites (rarely positive)

Serology

Amoebic antibody (ELISA/IHA) – positive in >95% ALA

Others

Anaerobic culture (aspirate), fungal culture if immunocompromised


B. Imaging

Modality

Findings

Ultrasound

Hypoechoic or complex lesion with irregular margins; may be multiloculated in PLA

CT scan (preferred)

Hypodense lesion with enhancing rim (“double target sign”) and possible gas formation in Klebsiellaabscess

MRI

Helpful in complex or multiple abscesses

Typical sites:

  • Right lobe (posterior superior segment) – ~75% cases (due to portal venous flow pattern).


8. Diagnostic Differentiation

Feature

Pyogenic Abscess

Amoebic Abscess

Number

Multiple

Usually single

Location

Any lobe (right > left)

Right lobe predominant

Pus appearance

Thick, foul-smelling, purulent

“Anchovy sauce” pus — thick, reddish-brown, sterile

Culture

Positive for bacteria

Sterile

Serology (E. histolytica)

Negative

Positive

Response to Metronidazole

Poor

Excellent (rapid improvement)


9. Complications

  • Rupture into:
    • Pleural cavity → empyema
    • Pericardium → cardiac tamponade
    • Peritoneum → peritonitis
    • Colon → hepatic-colonic fistula
  • Septicemia and shock
  • Secondary bacteremia or metastatic abscess (lung, brain)
  • Subphrenic abscess


10. Management

A. General Principles

  1. Prompt antimicrobial therapy
  2. Drainage of abscess
  3. Treatment of underlying cause (biliary disease, etc.)
  4. Supportive care – fluids, nutrition, glycemic control


B. Pyogenic Liver Abscess

Antibiotic Therapy

  • Empiric (broad-spectrum) coverage for:
    • Gram-negatives, anaerobes, streptococci, and enterococci

Recommended Regimens:

  • Ceftriaxone or cefotaxime + Metronidazole
    (Covers Enterobacteriaceae + anaerobes)
  • Piperacillin–tazobactam or carbapenem – monotherapy alternative
  • Add Vancomycin if MRSA or healthcare-associated infection suspected

Duration:

  • 4–6 weeks (IV 2 weeks → oral step-down once afebrile and improving)

Drainage

  • Indications:
    • Size >5 cm
    • Poor response to antibiotics within 4–7 days
    • Multiloculated abscess
    • Suspicion of rupture
  • Methods:
    • Percutaneous needle aspiration (single abscess, thin pus)
    • Percutaneous catheter drainage (preferred for large or multiloculated)
    • Surgical drainage (if percutaneous fails or rupture)


C. Amoebic Liver Abscess

Medical Management

  • Metronidazole 750 mg PO/IV q8h × 10 days (or tinidazole 2 g/day × 5 days)
  • Follow with luminal agent to eradicate cysts:
    • Paromomycin 25–30 mg/kg/day × 7 days
    • Diloxanide furoate (if available)

Drainage Indications

  • Risk of rupture (left lobe abscess near pericardium)
  • Lack of clinical improvement after 5–7 days
  • Diagnostic uncertainty


D. Fungal Abscess

  • Fluconazole or echinocandins
  • Often needs prolonged therapy and drainage


11. Prognosis

  • Amoebic abscess: Excellent prognosis with early therapy.
  • Pyogenic abscess: Mortality ~10% (higher with multiple abscesses, sepsis, or underlying malignancy).
  • Fungal abscess: Poor prognosis (up to 50% mortality).


12. Prevention

  • Early treatment of intra-abdominal sepsis and biliary infections
  • Proper sanitation and safe drinking water (for amoebic)
  • Diabetes control
  • Avoid unnecessary invasive procedures in immunocompromised