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Pyogenic liver abscess

Last updated: May 11, 2021

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Pyogenic liver abscess (PLA) is an uncommon condition characterized by solitary or multiple collections of pus within the liver. The infection is caused by bacteria and is often polymicrobial, with Escherichia coli, Streptococcus spp. and Klebsiella pneumoniae being common causative organisms. The majority of cases are caused by ascending infection from a biliary tract pathology (e.g., cholangitis due to choledocholithiasis or biliary strictures). Infection in the gastrointestinal tract or bacteremia can expose the liver to high bacterial loads because of the liver's dual blood supply from the portal vein and hepatic artery. Patients may present with nonspecific symptoms, such as fever, malaise, and weight loss. Right upper quadrant pain and tender hepatomegaly are specific features of a liver abscess but are not seen in all cases. Diagnosis is confirmed on abdominal imaging (ultrasound or CT), which would typically show intrahepatic fluid-filled lesions with surrounding edema. Broad-spectrum IV antibiotics and percutaneous or surgical drainage of the abscess cavity are the mainstays of treatment. Complications include sepsis, pneumonia, and abscess rupture into the peritoneum or thorax. Advances in diagnostics and treatment have reduced the complications and mortality rates of PLA.

  • Incidence: 2–3 cases per 100,000 people in the United States
  • Peak incidence: 50–60 years
  • Sex: slight male predominance

References:[1][2][3]

Epidemiological data refers to the US, unless otherwise specified.

Risk factors for PLA [2][4][5]

Etiology by source [1][2][4][6]

The source of infection often remains unclear, but if an etiology is identified, the cause is most often found in the biliary tract. Other routes of infection include hematogenic spread via the portal vein or hepatic artery and direct extension.

Common causes of PLAs
Source Etiology Pathogenesis

Biliary tract: most commonly identified cause (24–60%) [6][7]

Hepatic artery (∼ 10%) [6]

Portal vein (∼ 7%) [6]

Contiguous area (< 5%) [6]

Others

  • Cryptogenic (10–66%) [1][2][4][9]
  • Unknown pathogenesis

Common pathogens [1][2][3][5][6][9]

The symptoms of PLA are often non-specific (e.g., fever, weight loss, nausea).
References:[1]

General principles

Laboratory studies [1][6][7][11]

Blood cultures should preferably be obtained before initiating empiric antibiotic therapy for PLA.

Imaging [1][4][6][12]

  • Indications: all patients with suspected PLA to confirm the diagnosis and possibly identify the underlying etiology (e.g., choledocholithiasis, biliary strictures)
  • Characteristic findings
    • Solitary; (more common) or multiple intrahepatic lesion(s) usually within the right lobe [1][6]
    • Lesions may be fluid-filled or solid, or contain gas, debris, or septations/loculi
    • Surrounding parenchyma appears edematous and hyperemic
    • See individual modalities below for additional findings.

Abdominal ultrasound (preferably duplex scan) [13]

  • Indication: first-line imaging modality for suspected PLA
  • Findings
    • Typically hypoechoic but may also be hyperechoic
    • Early lesion(s) may be poorly demarcated; advanced PLAs may appear spherical with central necrosis

CT abdomen (preferably with IV contrast) [12]

  • Indication: alternative first-line imaging modality for suspected PLA
  • Findings
    • Hypodense lesions that do not take up IV contrast [7]
    • Peripheral rim enhancement on IV contrast administration
    • Double target sign: a concentric appearance of the peripheral rim on CT with IV contrast, composed of an inner hyperdense layer surrounded by an outer hypodense layer

MRI abdomen/liver [12]

  • Indication: Consider if US or CT findings are inconclusive but the index of suspicion for PLA is high.
  • Findings: intrahepatic hypointense (T1) or hyperintense (T2) lesions

Contrast-enhanced ultrasound (CEUS)

  • Indication: Typically performed to evaluate indeterminate hepatic lesions [14]
  • Findings: peripheral rim enhancement and late phase washout [4]

X-ray abdomen

Not routinely indicated but, if performed to rule out differential diagnoses of PLA, may show the following:

  • Gas bubbles within an ill-defined intrahepatic lesion
  • Elevated right hemidiaphragm
  • Lower lobe atelectasis of the right lung with/without pleural effusion

Percutaneous aspiration with Gram stain and culture [4][7]

  • Allows for identification of the causative pathogen and its antibiogram [11]
  • Positive in 70–80% of cases [1]
  • See “Treatment” for further details on this procedure.

PLA needs to be differentiated from nonpyogenic abscesses and other space-occupying lesions of the liver. [6]

The differential diagnoses listed here are not exhaustive.

General principles [1][4][6]

Empiric antibiotic therapy [1][6]

  • General principles
    • There are no specific recommendations regarding preferred antibiotic regimens.
    • Select an empiric regimen based on suspected infection route, suspected pathogen, and local resistance patterns.
    • Switch to culture-specific antibiotics once culture results are available; deescalate if possible.
    • Continue IV antibiotics for ≥ 2 weeks before switching to oral antibiotics. [1][4]
    • Total duration of therapy: typically 4–6 weeks
  • Coverage required: anaerobes, gram-negative bacteria, and gram-positive cocci
Empiric antibiotic therapy for PLA [17][18]
Single-agent regimens (any of the following)
Combination therapy regimens

Drainage of the abscess cavity [7]

Indications

Image-guided percutaneous drainage [1][4][6]

  • Indication: standard procedure in solitary, interventionally accessible abscesses
  • Contraindication: coagulopathy (INR > 1.5; platelets ≤ 50.000/mm3) [19][20]
  • Procedure: performed under ultrasound or CT guidance
    • Percutaneous catheter drainage: generally preferred [12]
      • An intracavitary catheter is placed and irrigated with saline every 8 hours
      • Serial imaging is typically required to confirm adequate drainage and catheter placement.
      • The catheter is typically removed when drainage is < 10 mL per day and the white blood cell count has normalized.
    • Percutaneous needle aspiration: Consider in patients with smaller PLAs or in those with coagulopathy. [21]

Correct coagulopathy before attempting percutaneous drainage of a PLA.

Ensure decreased catheter output is not due to catheter blockage or malposition before catheter removal.

Surgical drainage [1][4][6]

The underlying etiology (e.g., choledocholithiasis, biliary stricture) should also be treated to prevent recurrent PLAs.

References:[23][24]

We list the most important complications. The selection is not exhaustive.

References:[25]

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