The clinical manifestations of pyogenic liver abscess usually include fever and abdominal pain; other symptoms may include nausea, vomiting, anorexia, weight loss and malaise.
The diagnosis of pyogenic liver abscess is confirmed by radiographic imaging (computed tomography or ultrasound) followed by aspiration and culture of the abscess material.
Most pyogenic liver abscesses are polymicrobial. Amebic abscess is best distinguished from pyogenic liver abscess by serology.
We recommend draining liver abscesses (Grade 1B). For drainage of abscesses ≤5 cm in diameter, we suggest needle aspiration rather than percutaneous catheter drainage (Grade 2C). Repeat needle aspiration may be required.
For drainage of abscesses >5 cm in diameter, we suggest percutaneous catheter drainage rather than needle aspiration (Grade 2B). Drainage catheters should remain in place until drainage ceases (usually up to seven days).
We suggest surgical drainage (rather than percutaneous drainage) in the following circumstances (Grade 2C).
- Multiple abscesses (depending on number, position, and size)
- Loculated abscesses
- Abscesses with viscous contents obstructing drainage catheter
- Underlying disease requiring primary surgical management
- Inadequate response to percutaneous drainage within seven days
We recommend empiric parenteral antibiotic therapy pending culture and susceptibility results (Grade 1C).
When there is a clinical response to therapy, oral antibiotics may be substituted for parenteral therapy (with the guidance of susceptibility testing) to complete a four to six week course of treatment.
Material obtained from CT or ultrasound-guided aspiration should be sent to the laboratory for Gram stain and culture (both aerobic and anaerobic). Anaerobic culture should be specifically requested on the laboratory requisition.
Blood cultures are essential; they are positive in up to 50 percent of cases.
Cultures obtained from existing drains are not sufficiently reliable for guiding antimicrobial therapy, since they are often contaminated with skin flora and other organisms. This was demonstrated in a study of 66 cases of liver abscess; cultures results obtained via radiographic guidance were compared with culture results obtained from a drain that had been in place for at least 48 hours. Cultures from percutaneous specimens correlated with cultures from drainage catheters in only one-half of cases. Treatment based upon drainage culture results alone would have led to inappropriate therapy for the remaining patients.
No randomized controlled trials have evaluated empiric antibiotic regimens for treatment of pyogenic liver abscess. Treatment recommendations are based upon the probable source of infection and should be guided by local bacterial resistance patterns, if known.
Empiric broad-spectrum parenteral antibiotics should be administered pending abscess Gram stain and culture results. We suggest one of the regimens outlined in the table.
Regardless of the initial empiric regimen, the therapeutic regimen should be revisited once culture and susceptibility results are available. Recovery of more than one organism should suggest polymicrobial infection including anaerobes, even if no anaerobes are isolated in culture. In such circumstances, anaerobic coverage should be continued.
Duration of therapy
There are no randomized controlled trials evaluating the optimal duration of therapy. This is typically determined by the extent of infection and the patient's clinical response to initial management. Patients with abscess(es) that are difficult to drain usually require longer courses of therapy.
Useful clinical indicators to follow are pain, temperature, white blood cell count, and serum C-reactive protein. Follow-up imaging should only be performed in the setting of persistent clinical symptoms or if drainage is not proceeding as expected; radiological abnormalities resolve much more slowly than clinical and biochemical markers. Among 102 pyogenic liver abscess patients in Nepal, the mean time to ultrasonographic resolution of abscesses <10 cm was 16 weeks; mean time to resolution for abscesses >10 cm was 22 weeks.
Drainage catheters should remain in place until drainage is minimal (usually up to seven days). If percutaneous needle aspiration was performed without catheter placement, repeat aspiration may be required in up to one-half of cases.
Antibiotic therapy should be continued for four to six weeks. Patients who have had a good response to initial drainage should be treated with two to four weeks of parenteral therapy, while patients with incomplete drainage should receive four to six weeks of parenteral therapy. The remainder of the course can then be completed with oral therapy tailored to culture and susceptibility results. If culture results are not available, reasonable empiric oral antibiotic choices include amoxicillin-clavulanate alone or a fluoroquinolone (ciprofloxacin or levofloxacin) plus metronidazole.