The diagnosis of pyogenic liver abscess is made through radiographic imaging and aspiration and culture of abscess material. Ultrasonography is the preferred initial test for diagnosing liver abscesses, with a sensitivity of 75% to 95%. Examination of the liver shows a round, focal defect with irregular walls and variable echogenicity. Abscesses may be septated or multiloculated and contain internal echoes caused by debris. Small abscesses, <2 cm in diameter, may not be detected. Contrast-enhanced computed tomography (CT) has a sensitivity of 95% and can detect abscesses as small as 0.5 cm. It can also identify associated intra-abdominal pathology. CT typically shows a fluid collection with surrounding edema or stranding. It is important to distinguish liver abscesses from tumors and cysts. Magnetic resonance imaging and tagged white blood cell scans are less effective at detecting and distinguishing abscesses from other liver lesions.
Treatment
The mainstay of treatment of pyogenic liver abscess is systemic antimicrobial therapy in combination with drainage. When pyogenic liver abscess is suspected, blood cultures should be obtained immediately, followed by initiation of broad-spectrum parenteral antibiotics before blood culture results are available, based on the most probable source of infections (Table 46.2). Initial antibiotic therapy should be tailored to information obtained from the Gram stain and cultures of aspirated abscess contents and blood cultures. Anaerobic coverage should be continued if multiple organisms are recovered, regardless of whether anaerobes are isolated, since they are difficult to culture. Most abscesses require at least 4 to 6 weeks of total antibiotic therapy with 2 to 4 weeks of parental therapy.
Table 46.2Empiric antibiotic therapy for pyogenic liver abscess
Potential source
Suggested regimen
Biliary
PipTz 4.5 g q8h IV or
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