Clinical characteristics and treatment outcomes in a cohort of patients with pyogenic and amoebic liver abscess

Background: We describe the clinical features of a cohort of patients with liver abscesses and investigate relationships between clinical, radiological and microbiological findings and mortality. Methods: Retrospective review of pyogenic (PLA) or amoebic liver abscesses (ALA) diagnosed and treated at a major infectious diseases department in London over 9 years. Results: One hundred forty-one patient records were identified; 132 (93.6%) had PLA and 9 (6.4%) ALA. No organism was identified in 38.6% (51/132); a single bacterial species was isolated in 47.0% (62/132) of PLA, ≥ 2 in 14.4% (19/132). There was weak evidence of variation in abscess size by type of microorganism, with streptococcal PLA typically larger (p = 0.03 for Streptococcus milleri group, p = 0.05 for non-milleri streptococci). Patients with ALA were younger (median 41, IQR 37-51 years) than those with PLA (median 68, IQR 50.5-78 years) (p = 0.003) and all were male (9/9, 100%, (p = 0.03)), with a history of recent travel in the majority (6/9, 66.7% (p = 0.003)). C-reactive protein was higher in ALA than in PLA (p = 0.06). In the entire cohort, loculation (HR = 2.51 (95% CI 1.00-6.32), p = 0.04) and baseline ALP (HR = 4.78 (95% CI 1.19-19.2) per log₁₀ increase, p = 0.03) were associated with mortality. 16S ribosomal RNA (rRNA) analysis was used in a subset of culture-negative cases and increased the diagnostic yield by 13%. Conclusions: Clinical or radiological features cannot be used to distinguish between PLA and ALA, or help identify the bacterial cause of PLA. However, ALA is more common in young, male patients with a history of travel. 16S rRNA analysis of abscess fluid has a role in improving microbiological diagnosis in culture-negative cases.