A Population-Based Study of Pyogenic Liver Abscesses in the United States: Incidence, Mortality, and Temporal Trends

OBJECTIVES: Few population-based studies have evaluated pyogenic liver abscess (PLA) in North America. We assessed the incidence of PLA and evaluated predictors of mortality. METHODS: We used the Nationwide Inpatient Sample to identify all patients with discharges for PLA (ICD-9 572.0) between 1994 and 2005. Multivariable logistic regression analysis was performed to determine whether mortality was associated with patient and hospital characteristics including comorbidities, interventions, and bacterial cultures. We determined the annual incidence for PLA in the US population and assessed for temporal changes using generalized linear regression models. RESULTS: We identified 17,787 PLA discharges for an overall incidence of PLA of 3.6 (95% confidence interval (CI): 3.5-3.7) per 100,000 population. From 1994 to 2005, the annual average percent increase in incidence was 4.1% (95% CI: 3.4-4.8; P<0.0001). In-hospital mortality was 5.6% (95% CI: 5.3-6.0). Mortality was associated with older age (65-84 vs. 18-34: odds ratio (OR)=2.28 (1.48-3.51)); Medicaid (OR=1.74 (1.36-2.23)) and Medicare (OR=1.48 (1.18-1.85) vs. private insurance; and comorbidities such as cirrhosis (OR=2.48 (1.85-3.31)), chronic renal failure (OR=1.99 (1.28-3.09)), and cancer (OR=2.32 (1.97-2.73)). Patients who underwent percutaneous liver aspiration (OR=0.45 (0.39-0.52)) had lower mortality, whereas surgical drainage (OR=0.87 (0.68-1.10)) and endoscopic retrograde cholangiopancreatography (OR=0.73 (0.52-1.03)) were not associated with mortality. The most commonly recorded bacterial infections were Streptococcus species (29.5%) and Escherichia coli (18.1%). Patients with bacteremia or septicemia (OR=3.88 (3.36-4.48)) had an increased risk of death. CONCLUSIONS: The incidence of PLA is increasing and is associated with significant mortality that is attributable to several modifiable risk factors.