BACKGROUND Spontaneous bacterial empyema (SBE) occurs when a hepatic hydrothorax becomes infected and runs a course similar to spontaneous bacterial peritonitis (SBP). It remains underdiagnosed as patients with cirrhosis do not routinely undergo diagnostic thoracentesis. Current understanding is limited by small cohorts, while studies reporting its association with ascites/SBP are conflicting. AIM To explore the incidence of SBE, to determine its association with ascites, and to summarize what is known regarding treatment and outcomes for patients with SBE. METHODS Major databases were searched until June 2021. Outcomes include the incidence of SBE in pleural effusions, SBP in peritoneal fluid, and SBE in patients without ascites within our cohort of patients with cirrhosis. We performed a meta-analysis using a randomeffects model with pooled proportions and 95% confidence intervals (CI). We assessed heterogeneity using I2 and classic fail-safe to determine bias. RESULTS Eight studies with 8899 cirrhosis patients were included. The median age ranged between 41.2 to 69.7 years. The majority of the patients were Child-Pugh B and C. Mean MELD score was 18.6 ± 8.09. A total of 1334 patients had pleural effusions and the pooled incidence of SBE was 15.6% (CI 12.6-19; I2 50). Amongst patients diagnosed with SBE, the most common locations included right (202), left (64), and bilateral (8). Amongst our cohort, a total of 2636 patients had ascites with a pooled incidence of SBP of 22.2% (CI 9.9-42.7; I2 97.8). The pooled incidence of SBE in patients with cirrhosis but without concomitant ascites was 9.5% (CI 3.6-22.8; I2 82.5). CONCLUSION SBE frequently occurs with concurrent ascites/SBP; our results suggest high incidence rates of SBE even in the absence of ascites. The pleura can be an unrecognized nidus and our findings support the use of diagnostic thoracentesis in patients with decompensated cirrhosis after exclusion of other causes of pleural effusion. Thoracentesis should be considered particularly in patients without ascites and when there is a high suspicion of infection. The need for diagnostic thoracentesis will continue to be important as rates of multi-drug resistant bacterial infections increase and antibiotic susceptibility information is required for adequate treatment.
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