Spontaneous bacterial empyema (SBE), defined as spontaneous infection of the pleural fluid, represents a distinct and often underdiagnosed complication of hepatic hydrothorax in patients with cirrhosis. Although the transudative nature of hepatic hydrothorax is well established, the characteristics and risk factors for SBE have not been well investigated. We performed a systematic review and meta-analysis on the incidence and risk factors for this elusive entity.


A systematic and detailed search was run in June 2021 with the assistance of a medical librarian for studies reporting on the incidence, associations, and outcomes of SBE in cirrhosis patients. Meta-analysis was performed using random-effects model and results were expressed in terms of pooled proportions along with relevant 95% confidence intervals (CI).


Eight studies with 8899 cirrhosis patients were included in the final analysis. Mean age ranged from 41.2 to 69.7 years. Majority of the patients were Child-Pugh B and C. The diagnostic criteria of SBE were positive pleural fluid culture and polymorphonuclear leukocytes (PMN) count >250 cells/mm3 or negative pleural fluid culture and PMN count >500 cells/mm3, without evidence of pneumonia/parapneumonic effusion on imaging. A total of 1334 patients had pleural effusions and the pooled incidence of SBE was 15.6% (CI 12.6-19; I2 50). A total of 2636 patients had ascites and pooled incidence of SBP among these patients was 22.2% (CI 9.9-42.7; I2 97.8). Interestingly, the pooled incidence of SBE in patients without concomitant ascites was 9.5% (CI 3.6-22.8; I2 82.5).


Bacterial infections account for about 30%-50% deaths in patients with cirrhosis and clinicians should have a high index of suspicion for the timely diagnosis and treatment of SBE. Although this entity is thought to arise through the flow of infected ascites from the peritoneal to the pleural cavity via defects in the diaphragm owing to negative intrathoracic pressure, we found that SBE can occur even in the absence of concomitant ascites. Our results suggest that a diagnostic thoracentesis with subsequent analysis of pleural fluid should be performed in cirrhosis patients presenting with pleural effusions.

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The American Journal of Gastroenterology