Incidence and Prognostic Role of Pleural Effusion in Patients with Pulmonary Embolism: A Systematic Review and Meta-Analysis

Background: Pleural effusion is a common pulmonary embolism (PE) complication, which has been documented to increase the risk of death in PE and relate to disease progression. However, the incidence of pleural effusion varies among studies and its association with PE outcome is still unclear. This study sought to determine the pooled incidence and prognostic value of pleural effusion events in patients with PE. Methods: We systematically searched the PubMed, EMBASE, SCOPE, Web of Science, Cochrane, LILACS, CINAHL, EBSCO, AMED, and OVID databases from the inception of each database to 7 September 2022 with a restriction on human studies, to identify studies assessing the association between pleural effusion and PE including all prospective and retrospective clinical studies. An exploratory meta-analysis was performed using a random-effects model. We evaluated the heterogeneity and performed subgroup analyses. Results: The final meta-analysis included 29 studies involving 13,430 PE patients. The pooled incidence of pleural effusion in PE patients was 41.2% (95% CI: 35.7-46.6%), which tended to be unilateral (pooled incidence: 60.8%, 95% CI: 45.7-75.8%) and small (pooled incidence: 85.9%, 95% CI: 82.6-89.1%). Pooled analysis using a random-effects model (I-2 = 53.2%) showed that pleural effusion was associated with an increased risk of 30-day mortality (RR 2.19, 95% CI: 1.53-3.15, p < 0.001, I-2 = 67.1%) and in-hospital mortality (RR 2.39, 95% CI: 1.85-3.09, p < 0.001, I-2 = 37.1%) in patients with PE. Conclusions: Our meta-analysis found that PE patients had a high incidence of pleural effusion, which was usually unilateral and small. Pleural effusion generally increases 30-day and in-hospital mortality in patients with PE, and it is recommended that physicians be aware of the risk of death from PE, especially when patients have pleural effusion. Further investigations focusing on PE with pleural effusion are warranted.