Post-Thoracentesis Ultrasound versus Chest Radiography for the Evaluation of Effusion Evacuation and Lung Reexpansion: A Multicenter Study.

Rationale: Post-thoracentesis chest radiography (CXR) is often used to evaluate the degree of residual fluid after thoracentesis. Whether post-drainage ultrasound examination is comparable to CXR in the evaluation of pleural space evacuation is unknown. Objectives: How do post-thoracentesis ultrasound and CXR compare in assessing the effectiveness of pleural space evacuation? Methods: In this prospective, multicenter study, patients with free-flowing pleural effusions with minimal to no septations requiring thoracentesis were recruited. Post-thoracentesis ultrasound was performed immediately postprocedure; CXR was performed within 4 hours postprocedure. The primary outcome was agreement on complete pleural space evacuation between ultrasound and CXR. Complete pleural space evacuation was defined as the absence of pleural fluid on anterior, midaxillary, and posterior ultrasound views and lack of costophrenic angle blunting on CXR. Interobserver reliability was assessed via independent image reviews by two pulmonologists and two radiologists blinded to patient and procedure data, with disagreements resolved by a third reviewer. Results: Of the 147 patients enrolled (February 2021-May 2022), 145 were included in the final analysis. The median age was 64 years (56-75), and malignancy was the most frequent effusion etiology (n = 49). The lung was considered trapped in 50% (n = 73). A total of 826 ultrasound images were collected for blind review. The Gwet's agreement coefficient 1 assessing complete pleural evacuation between ultrasound and CXR was 0.93 (95% confidence interval [CI], 0.83-1.00). When assessing agreement on the basis of pre-specified criteria of effusion size (small vs. large), a substantial level of agreement was observed between ultrasound and CXR, indicated by a kappa of 0.64 (95% CI, 0.51-0.77). There was strong agreement (kappa = 0.81; 95% CI, 0.71-0.90) between proceduralist and blind ultrasound reviewers regarding complete pleural space evacuation. Conclusions: Post-thoracentesis ultrasound is an equally effective alternative to CXR in evaluating pleural space evacuation in simple pleural effusions.