To assess the clinical value of contrast-enhanced ultrasound (CEUS) guided urokinase injection for precise treatment of encapsulated pleural effusion.

From January to June 2021, 32 patients with capsulated pleural effusion (low to medium volume) treated at The First Affiliated Hospital of Guangzhou Medical University were included in the study. CEUS examinations were performed by injection of the contrast agent into the capsulated pleural effusion to observe the diffusion of the contrast agent. And then, 20000-30000 U of urokinase was injected into pleural effusion with a 22G fine needle, which was retained for 30-90 minutes. At the same time, CEUS examinations were performed dynamically to monitor the diffusion of the contrast agent and the dissolution of the fibrous separations in the pleural effusion, to determine the catheterization drainage occasions. The ultrasound images, pulmonary function examinations, drainage volume of pleural effusion, and complications were analyzed to make a comprehensive evaluation of the therapeutic effect. Differences in ultrasound parameters and lung function measures before and after treatment were compared using a paired t-test.

Among the 32 patients with encapsulated pleural effusion included, the overall efficiency of CEUS guided urokinase injection treatment was 93.75% (30/32). After treatment, the fibrous separation score (2.39±0.66 vs 1.22±0.66), the diffusion percentage of contrast agent [(26.96±12.22)% vs (75.65±16.94)%], the maximum depth of pleural effusion [(44.30±20.65) mm vs (18.04±12.04) mm], and the maximum range of pleural effusion [(1906.17±905.13) mm² vs 658.91±617.82) mm²] changed significantly compared with the values before treatment (t=6.010, -13.371, 7.337, and 7.793, respectively, P＜0.001 for all). In terms of pulmonary function, the changes of forced vital capacity (FVC) and the forced expiratory volume in the first second/FVC ratio after treatment were also statistically significant [(3.11±0.94) L vs (3.05±1.01) L and (80.51±2.49)% vs (79.34±3.27)%; t=-2.377 and -2.421; P=0.031 and 0.029, respectively]. No severe complications occurred in the study.

CEUS examination could be used to observe and monitor the dissolution of the fibrous separations in the pleural effusion dynamically, to evaluate the therapeutic efficiency and determine the drainage occasions, and to reduce the using of urokinase and shorten the time of treatment. CEUS guided urokinase injection represents a safe, effective, and precise method with important clinical value.