Ultrasonographic characterization of malignant pleural effusion in a murine experimental model

Malignant pleural effusion (MPE) is a common manifestation of advanced malignancies and is associated with high morbidity and poor prognosis. Thoracic ultrasound (TUS) has emerged as a sensitive, non-invasive imaging modality for pleural evaluation; however, standardized ultrasonographic criteria for MPE in murine experimental model remains limited. The aim of this study was to describe and characterize the TUS findings of MPE in an experimental murine model.

MPE was induced in C57Bl/6 mice by intrapleural injection of Lewis lung carcinoma (LLC) cells. TUS examinations were performed longitudinally at predefined time points to assess pleural fluid depth, pleural line characteristics, pleural thickening, nodules, subpleural consolidations, lung parenchymal alterations, and ultrasound artifacts. Pleural fluid volume, cytology, and histological analyses were obtained after euthanasia and correlated with ultrasonographic findings.

TUS detected early pleural changes as early as day 7, preceding large-volume effusion. Pleural fluid depth measured by TUS showed a strong correlation with pleural fluid volume obtained by direct puncture (R = 0.927, p < 0.001). Progressive pleural thickening and nodularity (R = 0.704 e p = 0.002) correlated with histopathological tumor involvement.

TUS reliably characterizes and quantifies MPE progression in a murine model, closely reproducing human disease patterns. This experimental model supports translational research by enabling longitudinal and non-invasive assessment of biological and pathological processes over time, thereby allowing repeated evaluations within the same subject and significantly reducing the need for animal euthanasia at multiple experimental endpoints, while also providing a robust framework that may corroborate and facilitate future studies in related research fields.