Fluorescein-aided confocal laser endomicroscopy of the lung.

BACKGROUND There are only few reports about confocal laser endomicroscopy (CLE) for pulmonary imaging. In these studies, in contrast to gastrointestinal endoscopy, CLE was performed without fluorescein. OBJECTIVES The aim of the present study was to evaluate the value of fluorescein usage for CLE of the lung. METHODS Fluorescein-aided CLE was performed in 15 consecutively recruited patients and in 4 young healthy volunteers with a miniprobe during flexible bronchoscopy. Before and after intravenous administration of fluorescein, central airways and alveolar structures were evaluated. RESULTS Fluorescein administration did not permit imaging of epithelial cells in the central airways. In the lung periphery, alveolar walls and partially macrophages could be seen in native imaging, as expected. After administration of fluorescein, alveoli were almost filled with foam in areas with normal lung tissue. The origin of this foam was shown to be artificial. Furthermore, in patients with pathologies of the lung parenchyma, dark neoplastic and inflammatory cells adjacent to the alveolar walls were identified. No relevant side effects of fluorescein administration could be observed. CONCLUSIONS Fluorescein-aided CLE of the lung appeared to be safe and well tolerated. While the lack of staining of cells in the central airways was a major limitation, it permitted analysis of the lung interstitium and alveolar space and thus emerges as a new approach for the in vivo analysis of interstitial lung diseases.