Background: Endobronchial ultrasonography (EBUS) has been shown to be an adequate tool to visualize the laminar structure of the bronchial wall. The purpose of this study was to investigate the potential of EBUS to identify and quantitatively assess bronchial wall structures in lung transplant recipients.
Methods: EBUS was performed with a radial 20-MHz ultrasonic miniprobe in lung transplant recipients undergoing surveillance bronchoscopies. Sequential pictures were taken of the main bronchus (proximal of anastomosis) and proximal right intermedius bronchus or proximal left lower lobe bronchus (distal of anastomosis), respectively. From every localization, five slides were chosen. The quantitative assessment of the digitized pictures was done with the aid of image analysis software. In addition to the comparison of the different layers between patients with and without infection and rejection, respectively, the intraclass correlation coefficients (ICCs) of the different measurements were calculated.
Results: From 20 EBUS examinations performed in 10 lung transplant recipients, 200 slides were selected for quantitative assessment. A five-layer composition could be identified in all selected slides. The relative area of layer two (hypoechoic submucosal tissue) of the autologous part was significantly smaller in patients with graft rejection (p = 0.04) compared to patients without rejection, and significantly larger in patients with graft infection (p = 0.02) compared to patients without graft infection. The ICC values were calculated in 50 different slides in a subset of five consecutive patients (0.91, 0.95, 0.88, and 0.91 for layers 1, 2, 3, and 5 of the autologous and 0.70, 0.92, 0.88, and 0.84 for the allogeneic parts, respectively).
Conclusions: EBUS enables to discriminate different layers of the bronchi in humans and to measure the thickness of these layers in a reproducible fashion. Therefore, EBUS may be used to investigate and quantify inflammatory alterations of bronchial wall structures in vivo.