Lung Ultrasound for Imaging of B-Lines in Dogs and Cats-A Prospective Study Investigating Agreement between Three Types of Transducers and the Accuracy in Diagnosing Cardiogenic Pulmonary Edema, Pneumonia and Lung Neoplasia.

Abstract

Simple SummaryThe high usefulness of thorax ultrasound examination in diagnosing lower respiratory tract diseases is well-evidenced in both human and veterinary medicine. However, the type of transducer (microconvex, linear, and phased array) which is most effective in the examination of dogs and cats remains unknown. In this study we examined dogs and cats using the three types of transducers and we assessed how consistent they were in detecting and quantifying B-lines. Moreover, we developed a method that allowed to quantitatively evaluate the occurrence of B-lines in cardiogenic pulmonary edema (CPE), pneumonia and lung neoplasm, referred to as the lung ultrasound score (LUSscore). Our results indicate that microconvex and linear transducers can be used interchangeably. LUSscore may help distinguish between lung neoplasms (lower values) and CPE or pneumonia (higher values) in dogs, and between CPE (higher values) and pneumonia or lung neoplasms (lower values) in cats.Transthoracic heart and lung ultrasound (LUS) was performed in 200 dogs and cats with dyspnea to evaluate the agreement between the results obtained using three types of transducers (microconvex, linear, and phased array) and to determine the accuracy of LUS in discriminating between three conditions commonly causing dyspnea in companion animals: cardiogenic pulmonary edema (CPE), pneumonia, and lung neoplasm. The agreement beyond chance was assessed using the weighted Cohen’s kappa coefficient (κw). The highest values of κw (>0.9) were observed for the pair of microconvex and linear transducers. To quantify B-lines the lung ultrasound score (LUSscore) was developed as a sum of points describing the occurrence of B-lines for each of 8 standardized thoracic locations. The accuracy of LUSscore was determined using the area under ROC curve (AUROC). In dogs AUROC of LUSscore was 75.9% (CI 95%: 65.0% to 86.8%) for distinguishing between lung neoplasms and the two other causes of dyspnea. In cats AUROC of LUSscore was 83.6% (CI 95%: 75.2% to 92.0%) for distinguishing between CPE and the two other causes of dyspnea. The study shows that results obtained with microconvex and linear transducers are highly consistent and these two transducers can be used interchangeably. Moreover, the LUSscore may help identify dogs with lung neoplasms and cats with CPE, however its diagnostic accuracy is only fair to moderate.