Objective

To compare two point-of-care lung ultrasound (LUS) protocols for quantification of B-lines in cats without evidence of respiratory disease based on history, physical examination and thoracic radiography.

Methods

A prospective observational study was conducted at a single veterinary teaching hospital. Fifty-seven cats without respiratory disease based on history, physical examination, and thoracic radiographs were enrolled. All cats had two point-of-care LUS protocols performed bilaterally: a regional protocol (VetBLUE), and a more comprehensive vertical sweeping protocol (VS). The total number of B-lines per cat, number of sites with B-lines, and maximal number of B-lines at each site were recorded and compared.

Results

Ten cats (18%) had at least 1 B-line identified with VetBLUE, vs. twenty-nine (51%) with VS. Comparing protocols, VS had a statistically higher total number of B-lines per cat, higher number of sites with B-lines, and higher maximal number of B-lines per site. B-lines that were too numerous to count were identified at a single location in 1 cat with VetBLUE and 2 cats with VS. A maximum of three B-lines were identified at all other positive sites regardless of the protocol used. On average, it took 1.7 times longer to complete VS bilaterally compared to VetBLUE (mean 142±4.2 vs. 82±2.3 seconds, respectively, p=0.001).

Conclusions

This study demonstrates it is not uncommon to identify a single or even multiple B-lines in one or several sites on LUS in cats deemed to be clinically free of respiratory pathology; essential knowledge when using LUS as a screening test and to monitor intrathoracic lesions. In cats asymptomatic for respiratory disease, VS generally identifies more B-lines than VetBLUE, likely because it assesses a larger lung surface area. The sonographic identification of B-lines should be interpreted considering the LUS protocol used, history, and other diagnostics to determine their clinical significance. This research was made possible with the financial support of the Pet Health Fund, supported by Zoetis.

E-mail: jo-annie.letendre@umontreal.ca