Objective: To assess agreement between a previously described lung ultrasound protocol, Vet BLUE, and thoracic computed tomography (CT).

Methods: Animals presenting to an emergency department were prospectively recruited between May 2017 and September 2018. The Vet BLUE protocol (whereby 4 set points on each hemithorax are assessed by ultrasound for the presence of B-lines, pleural fluid, lung consolidation or any other abnormal findings) was followed on all animals at the time of admission by a veterinarian with basic training in emergency ultrasound. Those animals that had a thoracic CT performed within 24 hours were then subsequently enrolled. A board-certified radiologist, blinded to the Vet BLUE findings, reviewed the CT images. Accuracy of the Vet BLUE protocol for detection of regional CT abnormalities was determined and a Cohen’s kappa statistic was calculated to assess agreement between CT and Vet BLUE.

Results: 31 animals (26 dogs and 5 cats) were enrolled. CT revealed alveolar-interstitial disease in 64.5% (20/31) cases, pneumothorax in 9.68% (3/31) cases, pleural fluid in 9.68% (3/31) cases, mediastinal masses in 6.45% (2/31) cases and no abnormalities in 35.5% (11/31) cases. When using CT as gold standard, Vet BLUE had an overall accuracy of 70%. There was good agreement between CT and Vet BLUE for detection of pleural effusion (κ=0.783), and fair to moderate agreement for detection of pneumothorax (κ=0.475), lack of intra-thoracic disease (κ=0.516) and alveolar-interstitial disease (κ=0.321). Discordance occurred with the reporting of a cranioventral soft tissue mass in one case on Vet BLUE examination that was not present on thoracic CT. Conversely, a pneumothorax was not detected on Vet BLUE in 2/3 cases and CT revealed alveolar-interstitial disease in 8 cases which did not fulfil the criteria for Vet BLUE diagnosis of alveolar-interstitial disease (≥3 B lines), however 6/8 of these cases had 1–2 B lines present.

Conclusion: The Vet BLUE protocol is a useful technique to detect intrathoracic disease when performed by veterinarians with basic training. Detection of 3 or more B lines is highly suggestive of significant alveolar-interstitial disease and their detection should prompt further diagnostics.