Diagnostic Accuracy of Lung Ultrasound in Rabbit Subclinical Lung Lesions

Abstract

Rabbits are commonly affected by subclinical lung diseases. Computed tomography (CT) is the gold standard for diagnosing rabbit lung diseases but is not widely available and requires anesthesia, delaying diagnosis. Lung ultrasound (LUS) has emerged as a radiation-free, bedside diagnostic tool in human and veterinary medicine, though its use in rabbit medicine is not routine. This study aimed to evaluate LUS for detecting subclinical lung lesions in rabbits. Thirty healthy, five-month-old male New Zealand white rabbits underwent lung ultrasound, exploring four regions in each hemithorax, followed by thoracic CT under sedation with midazolam and butorphanol. The ultrasound images were scored as positive or negative, and the CT exams were assessed for aeration using threshold masks. The results showed that 63% of rabbits had one or more affected regions in the ultrasound images, and 19% of the regions were positive. CT identified 54% of the regions as positive for poorly aerated tissue, with 26/30 rabbits showing at least one positive region. The sensitivity and specificity of LUS were 33.33% and 93.48%, respectively, with an accuracy of 67.92% for detecting subclinical lesions. While LUS demonstrated a high specificity, its sensitivity was low compared to CT, highlighting the need for further refinement in its use for rabbit respiratory disease diagnosis.

Keywords: B-lines; computed tomography; lung ultrasound (LUS); non-invasive imaging.

Figure 1

Lung ultrasound images of different regions of a study rabbit’s lung, showing identified patterns observed during the study: (a) Normal lung—air-filled zones showing the rib acoustic shadows (*), the hyperechoic pleural line (short arrow), and A-line artifacts representing horizontal reverberation artifacts of the hyperechoic pleural line (long arrows). (b) B-line (*) vertical, hyperechoic artifact that extends from the pleural line to the bottom of the screen without fading. (c) Multiple B-lines (*). (d) Coalescent B-lines (*). (e) Tissue sign (#), hepatization-like appearance of the lung. (f) Shred sign (ψ), subpleural consolidation with an irregular or “shredded” border between the aerated and consolidated lung. Ultrasound was performed using a musculoskeletal preset (15 MHz), with a depth of 3 cm and the focus set at the level of the pleural line.

Figure 2

Thoracic CT scan in transverse plan of a rabbit. (A) Normal view, a circle marks an area of increased attenuation in the periphery of the right lung, caudodorsal region. (B) Threshold masking highlights an area of poorly aerated tissue. Aerated tissue is shown in blue (−899 to −500 HU), while infiltrated lung/ground-glass opacity (GGO) is shown in orange (−499 to −101 HU).