Assessment of survey radiography as a method of diagnosing bilateral laryngeal paralysis in dogs.

The gold standard for diagnosis of laryngeal paralysis is laryngoscopy under light anesthesia. This prospective analytical cross-sectional study aimed to determine whether a radiographic assessment of the larynx could be used as a non-invasive screening tool for diagnosing laryngeal paralysis in non-sedated animals, as the laryngeal ventricles may appear wider in affected animals. The laryngeal ventricles of 18 dogs with bilateral laryngeal paralysis composing the affected group and 25 non-sedated dogs presenting no respiratory abnormality composing the control group were evaluated using right lateral radiography of the larynx. Three observers measured the ratios of the maximal ventricular length and surface to the body length of the third cervical vertebra (MVL/LC3 and VS/LC3, respectively). They also subjectively assessed the ventricular shape as either normal or rounded. The most accurate criterion was found to be MVL/LC3, as the respective areas under the ROC curves were 0.96 (95% confidence interval [CI]: 0.95-0.97), 0.89 (95% CI: 0.87-0.91), 0.80 (95% CI: 0.65-0.95) for MVL/LC3, VS/LC3, and ventricular shape evaluation, respectively. Based on ROC curve analysis, two thresholds of clinical interest were set for the MVL/LC3; bilateral laryngeal paralysis was very unlikely for values < 0.3 and very likely for values > 0.5. The findings of this study support the use of lateral laryngeal radiography as a screening tool for diagnosing bilateral laryngeal paralysis. However, further diagnostic tests remain required if MVL/LC3 lies between these threshold values or if clinically indicated. Further studies are warranted to explore the use of laryngeal radiography in unilateral paralysis and other laryngeal or oropharyngeal diseases.