Computed tomographic grading of middle ear disease in domestic rabbits (Oryctolagus cuniculi)

Ear disease, involving the middle and external ear, is commonly reported in pet rabbits, with lop eared breeds predisposed. Computed tomography (CT) scanning is the most reliable imaging modality for identifying otitis media (OM) in rabbits. This study aimed to develop a CT-based grading scale to classify the severity of CT changes in rabbits with presumed OM.
A high proportion of rabbits (83%) underwent CT scanning conscious, demonstrating that diagnostic quality CT images are achievable without the need for anaesthetic intervention, minimising the risk to the patient.
Three observers independently reviewed CT images of 36 rabbits with OM. The images of both the middle and external ear canals, were graded for the extent of deviation from normal anatomy. A grade of I to IV (I = mild, IV = severe) was awarded, and the level of agreement between reviewers was statistically evaluated. The study demonstrated that grades from the three reviewers showed a strong level of inter-observer agreement. Comparisons between reason for presentation, clinical signs and CT grade were also evaluated to assess correlation between the three.
This novel CT-based grading scale will facilitate future objective studies to correlate grade of disease with clinical signs, ear canal cytology, predisposing factors, treatments options and outcomes for rabbits with ear disease.