Objective: To describe and compare CT abnormalities of the middle ear in rabbits (Oryctolagus cuniculus) that had clinical or subclinical middle ear disease and to determine the prevalence of otitis media and evaluate the role of predisposing factors for otitis media in that species.
Design: Retrospective case series.
Animals: 88 domestic rabbits.
Procedures: Medical records for rabbits that underwent CT of the head in June 2007 through February 2014 were searched and classified on the basis of reason for head CT (i.e., ear-related disease vs non-ear-related disease). The ears, upper respiratory tract, teeth, and other important structures of each rabbit's head were evaluated. Follow-up information was obtained for rabbits with CT abnormalities of the middle ear without clinical signs (i.e., subclinical disease).
Results: 12 of 21 (57%) rabbits with clinical signs of ear disease and 18 of 67 (27%) rabbits without clinical signs of ear disease had CT abnormalities of the middle ear. In CT images, all affected ears had soft tissue-attenuating material within the tympanic bulla. Tympanic bulla lysis was associated with clinical middle ear disease. Most (12/18) rabbits with subclinical middle ear disease remained subclinical after CT examination. Middle ear CT-detected changes and lop-ear conformation or otitis externa were strongly correlated; middle ear disease and upper respiratory tract disease were not correlated.
Conclusions and clinical relevance: Data suggested that subclinical otitis media frequently affects rabbits, and those with bulla lysis should be closely monitored. Lop-eared rabbits and rabbits with otitis externa had a higher risk of developing otitis media.