Huynh E, Reichle JK.
Introduction/Purpose: Lagomorphs (rabbits) and small rodents are popular pets that often present to veterinarians for dental disease, otitis, rhinitis, exophthalmos, and/or palpable masses of the jaw. Diagnosis of these disorders can be difficult; common diagnostic procedures for these patients include oral examination, radiography, and more recently, computed tomography (CT). CT is a valuable tool that overcomes several limitations of conventional radiography, provides detailed information of specific structures , and allows multi-planar reformat ion. Normal anatomical structures have been described in recent studies. The purpose of this study is to describe the various CT abnormalities of lagomorph and small rodent skulls.
Methods: Scans of lagomorph and rodent skulls spanning June 2011 through May 2014 performed with a 16 multi-slice CT scanner (GE BrightSpeed, General Electric Company, Milwaukee, WI) were reviewed. Fifty-four scans of 48 patients (40 rabbits, 8 guinea pigs, 5 chinchillas, and 1 rat) that underwent CT scans of the skull while in sternal recumbency were collected. Ten patients were scanned while anesthesia was maintained via face mask (9) or tracheal intubation (1) with sevoflurance and oxygen. Forty-four of these scans were performed without sedation or anesthesia (confined to a chamber and surrounded by towels to limit motion). CT acquisition parameters were 100.0 kV and 120.0-248.0 mA with 0.625mm slice thickness. Two patients were administered intravenous contrast medium after an initial scan. Images were reviewed in 0.625mm or 1.25mm axial bone and soft tissue windows, as well as sagittal and coronal reformations, by one board certified veterinary radiologist (JKR) and one veterinary radiology intern (EH).
Results: All images included in this study were deemed to be of diagnostic quality. Indications for CT scans included upper respiratory noise , sneezing , nasal and/or ocular discharge, ptyalism, exophthalmos, head tilt, inappetance, a palpable mass, and/or radiation therapy planning. CT findings included 39 cases of significant dental abnormalities (including malocclusions, caries, apical overgrowth), osteomyelitis (22), rhinitis (15), otitis externa (10) media (15) and/or interna (2), retrobulbar mass (5), and meningoencephalitis (1).
Discussion/Conclusion: CT scans of the skulls of rabbits, guinea pigs, chinchillas, and a rat yielded vital diagnostic information and were successfully performed with a multi- slice CT scanner in non-sedated patients (81% of our cases).