Magnetic Resonance Imaging in Differential Diagnosis of Canine Nasal Disease: A Preliminary Study
*M. E. Herrtage, J. Sales, E. A. Baines
Nasal discharge, sneezing, epistaxis and stertor are common signs of nasal disease in dogs. Differential diagnosis includes chronic hyperplastic rhinitis, nasal aspergillosis and nasal tumours. Diagnosis is usually established from a combination of results from the clinical history, physical examination, serology, radiography, rhinoscopy and biopsy. In a number of dogs, radiography allows differentiation between chronic rhinitis, nasal aspergillosis and nasal neoplasia, but in other cases the differentiation is not clear-cut. More recently, the use of computed tomography has been reported to help differentiate nasal diseases. The purpose of this study was to investigate the use of magnetic resonance (MR) imaging in the diagnosis and assessment of canine nasal disease.
Eight dogs were referred to the Queen's Veterinary School for investigation of nasal disease. MR imaging was performed in each dog under general anaesthesia using a dedicated veterinary MRI unit (Vet-MR®, Esaote) incorporating an open 0.2 Tesla permanent magnet. The head was placed in a dual phased array coil (143mm x 158mm). T1-weighted, T2-weighted and proton density weighted images of the nasal chambers and paranasal sinuses were acquired in the dorsal, transverse and sagittal planes. T1-weighted images were also acquired following intravenous administration of either 0.2 mmol/kg gadoteridol (ProHance®, Bracco) or 0.1 mmol/kg gadobenate dimeglumine (MultiHance®, Bracco). The diagnosis of nasal disease was made on the basis of serology, rhinoscopic findings and biopsy results. The images were compared to MR scans of the nasal chambers and paranasal sinuses from six normal dogs.
Four dogs had intra-nasal tumours characterised by an isointense mass replacing the nasal turbinates and extending into the surrounding tissues in all sequences. Three dogs had nasal aspergillosis characterised by marked hyperintensity of the nasal mucosa in the affected areas of the nasal chamber and paranasal sinuses in all sequences. The mucosa was often thicker in the affected areas and there was moderate to severe destruction of the nasal turbinates with large areas of cavitation. One dog had chronic rhinitis which was characterised by thickening of the nasal mucosa and isointense filling of the spaces between the turbinates in the affected areas.
Following contrast administration, there was good enhancement of the mucosa in both the normal and abnormal areas of the nasal chamber and paranasal sinuses. Mucoid discharge could be identified between the turbinates and in the paranasal sinuses because it did not enhance.
The MR features of canine chronic rhinitis, nasal aspergillosis and nasal tumour were significantly different to allow identification of the underlying disease process in each case.