by Ronald Lyman, DVM, DACVIM and Beatrix Nanai, DVM
from DVM Newsmagazine.
For some time rhinoscopy alone has been the procedure most often chosen to obtain visual and histopathologic evidence of the disease process(es) occurring in canine patients with persistent nasal signs.
A recent paper by Lynette Johnson, DVM, PhD, diplomate of the American College of Veterinary Internal Medicine (ACVIM) et al in the March 1, 2006 issue of the JAVMA reviewed cases of canine upper respiratory aspergillosis diagnosed at the University of California-Davis. The authors pointed out that in 46 dogs eventually diagnosed with nasal aspergillosis, 83 percent of the time (38 dogs) a fungal plaque was found in the nasal passages, and that 17 percent of the time (eight dogs) a plaque was not found in the nose, but instead only in the frontal sinus (via sinuscopy).
All of these cases had been imaged by computed tomography of the skull, with nasal turbinate destruction found in every patient. CT images of the sinuses were abnormal in more than 75 percent of the cases. Plain skull radiographs were not performed in most of these cases.
Results of fungal culture were positive in only 39 percent of nasal specimens where plaques were observed in the nose, and 40 percent of the specimens obtained from the sinuses (when plaques were observed in that location).
In 13 of these patients, serology by agar gel immunodiffusion for Aspergillus was performed. Five of eight dogs with nasal plaques tested positive, and three of five dogs with sinus plaques also had positive serology.
Finally, biopsy specimens were not as specific as one might think. Only 16 of 34 dogs with fungal plaques visualized in the nasal passages had fungal hyphae visible in the microscopic histopathologic sections. It was surprising that only one of seven dogs with plaques visualized in the frontal sinus had visible hyphae on the examined sections of the biopsies.
The authors made a diagnosis of nasal aspergillosis if at least two out of three following diagnostic tests were in support (CT, visualization of a plaque via a scope, or histopathologic evidence). They noted that no complications were reported in the cases where sinuscopy was performed.
This paper did not address diagnosis via nasal and/or frontal sinus exploratory surgery, or the therapy of this serious disease. Its impact implies that a veterinary clinician presented with a canine displaying chronic nasal signs should now consider sinuscopy in conjunction with rhinoscopy as part of the diagnostic process.
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