When to consider aspergillosis in dogs - Veterinary Medicine
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When to consider aspergillosis in dogs
Sinonasal and disseminated aspergillosis—the two classic presentations—are caused by different Aspergillus fungi. Learn how to manage these clinically distinct infections, and find out how the prognoses for affected dogs differ between the two.


VETERINARY MEDICINE



Figure 2. A transverse CT image of the nasal passages of a dog with bilateral sinonasal aspergillosis. Note the loss of turbinate structures. (Image courtesy of Dr. Kyle Mathews, North Carolina State University College of Veterinary Medicine.)
The diagnostic sensitivity of radiography is limited by superimposition of bony structures and the complexity of the nasal turbinates. Various studies have shown that magnetic resonance imaging (MRI) and computed tomography (CT) are superior imaging choices in these patients. In 25 dogs with confirmed aspergillosis, CT had a sensitivity of 88% vs. 72% for standard skull radiography.11 In addition, CT and MRI can distinguish unilateral vs. bilateral disease and identify destruction of the bony nasal septum (Figure 2). MRI provides more information about the soft tissue structures of the face, but CT permits detailed evaluation of the cribriform plate and is presently the more popular imaging modality in veterinary patients with overt nasal or sinus disease. Both techniques are useful in determining the best place for a nasal biopsy or the collection of other samples.


Figure 3. A rhinoscopic image of the nasal cavity of a dog with sinonasal aspergillosis. Note the extensive loss of the normal turbinate structures. (Image courtesy of Dr. Kyle Mathews, North Carolina State University College of Veterinary Medicine.)
Rhinoscopy and sinuscopy. Rhinoscopy allows visualization of the nasal cavity and guided collection of biopsy samples and is routinely performed after imaging studies. In addition, direct examination of the nasal passages may reveal other causes of nasal discharge such as neoplasia or a foreign body. A rigid endoscope (e.g. a cystoscope) or a narrow flexible endoscope (e.g. a pediatric bronchoscope) can be used for this purpose. Premeasure the endoscope from the nasal planum to the ipsilateral medial canthus to avoid penetrating the cribriform plate.


Figure 4. A rhinoscopic image of the left nasal cavity of a dog with sinonasal aspergillosis. The white fuzzy object is a fungal plaque. (Image courtesy of Texas A&M College of Veterinary Medicine & Biomedical Sciences.)
Dogs with aspergillosis typically have substantial turbinate loss (Figure 3) and copious, mucopurulent discharge. In addition, fungal plaques may be noted; these are off-white or greenish fuzzy lesions adherent to the mucosa (Figure 4), which may be confused with mucoid material by inexperienced clinicians.1,2 Biopsy samples can be collected through the endoscope or by adjacent placement of a rigid device. It can be helpful to gently roll one sample over a slide for cytologic evaluation before placement in formalin. In addition to nasal passage examination, the nasopharynx can be viewed by using a small retroflexed endoscope or a dental mirror with a rigid endoscope. Biopsy collection is difficult in this area, but a brush may be passed through a flexible endoscope to obtain cytologic samples.

Although the frontal sinuses may be accessed by using a rostral nasal approach, it can be technically challenging. Alternatively, trephination may be performed to permit insertion of a rigid endoscope.5 Trephination prolongs anesthesia time and increases postoperative discomfort but may provide essential diagnostic information in veterinary patients without rhinoscopic evidence of fungal disease. In one study of 46 dogs with sinonasal aspergillosis, 17% had fungal plaques in the sinuses but not in the nasal cavity.12


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Source: VETERINARY MEDICINE,
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