Specialty Spotlight: Nasal Disease in Dogs and Cats
Nasal Disease in Dogs and Cats
Sara Arnold, DVM, DACVIM
As the warmer months roll around, there also seems to be a recrudescence of nasal disease. The chronically sneezing, snotty dog or cat tends to be something that plagues owners and veterinarians alike. Many owners who present to our specialty hospital are looking for a nasal foreign body to be the source of all their evils, but (unfortunately for them and us) nasal foreign bodies are few and far between. Instead, we are frequently left with chronic, uncurable conditions such as allergic, lymphoplasmacytic, and herpesvirus rhinitis. Further complicating the issue is that a definitive workup of nasal disease can frequently be cost-prohibitive for owners. So, how do we practically approach this uniformly frustrating condition?
As in most diseases, the history and physical exam findings for nasal disease can help prioritize differentials and diagnostic testing. Common clinical findings can include:
- Facial deformity– most typical of underlying neoplasia or fungal disease though chronic inflammatory/bacterial rhinitis is still possible
- Depigmentation of the nasal planum– characteristic of canine nasal aspergillosis
- Absent nasal airflow with minimal discharge or only hemorrhagic discharge– most commonly noted with underlying neoplasia, could be observed with a polyp in the nasal cavity or very caudal nasal/nasopharyngeal disease
- Acute onset severe (near constant, very protracted episodes for several days) sneezing or reverse sneezing +/- pawing at the face– most characteristic of nasal foreign body
- Concurrent ocular disease and rhinitis– most typical of environmental allergies or feline herpesvirus
- Largely reverse sneezing –classically due to nasopharyngeal lesions. Allergic rhinitis is the most common cause of nasopharyngeal inflammation but gastro-esophageal reflux into the nasopharynx (particularly in brachycephalic breeds), nasopharyngeal foreign bodies, or underlying neoplasia would also be a consideration
- Upper airway stertor that does not resolve when the mouth is opened –This isolates disease to the caudal pharynx/larynx, not the nasal cavity or nasopharynx.
Definitive workup of most nasal diseases will require advanced diagnostic testing and is frequently cost-prohibitive for owners; however, there are some minimally invasive diagnostic options for nasal disease:
- Herpesvirus PCR or trial course of famciclovir (90mg/kg PO q 12)
- Cryptococcus capsular antigen titers
- Cytology of submandibular lymph node aspirates to screen for metastatic neoplasia
* Please note urine and serum testing for canine aspergillosis is available, but this is only useful for disseminated disease and cannot diagnose isolated, nasal aspergillosis.
- Skull radiographs – these are of limited diagnostic value as they generally require heavy sedation or general anesthesia for appropriate positioning. Though radiographs can document turbinate destruction, it is unlikely that they will be able to further elucidate the underlying etiology (neoplasia vs. Chronic inflammation vs. Fungal infectionetc).
If owners are interested in a more advanced workup, then they should be prepared for costs ranging from $3,500 – $6,000, depending on the exact diagnostics that are indicated. Typically a CT scan is our top priority with our nasal workups. CT allows us a global picture of the nasal cavity, sinuses, nasopharynx, oral cavity, and larynx. If underlying neoplasia is strongly suspected and owners would consider radiation therapy, then it is best to perform the initial diagnostic CT scan at a facility that also has radiation capability. This allows radiation planning markers to be included in the initial CT and eliminates the need for a repeat CT for radiation planning. CT also allows us to ensure that the cribriform plate is intact before pursuing a nasal flush or biopsy. If the cribriform plate is not intact, then manipulation of the nasal cavity could result in intracranial swelling and brainstem herniation. If owners decline a CT scan before nasal biopsies or a nasal flush, they should be made aware of this possible complication. A CT scan cannot assess for dental disease or small oronasal fistulas, so it is essential to rule this out in older animals with compatible clinical findings before referral.
Based on CT results, a rhinoscopy may be recommended. Rhinoscopy is most beneficial in cases of canine sinonasal aspergillosis, nasal foreign bodies, and nasopharyngeal disease. Biopsies obtained with rhinoscopy can be better directed but are often times exceedingly small in size, limiting their diagnostic quality. Therefore, blind biopsies are almost always obtained utilizing a larger, rigid cup biopsy forceps. In order to safely obtain blind biopsies, forceps should never be inserted past the level of the medial canthus. To ensure forceps are not inserted too deeply, we measure to the depth of the medial canthus and place a tape marker directly on our biopsy forceps (Figure 1). Clotting times and platelet counts should always be assessed before performing nasal biopsies, as life-threatening hemorrhage can occur in patients with coagulopathies. Nasal biopsy tissue is submitted for aerobic +/- fungal culture and histopathology. Culture of nasal discharge is often times inaccurate since it only represents the superficial flora. Chronic rhinitis will often result in a deeper tissue infection and osteomyelitis. Therefore, it is necessary to culture the bone of the turbinates for the most accurate assessment.
Nasal flushing can be helpful to dislodge foreign material and may even provide tissue samples for analysis. When flushing large volumes of fluid through the nasal cavity, the patient’s head is hung off the edge of the table to reduce pooling around the endotracheal tube. The seal of the endotracheal tube cuff should also be carefully evaluated prior to flushing, and Parafin tape can be wrapped around the tube juncture to prevent fluid from wicking into the endotracheal tube (FIGURE 2). A slip-tip syringe is placed in one nare, and the opposing nare is occluded digitally (FIGURE 2). Approximately 30-60cc of cold saline is rapidly flushed through that nare 1-3 times. The back of the oropharynx should then be swabbed with gauze to clear any accumulated mucous or water and to screen for the presence of tissue chunks. Occasionally we have obtained large (1-3cm) samples of tissue with this technique which can then be submitted for histopathology. This type of tissue retrieval is almost exclusively noted with cases of nasal lymphoma. It is unlikely that sufficient tissue will be obtained with this technique in cases of inflammatory rhinitis or other forms of neoplasia (carcinoma, osteosarcoma , etc).
For nasal foreign bodies, antegrade and retrograde flushing can be beneficial since foreign bodies can be lodged just within the nare or in the nasopharynx. In order to easily position catheters in the nasopharynx, we generally insert a red rubber catheter into the nare and down the ventral meatus, similar to the placement of a nasogastric feeding tube. The tip of the catheter is retrieved from the oropharynx and secured to a second catheter (Figure 3 – image B). Fishing line or suture on a reel could be used for this purpose. The catheter tips are then pulled back into the nasopharynx. The pharynx/oropharynx is packed with gauze to provide occlusion of the nasopharynx and force the flush through the nasal passages. Packing the pharynx also helps to reduce pooling of fluid around the endotracheal tube, thereby lessening the risk of aspiration pneumonia. A gauze count should be performed during this packing and after removal in order to ensure that no gauze remains behind. This type of catheter positioning can also be utilized for nasal flossing. This involves moving the two catheters back and forth through the nasal passages. This can be used to dislodge foreign bodies or fungal plaques and can rarely provide tissue samples.
Overall, the workup of chronic nasal discharge can be overwhelming for owners. If they are unwilling or unable to pursue more advanced diagnostic testing for the workup of nasal disease, then we generally pursue a stepwise approach with empiric therapy. For cats, we generally begin with a trial course of famciclovir +/- concurrent antibiotics (depending on the appearance of the nasal discharge). For canine patients, we will consider antihistamines, antibiotics, or even topical anti-inflammatories as part of the initial treatment depending on the clinical presentation. Bacterial rhinitis is always secondary to another underlying etiology. So, if the nature of the nasal discharge suggests the presence of a bacterial infection (thick, dark yellow to green discharge,) it is important to address both conditions concurrently. If patients do not respond to initial antihistamines, topical anti-inflammatories (prednisolone acetate 1% O.S. 1-2 drops in each nare q 12), antibiotics, or antivirals (felines), then we can move on to consider systemic steroids, nebulized antibiotics (amikacin) or nebulized steroids (dexamethasone). Topical decongestants (Afrin 1 drop in each nare q 24 for a maximum of 3 consecutive days) can also be helpful in cases of herpesvirus or allergic rhinitis.
-Sara Arnold, DVM, DACVIM
Small Animal Internal Medicine