Celia L. Cox, BVetMed, CertVR, FRCVS, RCVS
Nasal disease in the dog generally presents with a combination of discharge, sneezing, epistaxis, stertor and gagging. To diagnose the cause of these nasal symptoms, a good diagnostic protocol is required. This should include a full clinical history, physical examination, radiology, rhinoscopy, biopsy, laboratory tests, and in some cases magnetic resonance imaging or computed tomography.
It is worth taking time and trouble over the history and physical examination as they can provide many clues to the underlying diagnosis. For example:
Look for stenotic nares in brachycephalic breeds e.g., Pekinese with their typical bilateral spluttering nasal discharge. Mesocephalic and doliocephalic breeds are candidates for rhinomycosis, whilst brachycephalics are rarely affected. Dachshunds and Irish wolfhounds are candidates for hyperplastic rhinitis.
Nasal tumours are more commonly found in middle or old aged dogs. Aspergillosis sp is more prevalent in young to middle aged dogs. Congenital cleft palates and the rarer "immotile cilia syndrome" are seen in young puppies.
c) Acute vs. Chronic
Dogs with a history of sudden onset violent sneezing fits, pawing, or ipsilateral involuntary facial muscle contractions are typical candidates for intra-nasal foreign bodies. Nasal discharges are considered chronic when present for at least seven days.
d) Unilateral vs. Bilateral
Unilateral nasal discharge is more commonly associated with foreign bodies, neoplasia, fungal infections and oro-nasal fistulae. Bilateral discharge is more common in dogs with congenital cleft palate, severe dental problems, hyperplastic rhinitis or systemic disease e.g., distemper.
This is commonly due to trauma, rhinomycosis and neoplasia. If no intra-nasal causes are found, extranasal diagnoses should be pursued.
f) Malodorous Discharge
This is generally associated with dental disease or foreign bodies.
g) Nasal Pain
Aspergillosis sp infection is the commonest cause of nasal pain, accompanied by ipsilateral enlargement of the submandibular lymph node and lethargy.
If unrelated to eye disease and ipsilateral with the nasal discharge in an elderly dog, this often indicates obstruction of the nasolacrimal duct by a mass. If bilateral, systemic disease is more likely.
i) Other Questions
History of trauma, terrain, and poisoning can sometimes be helpful in achieving a diagnosis.
3. Physical Examination
During physical examination, the affected dog should be examined for conditions such as nasal discharge, smell, pain, discoloration of the nares, air flow and facial swelling. It is important to obtain answers to the following questions:
Is the discharge unilateral or bilateral?
What colour is it?
Are the nares painful?
Does it smell?
Is there discoloration or ulceration of the nares?
Are there systemic signs e.g., lethargy, local lymphadenopathy?
By determining the airflow though through each nasal chamber, the clinician can assess if the disease is uni or bilateral and estimate the degree of nasal obstruction. This will vary with the amount of discharge present at that time.
Airflow may be assessed either by observing movement of a thin wisp of cotton wool held in front of each nares, or by looking for condensation from each side on a cool glass slide. The lateral movement of the alar cartilage with each respiration can also help indicate nasal obstruction.
i) Reduced airflow = discharge +/- mass
ii) Increased airflow = normal or rhinomycosis, e.g., Aspergillosis sp infection.
b) Anterior vs. Posterior Disease
Sneezing and nasal discharge are often associated with nasal disease affecting the rostral half of the nasal chamber. Snorting, gagging and increased snoring at night tend to be associated with pathology affecting the posterior half of the nasal chamber(s) or nasopharynx.
This requires general anaesthesia, and is a very useful aid to diagnosis. The dorso-ventral intra-oral film is far more useful than the ventro-dorsal skull, as the nasal chambers can be examined without superimposition of the mandibles. A flexible 13cm x 18cm cassette provides more information than a rigid cassette, because it can be pushed further into the mouth so that the caudal nasal chambers are included. The cassette consists of a screen film trapped between two rare earth screens. The beam is normally directed at 90 degrees to the plate in the midline between the eyes. In apple head dogs, e.g., Chihuahua, the beam needs to be slightly angled to avoid the caudal nasal chambers being screened by the calvarium.
The lateral skull radiograph is occasional useful to detect radio-opaque nasopharyngeal foreign bodies, but a lateral oblique skull is more useful because it separates the two sides of the skull, e.g., for assessment of dental disorders and integrity of the frontal bone for nasal tumours.
The rostro-caudal skull view is used to highlight changes in the frontal sinuses e.g., for the diagnosis of aspergillosis sp invasion, where fungus is not seen in the nasal chambers or tumours. It is quite difficult to achieve.
When assessing radiological changes, the identification of normality must be achieved before pathology can be appreciated.
Signs of pathology include:
Loss of turbinate pattern
Increased soft tissue opacity
Vomer bone destruction
Extra-nasal signs, e.g., frontal sinus opacity or destruction, soft tissue swelling
Radio-opaque foreign bodies
With the appropriate equipment, this can be particularly useful for the diagnosis or elimination of specific conditions. The nose can be examined from both the anterior and retrograde route. The limitations are the size of the dog's nasal passages, the size of the scope, and the presence and thickness of any nasal discharge.
a) Retrograde Rhinoscopy
This is performed using a flexible bronchoscope e.g., 4.5mm inserted backwards over the soft palate. This is usually done before anterior rhinoscopy to stop any blood caused by the latter obscuring the view. The procedure allows visualisation of the posterior choanae and nasopharynx for any masses, discharge or foreign bodies. One could also use a dental mirror warmed or coated with anti-fogging agent.
b) Anterior Rhinoscopy
An otoscopy is often used in practice, however a rigid scope is far superior. A 2.7mm rigid scope is suitable for most sizes of dogs, especially when combined with fine suckers to remove nasal discharge or biopsy instruments for taking guided samples for histopathology or cytology. The chambers should be examined systematically, e.g., dorsal, middle and ventral nasal meatus, starting with the non-affected side in unilateral disease, to prevent cross contamination, and provide a normal side for comparison.
After performing rhinoscopy, the clinician should have identified the colour and side of any discharge, observed the nasal mucosa, the size of the meatae, the presence of absence of normal turbinates, neoplasia, fungal plaques or foreign bodies.
6. Laboratory Analysis
A biopsy often allows a definitive diagnosis to be made. Guided biopsies via anterior rhinoscopy for histopathology are far superior and safer than those unguided. The instrument used must provide sufficient material to be representative of the lesion. A turbinectomy forceps is suitable for sampling masses in most sizes of dog. Samples taken though a flexible scope are often not big enough for analysis. Also, several samples are required which makes the procedure more difficult as each biopsy causes increased bleeding. The head and neck and any blood sucked from the pharynx prior to extubation.
Other biopsying techniques are generally less accurate and less safe. These include blind biopsying using the radiograph as a guide, suction of intranasal materials via a urinary catheter attached to a 50ml syringe, or flushing material via a nasal catheter into a specimen jar placed in the nasopharynx. Flushing is helpful to remove discharge, but is generally unsuccessful for flushing out foreign bodies, as they would have dislodged with the force of sneezing. Biopsy via rhinotomy carries a much higher morbidity rate and the relevant area may not be easy to locate if situated in the mid or ventral meatus, due to bleeding in this vascular area.
When obtaining samples, great care must be taken to avoid aspiration of fluid or solid, by ensuring the endotracheal tube is well cuffed and the throat is packed.
Serum can be sent for testing for aspergillosis sp. However the test is not 100% reliable with both false negatives and positives.
Bacterial culture and sensitivity of nasal discharge is of dubious value as most bacteria are secondary. Positive fungal culture of aspergillosis from nasal swabs has been reported in approximately 30% of cases in one study, but as aspergillosis is ubiquitous, treatment should only be performed if these findings correlate with clinical signs.
d) Haematology and Biochemistry
Information obtained from blood samples may be useful for dogs with epistaxis where no intra-nasal disease has been found, especially for the diagnosis of thrombocytopenia and coagulopathies.
7. MRI and CT
Both magnetic resonance imaging (MRI) and computed tomography (CT) may help with the diagnosis of nasal disease, where other methods have been inconclusive.
CT is better for subtle bony changes affecting structures such as the nasal turbinates, vomer bone, and frontal bone. CT has the advantage of being cost-effective and quick, plus it is readily available in local hospitals and does not require non-magnetic anaesthetic equipment. Coronal and axial views are generally taken.
MRI is a better approach for subtle soft tissue changes, and has the advantage of being able to take sections in any plane. The technique is more expensive than CT, and it is also important for the patient to remain absolutely still.
With a systematic approach and appropriate equipment, the definitive diagnosis of nasal disease can be achieved in the vast majority of cases.
With a systematic approach and appropriate equipment, the definitive diagnosis of nasal disease can be achieved in the vast majority of cases. Appropriate treatment options and prognosis may then be provided.