Canine and Feline Respiratory Medicine. Lynelle R. Johnson
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Inflammatory
a Reported causes include canine adenovirus‐2, canine parainfluenza‐3 virus, canine respiratory coronavirus, canine herpesvirus, canine distemper virus, Bordetella, Mycoplasma, and Streptococcus equi subsp. zooepidemicus. Canine influenza viruses and pneumovirus are new additions to the list of etiologic agents and novel viral organisms are continually being identified.
b Reported causes include feline herpesvirus‐1, feline calicivirus, Chlamydia, Bordetella, and Mycoplasma.
With many causes of nasal signs including viral disease or foreign body, discharge is serous initially and then progresses to a mucoid character when inflammation induces mucus production or when secondary bacterial infection develops. Yellow‐green nasal discharge can be an indicator of eosinophilic disease, but is also encountered in other infectious or inflammatory conditions, while brown‐tinged discharge suggests the presence of blood within the mucus. Bright red blood can be found in combination with nasal discharge because of trauma to blood vessels associated with the primary disease process or due to the severity of sneezing. Epistaxis with or without nasal discharge has been associated with local causes of disease, including inflammatory rhinitis, canine aspergillosis, and neoplasia; however, in animals with pure epistaxis, systemic vascular disorders must be considered, including coagulopathies and systemic hypertension.
Nasal discharge that is strictly unilateral is most suspicious for local disease due to a foreign body, trauma, tooth root abscess or oronasal fistula, or an early fungal infection or neoplasm. However, systemic vascular disease or a coagulopathy can also result in unilateral nasal bleeding. Also, inflammatory diseases such as lymphoplasmacytic rhinitis in the dog and feline chronic rhinosinusitis can present with lateralizing clinical signs, although in most cases imaging and histology reveal that both sides of the nasal cavity are affected.
Non‐respiratory history that should be collected includes environmental exposure to foreign bodies, previous trauma, and evidence of vomiting or regurgitation. For animals with epistaxis, potential exposure to vector‐borne diseases that can result in thrombocytopenia, thrombocytopathy, or vasculitis (such as Ehrlichia or Rocky Mountain Spotted Fever) should be identified along with systemic signs of diseases such as renal disease or Cushing's disease, which can result in hypertension.
Signalment
Young animals with nasal discharge are most often affected by infectious upper respiratory tract diseases. A nasopharyngeal polyp should be considered when discharge is accompanied by obstructed breathing. Primary ciliary dyskinesia is a defect of innate immunity that causes ineffectual mucociliary clearance, trapping of secretions, and recurrent infection. Therefore, this condition would be more frequently recognized in a younger animal. Affected dogs are often purebred, with an increased prevalence in the Bichon Frise, Old English Sheepdog (Merveille et al. 2014), and Newfoundland (Watson et al. 1999), although any breed of dog or cat can be affected. While neoplastic disease most typically affects older animals, it also occurs in young to middle‐aged animals (2–5 years of age) and can be particularly aggressive, especially in dogs. Nasal aspergillosis is most often encountered in younger dogs and older cats. Cryptococcosis and inflammatory rhinitis can affect dogs or cats of any age.
Nasal disease of most types (fungal, neoplastic, and inflammatory, as well as dental‐related and foreign body disease) is most commonly found in dolichocephalic dog breeds. An unusual combination of rhinitis and bronchopneumonia has been reported in the Irish wolfhound, where a genetic defect in respiratory immunity is suspected but has not been confirmed (Clercx et al. 2003).
Physical Examination
A complete physical examination is essential in every animal presented for evaluation of respiratory disease. In animals with nasal discharge, important features to focus on include the presence or absence of nasal airflow, changes in ocular retropulsion, ability to depress the soft palate easily into the dorsal nasopharyngeal wall, regional local lymph node enlargement, and facial asymmetry or pain. These parts of the physical examination are most important because they can help identify the space‐occupying nature of some causes of nasal disease, particularly nasal neoplasia, feline cryptococcosis, feline aspergillosis, and nasopharyngeal polyps, and because these physical examination findings can indicate local extension or metastasis.
Nasal airflow can be assessed by holding a chilled microscope slide in front of each nostril to show fogging of the glass or by using a wisp of cotton (from a cotton ball or swab) to watch for air movement. The mouth should be held closed during the procedure, and occlusion of the alternate nostril can be helpful for enhancing airflow through the side of the nasal cavity to be examined (Figure 1.1). Cats create minimal airflow and a very thin wisp of cotton should be used and held in front of the nostril from above and below to check for flow. Alternatively, the stethoscope can be used to listen for airflow from each nostril. An animal with a mass effect in the nasal cavity or nasopharynx will fail to fog the glass, move the cotton wisp, or generate a sound at the stethoscope, and will often object to having the nose partly obstructed because it inhibits airflow. Conversely, even animals with heavy mucus accumulation in the nasal cavity will typically retain nasal airflow.
Figure 1.1 Nasal airflow can be assessed by occluding one nostril and assessing flow from the alternate nostril with a cotton wisp or chilled microscope slide.
Facial palpation is performed to assess for a pain response, to locate swellings and depressions in bony structures, and to check for symmetry of the skull. Neoplastic processes and fungal infections are most likely to result in abnormal findings. Ocular retropulsion is a part of the facial examination and is performed by placing each thumb over the closed lids and pressing gently backward, upward, medially, and laterally (Figure 1.2). Nasal lesions that are producing a mass effect behind the globe (primarily a neoplasm, fungal granuloma, or retrobulbar abscess) will cause a lateralizing difference in the resistance to depression. Altered retropulsion is difficult to assess in a brachycephalic animal. Palpation within the oral cavity can reveal bony abnormalities in the hard palate or might suggest a mass lesion above the soft palate. To perform this examination, the mouth is held open, and the roof of the mouth is palpated from the front of the hard palate through to the end of the soft palate. In the normal animal, the soft palate is readily depressed upward into the dorsal nasopharyngeal wall (Figure 1.3). A mass in this area (most commonly a neoplasm, fungal granuloma, or polyp) will resist depression. The dental arcade should also be evaluated during the oral examination, although it is important to remember that tooth root disease can be present in the absence of external signs.