Diagnostic dilemmas of the upper respiratory tract (Proceedings)

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Diagnostic dilemmas of the upper respiratory tract (Proceedings)

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Oct 01, 2008

Clinical signs related to the upper respiratory tract, in both dogs and cats, are among the most common presenting complaints encountered in small animal practice and, interestingly, are frequent reasons for referral to specialty practices and veterinary teaching hospitals. The oral and nasal cavities are important portals of entry for foreign body entrapment and infectious agents. In addition to the occurrence of nasal neoplasia and trauma, it is not surprising that upper respiratory tract disease, in both dogs and cats, are common presentations. However, upper respiratory signs can be associated with significantly different underlying causes. Localizing the problem amid a variety of clinical signs in an anatomically complex area can represents significant diagnostic and therapeutic challenges to even the most astute clinician. The presentation addresses upper respiratory disease in the dog, with specific emphasis on clearly defining the presenting clinical sign, localizing the problem, and establishing the diagnosis.

Anatomic Limits


TABLE 1: Anatomic Limits of the Upper Respiratory Tract and Defining Clinical Signs.
Strictly speaking, the anatomic limits of the upper respiratory tract are not defined. For this presentation, the upper respiratory tract begins at the level of the external nares and ends at the level of the first tracheal ring. In the clinical setting, however, it is practical to establish anatomic limits, or "compartments", around the various clinical signs attributable to upper respiratory disease. For example, using the above anatomic limits, the upper respiratory tract can be categorized into 3 distinct compartments. EACH compartment is associated with a defining clinical sign (see TABLE 1). Defining the anatomic location is critical in pursuing the underlying problem, establishing a diagnosis, and effectively treating the patient.

Clinical Signs

The first, and most important, step in establishing a diagnosis of canine upper respiratory disease is to define the presenting sign. Experience has shown that an owner's ability to accurately describe the patient's clinical signs, particularly when signs are not present at the time of examination, is usually inconsistent and inaccurate...although it can be most entertaining. The 3 localizing clinical signs characteristically associated with upper respiratory are: sneezing and/or nasal discharge; stertor; and stridor. Each sign, considered independently, will focus the examination to the appropriate anatomic region of the upper respiratory tract.

Sneezing and/or Nasal Discharge

Definition of the clinical signs sneezing and nasal discharge is intuitive. These are also the most common presenting signs in dogs with upper respiratory tract disease. Owners that present a dog for sneezing are likely to be accurate in their description of the problem. However, establishing the presence or absence of a nasal discharge may be more difficult to establish. Volume, character, and frequency of the discharge ultimately determine whether or not the owner will have even observed a discharge. The astute owner will report whether the discharge is unilateral or bilateral. In the patient that presents with a history of sneezing and nasal discharge, instillation of a topical nasal decongestant into each nostril will occasionally provoke sneezing and elicit the nature of any discharge that is present.

Examination

Sneezing and/or nasal discharge localize the problem to the nose, nasal cavity, and paranasal sinuses. However, thorough examination of the nose and nasal cavity can be quite difficult, even with the availability of appropriate endoscopy equipment. In addition to careful examination of facial symmetry, the first part of the examination begins in the oral cavity, with emphasis on the maxilla, the hard palate, and the canine teeth. The hard palate is examined for evidence of trauma (penetrating or non-penetrating) and congenital cleft palate (puppies). The medial aspect of the maxillary canine teeth should be carefully probed for evidence of oro-nasal fistulae. Despite normal appearing teeth and gingiva, severe, occult periodontal disease with resulting necrosis of bone does result in a septic communication between the oral and nasal cavity. Paroxysms of sneezing associated with a sanguinous nasal discharge or "spray" is characteristically described by the owner.