Upper respiratory tract disease in cats (Proceedings)

A variety of disorders can affect the upper respiratory tract of cats; while the feline upper respiratory infection complex is one of the most common URT disorders, this lecture will focus more on more complex disorders such as chronic rhinitis, nasopharyngeal polyps and nasopharyngeal stenosis, as well as feline laryngeal disease.

Acute upper respiratory tract infection

Signalment:

      - especially common in kittens

Diagnostics:

      - diagnosis is based on history and physical examination (ocular and nasal discharge, stertor etc.)

      - no specific diagnostic tests are needed

      - PCR can be performed but rarely adds anything clinically

Treatment:

      - supportive care

           o parenteral fluids if dehydrated, and/or anorexic

           o antibiotics are warranted in some cases for secondary bacterial infection

               ■ azithromycin has gained popularity in high volume facilities due the prolonged dosing interval, but is not clearly a better antibiotic than others

               ■ amoxicillin / clavulanate is commonly used

           o nutritional support:

               ■ especially in small kittens as they have little reserves

      - role of antiviral agents is as yet undetermined

           o One recent report of chronic herpes viral infection suggested some benefit to oral famciclovir

      - Isolation!!! Given the contagious nature of the disease

Prognosis:

      - typically self-limiting in adult, immunocompetant cats

      - moribund kittens typically have a grave prognosis.

      - neurological complications are a negative prognostic factor.

Chronic rhinitis

Definition:

      - rhinitis that persists for greater than one month, particularly without signs of systemic disease

Etiology:

      - while idiopathic rhinosinusitis remains a common ultimate diagnosis, there is a reasonable chance of identifying another source with a complete diagnostic evaluation

      - possible underlying diseases include:

           o fungal infection (e.g. Nasal cryptococcosis) +/- concurrent FeLV

           o tooth root abscess

           o neoplasia etc.

      - Bartonella was recently excluded as a likely possible cause

      - most cats with idiopathic disease are considered to have had viral (FHV or FCV) infections in their early life

Diagnostics:

      - oral examination under anesthesia (looking for dental disease, oronasal fistula etc.)

      - upper airway imaging (radiographs vs. CT vs. MRI)

      - rhinoscopy and nasal flush

      - culture:

           o usually positive, documenting multiple organisms BUT

           o primary bacterial rhinitis is very, very rare.

      - blind nasal biopsy:

           o performed under anesthesia, with cat intubated and cuff inflated

           o oropharyngeal gag used (e.g. Gauze squares with tie)

           o insert a 5-8FR polypropylene (stiff!) catheter into the nostril- mark the distance to the medial canthus of the eye

           o aspirate several times, and submit material for histopathology.

           o additionally, using a 20-30 ml syringe, flush saline forcefully through the nose to attempt to dislodge some of the suspected mass.

Treatment:

      - If a diagnosis is reached, more specific therapy is more likely to be effective. In the event that no specific diagnosis is reached, methods of long term management include nasal flush, with or without antibiotics

      - nasal drops (in tolerant cats)

      - sinus flushes (with instilled tubing)

      - antimicrobials

           o used alone are typically not helpful, although there may be a transient decrease in the degree of nasal discharge; this can give the false impression that the cat has a bacterial rhinitis

      - prednisone (if evidence of lymphocytic-plasmacytic inflammation)

      - antihistamines:

           o rarely effective, but can be tried as they are unlikely to be harmful

      - surgical removal of the turbinates – rarely indicated

The best method of treatment may vary from cat to cat. It is recommended to have a family discussion early in the course of diagnosis, as to the concept of chronicity and control rather than cure. After turbinates are destroyed, regardless of the inciting cause, these cats remained predisposed to recurrent infection and inflammation. Affected cats will likely always have some dysfunction.

Nasopharyngeal polyps

Nasopharyngeal polyps. (originating in the Eustachian tube or middle ear) are a source of upper airway obstruction.

Etiology:

      - inflammatory in nature\

      - no viral (calici or herpes) elements were found in one PCR study

Signalment:

      - young cats

      - RARE in older cats, where neoplastic processes predominate.

Clinical Signs

      - stertorous breathing and/or otitis in young cats..

Treatment:

      - simple traction (estimated success ~ 50%), or

      - ventral bulla osteotomy.

Horner's syndrome is very commonly seen after removal; it tends to be transient, but may be permanent.

Nasopharyngeal stenosis

Nasal pharyngeal stenosis is an uncommon cause of upper disease.

Etiology:

      - congenital

      - vs. acquired, secondary to rhinitis, surgery or other trauma

Clinical signs:

      - loud and/or open mouth breathing

      - occasionally nasal discharge

Diagnosis:

      - oral examination (scope and/or spay hook/dental mirror)

      - CT may be useful to judge the length of the stenosis

Treatment:

      - balloon dilation

      - surgical resection

      - stenting

           o has been described recently as an effective method for permanently addressing the stenosis as reoccurrence has been common with other methods.

Laryngeal disease

Laryngeal diseases are relatively rare in the cat, but can cause upper airway obstruction.

Etiology:

      - consider benign vs. malignant etiology of a mass or proliferation

      - benign laryngeal disease:

           o proliferative granulomatous laryngitis is described

           o tends to occur in younger cats

      - neoplastic disease:

           o tends to occur in older cats. Although any age cat can be affected with either

           o reported laryngeal neoplasms include:

               ■ squamous cell carcinoma

               ■ other carcinomas

               ■ lymphoma

               ■ others (e.g. Rhabdomyosarcoma)

      - laryngeal paralysis:

           o unilateral more common in cats than bilateral

           o congenital vs. acquired

Clinical signs:

      - vary depending on the severity / extent of upper airway obstruction

Diagnosis:

      - laryngeal examination

      - direct visualization of laryngeal function:

           o probably best performed using propofol (NOT ketamine)

           o a 1 mg/lb (2.2 mg/kg) IV dose of doxapram may be used to stimulate laryngeal function if the initial examination is unclear

      - laryngeal biopsy required for definitive diagnosis

      - Be prepared to perform a temporary tracheostomy in cats with a laryngeal mass after biopsy as swelling and subsequent airway occlusion is very likely.

Treatment:

      - laryngitis:

           o Consider glucocorticoids +/- antibiotics

      - laryngeal neoplasia:

           o universally palliative

      - laryngeal paralysis:

           o consider medical management

           o surgery can be considered but generally reserved for more severe cases, and those with bilateral disease

Prognosis:

      - variable depending on the underlying laryngeal disease

      - poor long term survival in cats with laryngeal neoplasia

References available upon request.