Feline lower airway disease (Proceedings)


Feline lower airway disease (Proceedings)

Nov 01, 2010

      - feline lower airway disease describes a somewhat heterogeneous group of conditions affecting the lower airways of cats
      - no consensus definitions in veterinary medicine
      - different authors use different terminology to describe them
      - asthma may suggest reversible bronchoconstriction, and predominantly eosinophilic inflammation
      - chronic bronchitis may be associated with neutrophilic inflammation

Predisposing factors:
      - city cats (higher incidence than cats from more rural environments)
      - smoking households (anecdotal)
      - severe respiratory infection during kitten hood
      - environmental allergens (e.g. House dust mite, pollens etc.)

      - generally either chronic coughing and/or an acute onset of respiratory distress
      - seasonal variation (in some cats)

Physical examination:
      - may be normal in cats with chronic cough
      - may reveal moderate to severe respiratory distress
      - pronounced crackles or wheezes may be present on auscultation
      - predominantly expiratory dyspnea

      - Thoracic radiographs
           o Increased bronchial pattern
           o Hyperinflation
           o Right middle lung lobe collapse (occasionally)
           o May appear normal
           o Useful for excluding other causes of respiratory distress (e.g. CHF)
      - Lower airway cytology:
           o Samples can be obtained by various methods:
               ■ transoral / endotracheal wash vs. BAL (blind vs. bronchoscopic)
           o Eosinophilic inflammation (although other inflammatory cells may be present)
           o Rarely bacterial infection
      - Culture of lower airway fluid:
           o Some cats may have a secondary bacterial infection (particularly those with right middle lung lobe collapse)
           o Mycoplasma infection may also play a role in triggering an asthmatic response in some cats
      - Baermann fecal:
           o To evaluate for possible lung worm infection (Aelurostrongylus abstrusus); especially in young outdoor cats
           o Larvae may also be identified on a tracheal wash
      - Heartworm testing:
           o Antibody and/or antigen testing
           o Echocardiography is occasionally useful
           o Unfortunately diagnosis of feline HWD may be challenging due to a small worm burden
      - Routine blood tests:
           o usually normal
           o peripheral eosinophilia (> 1500 µL) may be present

*** It is important to realize that anesthetizing a cat with severe lower airway disease to obtain airway cytology may be stressful and exacerbate the respiratory status of the patient.