Contributors: Kathy Elwick, John P Hoover, Lesley G King

 Species: Canine   |   Classification: Miscellaneous

Introduction

  • Canine upper respiratory tract disease is a common problem in general veterinary practice.
  • Upper airway diseases are categorized by anatomic location, and clinical signs vary depending on the site of the disease:
    • Nose and nasopharynx:
      • Nasal discharge.
      • Sneezing.
      • Distortion of facial anatomy.
      • Stertorous breathing (snoring).
    • Larynx:
      • Stridor.
      • Decreased tolerance of heat and exercise.
      • Respiratory distress if severe.
      • Voice change.
      • Cough.
    • Trachea and mainstem bronchi:
      • Cough.
      • Respiratory distress if severe.

Nasal and nasopharyngeal disease

Larynx

  • Clinical signs may include:
    • Stridor: harsh noise caused by narrowed airway, can be ausculted without a stethoscope.
    • Respiratory distress if severe airway obstruction.
    • Change in voice: abnormal bark.
    • Decreased tolerance of environmental heat and of exercise.
    • Cough: does not always occur.
  • Clinical signs in dogs are usually related to airway obstruction. Airway obstruction may be:
    • Dynamic: airway diameter variable depending on phase of respiration. Evidence of obstruction is most severe when the laryngeal opening is narrowed by negative airway pressures during inspiration, but less severe during expiration because the larynx is passively blown open during this phase. Airway noise is primarily during inspiration, normal sounds during expiration. Example: laryngeal paralysis Larynx: paralysis.
    • Fixed: airway diameter is narrowed to the same degree during both inhalation and exhalation. Abnormal airway noise is evident during both phases of breathing. Example: mass Larynx: neoplasia.
  • Differential diagnosis includes:
    • Laryngeal paralysis.
    • Neoplasia:
      • Malignant (eg carcinoma, lymphosarcoma).
      • Benign (eg chondroma).
    • Inhaled foreign body.
    • Inflammation (laryngitis):
      • Inhaled noxious substance, eg smoke in house fire.
      • Voice abuse (excessive barking, eg during kennelling).
    • Laryngeal collapse:
      • End stage of chronic brachycephalic airway disease.
    • Trauma:
      • Choke chains.
      • Intubation.
      • Bites/puncture wounds.
  • Diagnostic testing may include:
    • Physical examination:
      • Auscultation of larynx to detect increased sounds or wheezes, note phase of respiration.
    • Imaging:
      • Radiographs: lateral cervical radiographs may be useful if there is a mass or foreign body.
      • Ultrasound: may be helpful in some cases with mass lesions.
      • CT scan: to evaluate lumen of airway, should be performed without an endotracheal tube in place.
      • MRI: useful for soft tissue lesions that cause narrowing of airway eg masses, enlarged lymph nodes.
    • Blood tests:
      • CBC usually normal but may show evidence of inflammation if there is an abscess or associated pneumonia.
    • Laryngoscopy:
      • Usually diagnostic.
      • Evaluate larynx for:
        • Normal function (bilateral abduction during inspiration).
        • Thickening.
        • Masses associated with arytenoids or vocal folds.
        • Extraluminal masses compressing airway.
        • Laryngeal collapse.
      • Plan for safe recovery from anesthesia including tracheostomy Tracheostomy: temporary if necessary, especially if the cause of airway obstruction is not corrected at the same time as diagnostic testing.
      • Biopsy if necessary.

Trachea and mainstem bronchi

  • Clinical signs may include:
    • Cough: productive, harsh, honking.
    • Respiratory distress if airway obstruction is severe.
  • Differential diagnosis includes:
  • Diagnostic testing may include:
    • Physical examination:
      • Palpation of trachea, neck and thoracic inlet.
      • Auscultation.
      • Induction of cough by brief compression of the trachea, allows determination of type of cough.
    • Blood tests:
      • CBC usually normal but may show evidence of inflammation if there is an abscess or associated pneumonia.
      • Viral serology occasionally useful.
    • Virus isolation or PCR Polymerase chain reaction :
      • In occasional cases of infectious tracheobronchitis Acute infectious tracheobronchitis , virus isolation or PCR may be performed on pharyngeal swab samples. Panels are available at selected commercial laboratories.
      • Note that bacterial culture of pharyngeal swabs is not useful, as results do not reflect bacteria present below the larynx.
  • Imaging:
    • Radiographs:
      • Lateral neck radiographs may be helpful in cases of tracheal collapse, avulsion, foreign body, hypoplasia, stenosis.
      • Thoracic radiographs Radiography: thorax help rule out pulmonary or cardiac disease.
    • Fluoroscopy:
      • Useful in tracheal collapse.
    • CT scan:
      • May be helpful in patients with masses, chronic bronchitis, or lung disease.
      • Helpful for diagnosis of structural abnormalities such as bronchiectasis and bronchial dysplasia.
    • Tracheal lavage:
      • Transtracheal wash Transtracheal wash or endotracheal lavage may be performed.
      • Cytology performed on samples may be helpful.
      • Culture and microbiologic sensitivity useful especially in chronic cases.
      • Parasitic organisms may be identified.
    • Tracheobronchoscopy Tracheoscopy :
      • Grading and confirming location of tracheal collapse.
      • Diagnosis of extraluminal or intraluminal masses.
      • Diagnosis of chronic bronchitis and mainstem bronchial collapse.
      • Diagnosis and removal of foreign bodies.
      • Obtaining cytology and biopsy samples.
      • Obtaining cultures by bronchoalveolar lavage Bronchoalveolar lavage.