Overview

• Clinical condition seen primarily in dogs; irreversible dilatation of the bronchi; caused by chronic infectious or inflammatory airway disease or associated with primary ciliary dyskinesia.
• Occurs occasionally in cats as a sequela to long-standing inflammatory lung disease or neoplasia.
• Airways are pulled open by surrounding lung tissue; pooling of secretions can occur, which perpetuates lung damage and allows colonization by bacteria.
• Can be cylindrical or saccular, focal or diffuse.

Signalment

• Primarily dogs and rarely cats.
• Cocker spaniels and perhaps West Highland white terriers predisposed.
• Young animals (<1 year) with primary ciliary dyskinesia.
• Middle-aged to old dogs with chronic pulmonary disease.

Signs

• Chronic cough-usually moist and productive; hemoptysis.
• Recurrent fever.
• Exercise intolerance.
• Tachypnea or respiratory distress.
• Chronic nasal discharge or sinusitis, particularly with primary ciliary dyskinesia.
• Moist, harsh inspiratory crackles; loud expiratory lung sounds or wheezes on physical exam.
• Tracheal hypersensitivity.

Causes & Risk Factors

• Primary ciliary dyskinesia.
• Inadequately treated infectious or inflammatory lung conditions (pneumonia, bronchitis, or eosinophilic lung disease).
• Smoke inhalation, aspiration pneumonia, radiation injury, and inhalation of environmental toxins-predispose animal to airway injury and colonization by bacteria.
• Chronic bronchial obstruction or foreign body pneumonia-development of bronchiectasis distal to the obstructed region common.
• Signs related to bronchiectasis may not be recognized until long after the primary injury.

Differential Diagnosis

• Recurrent bacterial bronchopneumonia
• Fungal pneumonia
• Chronic bronchitis
• Infectious or parasitic bronchitis
• Foreign body pneumonia
• Neoplasia

CBC/Biochemistry/Urinalysis

• Neutrophilia and monocytosis
• Hyperglobulinemia
• Proteinuria-may be seen with secondary amyloidosis, glomerulonephritis, or sepsis.

Other Laboratory Tests

Arterial blood gas analysis-hypoxemia; widened alveolar-arterial oxygen gradient.

Imaging

• Radiography-insensitive for the diagnosis. Abnormalities visible late in the course of disease include dilatation of the lobar bronchi with lack of normal tapering in the periphery; diffuse thickening of bronchial walls; mixed bronchial, interstitial, and alveolar pattern.
• Changes can be focal or diffuse.
• CT-bronchus > two times the width of the adjacent pulmonary artery in dogs, abnormally dilated bronchi near the lung periphery; thickened airways; cystic dilatations of the bronchi with or without fluid accumulation.

Diagnostic Procedures

• Bronchoscopy-saccular or tubular dilatation of the airways.
• Airway sampling-cytologic examination of bronchoalveolar lavage fluid or tracheal wash specimens; culture for aerobic and anaerobic bacteria and Mycoplasma; typically find suppurative inflammation with high numbers of neutrophils, or increased eosinophils may be observed indicating eosinophilic bronchopneuopathy; may culture a mixed population of bacteria; some cases appear to have sterile inflammation.

Pathologic Findings

• Dilated bronchi
• Diffuse peribronchial and alveolar inflammation and fibrosis
• Squamous metaplasia of bronchial epithelium

Drug(s)

• Intravenous antibiotics-may be required initially; good choices: ampicillin (10–20 mg/kg IV q6–8h) and enrofloxacin (5–10 mg/kg q24h).
• Broad-spectrum agents with efficacy against both aerobes and anaerobes and that offer good penetration of pulmonary tissue-preferred; combination of enrofloxacin (5–20 mg/kg PO q24h) and clindamycin (5–11 mg/kg PO q12h) or amoxicillin-clavulanate often effective.
• Azithromycin can be a good alternative antibiotic.
• Long-term use of antibiotics (2 months to life-long)-based on bacterial culture and sensitivity testing; may be required even if culture of airway specimens yields no growth.
• Bronchodilators-may be beneficial, although animals usually have irreversible airflow limitation; extended-release theophylline advised.
• Eosinophilic lung disease requires treatment with glucocorticoids.
• Nebulization and coupage highly beneficial in removing secretions.

Contraindications/Possible Interactions

• Theophylline derivatives and fluoroquinolones-concurrent use causes high and possibly toxic plasma theophylline concentration.
• Furosemide-avoid; dries airway secretions.
• Cough suppressants-avoid; will trap secretions and bacteria in lower airway and perpetuate damage.

Patient Monitoring

• Clinical response-outpatient
• Serial CBC, blood gas analysis, and thoracic radiographs

Prevention/Avoidance

• Antibiotics-complete a full course of therapy in patients that appear to have parenchymal infection.
• Early recognition and resolution of foreign body pneumonia.
• Appropriate treatment of eosinophilic pneumonia.

Possible Complications

Chronic recurrent pulmonary infection likely.

Expected Course and Prognosis

• Chronic and recurrent clinical signs expected; some degree of coughing will always be present.
• Animals can live for years with bronchiectasis if treated properly.
• Patient may succumb to respiratory failure.
• Other organs may fail if bacteremia or glomerulonephritis develops.

Associated Conditions

• Primary ciliary dyskinesia
• Chronic sinusitis
• Chronic bronchitis
• Pneumonia-bacterial, eosinophilic aspiration, foreign body
• Smoke inhalation

Author Lynelle R. Johnson

Consulting Editor Lynelle R. Johnson