Background: The etiology of canine bronchomalacia (BM), defined as segmental and subsegmental airway collapse, is unknown. Chronic bronchitis (CB), a non-infectious inflammatory airway disorder, is speculated to cause BM. If so, BM and CB should always be present as comorbid disorders. Using the criterion standard of histologic evaluation of lung tissue could help answer this question. Hypothesis/
Objectives: We hypothesized not all dogs with BM would have histologic evidence of CB. Animals: Thirty client-owned dogs with BM having lung histology.
Methods: Dogs with BM confirmed by bronchoscopy or paired inspiratory:expiratory breath-hold thoracic CT scans having histologic evaluation between January 2015-October 2024 were retrospectively evaluated. Chronic bronchitis was diagnosed by cough >2 months, mucus hypersecretion (productive cough, visually evident luminal mucus on bronchoscopy or CT, or Curshmann’s spirals on bronchoalveolar lavage (BAL) cytology), and airway neutrophilia (BAL or histology). Histology documented the presence or absence of CB and, along with the entire diagnostic picture, comorbid disorders.
Results: Only 7/30 dogs with BM had histologic evidence of CB. Based on clinical picture without histology, 10 dogs were diagnosed with CB, but 5/10 lacked histologic evidence of CB, having alternative explanations for BAL neutrophilia. Dogs were diagnosed on average with 5 comorbid conditions including cardiac, vascular, aerodigestive and respiratory diseases. Conclusion and clinical importance: Results of this study support that CB does not cause BM. Whether dogs with BM have defects in airway clearance or protection that might predispose to CB in a subpopulation of cases remains to be determined.
