Chronic Cough in Dogs: Tracheal Collapse vs Chronic Bronchitis

Chronic cough is a common respiratory presentation, but its underlying cause may vary considerably. Airway collapse and inflammatory airway disease, including chronic bronchitis and eosinophilic bronchopneumopathy, are among the non-malignant and non-infectious causes of chronic cough in dogs. Clinical signs and physical examination findings provide the initial direction for the diagnostic workup¹. 

Understand What the Cough Represents 

Coughing is an important physiological mechanism that helps expel foreign bodies, mucus, and debris from the airways. Cough receptors are located in the larynx, trachea, and bronchi, whereas irritation involving smaller bronchi, bronchioles, and alveoli does not produce coughing^1,2. 

Respiratory signs can vary from mild, unproductive coughing to severe pneumonia accompanied by systemic changes³. This range makes the overall clinical picture more useful than cough character alone. 

Tracheal Collapse: Look Beyond the Cough 

Tracheal collapse is defined as progressive dorsoventral flattening of the tracheal lumen. The highest incidence is reported in middle-aged, small-breed dogs, although large-breed dogs can also be affected. 

Clinical severity corresponds to the degree of collapse and can range from mild airway irritation and paroxysmal “goose-honking” coughing to respiratory distress and dyspnoea^1,4. 

The history should also include environmental and management factors. Obesity, pollutants, environmental allergens and kennel cough have been associated with the progression of the¹. 

Chronic Bronchitis Has a Different Airway Pattern¹ 

Chronic bronchitis is defined as a chronic inflammatory pulmonary disease resulting in cough and may also cause exercise intolerance and respiratory distress. 

Expiratory wheezes are considered a hallmark of chronic bronchitis. The airway lumen becomes narrowed because of airway thickening and excessive mucus production and accumulation, resulting in increased airway resistance. 

This provides an important clinical distinction: tracheal collapse involves progressive flattening of the tracheal lumen, whereas chronic bronchitis involves chronic inflammation, airway thickening and mucus accumulation. 

Use Imaging to Refine the Differential 

Thoracic radiography is useful in lower airway disease and can help differentiate primary cardiac disease from respiratory problems in coughing dogs¹. 

A bronchial pattern, described as doughnuts, tram lines, or train tracks, can occur with canine chronic bronchitis, allergic bronchitis, and canine infectious tracheobronchitis, and less commonly with bacterial and parasitic infection¹. 

Blood gas analysis can also demonstrate abnormalities in respiratory function. Mild hypoxemia, defined as PaO2 <80 mmHg, was documented in dogs with chronic bronchitis¹. 

Practical Clinical Insight 

When chronic cough persists, combine the history, body condition, physical examination, thoracic radiography and, where appropriate, airway sampling. 

In dogs with chronic bronchitis, reported transtracheal wash findings included increased cellularity, a moderate increase in neutrophils, mucus, and sloughed hyperplastic epithelial cells. These findings can add cytological support to the clinical and radiographic assessment rather than being interpreted in isolation. 

References 

1. Kaur J, Singh S. Respiratory diseases and their diagnosis in dogs: A review. Indian Journal of Animal Research. 2022. https://arccjournals.com/journal/indian-journal-of-animal-research/B-4994 

2. Mazzone SB. An overview of the sensory receptors regulating cough. Cough. 2005 Aug 4;1(1):2. https://link.springer.com/content/pdf/10.1186/1745-9974-1-2.pdf 

3. Vieson MD, LeRoith T. A review of the pathology and treatment of canine respiratory infections. Veterinary Medicine: Research and Reports. 2012 Jun 26:25-39. https://www.tandfonline.com/doi/pdf/10.2147/VMRR.S25021 

4. Tappin SW. Canine tracheal collapse. Journal of small animal practice. 2016 Jan;57(1):9-17. https://www.researchgate.net/profile/Simon-Tappin/publication/289502317 

5. Spasov K, Kunovska M, Dimov D. Lung patterns in the dog–normal and pathological. Tradition and Modernity in Veterinary Medicine. 2018 Jun 25;3(1):7-14. https://scij-tmvm.com/index.php/pub/article/download/55/55