Diagnosing Canine Chronic Bronchitis: A Case Study on the Role of Radiography and Tracheal Lavage

Chronic bronchitis is the most frequently occurring chronic respiratory impairment in dogs¹. It is a chronic inflammatory pulmonary disease characterised by neutrophilic inflammation and excessive mucus production, resulting in airway narrowing or obstruction and clinical signs such as cough, exercise intolerance and respiratory distress¹. Persistent inflammation may follow infection, allergy or exposure to inhaled toxins and irritants, contributing to mucus hypersecretion and impaired mucociliary clearance¹. 

A clinical investigation involving 11 dogs evaluated the diagnostic value of thoracic radiography and transtracheal wash (TTW) in canine chronic bronchitis. The findings demonstrate how clinical assessment, radiographic changes, and airway cytology can be brought together when evaluating a dog with persistent respiratory signs¹. 

Recognising the Clinical Presentation 

Cough was the predominant presenting complaint in the 11 dogs evaluated. It was described as loud, harsh, and non-productive, while exercise intolerance was reported in five dogs and respiratory distress or dyspnea in three. An inducible cough reflex was positive in seven dogs. Abnormal lung sounds were detected in nine dogs, including harsh sounds in seven, crackles in one and wheezes in one. 

The mean duration of coughing was 34±11.92 days, ranging from 15–120 days, and onset was generally insidious. Acute onset was reported only occasionally in situations such as kenneling or endotracheal intubation¹. 

Pneumonia was considered an important differential for cough. In contrast to chronic bronchitis, affected dogs with pneumonia more commonly demonstrate systemic signs such as fever and lethargy, a shorter duration of clinical signs and alveolar infiltrates on thoracic radiographs^1,2. 

What Thoracic Radiography Reveals^1,3 

Thoracic radiography was performed in all 11 dogs. Both lateral and ventrodorsal views showed mild-to-moderate bronchial patterns involving the cranial and caudal lung lobes, together with bronchial wall thickening and multiple “donuts.” A diffuse, non-structural interstitial pattern was additionally observed in six dogs. 

The radiographic changes described in canine chronic bronchitis include thick-walled ring shadows, increased numbers of rings and parallel-line shadows, commonly described as “doughnuts,” “tram lines” or “train tracks.” Interstitial patterns and decreased visibility of pulmonary vessels have also been described as radiographic markers. However, radiographic structural changes may not always correspond with the degree of functional abnormality observed clinically. 

Adding Transtracheal Wash Cytology 

While radiography provides information about structural airway changes, TTW cytology can help characterise the airway inflammatory process. TTW was successfully performed in eight of the 11 dogs. Cytological examination demonstrated increased cellularity, mild-to-moderate neutrophilic inflammation, mucus and hyperplastic epithelial cells. 

The cytological findings showed a mean neutrophil proportion of 48.5±6.48% and macrophage proportion of 30.63±4.84%. Small numbers of lymphocytes, goblet cells, eosinophils, ciliated cells and epithelial cells, along with variable numbers of alveolar macrophages, were also observed. 

Bacterial culture of TTW samples was negative in four dogs and positive in four. The positive cultures identified Staphylococcus aureus in two dogs, E. coli in one and Klebsiella species in one. Culture and antibiotic sensitivity testing therefore provided additional information when bacterial organisms were recovered. 

Conclusion 

The clinical investigation supports the use of a combined diagnostic approach when canine chronic bronchitis is suspected. Clinical findings and blood gas analysis can provide initial evidence, while thoracic radiography can demonstrate characteristic bronchial changes and TTW cytology can document airway inflammation, mucus and epithelial changes. The findings indicate that thoracic radiography and TTW cytology can support confirmation of canine chronic bronchitis, with bacterial culture and sensitivity providing additional information when infection is suspected. 

References 

1. Kaur J, Singh S, Gupta K, Anand A. Diagnosis of canine chronic bronchitis using radiography and tracheal lavage. Indian J. Vet. Med. 2021;41(2):27-33. https://isvm.org.in/backend/web/uploads/Paper5d.pdf 

2. Rozanski E. Canine Chronic Bronchitis: An Update. The Veterinary Clinics of North America. Small Animal Practice. 2019 Dec 4;50(2):393-404. https://doi.org/10.1016/j.cvsm.2019.10.003 

3. 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