Chronic cough in the dog: when bronchoscopy changes the diagnosis

The clinician facing a dog with chronic cough knows how frustrating it can be to stop at thoracic radiography with inconclusive results. The patient has been coughing for three months, the lungs appear normal, empirical therapy has failed, and it is still unclear what is happening in the lower airways. This is a common scenario, and clinicians often remain in this diagnostic gray zone longer than necessary.

Chronic cough in dogs, conventionally defined as a cough persisting for at least eight weeks, is one of the most common yet challenging clinical presentations in small animal practice. The initial diagnostic work-up is well established: thorough history, physical examination, complete blood count and biochemical profile, and thoracic radiographs. These steps are essential and should always be performed first. However, thoracic radiography has limited sensitivity for lower airway disease. Bronchial collapse may be underestimated, inflammatory changes of the mucosa are not visible, and many chronic conditions do not produce sufficiently specific radiographic findings to guide therapy accurately. In dogs with inconclusive radiographs or suspected lower airway disease, endoscopic evaluation represents a diagnostic step that can provide clinically relevant additional information.

The role of bronchoscopy in the dog

Bronchoscopy allows direct visualization of the larynx, trachea, and bronchial tree, making it possible to identify structural and mucosal abnormalities that cannot be adequately characterized by indirect methods: airway collapse, bronchiectasis, mucosal thickening and hyperemia, and mucus accumulation within the bronchi. A retrospective study in dogs with respiratory signs showed that tracheobronchoscopy provided useful findings even in patients with largely unremarkable thoracic CT scans, revealing abnormalities in a substantial proportion of cases. It should be emphasized that bronchoscopy requires appropriate equipment, proper anesthesia, and operator expertise; it is not a procedure to be improvised, and its diagnostic yield depends heavily on execution quality.

Bronchoalveolar lavage (BAL), performed during bronchoscopy, allows sampling of the lower airways for cytology and microbiological culture. Endoscopic guidance enables targeting of airway segments that appear most affected on visual examination, potentially improving sample representativeness. However, superiority over non-guided sampling is not consistently demonstrated across all patients and diagnostic endpoints. In some cases, blind BAL remains a reasonable and appropriate option.

Tracheobronchial collapse: a specific consideration

In cases of suspected tracheobronchial collapse, an important clarification is needed. Bronchoscopy allows direct visualization of airway dynamics and is therefore a valuable tool, but it should be considered complementary to fluoroscopy rather than a replacement. The dynamic component of airway collapse, particularly during coughing or exercise, may require multiple diagnostic modalities for accurate characterization. These techniques provide different types of information and are often best used together.

Practical indications and instrument selection

Bronchoscopy is indicated in dogs with chronic cough that does not respond to medical therapy after four to six weeks, particularly when radiographic findings are inconclusive or nonspecific. It is also indicated in cases of suspected tracheobronchial collapse, bronchiectasis, suspected airway neoplasia, and in patients with hemoptysis of unknown origin.

With regard to instrumentation, the following considerations reflect common clinical practice rather than formally validated comparative guidelines. In medium-sized dogs, bronchoscopes with an outer diameter of approximately 5 mm and a working length of 60 cm are commonly used and are sufficient to reach lobar bronchi in most patients. In large dogs, a 1-meter scope allows exploration of caudal lobar bronchi that may otherwise be difficult or impossible to reach with shorter instruments. A working channel of at least 2 mm is generally required for effective BAL and for the use of ancillary instruments.

Anesthetic management is an integral part of the procedure. This includes premedication with bronchodilators in patients at risk of bronchoconstriction, adequate pre-oxygenation, and continuous monitoring of oxygen saturation (SpO₂) throughout the examination.

Conclusion

In dogs with chronic cough that does not respond to initial medical therapy, bronchoscopy represents a diagnostic step that can significantly improve case characterization and guide more targeted treatment. It is not a “magic solution,” but rather a tool that helps resolve diagnostic pathways that would otherwise remain incomplete. The quality of the outcome depends on appropriate instrument selection and overall procedural management.

If you are considering introducing bronchoscopy into your practice or upgrading your existing equipment, feel free to contact us. We can help you define a configuration tailored to your clinical needs.info@endomac.com · www.endomac.com

References:Crouse BK, The Use of Bronchoscopy and Bronchoalveolar Lavage in Dogs with a Chronic Cough, 2023Smit I, Bronchoscopy and Bronchoalveolar Lavage in Dogs and Cats, Veterinarska Stanica, 2024Lhermette P, Sobel D, BSAVA Manual of Canine and Feline Endoscopy and Endosurgery, 2nd edition, 2008