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Canine Chronic Bronchitis
Kevin Kumrow, DVM, DACVIM (SAIM)

Orchard Park Veterinary Medical Center, Orchard, Park, NY, USA

Etiology/Pathophysiology History and Clinical Signs

Canine chronic bronchitis (CCB) is the most common The history and clinical signs of patients with CCB are
cause of a chronic cough. It is characterized by a cough similar to those presenting for collapsing trachea and
that is present for at least two months, inflammation in mitral valve insufficiency. Patients with collapsing trachea
the airways, and a lack of an identified underlying dis- have a chronic cough associated with narrowing of the air-
ease that may cause a cough. There is some evidence that way combined with chronic tracheal inflammation, and a
environmental pollutants, second‐hand smoke or other perpetual dry honking cough. Mitral valve insufficiency
inhaled noxious chemicals may be contributors to the can lead to enlargement of the left atrium and subsequent
etiology. A specific role of bacteria in CCB has not been compression of the mainstem bronchi that stimulates a
established. The diagnosis of CCB is largely through chronic coughing reflex. CCB is less commonly diagnosed
exclusion, and treatment is based on a patient’s clinical in large‐breed dogs. Exhaustive consideration of alterna-
history, diagnostic results and response to therapy. tive causes of a chronic cough in these patients should
Canine chronic bronchitis airway inflammation is neu- occur. For example, a Doberman with a history of cough
trophilic, and there is an increase in the production of should be thoroughly evaluated for dilated cardiomyopa-
mucus. The inflammatory response perpetuates the thy, and heart failure should be suspected until proven
coughing cycle, which in turn stimulates continued otherwise. A 12‐year‐old Labrador with a history of cough
inflammation. This positive feedback sets up a vicious should be evaluated for laryngeal paralysis with intermit-
cycle that ultimately leads to permanent changes in the tent aspiration pneumonia or pulmonary metastatic
airways, including hyperplasia of mucous glands and gob- disease. It is imperative that the clinician be astute in dif-
let cells, hypertrophy of smooth muscle, and fibrosis of the ferentiating between the potential causes of chronic cough
lamina propria. These changes are often accompanied by as a misdiagnosis could result in inappropriate treatment
obstruction of small airways and airway collapse. Some and a worsening of the patient’s condition.
cases of chronic bronchitis can progress to permanent A thorough history can assist in the differentiation of
dilation of the bronchi and destruction of the structural CCB from other causes of chronic cough. Patients that
integrity of the bronchial walls. This condition is known have had exposure to other dogs in any setting for any
as bronchiectasis. Cocker spaniels have an increased risk period of time should be suspect for canine infectious
of bronchiectasis. Left unidentified and untreated, the respiratory disease (CIRD). Commonly, exposure occurs
aforementioned changes to the airway can contribute to at a groomer, boarding facility, doggie day‐care, or dog
a progressive decline in lung function. Box 31.1 gives a list park, or via a visiting family pet or a new puppy in the
of many of the common differentials for CCB. household; however, any known interaction, even lim-
ited, should raise suspicion. These patients can be any
Epidemiology age or breed, and can have clinical signs that range from
a mild dry‐hacking cough to systemic illness. Pets with
evidence of systemic disease that have a history of cough
The most common signalment for CCB is middle‐aged are unlikely to have CCB as their primary ailment, and
to older, small‐breed dogs.

Clinical Small Animal Internal Medicine Volume I, First Edition. Edited by David S. Bruyette.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/bruyette/clinical