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Cough is a common clinical sign in dogs, and there are many possible causes. Identification and therapy of the specific cause is more likely to result in an amelioration of clinical signs than nonspecific supportive care. Kevin J. Kumrow, DVM, and Elizabeth A. Rozanski, DVM, Diplomate ACVIM (Small Animal Internal Medicine) & ACVECC Cough is a common clinical sign in dogs. There are many possible causes; identification and therapy of the specific cause is more likely to result in an amelioration of clinical signs than nonspecific supportive care. Common causes of cough include:
INTRODUCTION: CANINE CHRONIC BRONCHITISCanine chronic bronchitis (CCB) is defined as cough that is present most days for a minimum duration of 2 months, without evidence of other underlying diseases that may cause cough.
CLINICAL APPROACHSignalmentSignalment is very helpful in establishing a suspicion of chronic bronchitis as it is most common in older, small-breed dogs. Cocker spaniels have an increased risk of bronchiectasis, which commonly occurs with chronic bronchitis. Bronchiectasis is permanent dilation of bronchi that results from chronic inflammation and destruction of the structural integrity of bronchial walls.7 Dilated cardiomyopathy may present acutely with cough and tachypnea in Doberman pinschers; heart failure should be suspected until proven otherwise. In general, CCB is less common in large-breed dogs; careful consideration of alterative diagnoses, such as laryngeal paralysis with intermittent aspiration or pulmonary masses, should be considered in these dogs. HistoryPertinent historical considerations include:
Other considerations include:
Physical ExaminationMost dogs with CCB are systemically well, with persistent productive cough as the major complaint. A physical examination should focus on the cardiopulmonary system, as well as any signs of systemic disease, including:
Auscultation of the lungs can provide clues of lower airway disease, and presence or absence of a murmur should be noted. Although mitral murmurs and even congestive heart failure may co-exist with CCB, the presence of a sinus arrhythmia supports the cough being of airway/pulmonary, rather than cardiac, origin. A cough may be induced by palpation of the trachea; this may better characterize the cough as well as exclude other conditions, such as reverse sneezing, that may be mistaken for cough.
Voice change or reluctance to bark may support upper airway disease. Some dogs will have syncope associated with cough (the so-called cough-drop syndrome), which is most likely associated with high vagal tone. Causes of Canine Cough
Diagnostics for Canine Chronic Bronchitis
DIAGNOSTICSDiagnostic testing should be tailored to the individual patient; however, the following tests may be useful. Laboratory TestingBaseline laboratory testing, including a complete blood count, serum biochemical profile, and urinalysis, are useful in establishing general health and are anticipated to be largely normal in a dog with CCB. Other laboratory tests to consider include heartworm antigen testing, fecal analysis for both eggs and lungworm larva, and evaluation of NT pro-BNP, which is a useful biomarker that will become elevated in the presence of left atrial enlargement/congestive heart failure.9 Diagnostic ImagingChest radiographs are imperative when evaluating the coughing dog. In fact, if diagnostic testing is limited for an individual patient, chest radiographs are the most useful test.10
Figure 1. Lateral (A) and ventrodorsal (B) radiographs from a dog with chronic bronchitis; note the prominent bronchial thickening and obesity; obesity will contribute to chronic cough. Fluoroscopy may help evaluate the trachea and larger airways for collapse, but is less helpful for evaluation of chronic cough unless concurrent airway collapse is suspected. Ultrasound is useful to aid in diagnostic sampling if an isolated lesion is found on radiographs or in the presence of pleural effusion, but is not useful in CCB. Computed tomography (CT), which is widely used in people with airway disease, is growing in popularity for identification of canine bronchial disease as well.11 The airway detail is much improved from that of thoracic radiography (Figure 2). CT scanning requires brief general anesthesia, so is commonly combined with evaluation of laryngeal function, collection of airway cytology samples, and bronchoscopy in dogs suspected of having CCB. Figure 2. Comparison of a lateral thoracic radiograph (A) and reconstructed CT slice (B) from a dog with chronic bronchitis. Bronchoscopy, if available, is the preferred technique to evaluate and visualize the airway.
Airway SamplingAirway samples for cytology and bacterial culture are very useful in characterizing CCB.12 Cytology samples may be collected via a tracheal wash, a blind bronchoalveolar lavage, or with a bronchoscope. The technique chosen reflects clinician preference and availability of supplies and equipment. See Airway Sampling Techniques for a description of each method. Cytologic samples should be collected into EDTA tubes and processed promptly to avoid changes in cell counts and appearance. If analysis will be delayed, a small
aliquot of the sample may be centrifuged and a direct smear made.
Figure 3. Neutrophilic inflammation without evidence of intracellular bacteria is commonly observed in canine chronic bronchitis. Courtesy Perry Bain, DVM, PhD, Diplomate ACVP If a sample shows marked eosinophilia, an eosinophilic bronchopneumopathy should be suspected rather than CCB. Bacterial culture is commonly performed in association with airway cytology. However, the role of bacteria is unclear, as colonization is common, but may not reflect actual infection.14 Lung Function TestingPulmonary function testing is widely used in human medicine to better characterize specific defects associated with chronic bronchitis. However, due to patient cooperation, it is less widely used in dogs. Tidal breathing flow–volume loops have been described in dogs with CCB.15 More practically, 3 forms of pulmonary function testing may be used in dogs:
Arterial blood gas analysis may document mild hypoxemia (PaO2 < 80 mm Hg) or an increased alveolar–arterial (A–a) gradient (> 15) although these are uncommonly performed in CCB. Pulse oximetry is widely available in practice, and may be used to gauge arterial oxygen saturation with a value of > 97% considered normal. Pulse oximetry may also be measured after a short walk, as desaturation may be more commonly observed after exercise. The 6MWT formally measures the distance that a dog can walk over 6 minutes; distances less than 400 meters are supportive of significant lung disease.16 The 6MWT may also be combined with pre and post walk pulse oximetry to evaluate whether exercise-induced oxygen desaturation is present. Airway Sampling TechniquesObtaining cytologic samples from the airway can be performed by tracheal wash, blind bronchoalveolar lavage, or with a bronchoscope. A blind endotracheal wash for cytology and culture being performed in practice. Transtracheal washes (TTW) are best suited for cooperative medium- or large-size dogs.
Endotracheal washes (ETW) are commonly performed in smaller patients that may be less amenable to restraint.
Blind bronchoalveolar lavage (BAL) is performed similarly to an ETW; however:
Bronchoscopic bronchoalveolar lavage can be used to collect samples via bronchoscope by flushing sterile fluid through the chamber of the scope and re-aspirating it back through the biopsy channel.12 TREATMENTIf, following diagnostic testing, the clinical impression remains that the dog has CCB, it is important to initiate therapy. The treatment options for dogs with CCB include:
Environmental Exposure
Health Initiatives
MedicationsGlucocorticoids are the mainstay for treatment as they reduce inflammation, thereby, reducing cough. They may be administered orally or via inhalation.
Bronchodilators are commonly prescribed for dogs with CCB; evidence supports efficacy in approximately half of treated dogs.4
Antibiotics are warranted in dogs with an exacerbation of CCB or dogs with evidence of infection on tracheal wash cytology.
Cough suppressants help improve the quality of life for both dogs with CCB and their families. Additionally, on-going cough promotes inflammation, which results in more cough.
PROGNOSISThe clinical course of CCB is variable. In the majority of dogs, permanent changes are present in the airways at the time of diagnosis and the disease cannot be cured. Proper medical management can typically ameliorate clinical signs and stop or slow progression of bronchial damage. Periodic relapses of cough are not uncommon and require adjustments in the treatment protocol, such as temporary increase in glucocorticoids or addition of antibiotics. IN SUMMARY
6MWT = 6-minute walk test; CCB = canine chronic bronchitis; CIRD = canine infectious respiratory disease; CT = computed tomography References
Kevin Kumrow, DVM, is a member of the internal medicine team at the Animal Emergency and Specialty Center in Parker, Colorado. He has a special interest in respiratory diseases of dogs and cats, and has two other publications on the subject in progress. He received his DVM from Ontario Veterinary College at University of Guelph; then completed an internship at Oradell Animal Hospital in Paramus, New Jersey, and residency in small animal internal medicine at Tufts Cummings School of Veterinary Medicine. Elizabeth A. Rozanski, DVM, Diplomate ACVIM (Small Animal Internal Medicine) & ACVECC, is an associate professor in emergency and critical care in the Department of Clinical Sciences at Tufts Cummings School of Veterinary Medicine. She has a special interest in pulmonology, pursuing both research and publication of articles on this topic. She received her DVM from University of Illinois; then completed an internship at University of Minnesota and a residency at University of Pennsylvania. How can I soothe my dogs bronchitis?Humidifiers are an excellent way to soothe chronic cough by keeping the air moist. If you don't have a humidifier at your disposal, you can try running a hot shower for your dog with the bathroom door closed — all that steam will help clear out the bronchial tubes and impede the mucus from becoming lodged in the lungs.
Can dogs survive bronchitis?With proper disease management, clinical symptoms can be controlled, and lung damage can be slowed. As a result, the life expectancy for dogs with chronic bronchitis is not typically majorly impacted. With treatment, most dogs with COPD enjoy a normal life expectancy and an excellent quality of life.
How long does it take to cure bronchitis in dogs?The severity of the cough usually diminishes during the first 5 days, but the disease persists for 10 to 20 days. Affected dogs have few if any additional signs except for some loss of appetite.
How can I treat my dogs respiratory infection at home?Treating upper respiratory infection in dogs and cats. Steam it up. Increasing the humidity can help your dog or cat breathe easier, just as it does for humans! ... . Feed a cold. When pets have a stuffy nose, their sense of smell is dulled. ... . Wipe runny noses. ... . Keep your pet hydrated. ... . Rest, rest and more rest. ... . Bundle them up.. |