Diagnosing and managing canine eosinophilic bronchopneumopathy - Veterinary Medicine
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Diagnosing and managing canine eosinophilic bronchopneumopathy
A harsh, persistent cough with gagging and retching can signal this serious, but manageable disease. Here are the steps practitioners can to take to confirm a diagnosis and help improve a patient's clinical signs through corticosteroid therapy.


VETERINARY MEDICINE


Imaging

Thoracic radiography is necessary to check for other conditions that may result in cough and dyspnea, including cardiac disease, chronic bronchitis, a foreign body, pulmonary or tracheobronchial neoplasia, fungal granulomas, and pneumonia. Yet, as with physical examination findings, radiographic findings associated with EBP are often variable and nonspecific.3 The most common radiographic abnormality is a diffuse, mixed bronchointerstitial pattern that is usually more severe than the pattern seen with chronic bronchitis.1 Other radiographic lesions that may be noted include alveolar infiltrates, peribronchial cuffing, bronchiectasis, pulmonary nodules, and bronchial wall thickening (Figures 1A & 1B).1,3,7 The severity of radiographic abnormalities appears to correlate with the severity of clinical signs.3,6

Cytology

Since radiographic findings are not specific enough to confirm EBP, airway cytology is essential for diagnosis. Cytologic samples from the airways may be collected by transtracheal aspiration, endotracheal washing, bronchoalveolar lavage, or bronchial brushing. Samples should be centrifuged immediately after collection or kept on ice until sample preparation is possible. After centrifugation, the pelleted cells should be transferred to a slide, air-dried, and then stained with a modified Wright's stain (Diff-Quik—Dade Behring) for microscopic evaluation.

Bronchoalveolar lavage may be performed with or without the guidance of a flexible bronchoscope. Bronchoscopy carries the advantage of allowing the bronchial mucosa to be directly observed, providing additional data to support the diagnosis. Abnormalities observed during bronchoscopy of patients with EBP include irregular to polyploid bronchial mucosa, mucosal hyperemia, copious yellow-green exudates, and, rarely, dynamic collapse of the bronchi during expiration (Figures 2A & 2B).1,3,6


Figure 3. A bronchoalveolar lavage sample from a dog with eosinophilic bronchopneumopathy demonstrating eosinophilic and neutrophilic inflammation (modified Wright's stain). (Photo courtesy of Dr. Craig Thompson, Clinical Assistant Professor of Clinical Pathology, Department of Comparative Pathobiology, Purdue University.)
During and following bronchoscopy or bronchoalveolar lavage, it is imperative to diligently monitor the patient's respiratory rate and character and blood oxygen saturation with pulse oximetry. Profound dyspnea and cyanosis, probably due to bronchoconstriction, were described following the procedure in one dog with eosinophilic airway disease.8

EBP is characterized by the predominance of eosinophils on cytologic examination of airway samples (Figure 3).1,3,6-8 In contrast, macrophages are the predominant cell type in samples from healthy dogs.9 Eosinophils compose 50% to 90% of the inflammatory cells in airway samples obtained from most dogs with EBP.1,6,8 Increased numbers of airway eosinophils may also be noted with other respiratory conditions such as neoplasia, parasitism, and fungal infection. Microscopic examination of airway samples may help detect these conditions if atypical cells, parasite larvae, or fungal organisms are observed. Concurrently, an increased percentage of neutrophils is often found in airway samples from dogs with EBP.1,3,6

Airway samples should always be submitted for quantitative bacterial cultures to detect concurrent bacterial infection. Impaired function of the mucociliary clearance apparatus secondary to inflammation can predispose patients to an accumulation of infectious organisms within the airways. It has been shown that bacterial growth of 1.7 x 103 CFU/ml of bronchoalveolar lavage fluid is necessary to distinguish true bacterial infection from colonization of the lower airways by commensal organisms.10 To further distinguish between commensal or contaminant organisms and true infection, culture results should be interpreted in the context of cytology results. Observation of etiologic agents within phagoyctic cells is supportive of true infection.


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Source: VETERINARY MEDICINE,
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