Perspectives in veterinary medicine: Description and classification of bronchiolar disorders in cats

Abstract

This Perspectives in Veterinary Medicine article seeks to define, describe putative causes, and discuss key diagnostic tests for primary and secondary bronchiolar disorders to propose a classification scheme in cats with support from a literature review and case examples. The small airways (bronchioles with inner diameters <2 mm), located at the transitional zone between larger conducting airways and the pulmonary acinus, have been overlooked as major contributors to clinical syndromes of respiratory disease in cats. Because the trigger for many bronchiolar disorders is environmental and humans live in a shared environment with similar susceptibility, understanding these diseases in pet cats has relevance to One Health. Thoracic radiography, the major imaging modality used in the diagnostic evaluation of respiratory disease in cats, has low utility in detection of bronchiolar disease. Computed tomography (CT) with paired inspiratory and expiratory scans can detect pathology centered on small airways. In humans, treatment of bronchiolar disorders is not well established because of heterogeneous presentations and often late definitive diagnosis. A review of the human and veterinary medical literature will serve as the basis for a proposed classification scheme in cats. A case series of cats with CT or histopathologic evidence of bronchiolar lesions or both, either as a primary disorder or secondary to extension from large airway disease or interstitial lung disease, will be presented. Future multi‐institutional and multidisciplinary discussions among clinicians, radiologists, and pathologists will help refine and develop this classification scheme to promote early and specific recognition and optimize treatment.

Comparison of signalment, clinical, laboratory and radiographic parameters in cats with feline asthma and chronic bronchitis

“…CT scans in cats with respiratory diseases have been associated with a greater sensitivity regarding typical changes than conventional radiography and might therefore provide more detailed classification of bronchial diseases. 4,29 Significantly more cats with FA showed increased numbers of eosinophils on haematology compared with cats with CB ( Figure 1). Interleukin-5, which is released during mast cell degranulation in allergic asthma, stimulates eosinopoiesis.…”

“…1 The exact definition of FA and CB is still controversially discussed. [2][3][4][5] FA is thought to result from a T-cell-based type 1 hypersensitivity reaction. 6,7 CB has been defined as an inflammatory respiratory condition with increased neutrophilic content (>7%) in the bronchoalveolar lavage fluid (BALF) in the absence of increased eosinophils.…”

Presumptive Development of Fibrotic Lung Disease From Bordetella bronchiseptica and Post-infectious Bronchiolitis Obliterans in a Dog

“…While somewhat confusing, it is important to understand that “bronchiolitis obliterans” can be a clinical syndrome or a histologic descriptor. The former has not been characterized in pet dogs as it has been in humans and cats (19, 20) while the latter is fairly common. In humans, bronchiolar diseases can be classified as primary or secondary: in the former, pathology is anatomically limited to small airways and in the latter, disease extends either from large airways or from lung interstitium to small airways (19).…”

“…In humans, bronchiolar diseases can be classified as primary or secondary: in the former, pathology is anatomically limited to small airways and in the latter, disease extends either from large airways or from lung interstitium to small airways (19). Although a similar classification scheme has been adapted to cats, distinction between primary bronchiolar disease leading to pulmonary fibrosis and interstitial lung disease culminating in fibrosis with secondary involvement of small airways may be difficult to distinguish (20). The dog in this case report with persistent and progressive clinical signs and paired CT imaging/histopathologic lung examination 7 years apart, provided support that PIBO triggered pulmonary fibrosis.…”

Felines Asthma und chronische Bronchitis – Übersicht zu Diagnostik und Therapie

“…Computertomografie Eine computertomografische Untersuchung der Lunge ist dem herkömmlichen Röntgen bei der Diagnostik von Bronchialerkrankungen und ihrer Abgrenzung von anderen Krankheitsbildern (z. B. Neoplasie, interstitielle Lungenerkrankungen) in Sensitivität und Spezifität überlegen [38]. Auswertbare Aufnahmen ergaben sich sogar bei wachen, nicht narkotisierten Katzen [39].…”