Histologic patterns of chronic interstitial lung disease in dogs

Area of Science:

• Veterinary Pathology
• Pulmonology
• Comparative Medicine

Background:

• Canine chronic interstitial lung disease (cILD) is rare, with poorly understood pathogenesis, except in specific breeds.
• Existing knowledge is limited, necessitating a comprehensive characterization of cILD in dogs.

Purpose of the Study:

• To characterize histologic lesions in canine cILD.
• To compare lesions and clinical features.
• To classify histopathologic patterns using human criteria.

Main Methods:

• Postmortem examination of 24 dogs (>6 months) with subacute or chronic interstitial lung disease (ILD) and respiratory signs.
• Histologic evaluation of lung tissues for specific lesions.
• Classification of histopathologic patterns based on established human criteria.

Main Results:

• Histologic findings included attenuated bronchiolar epithelium, alveolar edema, type II pneumocyte proliferation, fibrosis, fibrin deposition, and hyaline membranes.
• Classifications included organizing diffuse alveolar damage (8 cases), organizing pneumonia (4 cases), acute fibrinous and organizing pneumonia (3 cases), and unclassifiable nonspecific interstitial lung disease (9 cases).
• No cases met criteria for usual interstitial pneumonia; potential causes included aspiration or failed pneumonia healing. Left-sided heart failure was present in 50% but not the direct cause of ILD.

Conclusions:

• Canine cILD exhibits diverse histologic patterns, some aligning with human classifications like organizing pneumonia and diffuse alveolar damage.
• Lesions may represent varied responses to common lung injury causes, not distinct diseases.
• Findings offer insights into cILD pathogenesis and progression, potentially guiding future therapeutic strategies.