Table 1.

Thoracic computed tomography (CT) disease severity scoring system in the dog, encompassing global changes reflective of pulmonary parenchymal disease, airway disorders, and pulmonary vascular disease.

Category		Sub-score	Final score
Attenuation	Volume	0.5 = <1/3 of lung volume affected 1.0 = ≥1/3 to <2/3 of lung volume affected 1.5 = ≥2/3 of lung volume affected	The sum of the averaged scores for volume and opacification for each lung lobe, maximum score of 3
	Opacification	0.5 = GGO (6) 1.0 = GGO and consolidation 1.5 = Consolidation predominant
Airway Caliber Changes	Tracheal or principal bronchial I/E narrowing	1.0 = <1/3 diameter reduction 2.0 = ≥1/3 to <2/3 diameter reduction 3.0 = ≥2/3 diameter reduction	Highest score from any category, maximum score of 3
	Bronchomalacia	1.0 = Subtle flattening with no PBVO (6) 2.0 = Distorted circular appearance or >50% narrowing with mild to moderate PBVO 3.0 = Near disappearance of airway lumen with marked PBVO
	Tree-in-bud (6)	1.0 = Mild and affecting <1/3 lung 2.0 = Moderate and affecting ≥1/3 to <2/3 lung 3.0 = Severe and affecting ≥2/3 lung
Vascular Changes	PT:Ao > 1.4 (17)	3.0 if present	Highest score from either category, maximum score of 3
	PTE	1.0 = Affecting subsegmental or smaller caliber arteries 2.0 = Affecting lobar or segmental arteries in <5 lobes 3.0 = Affecting left or right MPA or lobar or segmental arteries in 5–6 lobes

Inspiratory CT scans are scored for attenuation and vascular changes. Airway caliber changes require comparison of inspiratory and expiratory scans. GGO, ground glass opacity; I/E: inspiratory:expiratory; MPA: main pulmonary artery; PBVO, peribronchovascular opacification; PT:Ao, pulmonary trunk-to-aorta ratio; PTE, pulmonary thromboembolism.