Radiography underestimates the severity of tracheobronchoscopy-confirmed grade IV tracheal collapse in dogs

To evaluate the agreement between radiographic and tracheobronchoscopic assessments of grade IV tracheal collapse (TC) in dogs and characterize the prevalence of the radiographic axial-rotation pattern.

This retrospective study included dogs diagnosed with grade IV TC via tracheobronchoscopy from 2021 through 2024. Inspiratory and expiratory right-lateral thoracic radiographs and tracheobronchoscopy images were reviewed. Collapse at 4 sites (midcervical, thoracic inlet, midthoracic, and carina) was categorized as mild (≤ 50%) or severe (> 50%). The most severe radiographic observation per site, the dominant radiographic finding, was compared with tracheobronchoscopic grade by weighted κ statistics and percentages of agreement.

78 dogs had inspiratory radiographs, and 68 also had expiratory radiographs. Radiography identified severe collapse in 68 of 78 dogs (87.2%) at the thoracic inlet but less frequently at midcervical (38 of 78 [48.7%]), midthoracic (9 of 78 [11.5%]), and carinal sites (9 of 78 [11.5%]). Agreement was fair for the midthoracic trachea (weighted κ = 0.24) and slight to poor elsewhere. The percentage of agreement for severe versus nonsevere collapse was 87.2% (68 of 78) at the thoracic inlet, followed by midthoracic (76.9% [60 of 78]), carina (66.7% [52 of 78]), and midcervical (47.4% [37 of 78]) sites. Mild or no radiographic collapse was observed in 11 of 78 cases (14.1%) despite grade IV collapse on tracheobronchoscopy. Radiographic pattern, known as TC with axial-rotation (Rad-AR) confined to the thoracic inlet was present in 17 of 78 cases (21.8%).

Thoracic radiographs often underestimate the grade IV TC and cannot exclude disease when collapse is not visible.

Radiography is a useful screening tool for localizing severe TC when collapse is evident, but tracheobronchoscopy remains essential for definitive staging and therapeutic planning.