X-ray often misses severe tracheal collapse in dogs compared to scope

Abstract

OBJECTIVE: 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. METHODS: 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. RESULTS: 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%). CONCLUSIONS: Thoracic radiographs often underestimate the grade IV TC and cannot exclude disease when collapse is not visible. CLINICAL RELEVANCE: Radiography is a useful screening tool for localizing severe TC when collapse is evident, but tracheobronchoscopy remains essential for definitive staging and therapeutic planning.