Simple SummaryTracheal collapse is a common disease in small breed dogs, and imaging techniques such as radiography and fluoroscopy are important for diagnosis. However, there is limited agreement between these two methods in different regions of the trachea. A study was conducted on 29 dogs with tracheal collapse to investigate the agreement between thoracic radiography and fluoroscopy. The results showed that radiography underestimated the degree of collapsing trachea compared to fluoroscopy significantly at carina area. However, the agreement between the methods was found to be only slight at the cervical region. The study suggests that while radiography can be useful for screening, fluoroscopy can detect a greater degree of collapsing trachea than the two-image radiography method.AbstractTracheal collapse is a common disease in small, middle-aged dogs, and imaging tools are essential for its diagnosis. Radiography and fluoroscopy are the main diagnostic modalities used, but their agreement in different regions is not well documented. In this study, the agreement between thoracic radiography and fluoroscopy in tracheal collapse was investigated in 29 dogs. The results showed that radiography detected a lower degree of collapsing trachea compared to fluoroscopy at the carina region (p< 0.001). However, there was no significant difference observed between the degree of collapsing trachea detected by radiography and fluoroscopy at the cervical, thoracic inlet, and intra-thoracic regions (p= 0.780, 0.537, and 0.213, respectively). The kappa statistic indicated a slight agreement at the cervical region at a 16.4% cut-off (κ = 0.20), while the other regions showed a non-agreement. In conclusion, although radiography is useful for screening, fluoroscopy was able to detect the degree of the collapsing trachea greater than radiography in the carina region. Additionally, if a collapse in the cervical region is detected by radiography, it is prone to have a positive relationship with fluoroscopy as well.