Tracheal collapse is a common cause of cough in mature, small-breed dogs. This disease is defined either by narrowing of the lumen of the trachea, prolapse of the dorsal tracheal membrane, or a combination of those abnormalities.1 Tracheal narrowing is a multifactorial process that results from weakening of the tracheal cartilage.2,3 It has been proposed that tracheal collapse is often associated with concurrent weakening of the bronchial cartilage.1 In dogs, collapse is frequently exacerbated by coexisting conditions such as laryngeal paralysis, heart disease, or bronchitis and identifying these concurrent conditions is critical in the medical management of tracheal collapse.1,4 Grading the degree of collapse is important for recognition of the location and severity of airway collapse, monitoring progression of disease, and identification of potential surgical candidates among affected animals.1
For evaluation of coughing dogs in which tracheal collapse is a potential cause, currently available methods include radiography (preferably including inspiratory and expiratory views),5 fluoroscopy,6 ultrasonography,7 CT,8 and bronchoscopy.1 Disadvantages of ultrasonography include the inability to simultaneously evaluate the thorax for coexisting diseases and a poor-quality image because of air in the trachea. A disadvantage of CT and bronchoscopy is the requirement for anesthesia; dogs with airway collapse can have a difficult recovery from anesthesia as a result of complications, such as increased respiratory effort, that lead to further airway irritation or collapse. Also, endotracheal intubation can exacerbate tracheal inflammation, thereby initiating a vicious cycle of tracheal irritation and collapse.1,9 Nevertheless, bronchoscopy allows for assessment of the extent and degree of airway collapse, analysis of airway injury associated with collapse, and collection of airway samples for detection of additional diseases.
Fluoroscopy can be used for detection and grading the severity of tracheal collapse in veterinary patients6; however, this technique is generally available only at university and large referral hospitals, whereas conventional radiography can be performed at most small animal hospitals and clinics. Furthermore, fluoroscopic procedures result in exposure of the patient and the technical staff who perform the examination to doses of radiation that are greater than those sustained during standard radiographic procedures. Radiography has been reported to detect tracheal collapse in 59%10 to 84%11 of dogs, but to our knowledge, the accuracy of radiography for the detection and severity assessment of tracheal collapse, compared with a real-time diagnostic technique such as fluoroscopy, has not been assessed in dogs. The purpose of the study reported here was to compare the use of radiography and fluoroscopy for detection and grading of tracheal collapse in dogs with fluoroscopically confirmed tracheal collapse. The intent was to determine the ability of radiography to provide diagnostic evidence of tracheal collapse when it is present in dogs. An additional goal of the study was to determine whether the location and degree of collapse (as detected fluoroscopically) were accurately represented by radiographic findings.
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