Fluoroscopic Characteristics of Tracheal Collapse and Cervical Lung Herniation in Dogs

Abstract

Tracheal collapse is a common disease in small breeds and known as cause of chronic cough. Cervical lung herniation is protrusion of the lung through the apex of each hemithorax and there are not many reports in veterinary society. The purpose of the present study was to investigate fluoroscopic characteristics of tracheal collapse and cervical lung herniation (CLH), and pursue any potential relationship to various influencing factors in dogs. From 2012 to 2014, cases performed fluoroscopic examination of trachea with coughing phase were included and cases with lacking of records about a history of cough were excluded. Medical records were reviewed for history, signalment, clinical signs and physical examination findings of patients performed fluoroscopy examinations. Presence and grade of tracheal collapse, CLH were investigated and presence of kinking of trachea is recorded on fluoroscopic examination. Severity of CLH was graded by comparing level of apex of the lung lobe and the adjacent cervical vertebrae. In 330 cases performed fluoroscopic examination, 306 cases met inclusion criteria. Many of cases with a history of cough and most of the cases without a history of cough were proceeded examination for pre-anesthesia evaluation. Tracheal collapse was shown in 270 cases and there was no correlation with a history of cough. The mean age of the cases was 10.853 ± 3.109 years old (range 1~18) and the cases with tracheal collapse (11.041 ± 2.996) older than cases without tracheal collapse (9.444 ± 3.597). To evaluate CLH, cases with unknown duration of cough and failed to induce coughing phase in dorsal recumbence were excluded and 238 cases met the inclusion criteria. In 238 cases, there were 132 cases showed CLH. CLH showed significant association with a history of cough and intrathoracic tracheal collapse. But in cases without a history of cough or without tracheal collapse, CLH was not rare phenomenon. In univariate analysis significant correlation was shown between CLH and duration of cough, but in multivariate analysis, there was no correlation between them. There was no significant association between the severity of CLH (grade of CLH) and cough. In 10 dogs of grade 3 and 4, Shih Tzus (4/10, 40.0%) and Pekingeses (3/10, 30.0%) occupied large portion and Pekingese and Shih Tzu dogs presented wider thoracic compared to other breeds. And cases with high grade of CLH closed to barrel chested. The cases with higher grade of CLH showed the larger portion of tracheal kinking. No patient with tracheal or esophageal obstruction resulted from cervical lung herniation in the present study. In conclusion, tracheal collapse can be seen without a history of cough. So when tracheal collapse is regarded as critical factor, such as anesthetic situation, it should be ruled out using physical examination and diagnostic image. CLH is a common appearance in dogs and associates a history of cough, breeds and intrathoracic tracheal collapse. Without a history of chronic cough, transient cough can elicit cervical herniation of the lung. The greater grade of CLH, the more tracheal kinking were identified and there was possibility, mechanical irritation of trachea deteriorate the clinical sign.