Computed tomographic assessment of the trachea in the German shepherd dog.

Computed tomographic (CT) examination of the trachea was performed in 10 German shepherd dogs to determine the normal value of some tracheal measurements under general anesthesia and in sternal recumbence position. Measurements obtained from nine segments were evaluated in four groups as the cranial cervical, caudal cervical, thoracic inlet and the thoracal tracheas. The inner transverse (T) and vertical (V) diameters were measured with the aid of electronic calipers from the software of the CT scanner. The cross-sectional lumen area (CSA) was calculated by using vertical and transverse diameters. The ratio of the transverse and vertical diameters (T/V) was also calculated. There was not any significant difference between thoracic inlet and thoracic tracheas, however, the mentioned regions were found to be significantly different from both cranial and caudal cervical regions in all measurements except the ratio of T/V. The ratio of T/V between 0.92 and 1.06 gradually changed and there was not any statistical difference between subsequent regions while differences were found among further regions. The largest CSA, seen in cranial cervical trachea was as 364.62 mm2 and decreased gradually to 309.29, 245.69 and 226.50 mm2 in caudal cervical, thoracic inlet and thoracic tracheas, respectively. From the point of view of technique, CT examination of the dog trachea was very easy and it was possible to take sensitive and repeated measurements. It, however, may be accepted as expensive and that it is disadvantageous to require general anesthesia. The data presented in this study represent tracheal values in the healthy German shepherd dog under the conditions of the study.