TRANSESOPHAGEAL ULTRASONOGRAPHY OF THE NORMAL CANINE MEDIASTINUM

The mediastinum of eight normal research dogs was examined by transeso phageal ultrasonography with a 5MHz frequency transducer to establish a baseline for future use of this new imaging modality as a diagnostic tool. Each examination consisted of 360 degree scans in both transver se and sagittal planes from the thoracic inlet to the esophageal hiatu s. Dissections of four of these research dogs were then performed to c onfirm transesophageal ultrasonography findings, Transesophageal ultra sonography of the mediastinum was a good imaging modality for the eval uation of the heartbase, the major cranial mediastinal vessels, the de scending aorta, and occasionally part of the azygos vein. Anatomic ori entation was best obtained by beginning the examination at the heart b ase. Lymph nodes and smaller caliber vessels could not be distinguishe d from surrounding tissues; however, Doppler ultrasound was useful for identifying the smaller vessels, Although a 5 MHz frequency transduce r is preferred for transesophageal echocardiography, a higher frequenc y transducer would improve the resolution of the images of small near- field structures and may be more appropriate for mediastinal imaging.