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EQUINE VETERINARY EDUCATION
Equine vet. Educ. (2022) 34 (11) 564 doi: 10.1111/eve.13614_1
Case Report
Left rotation and dorsoventral collapse of the trachea on an adult Dartmoor cross-gelding: Imaging diagnosis
M. J. Rosa and L. M. Rubio-Martinez* Sussex Equine Hospital, Ashington, West Sussex, UK *Corresponding author email:
luis.rubiomartinez@
hotmail.com
M. J. Rosa's present address: Anglesey Lodge Equine Hospital, The Curragh, R56 YX98, Ireland Keywords: horse; tracheal collapse; tracheal rotation; inspiratory noise; dyspnoea Summary
A 9-year-old Dartmoor cross-gelding was presented for the investigation of exercise intolerance, cough and abnormal respiratory noise of approximately 4 months’ duration. On admission, the gelding did not show signs of respiratory distress, but loud respiratory sounds and episodes of regular, short shallow breaths were noted occasionally, especially when the horse was excited. The loud respiratory sounds were mostly inspiratory and resembled a honking sound. Light lungeing exacerbated these sounds. Endoscopic examination of the trachea revealed marked
laterolateral collapse of the tracheal lumen immediately caudal to the larynx. Upon detailed review, the dorsal tracheal ligament was noted to lie on the left side of the trachea, whereas flattened tracheal cartilage rings were on the right side and extended from the dorsal to the ventral limits of the tracheal lumen. At the entrance into the thoracic trachea, the dorsal tracheal ligament returned to its normal dorsal location, where the tracheal lumen presented a more normal circular shape. These endoscopic findings confirmed the presence of 90-degree left rotation and dorsoventral collapse of the entire cervical length of the trachea. Subsequent radiographic examination of the trachea was
performed. On the laterolateral views (Fig 1), the dorsoventral diameter of the tracheal lumen was large and consistent all along the neck; in fact, it subjectively appeared larger than expected. In addition, tracheal cartilages could be identified on the dorsal and ventral borders of the cervical trachea. Dorsolatero-ventrolateral oblique projections demonstrated the collapse of the caudal cervical portion of the tracheal lumen.
Fig 2: Transverse ultrasound image at the ventral aspect of the neck (left to the left of the image), note the presence of the oesophagus (star) next to the dorsal tracheal ligament (arrowhead) and the curvilinear shape of the tracheal ring (arrow).
Ultrasonographic examination of the trachea (Fig 2) confirmed the presence of the smooth outlined tracheal ligament along the left side and the tracheal cartilages on the right aspect of the trachea. The junction between the dorsal tracheal ligament and the incomplete tracheal cartilage was visualised coursing on the ventral midline of the neck. A 90-degree left rotation and dorsoventral collapse of the
entire cervical trachea were diagnosed. Medical and surgical treatment options were discussed with the owner, who opted to pursue conservative management. No further follow-up was available.
Key points
• When tracheal rotation is present in combination with tracheal collapse, a decreased dorsoventral tracheal diameter may not be apparent on laterolateral radiographs. Attention to the outline of the tracheal margins is important as, in normal horses, the dorsal outline of the trachea should be linear and smooth in laterolateral radiographs.
• Radiographic dorsoventral and oblique projections are useful to confirm the presence of concurrent tracheal collapse and rotation.
Fig 1: Laterolateral radiographic views of the cervical trachea, showing wide dorsoventral diameter of the tracheal lumen and presence of tracheal cartilages (arrowheads) along the dorsal and ventral limits of the tracheal lumen.
• Ultrasound is a useful technique to confirm tracheal rotation. With this condition, the junction between the dorsal tracheal ligament and the incomplete tracheal cartilage can be visualised coursing along the ventral or lateral aspects of the neck.
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