Veterinarians often choose upper airway endoscopy when working to diagnose equine arytenoid chondritis--an uncommon but problematic respiratory condition--but in some cases a definitive diagnosis lies out of reach. Ultrasonography could offer a valuable adjunct tool for diagnosing this respiratory condition, however, especially in cases lacking a definitive diagnosis.
At the 2012 American Association of Equine Practitioners convention, held Dec. 1-5 in Anaheim, Calif., Katherine Garrett, DVM, Dipl. ACVS, of Rood & Riddle Equine Hospital, in Lexington, Ky., presented results of a study in which she and colleagues evaluated ultrasonographic features of horses with arytenoid chondritis.
Arytenoid chondritis is inflammation involving one or both arytenoid cartilages, which close over the opening to the trachea when a horse swallows. Affected performance horses often exhibit diminished performance, cough when exerted, and make abnormal noise during exercise (similar to "roaring").
Garrett noted that while ultrasonography has potential to help veterinarians diagnose arytenoid chondritis, specific ultrasonographic parameters had not been identified. This led Garrett and colleagues to compare ultrasonographic findings of horses with confirmed arytenoid chondritis (diagnosed via endoscopy) and horses with normal arytenoid cartilage function and structure.
"We hypothesized that arytenoid cartilages with arytenoid chondritis would have a larger cross-sectional area, an irregular margin (i.e., edge), and abnormal echogenicity as compared with normal arytenoid cartilages," she said. Echogenicity refers to how the ultrasound's waves reflect off, are absorbed by, or are transmitted through an object.
The team reviewed the medical records of 33 Thoroughbreds diagnosed with arytenoid chondritis and 79 Thoroughbreds that served as control horses. Garrett relayed that veterinarians had taken ultrasound images of the horses' larynges at the level of the arytenoid cartilages.
They found that 98% of affected horses had abnormally shaped arytenoid cartilages, and affected cartilages were significantly larger than unaffected ones (approximately twice the size). They noticed abnormal echogenicity in the ultrasound images of affected arytenoid cartilages, she said, as compared with normal cartilages. Garrett noted these findings showed that the ultrasound produced accurate, consistent, and reproducible results.
Additionally, Garrett noted that 17 case horses were available for follow-up examination. No difference in arytenoid cartilage size was observed when horses underwent multiple examinations, suggesting that once enlarged, arytenoid cartilages affected with arytenoid chondritis do not return to a normal size.
Garrett concluded that when used in combination with upper airway endoscopy, "ultrasonography is a valuable diagnostic modality when investigating cases of possible arytenoid chondritis or abnormal arytenoid cartilage movement," including recurrent laryngeal neuropathy (roaring) and laryngeal dysplasia.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.