Radiographic tracheal lumen to vertebral ratios in the normal American Miniature Horse

Abstract

Summary Background Tracheal collapse in horses is reportedly uncommon; however, American Miniature Horses are more commonly affected. There is no description of the tracheal luminal diameter of American Miniature Horses, making early detection of tracheal luminal narrowing difficult. Objectives To 1) describe radiographic tracheal luminal diameter in clinically normal American Miniature Horses, 2) report the prevalence of subclinical tracheal collapse in a population of American Miniature Horses, and 3) use tracheal videofluoroscopy to quantify variation in tracheal luminal diameter throughout the respiratory cycle in horses with no clinical respiratory disease. Study design Descriptive observational reference interval study. Methods Thirty‐four American Miniature Horses with no reported history of respiratory illness were recruited. Lateral cervical and thoracic radiographs were obtained in unsedated standing horses. Dynamic fluoroscopic images were obtained of the cervical and thoracic trachea throughout the respiratory cycle. Horses were then sedated as needed and tracheoscopy was performed. Twenty‐nine horses were categorised as normal, and five horses were categorised as subclinically affected based on 25% or greater tracheal narrowing using tracheoscopy for visual assessment. Radiographic tracheal lumen to vertebral body measurements were obtained throughout the cervical and thoracic trachea. Maximum and minimum fluoroscopic tracheal diameter at each site throughout the respiratory cycle was recorded. Results A mean, median, 95% confidence interval and bootstrapped 95% reference interval of radiographic tracheal diameter to vertebral body ratios were generated in normal horses. The prevalence of subclinical tracheal collapse in this population of American Miniature Horses is 14.7%. Main limitations Bootstrapped reference range was generated from 29 horses. Conclusions Radiographic tracheal measurements and ratios of the tracheal diameter to vertebral body in the normal American Miniature Horse are described herein and can be used as a guideline when screening for tracheal disease in American Miniature Horses. The prevalence of subclinical tracheal collapse in American Miniature Horses may be higher than previously reported.

Left rotation and dorsoventral collapse of the trachea on an adult Dartmoor cross‐gelding: Imaging diagnosis

“…Tracheal collapse due to chondrodysplasia was diagnosed and confirmed by histological examination in a 2‐month‐old AMH foal (Aleman et al., 2008; Couëtil et al., 2004). Acquired primary tracheal collapse is more common and represents the end result of the progressive degenerative process of the hyaline cartilage of the tracheal rings (chondromalacia) and weakening of the dorsal trachealis muscle, culminating in a loss of mural structural integrity (Every et al., 2020; Ida et al., 2018; Prange, 2019). The pony presented in this report had been recently adopted by the current owners and the previous history was not available.…”

“…Most commonly, dorsoventral collapse is recognised as a widespread or segmental dorsoventral flattening of the tracheal rings with elongation of the dorsal tracheal membrane. It is mainly reported in small pony breeds such as Shetland ponies and American Miniature Horses (Aleman et al., 2008; Barakzai, 2007, 2013; Barakzai & Dixon, 2020; Couëtil & Hawkins, 2013; Dixon et al., 2007; Every et al., 2020; Prange, 2019; Tetens et al., 2000). The most common cause of tracheal dorsoventral collapse is cartilage ring deformity, with the deformed tracheal rings being flattened, resulting in a significantly reduced dorsoventral diameter of the tracheal lumen.…”

“…Clinical signs may go unnoticed in some mildly affected ponies and donkeys due to their sedentary lifestyle. When present, clinical signs include loud ‘honking’ noises on inspiration, dyspnoea, increased abdominal expiratory effort and cough (Aleman et al., 2008; Barakzai, 2007, 2013; Barakzai & Dixon, 2020; Busschers et al., 2010; Couëtil & Hawkins, 2013; Dixon et al., 2007; Every et al., 2020; Graham et al., 2010; Prange, 2019).…”

Diagnóstico de colapso traqueal em pônei: relato de caso

“…Dentre os equinos, os pôneis e os cavalos em miniatura são as raças mais acometidas pelo colapso traqueal, enfermidade multifatorial que apresenta como fatores predisponentes a falha congênita no desenvolvimento da cartilagem, degeneração e doenças inflamatórias relacionadas ao trato respiratório inferior (Couëtil e Hawkins, 2013), geriatria (Every et al, 2019) e o processo de miniaturização (Freeman, 2005).…”

“…O diagnóstico de colapso traqueal foi realizado com base no estudo radiográfico da traqueia em projeções látero-laterais, apontada por Every et al (2019) como uma técnica sensível que permite visualizar a redução do lúmen traqueal e o local exato da lesão. Wong et al (2008) sugere ainda a realização de projeções cervicais dorsoventrais, as quais permitirão visualizar o aumento do diâmetro traqueal resultante do seu achatamento.…”