Tracheal Collapse in Equines: Diagnosis, Management, and Surgical Challenges

This article briefly reviews tracheal collapse as it is seen in horses, ponies, miniature horses and donkeys. Diagnosis is straightforward with medical management of lower respiratory tract diseases, when possible, an important component of therapy. Surgical correction of the condition is possible with long term outcomes having variable results. Tracheal Collapse in Equines: Diagnosis, Management, and Surgical Challenges This article briefly reviews tracheal collapse as it is seen in horses, ponies, miniature horses and donkeys. Diagnosis is straightforward with medical management of lower respiratory tract diseases, when possible, an important component of therapy. Surgical correction of the condition is possible with long term outcomes having variable results.

The case reports presented by Watkins et al in this issue (2025) describe surgical treatment of two cases of tracheal collapse in Miniature Horses. In both cases, a single intra-luminal nitinol stent was used. The stent was manufactured specifically for the individual patient’s tracheal dimensions, accounting for the length and varying width of the trachea. This technique is novel with currently used techniques including extra-luminal stenting and multiple intra-luminal stents. Short term resolution of the clinical signs were achieved with the novel treatment, though both cases were ultimately unsuccessful in the long term. The case reports highlight the challenges faced with surgical treatment of tracheal collapse. Etiology of Tracheal Collapse Causes of tracheal collapse in horses include congenital and degenerative abnormalities of the cartilaginous tracheal rings, intra- and extraluminal masses and external trauma. (Aleman & Neito, 2008; Theimann, 2012). Tracheal collapse is uncommon in horses but has an increased prevalence in ponies and was up to 6% of a referral case load of American Miniature Horses (Aleman & Neito, 2008). Donkeys also have age related dorsoventral flattening of the trachea, with 8.7 -12% of aged donkeys showing tracheal collapse, as diagnosed on post-mortem examination (Theimann, 2012, Powell 2010). Miniaturization increases the prevalence of tracheal collapse in dogs and this appears to be consistent in equines (Every & Hostnik, 2020). When degenerated or weakened tracheal cartilages are unable to withstand respiratory pressures, collapse of the cervical or intra-thoracic trachea results. Tracheal collapse is more likely to occur when an increased respiratory effort and inspiratory pressure strains the intra and/or extra-thoracic tracheal cartilages. As subclinical disease can be present with no indications (Every & Hostnik, 2020), symptoms may only occur with conditions occur that increase respiratory tract demands such as pneumonia, asthma, pregnancy, exercise, dusty environments and eating (Aleman & Neito, 2008; Fenger 1992). Clinical signs range from exercise intolerance, coughing and respiratory noises (honking, squeaking or wheezing) to severe dyspnea, cyanosis and death (Aleman & Neito, 2008; Busschers & Epstein 2010). The symptoms seen in Watkins (2025) Case 1 included an infrequent honking cough and exercise intolerance. Abnormal physical exam findings documented bilaterally increased bronchovesicular sounds. Case 2 complained of abnormal respiratory noises as well as coughing and exercise intolerance. Diagnosis Diagnosis of the condition in Watkins et al. (2025) included resting endoscopy to the level of 40 to 65-70 cm from the nares and standing radiographs of the cervical and thoracic region. Normal pharyngeal and laryngeal anatomy and function were noted on resting endoscopy in both cases. Moderate mucous accumulation in the trachea was seen in Case 1. No grading of the tracheal collapse was supplied in the 2025 case reports by Watkins et al, with surgery typically reserved to cases with clinical signs and a grade 3 or above tracheal collapse score (Aleman & Neito, 2008). Figure 1 describes the grading system used for equines. Treatment Treatment of tracheal collapse includes medical management of any lower respiratory tract conditions such as asthma or pneumonia. Case 1 described here had concurrent lower respiratory signs that were treated with antimicrobials (minocycline), systemic steroids (prednisolone) and broncho dilators (clebuterol). Surgical treatments, as described by Watkins (2025), are offered when medical management is not successful, or the structural integrity of the trachea is compromised to the point of medical management not being sufficient to prevent dyspnea (Graham & Schilpp, 2010). Fluoroscopy was also used to image the trachea of the cases in Watkins et al (2025). This was performed under general anesthesia, with inspiratory pressures of 20 and 30 cm of H 2 O to measure the diameter of the trachea. This technique is used in small animals for tracheal measurements to maintain the diameter of an airway under positive pressure according to Watkins et al (2025). The precision used in these measurements was necessary to construct a custom made intra-luminal nitinol stent. Recommendations for selection of the appropriate size of the stent have been made in humans and dogs, with 25-50% larger than the normal airway recommended for canine surgeries (Couёtil & Gallatin, 2004). For equine surgeries, intra-luminal stenting is limited to Miniature Horses and foals currently, due to restrictions on the size of stents manufactured. It is suggested the stent should extend past the length of the collapsed trachea by 10-15 mm and be at least 2 mm in diameter greater than the lumen of the normal tracheal (Wong & Sponseller, 2010). The custom-made nature of the stent in Watkins et al (2025) was used to avoid the issues of inadequate length of commercially available stents which require the placement of multiple stents to stabilize the entire length of the collapsed trachea. The non-covered area metallic stents are prone to the development of granulation tissue. This may be from constant movement of the stents against the mucosa resulting in chronic inflammation or tissue reaction to the stent material may be another cause (Wong & Sponseller, 2010). Intensive management of the obstructive nature of this condition in another case report by Couёtil & Gallatin (2004) required multiple repeat endoscopies and treatments involving intra-luminal and systemic steroids as well as electrocautery. The impairment of the mucociliary apparatus and stenosis of the trachea also caused mucous accumulation in the airway, leading to sequelae such as pneumonia and lower respiratory tract inflammation (Couёtil & Gallatin, 2004). Surgical Challenges and Outcomes When compared to extra-luminal surgical stabilization of the trachea, advantages of intra-luminal stents include decreased invasiveness of the placement surgery, intrathoracic trachea access, decreased tracheal necrosis and surgery site infection and decreased risk to vital structure damage. The vagosympathetic trunk, vasculature and recurrent laryngeal nerve which all intimately associated with the trachea and vulnerable to damage during extra-luminal tracheal surgery. Placement of intraluminal stents is also a rapid procedure and less technically demanding with the option for endoscopic adjustments of the stent placement, if required, post-surgery (Wong & Sponseller, 2010). Placement of intra-luminal stents in Watkins et al. (2025) report was uneventful with immediate resolution of clinical signs. After an uneventful recovery, Case 1 was discharged 2 days after surgery and then found dead 36 days after the procedure. Necropsy findings included granulation tissue at the cranial aspect of the stent with a resulting obstruction of the trachea. Case 2 in Watkins et al (2025) had a similar uneventful placement of the stent. Re-check endoscopy at 6 weeks post-surgery showed integration of the mucosa dorsally and ventrally, with poorer mucosal integration laterally on those aspects of the stent. A 25% narrowing of the lumen was seen cranial to the stent that was static in nature between 6 and 10 weeks post-surgery when viewed endoscopically. 1 year after stent placement, endoscopy was performed due to purulent nasal discharge, respiratory noises, dyspnea and foul odor. Significant continued narrowing of the cranial lumen was visualized. At this evaluation, decreased sensitivity of cough receptors was suggested, as there was minimal coughing after exercise and significant mucous accumulation visualized on endoscopy. Further treatment was declined at this time and euthanasia was opted 2 years later, for quality of life concerns. Treatment of obstruction of the tracheal lumen post- intraluminal stent placement have been managed with intra-lesional steroid injections at 2-3 week intervals, placement of further stents to bridge non-overlapping areas and reduced granulation tissue formation at those sites (Wong & Sponseller, 2010). Systemic steroids were also administered to control respiratory tract inflammation. This is relatively intensive management and, in the case, described by Wong & Sponseller et al (2010), ultimately ended in euthanasia due to laminitis, potentially from corticosteroid use to manage the case. The surgical repair of tracheal collapse is challenging with extra-luminal support methods requiring intensive surgeries and reporting complications such as esophageal dysfunction and right sided hemiplegia post-surgery (Busschers & Epstein, 2010). Intraluminal tracheal stenting is technically less demanding to insert initially, requires intensive endoscopic follow up with limited treatment options of complications such as migration of the devices, stenosis, proliferative granulation tissue and impairment of the mucociliary apparatus (Couёtil & Gallatin, 2004). Promising aspects of intraluminal stenting include immediate resolution of clinical signs and the potential reduction in complications as measuring techniques to ensure appropriate stent placement are refined. Traumatic Causes of Tracheal Collapse & Tracheal Collapse in Working Donkeys Trauma to the trachea has been recognized as a cause of tracheal collapse in horses and donkeys (Theimann, 2011, Graham & Schilpp, 2010, Tetens & Hubert, 2000). The cranial and mid-cervical portions of the trachea are most affected by external trauma, due to their superficial location in the ventral neck. Trauma can separate the trachealis muscle from its attachments to the tracheal rings or result in tracheal ring crushing. Either insult results in a reduction of tracheal diameter acutely and when healed, if misalignment occurs. This reduction is typically seen through dorsoventral reduction in height of the tracheal lumen. Standing endoscopy is a valid method to evaluate a decrease in diameter of the tracheal lumen. Functional evaluation, used with increased respiratory tract pressures, as seen with exercise in dynamic endoscopy can be helpful in cases that do not show evidence of tracheal collapse at rest (Tetens & Hubert, 2000). Repeated trauma due to improper harnessing is being suggested as a cause of tracheal collapse seen in working donkeys (Mellish & Burns, 2025). Resting respiratory rate, heart rate, temperature and bronchovesicular sounds were not different between working cart donkeys diagnosed with grade 3 tracheal collapse when compared to working donkeys with grade 2 or lower tracheal collapse. This could be an indication of the subclinical nature of tracheal collapse. Evaluation of physical exam parameters, including oxygenation and tracheal compression/collapse during work would be valuable to capture the dynamic component of this population of equids suffering from tracheal collapse. Aged donkeys can also suffer from tracheal collapse, with no known specific cause. Clinical signs can be seen as previously subclinical disease progresses or exacerbation of the condition occurs due to lower respiratory tract disease such as pulmonary fibrosis or asthma (Thiemann, 2011).

Due to the significant challenges in managing tracheal collapse either medically or surgically, measures to prevent clinical signs from this condition are prudent. This includes responsible breeding of animals that may carry the condition genetically, maintaining good air quality in housing, prompt treatment of respiratory diseases and prevention of trauma to the external trachea. Information & Authors Information Version history Peer review timeline Published Equine Veterinary Education Version of Record19 Mar 2025Published Copyright This work is licensed under a Non Exclusive No Reuse License. Collection Authors Metrics & Citations Metrics Article Usage 351views 170downloads Citations Download citation Martha Mellish. Tracheal Collapse in Equines: Diagnosis, Management, and Surgical Challenges. Authorea. 28 February 2025. DOI: https://doi.org/10.22541/au.174076077.75763811/v1 DOI: https://doi.org/10.22541/au.174076077.75763811/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu.