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Tracheal stenting in dogs with end-stage trachea collapse | VETgirl Veterinary Continuing Education Podcasts

In today’s VETgirl online veterinary continuing education podcast, we review tracheal collapse. Tracheal collapse is found in smaller breed dogs, especially Yorkshire terriers, miniature poodles and Pugs and presents as airway obstruction with the classic “goose honking” cough. Possible contributing factors include:

  • weakness of the tracheal cartilage (either congenital or acquired)
  • obesity
  • environmental allergens
  • cigarette smoke
  • lower airway disease
  • infectious disease (e.g., Canine Infectious Respiratory Diseases such as Bordatella, Canine Influenza virus, etc.).

In general, an estimated 65-78% of dogs are reported to respond well to medical therapy; surgical management is often considered only after patients fail medical therapy. What type of surgery is done for tracheal collapse? Surgical options include:

  • tracheal ring chondrotomy
  • plication of the dorsal tracheal membrane
  • mesh reconstruction
  • extraluminal ring placement
  • intraluminal stenting.

Intraluminal stenting has become popular due to the non-invasive nature of the procedure, a short anesthetic time and immediate improvement in clinical signs in these patients. These stents can also be used to treat both tracheal and intra-thoracic collapse.

So, Durant et al out of University of Tennessee wanted to evaluate the use of nitinol stents for the treatment of end-stage tracheal collapse in dogs. This paper looks specifically at the Vet-Stent®, a woven nitinol stent designed specifically for veterinary medicine. These stents can tolerate significant strain before permanent changes in shape are noted. These stents are also reconstrainable (e.g., they can be re-sheathed following partial deployment, allowing for more accurate placement) and foreshortening stents (e.g., stent length is longer if not deployed to its full diameter). The flexibility of nitinol has been reported to be similar to that of tracheal cartilage.

So, the authors placed endoscopically-assisted intraluminal stents and reported outcomes after use of the stents in 18 end-stage tracheal collapse dogs. They also looked at stent dimensions immediately post-procedure and at follow-up. Overall, they found that certain breeds were overrepresented. Yorkshire terriers represented 61% of patients, followed by Pomeranians (22%) and miniature poodles (11%). The mean age at onset of clinical signs was 7.6 years and the mean duration of signs was 2.3 years prior to stenting. Most patients were obese and had an increased BCS (mean BCS 4/5 or 6/9), along with a combination of cervical and thoracic tracheal collapse.

3 dogs had complications associated with endoscopically-guided stent placement (e.g., stent migration with scope removal); however, all patients went on to successful stent placement during the first anesthetic period. 3 dogs developed aspiration pneumonia within 24 hours of the procedure, but did not suffer any long-term consequences. No other complications were noted immediately post-operatively and all patients were discharged from the hospital. Minimum tracheal diameter was significantly higher after stent placement in these dogs; however, maximum tracheal diameter was not.

In this study, all stents spanned the entire length of the trachea. This was done as there has been reports of recurrence of tracheal collapse with segmental stents. Other complications that were reported post-operatively included stent fracture (4 dogs), perineal hernia (1 dog) and rectal prolapse (1 dog). Stent fracture in 2 dogs was associated with severe respiratory distress and cyanosis; these patients were euthanized. The other 2 dogs with stent fracture were noted to have an increase in frequency and severity of cough prior to fracture diagnosis, and were managed medically. On tracheoscopic follow-up, findings included hyperplastic mucosal tissue, inflammatory tracheitis and bacterial tracheitis. All patients were managed medically (e.g., with steroids, antibiotics, etc.). As for tracheal stent dimensions, at follow up, change in the minimum tracheal diameter was greater and stent length was shorter versus post-placement measurements. While the minimum tracheal diameter was greater, the maximum diameter was still unchanged.

Overall, 88.9% of the dog owners reported fair to excellent outcome at a mean time of 270 days. However, an 11.1% mortality rate was reported within 60 days of stent placement. Survival times ranged from 44 days to > 2.7 years after stent placement. 16/18 dogs were reported as alive at 6 months or more following stent placement. Also, the authors did not find any association between outcome and location of the tracheal collapse.

So, what can we take away from VETgirl podcast? Intra-thoracic stent placement in end-stage tracheal collapse patients can lead to fair to excellent outcomes in the majority (almost 89%) of patients. Patients that don’t respond well are typically identified within 60 days of the procedure. In contrast to previous studies that have suggested dogs with intra-thoracic tracheal collapse have a poorer outcome, no association was found between location of collapse and outcome in this study. Keep in mind that most patients still require some degree of medical management; however, intra-luminal stenting alleviated clinical signs in almost all of the patients, and a majority of owners were satisfied with the outcome, despite the need for continued medical management.

What are some limitations of this study? This study included a small number of dogs, and had outcomes similar to previous reports with the use of extra-luminal rings and a different brand of nitinol stents. These values may change with increased case numbers and as availability of the stent increases. Another limitation was that the contribution of bronchial collapse in these patients was not evaluated. This is an area where a prospective study that included bronchoscopy in the pre- and post-operatively assessment would be helpful. Finally, outcomes were based on owner perception, and may be biased due to the fact that all patients were end-stage at the time of stent placement, and did not have other good alternatives. A blinded, objective measurement of outcome would remove some bias. That said, this study was great in that it showed an excellent outcome for dogs with end-stage tracheal collapse. However, a prospective study would allow a more thorough comparison of pre-operative and post-operative management.

In conclusion, end-stage tracheal collapse can be successfully treated using nitinol tracheal stents placed bronchoscopically, and prognosis is fair to good in these patients. Make sure to medically treat your patient aggressively first. If they fail medical management, then tracheal stent placement is recommended. However, make sure to educate your pet owners about the risk of rare complications, most of which can be corrected during the procedure. Specifically, the stent “Vet-Stent” evaluated in this paper is a good alternative for end-stage tracheal collapse patients. The clinical significance of stent shortening is not known and should be investigated further, however, as we know complications can occur.

References:
Durant AM, Sura P, Rohrbach B, et al. Use of Nitinol Stents for End-Stage Tracheal Collapse in Dogs. Vet Surg 2012;41:807-817.

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