Surgery STAT: Tracheal collapse: rings or stents?

EDITOR'S NOTE: SurgerySTAT is a collaborative column between the American College of Veterinary Surgeons (ACVS) and DVM Newsmagazine. In September, Shawn Mattson, DVM, DVSc, BSc will discuss "Treating Subchondral Bone Cysts in the Fetlock Joint." Dr. Mattson is an ACVS board-certified surgeon who practices at Moore and Company Veterinary Services, a full-service equine hospital in Calgary, Alberta, Canada. Dr. Mattson, previously at the Ontario Veterinary College in Guelph, Ontario, has published scientific articles in the American Journal of Veterinary Research and Veterinary Surgery related to research on orthopedic infections in horses.

Tracheal collapse, or tracheal chondromalacia, is a progressive, degenerative condition of the trachea that can ultimately result in severe respiratory compromise.

Different underlying causes are recognized that can occur alone or in conjunction with one another and include: (1) Hyaline cartilage rings that lose integrity and can no longer support the tracheal lumen or (2) weakening of the trachealis muscle that contributes to the loss of tracheal lumen during different phases of respiration.

The resulting clinical syndrome typically manifests as a "goose honk" cough with varying degrees of dyspnea and is most commonly identified in toy breed dogs. Non-surgical management techniques can be useful to palliate clinical signs for years, but more aggressive treatment often is required for those animals that eventually fail these more conservative approaches.

Aggressive medical therapy always is performed before any more invasive techniques, because these treatments are basically salvage procedures associated with considerable risk to the patient. Other concurrent conditions, such as underlying pulmonary, cardiac, laryngeal/upper airway and endocrine diseases should be managed before invasive tracheal procedures are considered.

Photo 1: Lateral radiographs demonstrating dynamic tracheal collapse during inspiration (above) and expiration (below), suggesting the weakness of static radiographs for determining the extent of tracheal collapse.

If conservative therapy fails to provide a reasonable quality of life for the patient, surgical rings and tracheal stents are the more commonly used surgical treatments available. There is a tendency to choose one or the other of these two options; however, both should have important roles in the management of tracheal collapse.

Photo 2a: Polypropylene rings used for external tracheal support.

I consider the location of the collapse to be one of the most important factors in deciding which technique to recommend. Routine radiography can be useful for the diagnosis of concurrent conditions and the presence of tracheal collapse, but more dynamic studies obtained during coughing are needed to fully identify the extent of the collapse.

During inspiration, the subatmos-pheric airway pressures generated in the cervical trachea lead to collapse in that location, whereas during exhalation the increased intrathoracic pressures lead to collapse of the intra-thoracic trachea. This often can be appreciated upon careful evaluation of the respiratory pattern during physical examination as well.

Individual static radiographs may fail to document fully the extent of the collapse, as demonstrated in Photo 1 with two subsequent radiographs of the same dog during two different phases of respiration (cervical tracheal collapse during inspiration and intra-thoracic tracheal collapse during expiration).

Photo 2b: Partially deployed self-expanding nitinol stent used for intraluminal tracheal stenting.

Rings or stents?

The placement of either tracheal rings (Photo 2a) or a tracheal stent (Photo 2b) remains one of the most difficult and controversial decisions regarding the treatment of this disease. The choice of tracheal rings vs. tracheal stent should be made on an individual basis. I use the following guidelines for animals that have failed aggressive medical management:

• Young, otherwise healthy patients with cervical collapse alone: Consider tracheal rings.

• Any debilitated patients that are a considerable anesthetic risk: Consider tracheal stent.

• Animals with diffuse tracheal collapse: Consider either a single tracheal stent or combination of cervical rings and intrathoracic stent.

Although there is minimal literature available assessing outcomes following these procedures, I provide the following information to pet owners to help them make a decision:

Tracheal rings (Photo 3) have been associated with a 75 percent to 85 percent success rate, but also with approximately 5 percent surgical mortality, 10 percent laryngeal paralysis and 20 percent permanent tracheo-stomy placement. Intrathoracic ring placement (beyond the first or second intercostal space) is associated with excessive morbidity, and is not currently recommended for patients with intrathoracic collapse.

Photo 3: Intra-operative images demonstrating placement of external tracheal rings to provide support for a collapsing trachea.

Tracheal stents (Photo 4) have a 75 percent to 90 percent success rate, but also carry a reported 5 percent to 10 percent mortality rate (which is greater than my experience). Short-term complications typically are minor and minimal, but long-term complications include uncertain risk of stent fracture, inflammatory tissue development at the stent ends and a low risk (when placed appropriately) of stent migration.

Photo 4: Lateral fluoroscopic images demonstrating esophageal marker catheter and severe diffuse tracheal collapse, before (above) and immediately following placement of an intraluminal tracheal stent (below).

Regardless of the treatment used, considerable discussion with the client is important to ensure outcome expectations are clear. Tracheal collapse is a progressive disease, and all current treatments are palliative. The majority of patients will require lifelong medical treatment following stenting.

In addition, it is my opinion that concurrent bronchial collapse appears to carry a worse long-term prognosis; however, this does mean the patient may not benefit from one of these treatments.

It is important to appreciate that the outcomes of tracheal rings and tracheal stenting cannot easily be evaluated against one another; these are treatments for patients with very different extents of disease and prognoses.

Dr. Weisse

Dr. Weisse is an ACVS board-certified veterinary surgeon with a research interest in interventional radiology techniques. He is currently director of the Interventional Radiology Service and assistant professor of surgery at the Veterinary Hospital of the University of Pennsylvania and he has a dual appointment in the department of radiology at the Hospital of the University of Pennsylvania.