Correlations among tracheal dimensions, tracheal stent dimensions, and major complications after endoluminal stenting of tracheal collapse syndrome in dogs

A systematic review and meta-analysis of prevalence of complications after tracheal stenting in dogs

BACKGROUND

Stenting has become popular to treat tracheal collapse in dogs, but complications might arise and negatively affect treatment outcome.

OBJECTIVES

Determine the overall prevalence of complications of tracheal stenting in dogs.

METHODS

A bibliographic search was performed of publications from 2000 to 2020. Studies were assessed for quality of evidence and measured prevalence of the 8 most commonly reported complications after tracheal stenting in dogs (stent fracture, stent migration, relapsing collapse, granuloma formation, tracheobronchial infections, and early, late, and clinically relevant late cough). Random effects meta-analyses were used to estimate pooled complications prevalence.

RESULTS

Fifteen studies met inclusion criteria. Cough (early: 99%; 95% confidence interval [95% CI]: 95%-100%, late: 75%; 95% CI: 63%-85%, and clinically relevant: 52%; 95% CI: 42%-61%), tracheobronchial infections (24%; 95% CI: 14%-35%), and granulomas (20%; 95% CI: 11%-30%) were common after tracheal stenting. Stent fractures (12%; 95% CI: 5%-20%), relapsing collapse (10%; 95% CI: 5%-15%), and stent migration (5%; 95% CI: 1%-9%) were less frequent. Significant heterogeneity among studies was identified for the estimated prevalence of stent fracture, granulomas, infections, and late cough.

CONCLUSIONS AND CLINICAL IMPORTANCE

Tracheal stenting in dogs is associated with a high risk of coughing and a moderate risk of tracheobronchial infections and granuloma formation. Because most complications will impact a dog's quality of life, owners must be informed that tracheal stenting is a second-line procedure that does not necessarily alleviate the need for medical treatment and frequent follow-up visits. Additional studies are warranted to identify the risk factors of these complications.

Fatigue analysis of canine tracheal stents using the finite element method

This study aimed to evaluate fatigue of three stent designs when various forces are applied and perform a comparative analyses. A computer simulation using the finite element method was performed. In particular, we constructed a three-dimensional finite element model of nitinol stents with three designs (S6: single-woven wire, wire diameter: 0.006 inch; D6: double-woven wire, wire diameter: 0.006 inch, and D7: double-woven wire, wire diameter: 0.007 inch) that are used to treat canine tracheal collapse (TC). The stents were subjected to a 200 mmHg compression force, a pure torsion force in a perpendicular direction, and a bending-torsion force combining perpendicular and axial forces. The von Mises stress was calculated to evaluate the extent of stent displacement, and Goodman diagrams were plotted to compare fatigue life cycles. D7 exhibited a longer fatigue life compared to S6 and D6. Under compression, pure torsion, and bending-torsion forces, displacement was the smallest for D7, followed by D6 and S6. Similarly, the fatigue life was the longest for D7, followed by D6 and S6. S6 showed the greatest displacement when subjected to external forces; among stents designed using the same wire, D6 displayed less displacement than S6, and D7 exhibited superior fatigue life when subjected to varying degrees of force. This study showed that the structural stability and fatigue life of stents could be effectively compared using finite element method D7 has the greatest stability and structural rigidity under cyclic load.

Bronchial collapse and bronchial stenting in 9 dogs

BACKGROUND

Principal and lobar bronchial collapse is increasingly recognized as an isolated entity.

OBJECTIVE

Retrospectively describe the procedure and outcomes of dogs undergoing bronchial stenting at a single referral hospital.

ANIMALS

Nine client-owned dogs with variable degrees of collapse of the left principal bronchus (LPB), lobar bronchus 1 (LB1), and lobar bronchus 2 (LB2), and with clinically relevant signs of respiratory dysfunction.

METHODS

Data were collected from patient records. All dogs underwent stenting of the LPB and LB2. Anatomic and functional impairment grades were assigned to each case before and 4 weeks after stenting. Data regarding response to stenting and complications were evaluated.

RESULTS

Bronchial stenting was considered successful in all cases, with all dogs experiencing improved quality of life (QOL), and decreased functional impairment grade at 4 weeks post-stenting. Follow-up of >6 months was available for 6 dogs and of these, 5 were alive at 12 months, 3 were alive at 18 months, and 1 was alive at 24 months. Stent-related complications occurred in 4 dogs, and were resolvable in 3. Two dogs developed pneumothorax, 1 developed recurrent pneumonia, and 1 developed new-onset coughing. All dogs had mild and manageable coughing post-stenting.

CONCLUSIONS AND CLINICAL IMPORTANCE

Stenting of the LBP and LB2 might be an effective option for dogs with advanced collapse of these bronchi and associated signs. Although all included dogs had resolution or improvement of clinical signs considered life-threatening or as affecting QOL, ongoing coughing is expected. Patient selection appears important with regard to achieving successful outcomes.

Antimicrobial and Antiproliferative Coatings for Stents in Veterinary Medicine-State of the Art and Perspectives

Microbial colonization in veterinary stents poses a significant and concerning issue in veterinary medicine. Over time, these pathogens, particularly bacteria, can colonize the stent surfaces, leading to various complications. Two weeks following the stent insertion procedure, the colonization becomes observable, with the aggressiveness of bacterial growth directly correlating with the duration of stent placement. Such microbial colonization can result in infections and inflammations, compromising the stent's efficacy and, subsequently, the animal patient's overall well-being. Managing and mitigating the impact of these pathogens on veterinary stents is a crucial challenge that veterinarians and researchers are actively addressing to ensure the successful treatment and recovery of their animal patients. In addition, irritation of the tissue in the form of an inserted stent can lead to overgrowth of granulation tissue, leading to the closure of the stent lumen, as is most often the case in the trachea. Such serious complications after stent placement require improvements in the procedures used to date. In this review, antibacterial or antibiofilm strategies for several stents used in veterinary medicine have been discussed based on the current literature and the perspectives have been drawn. Various coating strategies such as coating with hydrogel, antibiotic, or other antimicrobial agents have been reviewed.

Stents in Veterinary Medicine

Stenting in veterinary medicine has been a rapidly growing method of interventional surgery for several years. This procedure is usually performed in the respiratory and urinary tracts, but there are cases of stenting of blood vessels or gastrointestinal structures. It is based on maintaining the permeability of a given tubular structure, thus allowing the passage of gas or liquid. This procedure is often performed as a first-line treatment in situations where pharmacological agents do not work and as an alternative method, often cheaper than the classically performed ones. There are also cases where stenting is used as a palliative treatment, e.g., to enable defecation in colonic obstruction due to tumour infiltration of the colon wall. Stenting is often a life-saving or comfort-improving procedure for animals, but one should also be aware of possible postoperative complications and be prepared for any adversity. For this reason, this review provides an insight into the current knowledge in veterinary medicine about stenting and the consequences associated with this procedure.

A New Removable Helical Metallic Stent for the Treatment of Tracheomalacia in Children: Study in Pathological Animal Model

BACKGROUND

Congenital tracheomalacia is a pathology with no consensus of medical or surgical approach. The permanent nature and the major complications associated with metallic stents have limited their use over the years. The purpose of this study was to evaluate the feasibility of a helical stent design removal.

METHODS

Ten dogs diagnosed with tracheal collapse and treated with the helical stent were involved in the study. Animals were classified into three groups depending on stent indwelling time. Prior to the removal, endoscopic evaluation was performed to assess endothelization grade, mucous accumulation, and the presence of stenosis. During the removal, bleeding, fracture, or impossibility of removal were noted. After the removal, all macroscopic mucosal changes were recorded.

RESULTS

Technical success was 100%, without any complications. Complete epithelization of the stent was visualized in 7/10 animals. The removal procedure duration ranged from 2-12 min. At post-removal endoscopy, bleeding or epithelial damage, was visualized in any case. Stent fracture during removal occurred in one animal.

CONCLUSIONS

The removal of a metallic stent with spiral geometry is feasible, simple, and without complications, regardless of the degree of neo-epithelialization.

Surgical outcomes in dogs with tracheal collapse treated with a novel cross-and-hook braided endoluminal stent

Background

Stenting is an effective treatment option for tracheal collapse in dogs. Cross-braided tracheal stents are currently the norm in veterinary medicine, but cross-and-hook braided stents have recently been adopted in human medicine. We examined whether stents manufactured using this novel braiding technique provided additional advantages for the treatment of tracheal collapse in dogs.

Objectives

To evaluate the outcomes of cross-and-hook braided stent implantation in the treatment of tracheal collapse in dogs.

Methods

The medical records of 22 client-owned dogs that underwent luminal placement of cross-and-hook braided Fauna Stents for the treatment of tracheal collapse between January 2018 and July 2021 were examined and data on canine signalment, clinical signs, diagnostic test results, surgical outcomes, and postoperative complications were retrieved and analyzed statistically.

Results

Twenty-six stents were surgically implanted, with 20 dogs (90.9%) receiving one stent and the remaining two (9.1%) receiving two or more stents. All dogs survived the procedure. The median survival time at a median follow-up of 990 days was 879 days. At the final follow-up examination, loss or mild improvement of cough was observed in all dogs.

Conclusions

Compared with conventional lumen stents, the cross-and-hook braided Fauna Stent offered a higher survival rate and improved clinical symptoms in all patients. The results of this study suggest that the Fauna Stent may be a promising treatment option for dogs with tracheal collapse.

State of the Science in Tracheal Stents: A Scoping Review

OBJECTIVE

Recent material science advancements are driving tracheal stent innovation. We sought to assess the state of the science regarding materials and preclinical/clinical outcomes for tracheal stents in adults with benign tracheal disease.

METHODS

A comprehensive literature search in April 2021 identified 556 articles related to tracheal stents. One-hundred and twenty-eight full-text articles were reviewed and 58 were included in the final analysis. Datapoints examined were stent materials, clinical applications and outcomes, and preclinical findings, including emerging technologies.

RESULTS

In the 58 included studies, stent materials were metals (n = 28), polymers (n = 19), coated stents (n = 19), and drug-eluting (n = 5). Metals included nitinol, steel, magnesium alloys, and elgiloy. Studies utilized 10 different polymers, the most popular included polydioxanone, poly-l-lactic acid, poly(d,l-lactide-co-glycolide), and polycaprolactone. Coated stents employed a metal or polymer framework and were coated with polyurethane, silicone, polytetrafluoroethylene, or polyester, with some polymer coatings designed specifically for drug elution. Drug-eluting stents utilized mitomycin C, arsenic trioxide, paclitaxel, rapamycin, and doxycycline. Of the 58 studies, 18 were human and 40 were animal studies (leporine = 21, canine = 9, swine = 4, rat = 3, ovine/feline/murine = 1). Noted complications included granulation tissue and/or stenosis, stent migration, death, infection, and fragmentation.

CONCLUSION

An increasing diversity of materials and coatings are employed for tracheal stents, growing more pronounced over the past decade. Though most studies are still preclinical, awareness of tracheal stent developments is important in contextualizing novel stent concepts and clinical trials. Laryngoscope, 2021.

The Effects of Mycophenolate on the Formation of Granulation Tissue Post-operatively in Canine Tracheal Stent Patients (2014-2020)

Objectives: To determine if mycophenolate mofetil reduces the incidence and severity of granulation tissue in-growth in canine tracheal stent patients. Study design: Randomized clinical trial. Animals: 111 dogs from the hospital population. Methods: Client-owned dogs that received an endoluminal self-expanding tracheal stent for canine tracheal collapse between 2014 and 2020 were randomly assigned into one of two treatment groups. Control group medication protocol consisted of prednisone 0.5 mg/kg PO BID/SID/EOD × 30 days, hydrocodone 0.25 mg/kg PO TID × 30 days, and cefovecin 8 mg/kg SQ post-placement. Mycophenolate group medication protocol was identical to the control group medication protocol with the addition of mycophenolate mofetil 10 mg/kg PO BID × 30 days, SID for life. Recheck tracheoscopy was performed at 1, 3, and 6 months post-stent placement. Presence and severity of granulation tissue were determined by tracheoscopy and were recorded as a percentage of tracheal lumen obstruction by blinded evaluators (none present, <25%, >25-50%, and >50%). Results: At none of the three time points was there a statistically significant difference in grade between controls and those receiving mycophenolate (p = 0.467, p = 0.330, and p = 0.410). Conclusions and Clinical Significance: Our results suggest that mycophenolate can be safely given to these patients but do not support that its administration will reduce the incidence and severity of granulation tissue. Although a difference was observed in the severity of granulation tissue between the two groups, loss to follow-up may have influenced conclusions. A larger study would be warranted to further evaluate the effect of mycophenolate on the development of granulation tissue.

An Update on Tracheal and Airway Collapse in Dogs

Tracheal and airway collapse (bronchomalacia) are common causes of chronic cough in middle-aged to older dogs in which weakening of cartilage within the respiratory system leads to narrowing of airways, irritation, inflammation, partial to complete airway obstruction, and other secondary effects. Tracheomalacia occurs in small-breed dogs, whereas bronchomalacia can occur in any size dog. Successful treatment involves correct identification of the problem, recognition of concurrent disease processes, and appropriate medical therapy. Surgical intervention and intraluminal stenting are readily available so it is important to understand indications for such procedures.

Correlations among tracheal dimensions, tracheal stent dimensions, and major complications after endoluminal stenting of tracheal collapse syndrome in dogs

Background

Endoluminal tracheal stenting can relieve signs associated with tracheal collapse syndrome (TCS) in dogs, but major complications can result.

Objective

To identify associations among tracheal dimensions, stent dimensions, and subsequent complications requiring additional stent placement after endoluminal stenting for TCS.

Animals

Fifty‐two dogs from the hospital population.

Methods

Medical records of dogs that received an endoluminal self‐expanding tracheal stent for TCS by the interventional radiology service between 2009 and 2014 were reviewed for relevant data. Signalment and clinical details, including tracheal collapse type, tracheal measurements, nominal stent dimensions, follow‐up evaluation times, and stent complications, were recorded.

Results

Fifty‐two dogs that received an endoluminal stent for TCS met the inclusion criteria. Major complications included stent fracture (13/52; 25%), obstructive tissue ingrowth (10/52; 19%), and progressive tracheal collapse (6/52; 12%). Natural tracheal taper (P = .04) and more stent diameter oversizing (P = .04) in the intrathoracic (IT) trachea were associated with caudodorsal stent fracture. Only stents with a 14‐mm nominal diameter fractured. Progressive tracheal collapse was associated with smaller maximum tracheal diameters (P = .02). The majority of dogs with obstructive tissue ingrowth (7/10; 70%; P = .30) and all dogs with thoracic inlet fractures (3/3; 100%) had tracheal malformations.

Conclusions and Clinical Importance

A higher taper in tracheal diameter may lead to increased risk of fracture in the IT location. Dogs with tracheal malformations may have higher risk for thoracic inlet fracture and development of obstructive tissue ingrowth. Clinicians should be aware of the possible risk factors for tracheal stent complications.