Types of Stents Used in Veterinary Medicine: Comparison
View Latest Version
Please note this is a comparison between Version 2 by Jessie Wu and Version 1 by Szymon Graczyk.

Stents are tubular ducts made of non-invasive materials designed to maintain the continuous flow of air through the airway lumen, or various types of fluid in the case of the urinary and circulatory systems. Stenting in veterinary medicine has been a rapidly growing method of interventional surgery. 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. 

  • stent
  • obstruction
  • dog

1. Introduction

Their use in medicine has become increasingly important since 1986, when one of the first self-expandable stents was implanted in coronary arteries with long-term positive results [1]. At the same time, stenting was being attempted in dogs but with unsatisfactory results [2,3][2][3]. This encouraged researchers to explore new possibilities for the use of stents in human medicine and later in veterinary medicine. They have become an attractive alternative for several procedures, including tracheal collapse or urinary tract obstruction [4[4][5][6],5,6], due to the reduction in adverse effects compared to previous procedures. Stents have also found application in procedures where traditional methods have become ineffective due to the atypical morphology of the structure in question, e.g., during the occurrence of a persistent arterial duct with two different diameters at the ends of the vessel [7]. Stent placement has also found its way into palliative treatment, which has significantly alleviated the clinical symptoms of concomitant disease, i.e., in the case of stenting of a part of the colon affected by mucosal cancer, making defecation difficult [8]. The locations of the described stent sites are shown in Figure 1.
Materials 16 01480 g001 550
Figure 1.
Use of stents in the treatment of canine and feline diseases.
Currently, stents made of different types of materials, including various metallic, polymeric, and silicone materials, as well as biodegradable fibres, are used in veterinary medicine [9,10][9][10]. In new generations of stents, these materials are coated with various types of layers that perform additional functions. These include stents that release immunomodulatory drugs (paclitaxel, biolimus, sirolimus, arsenic trioxidate, or zotarolimus) or antibiotics (cefotaxime, triclosan), which are particularly useful in highly invasive procedures that often induce inflammation [10,11,12,13,14,15,16,17,18,19][10][11][12][13][14][15][16][17][18][19]. The most commonly used seems to be the self-expandable nitinol stent (nickel-titanium alloy with a ratio of 55:45%) with different types of plexus, as shown in Figure 2 [20]. In favour of its use is spontaneous passivation, which prevents corrosion of the material and significantly increases its biocompatibility with surrounding tissues [21]. Passivation is a chemical process that generally only affects metals and involves the production of a film by reaction with the surrounding environment. This thin layer insulates the stent and makes it neutral to the organism. In addition to choosing the right type of stent, the size of the stent is also very important. In determining the diameter of stents, a scale defined by the French surgical instrument maker Joseph-Frédéric-Benoît Charrière is commonly used [22]. The abbreviation CH, or Ch, from his last name, was used to refer to the unit of measurement, but nowadays it is more common to use the abbreviation from the French word ‘Fr’ or ‘FR’. The abbreviations ‘Fg’ or ‘F’ may also be encountered, although these are rarely used. This unit defines the outer diameter of the catheter. To convert the diameter of the catheter into millimetres, the French size is divided by 3 (1 mm = 3 Fr).
Materials 16 01480 g002 550
Figure 2. (A) Tracheal stenting kit containing a nitinol stent with a cross-braid and a measure to assess the tracheal length. (B) View of the initial stent deployment process. (C–E) Different views of the fully expanded stent. The photographs come from the private archives of Dr Dariusz Jagielski.

2. Types of Stents 

The selection of proper material in relation to the stent placement site has enormous significance. The creation of the ideal stent has been a priority in interventional surgery for more than 30 years, but it is still difficult to combine all the characteristics that meet this criterion: elasticity, biocompatibility, thermostability, resistance to pressure forces, and a lack of reaction to surrounding tissue. Its properties determine the subsequent possibility of postoperative complications, which sometimes necessitate a second procedure. Currently, the most commonly used metal material in veterinary medicine is nitinol. It has gained its popularity due to two important characteristics, super-elasticity and shape memory. The super-elasticity of nitinol stents is defined by their incredible ability to adapt their shape in relation to the high mobility of a given structure, such as a vessel or trachea [24][23]. However, in some cases, defects related to stent flexibility are still reported, as in the case of peripheral artery disease in humans during stenting of the femoro-popliteal arteries [25][24]. Although in animals there is no predilection for atherosclerotic plaque accumulation in vessels, the site associated with high mobility is the trachea during rapid head movements, especially in impulsive dogs [26][25]. Shape memory, on the other hand, prevents any deformation of the stent due to the high temperature > 20 °C, thus disallowing any shape change after insertion due to the constant body temperature of the animals [24][23]. Another equally important property is its biocompatibility with surrounding tissues, which prevents inflammatory reactions and responses [24][23]. Other metals are not as common as nitinol, however, the use of materials such as stainless steel or elgiloy, which has very similar properties, has been reported [27,28][26][27].
Polymeric fibres are a forward-looking material used in human medicine and, more importantly, in veterinary medicine. In animals, they are used for urinary tract stenting with double-pigtail stents or for stenting the blood vessel wall with drug-eluting stents, which can be temporary—biodegradable—or permanent. Polymer stent materials include polyurethane, silicone, poly-lactide-co-glycolide, or l-lactide-glycolic acid copolymer [29][28]. Maintaining vessel patency in animals is rarely performed because vessel wall obstruction in animals generally occurs when other structures such as cancerous tumours are compressed [30][29]. In humans, the problem is much more exacerbated due to a predilection for the accumulation of atherosclerotic plaques concentrating on the inner vessel wall, leading to stenosis of the vessel lumen [31][30]. Stenting of the urinary tract is observed much more frequently in everyday veterinary practice and polymeric materials are the main raw material for ureteral stents. Postoperative complications related to restenosis, stent migration, or tissue encrustation are still a major problem. For this reason, developers are looking for newer and better solutions, with an emphasis on greater biocompatibility, durability, and flexibility. Future solutions using biodegradable polymers or metal drug-eluting stents for specific conditions are being considered [32][31]. However, the use of drug-eluting stents in veterinary medicine is poorly understood and requires much research into their efficacy and performance in animals, as evidenced by the small amount of documented work in this area. Materials for the production of stents in veterinary medicine are listed in Table 1. The data presented suggest that nitinol is the most commonly used material, mainly used for stenting of the respiratory tract, urethra, and some vessels, but in the latter case, it is much less common. This choice is undoubtedly due to the properties of nitinol described above, as well as the many papers available in the literature on efficacy and post-operative complications, which only confirms that nitinol may be the principal material for stents. The choice of this material in the context of ureteral stenting is not so obvious anymore, as the most commonly used materials in this type of surgery are polymeric fibres, mainly polyethylene. However, there is still too little information available on the efficacy of biodegradable and drug-eluting stents in the context of successful therapy and the impact on the animal body, which should certainly become a topic for future research.
Table 1.
Materials and composites used in the fabrication of stents, including the site of insertion in different animal species.
Type of Stent Stent Material Stent Placement Site Animal Author
Metallic Nitinol Trachea Dog [33][32]

[34][33]

[35][34]

[36][35]

[26][25]

[37][36]

[28][27]

[38][37]

[39][38]
Urethra Dog [40][39]

[41][40]

[42][41]

[43][42]
Colon Dog [8]
Azygos vein Dog [44][43]
Hepatic vein Dog [45][44]
Caudal Vena Cava Dog [46][45]
Elgiloy Trachea Dog [28][27]
Biodegradable Polylactide Bile ducts Dog [13]
Polydioxanone Bile ducts Porcine [14]
Polycaprolactone Trachea Rabbit [15]
Polymeric Polyethylene Ureter Cat [47][46]

[48][47]

[49][48]

[50][49]
Ureter Dog [51][50]

[52][51]

[6]

[53][52]
Silicone Medical-grade silicone Larynx Dog [16]
Drug eluting Paclitaxel Coronary artery

Iliac artery		 Porcine

Rabbit		 [12]
Bile ducts Dog [13]
Bile ducts Porcine [14]
Zotarolimus Coronary artery

Iliac artery		 Porcine

Rabbit		 [12]
Biolimus/sirolimus Coronary artery Porcine [11]
Iliac artery Rabbit [12]
Femoral artery Dog [17]
Cefotaxime Bile ducts Dog [19]
Arsenic trioxide Iliac artery Rabbit [10]
Triclosan Ureter Rabbit [18]

References

  1. Sigwart, U.; Puel, J.; Mirkovitch, V.; Joffre, F.; Kappenberger, L. Intravascular Stents to Prevent Occlusion and Re-Stenosis after Transluminal Angioplasty. N. Eng. J. Med. 1987, 316, 701–706.
  2. Stone, E.A.; Withrow, S.J.; Page, R.L.; Schwarz, P.D.; Wheeler, S.L.; Iii, H.B.S. Ureterocolonlc Anastomosis in Ten Dogs with Transitional Cell Carcinoma. Vet. Surg. 1988, 17, 147–153.
  3. Peterson, S.L.; Smith, M.M.; Senders, C.W. Evaluation of a stented laryngoplasty for correction of cranial glottic stenosis in four dogs. J. Am. Vet. Med. Assoc. 1987, 191, 1582–1584.
  4. Raske, M.; Weisse, C.; Berent, A.C.; McDougall, R.; Lamb, K. Immediate, Short-, and Long-Term Changes in Tracheal Stent Diameter, Length, and Positioning after Placement in Dogs with Tracheal Collapse Syndrome. J. Vet. Intern. Med. 2018, 32, 782–791.
  5. Lulich, J.P. Evaluation of Temporary Urethral Stents in the Management of Malignant and Nonmalignant Urethral Diseases in Dogs. Vet. Sci. 2022, 9, 63.
  6. Kuntz, J.A.; Berent, A.C.; Weisse, C.W.; Bagley, D.H. Double Pigtail Ureteral Stenting and Renal Pelvic Lavage for Renal-Sparing Treatment of Obstructive Pyonephrosis in Dogs: 13 Cases (2008–2012). J. Am. Vet. Med. Assoc. 2015, 246, 216–225.
  7. Patata, V.; Scalise, F.; Sorropago, G.; Marchesotti, F.; Nicoli, S.; Auriemma, E.; Rondelli, V.; Pesaresi, M.; Glaus, T.M.; Baron Toaldo, M.; et al. Closure of an Unusual Morphology Patent Ductus Arteriosus with a Covered Stent in a Dog. J. Vet. Cardiol. 2020, 32, 7–15.
  8. Culp, W.T.N.; MacPhail, C.M.; Perry, J.A.; Jensen, T.D. Use of a Nitinol Stent to Palliate a Colorectal Neoplastic Obstruction in a Dog. J. Am. Vet. Med. Assoc. 2011, 239, 222–227.
  9. Balsa, I.M.; Culp, W.T.; Palm, C.A.; Hopper, K.; Hardy, B.T.; Ben-Aderet, D.G.; Mayhew, P.D.; Drobatz, K.J. Factors associated with postobstructive diuresis following decompressive surgery with placement of ureteral stents or subcutaneous ureteral bypass systems for treatment of ureteral obstruction in cats: 37 cases (2010–2014). J. Am. Vet. Med. Assoc. 2019, 254, 944–952.
  10. Yang, W.; Ge, J.; Liu, H.; Zhao, K.; Liu, X.; Qu, X.; Li, W.; Huang, Y.; Sun, A.; Zou, Y. Arsenic trioxide eluting stent reduces neointima formation in a rabbit iliac artery injury model. Cardiovasc. Res. 2006, 72, 483–493.
  11. Hagiwara, H.; Hiraishi, Y.; Terao, H.; Hirai, T.; Sakaoka, A.; Sasaki, M.; Murota, S.; Inoue, K.; Kimura, J. Vascular responses to a biodegradable polymer (polylactic acid) based biolimus A9-eluting stent in porcine models. EuroIntervention 2012, 8, 743–751.
  12. Nakazawa, G.; Finn, A.V.; John, M.C.; Kolodgie, F.D.; Virmani, R. The significance of preclinical evaluation of sirolimus-, paclitaxel-, and zotarolimus-eluting stents. Am. J. Cardiol. 2007, 100, 36–44.
  13. Shi, J.; Lv, Y.; Yu, L.; Zhang, B.; Zhang, X.; Fan, C.; Geng, Z. Interest of a New Biodegradable Stent Coated with Paclitaxel on Anastomotic Wound Healing after Biliary Reconstruction. Eur. J. Gastroenterol. Hepatol. 2013, 25, 1415–1423.
  14. Grolich, T.; Crha, M.; Novotný, L.; Kala, Z.; Hep, A.; Nečas, A.; Hlavsa, J.; Mitáš, L.; Misík, J. Self-Expandable Biodegradable Biliary Stents in Porcine Model. J. Surg. Res. 2015, 193, 606–612.
  15. Liu, K.S.; Liu, Y.H.; Peng, Y.J.; Liu, S.J. Experimental Absorbable Stent Permits Airway Remodeling. J. Thorac. Cardiovasc. Surg. 2011, 141, 463–468.
  16. Théron, M.L.; Lahuerta-Smith, T. Laryngeal Silicone Stent as a Treatment Option for Laryngeal Paralysis in Dogs: A Preliminary Study of 6 Cases. J. Vet. Sci. 2022, 23, e58.
  17. Hou, R.; Wu, L.; Wang, J.; Yang, Z.; Tu, Q.; Zhang, X.; Huang, N. Surface-Degradable Drug-Eluting Stent with Anticoagulation, Antiproliferation, and Endothelialization Functions. Biomolecules 2019, 9, 69.
  18. Cadieux, P.A.; Chew, B.H.; Knudsen, B.E.; DeJong, K.; Rowe, E.; Reid, G.; Denstedt, J.D. Triclosan Loaded Ureteral Stents Decrease Proteus Mirabilis 296 Infection in a Rabbit Urinary Tract Infection Model. J. Urol. 2006, 175, 2331–2335.
  19. Gwon, D.; Lee, S.S.; Kim, E.Y. Cefotaxime-Eluting Covered Self-Expandable Stents in a Canine Biliary Model: Scanning Electron Microscopic Study of Biofilm Formation. Acta Radiol. 2012, 53, 1127–1132.
  20. Stoeckel, D.; Pelton, A.; Duerig, T. Self-Expanding Nitinol Stents: Material and Design Considerations. Eur. Radiol. 2004, 14, 292–301.
  21. Wever, D.J.; Veldhuizen, A.G.; De Vries, J.; Busscher, H.J.; Uges, D.R.A.; Van Horn, J.R. Electrochemical and surface characterization of a nickel–titanium alloy. Biomaterials 1998, 19, 761–769.
  22. Iserson, K.V.J.-F.-B. Charrière: The Man behind the “French” Gauge. J. Emerg. Med. 1987, 5, 545–548.
  23. Stöckel, D. Nitinol-A material with unusual properties. Endovasc. Upd. 1998, 1, 1–8.
  24. Maleckis, K.; Anttila, E.; Aylward, P.; Poulson, W.; Desyatova, A.; MacTaggart, J.; Kamenskiy, A. Nitinol Stents in the Femoropopliteal Artery: A Mechanical Perspective on Material, Design, and Performance. Ann. Biomed. Eng. 2018, 46, 684–704.
  25. Woo, H.M.; Kim, M.J.; Lee, S.G.; Nam, H.S.; Kwak, H.H.; Lee, J.S.; Park, I.C.; Hyun, C. Intraluminal Tracheal Stent Fracture in a Yorkshire Terrier. Can. Vet. J. 2007, 48, 1063–1066.
  26. Lopez-Minguez, S.; Serrano-Casorran, C.; Guirola, J.A.; Rodriguez-Zapater, S.; Bonastre, C.; De Gregorio, M.A. New Tracheal Stainless Steel Stent Pilot Study: Twelve Month Follow-up in a Rabbit Model. PeerJ 2019, 7, e7797.
  27. Violette, N.P.; Weisse, C.; Berent, A.C.; Lamb, K.E. Correlations among Tracheal Dimensions, Tracheal Stent Dimensions, and Major Complications after Endoluminal Stenting of Tracheal Collapse Syndrome in Dogs. J. Vet. Intern. Med. 2019, 33, 2209–2216.
  28. Liatsikos, E.N.; Kallidonis, P.; Stolzenburg, J.U.; Karnabatidis, D. Ureteral Stents: Past, Present and Future. Expert Rev. Med. Devices 2009, 6, 313–324.
  29. Baek, J.H.; Kim, B.M.; Heo, J.H.; Kim, D.J.; Nam, H.S.; Kim, Y.D. Outcomes of Endovascular Treatment for Acute Intracranial Atherosclerosis-Related Large Vessel Occlusion. Stroke 2018, 49, 2699–2705.
  30. Taylor, S.; Rozanski, E.; Sato, A.F.; Rush, J.E. Vascular Stent Placement for Palliation of Mass-Associated Chylothorax in Two Dogs. J. Am. Vet. Med. Assoc. 2017, 251, 696–701.
  31. Lange, D.; Bidnur, S.; Hoag, N.; Chew, B.H. Ureteral stent-associated complications—Where we are and where we are going. Nat. Rev. Urol. 2015, 12, 17–25.
  32. Mittleman, E.; Weisse, C.; Mehler, S.J.; Lee, J.A. Fracture of an Endoluminal Nitinol Stent Used in the Treatment of Tracheal Collapse in a Dog. J. Am. Vet. Med. Assoc. 2004, 225, 1217–1221.
  33. Tinga, S.; Thieman Mankin, K.M.; Peycke, L.E.; Cohen, N.D. Comparison of Outcome After Use of Extra-Luminal Rings and Intra-Luminal Stents for Treatment of Tracheal Collapse in Dogs. Vet. Surg. 2015, 44, 858–865.
  34. Sura, P.A.; Krahwinkel, D.J. Self-Expanding Nitinol Stents for the Treatment of Tracheal Collapse in Dogs: 12 Cases (2001–2004). J. Am. Vet. Med. Assoc. 2008, 232, 228–236.
  35. Durant, A.M.; Sura, P.; Rohrbach, B.; Bohling, M.W. Use of Nitinol Stents for End-Stage Tracheal Collapse in Dogs. Vet. Surg. 2012, 41, 807–817.
  36. Yoon, H.Y.; Choi, J.W.; Kim, J.H.; Kim, J.H. Use of a Double-Wire Woven Uncovered Nitinol Stent for the Treatment of Refractory Tracheal Collapse in a Dog: A Case Report. Case Rep. Vet. Med. 2017, 62, 98–104.
  37. Serrano-Casorran, C.; Lopez-Minguez, S.; Rodriguez-Zapater, S.; Bonastre, C.; Guirola, J.A.; de Gregorio, M.A.A. New Airway Spiral Stent Designed to Maintain Airway Architecture with an Atraumatic Removal after Full Epithelization—Research of Feasibility and Viability in Canine Patients with Tracheomalacia. Pediatr. Pulmonol. 2020, 55, 1757–1764.
  38. Uemura, A.; Ozai, Y.; Hamabe, L.; Yoshida, T.; Tanaka, R. Surgical Outcomes in Dogs with Tracheal Collapse Treated with a Novel Cross-and-Hook Braided Endoluminal Stent. J. Vet. Sci. 2022, 23, e46.
  39. Blackburn, A.L.; Berent, A.C.; Weisse, C.W.; Brown, D.C. Evaluation of Outcome Following Urethral Stent Placement for the Treatment of Obstructive Carcinoma of the Urethra in Dogs: 42 Cases (2004–2008). J. Am. Vet. Med. Assoc. 2013, 242, 59–68.
  40. Radhakrishnan, A. Urethral Stenting for Obstructive Uropathy Utilizing Digital Radiography for Guidance: Feasibility and Clinical Outcome in 26 Dogs. J. Vet. Intern. Med. 2017, 31, 427–433.
  41. Arnold, S.; Weber, U. Urethral sphincter mechanism incompetence in male dogs. In Kirks Current Veterinary Therapy, 15th ed.; Bonagura, J.D., Twedt, D.C., Eds.; Elsevier Saunders: Philadephia, PA, USA, 2014; Volume 9, pp. 896–898.
  42. Weisse, C.; Berent, A.; Todd, K.; Clifford, C.; Solomon, J. Evaluation of Palliative Stenting for Management of Malignant Urethral Obstructions in Dogs. J. Am. Vet. Med. Assoc. 2006, 229, 226–234.
  43. Schlicksup, M.D.; Weisse, C.W.; Berent, A.C.; Solomon, J.A. Use of Endovascular Stents in Three Dogs with Budd-Chiari Syndrome. J. Am. Vet. Med. Assoc. 2009, 235, 544–550.
  44. Hoehne, S.N.; Milovancev, M.; Hyde, A.J.; demorais, H.A.; Scollan, K.F.; Nemanic, S. Placement of a Caudal Vena Cava Stent for Treatment of Budd-Chiari–like Syndrome in a 4-Month-Old Ragdoll Cat. J. Am. Vet. Med. Assoc. 2014, 245, 414–418.
  45. Monnet, E. Biliary Stenting. In Gastrointestinal Surgical Techniques in Small Animals, 1st ed.; Monnet, E., Smeak, D.D., Eds.; John Willey & Sons: Hoboken, NJ, USA, 2020; Volume 39, pp. 293–296.
  46. Wormser, C.; Clarke, D.L.; Aronson, L.R. Outcomes of Ureteral Surgery and Ureteral Stenting in Cats: 117 Cases (2006–2014). J. Am. Vet. Med. Assoc. 2016, 248, 518–525.
  47. Berent, A.C.; Weisse, C.; Beal, M.W.; Brown, D.C.; Todd, K.; Bagley, D. Use of Indwelling, Double-Pigtail Stents for Treatment of Malignant Ureteral Obstruction in Dogs: 12 Cases (2006–2009). J. Am. Vet. Med. Assoc. 2011, 238, 1017–1025.
  48. Beal, M.W. Interventional Management of Urethral Obstructions. Vet. Clin. N. Am. Small Anim. 2018, 48, 863–874.
  49. Wormser, C.; Clarke, D.L.; Aronson, L.R. End-to-End Ureteral Anastomosis and Double-Pigtail Ureteral Stent Placement for Treatment of Iatrogenic Ureteral Trauma in Two Dogs. J. Am. Vet. Med. Assoc. 2015, 247, 92–97.
  50. Defarges, A.; Berent, A.; Dunn, M. New alternatives for minimally invasive management of uroliths: Ureteroliths. Compend. Contin. Educ. Vet. 2013, 35, E4.
  51. Berent, A.C. Ureteral obstructions in dogs and cats: A review of traditional and new interventional diagnostic and therapeutic options. J. Vet. Emerg. Crit. Care 2011, 21, 86–103.
  52. Pavia, P.R.; Berent, A.C.; Weisse, C.W.; Neiman, D.; Lamb, K.; Bagley, D. Outcome of Ureteral Stent Placement for Treatment of Benign Ureteral Obstruction in Dogs: 44 Cases (2010–2013). J. Am. Vet. Med. Assoc. 2018, 252, 721–731.
More
© Text is available under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)
ScholarVision Creations
Feedback