Gastrointestinal Radiology > Procedures > Metal Stents > Metal Stents (1)


Self-Expanding Metal Stents for Treatment of Esophageal Strictures and Esophagorespiratory Fistulas

Materials

At the time of this writing, several stent types are being commercially manufactured and  approved by the Federal Drug Administration for sale in the United States.  The use of these stents is presently restricted to treatment of esophageal strictures caused by malignant neoplasms.  The use of stents for benign lesions is currently not sanctioned by the FDA.

  • Ultraflex™ Esophageal Stent (Medi-tech or Microvasive, Boston Scientific Corp., Natick, MA.) is also know as the Nitinol, Strecker™, or Elastalloy™ stent.  This self-expanding, metal-mesh stent is made of knitted 0.15-mm nitinol (nickel-titanium alloy) wire.  The ends of the stent have smooth, looped wires with a special coating to reduce trauma to the esophageal wall.  The stent is flexible in its long axis, and has exceptional cross-sectional elasticity.  The fully expanded stent measures 18 mm in diameter.  Its proximal end is flared into a 5-mm long collar with a 21-mm diameter to provide fixation to the esophageal wall.  It is manufactured in lengths of 7 cm, 10 cm, and 15 cm.  The stent comes from the manufacturer in a sterile package and compressed inside its delivery system.  It is wrapped around the distal end of a 95-cm-long catheter that accepts an 0.038-inch guidewire.  The catheter has an olive-shaped widening distal to the stent and a 4-cm-long soft tip to reduce trauma during placement.  To minimize the diameter of the stent at insertion, it is longitudinally stretched, circumferentially compressed, and embedded in gelatin.  The catheter and compressed stent are then encased with an 8-mm (24-F) Teflon outer sheath.  Also available is a silicone-covered Ultraflex™ Esophageal Stent.

  • Wallstent® Esophageal Prosthesis (Schneider USA Inc., Plymouth, MN) is a self-expanding, flexible, compliant stent composed of a superalloy monofilament wire braided into a tubular mesh configuration   A proprietary silicone membrane is sandwiched between inner and outer layers of the mesh to inhibit tumor ingrowth or occlude an esophageal fistula.  The body of the stent has an 18-mm lumen and a 20-mm outer diameter.  The stent ends are flared to a diameter of 28 mm and are left uncovered to better anchor the device to the esophageal wall and retard stent migration.  This stent is currently available in three lengths:  8 cm, 10 cm, and 13 cm..  The stent delivery system of coaxial tubes has a diameter of 38 F and accommodates an 0.038-inch guidewire.

  • Silicone-covered Song modification of the Gianturco Z-stent (Sooho Medi-tech, Seoul, Korea).  This self-expanding stent is constructed of 0.3-0.5 mm stainless steel wire in a cylindrical zig-zag configuration of eight wires in diameters ranging from 14 mm to 20 mm and a length of 2 cm.  Two to 5 stent segments are connected together to form a barrel stent of the desired length.  Larger (22 mm) diameter segments, constructed of 10 wires each, are attached with metal struts to the proximal and distal ends of the “barrel”.  These expanded ends are designed to keep the stent from sliding upward or downward in the esophagus following deployment.  A nylon mesh is wrapped around the outside of the stent and covered with silicone rubber to inhibit tumor ingrowth or occlude an esophageal fistula.  The stent tube is compressed and inserted into a 12 mm introducer tube with a 8 mm pusher catheter

 


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