It is also available in models that deploy from the proximal or distal end. Deployment from the proximal end can be a good choice for proximal esophageal lesions. However, after deployment, the stent shortens by 30–40% and its expansile force is somewhat weaker than other stents.22 With uncovered stents, tumor ingrowth selleck chemicals llc occurs in up to 36% of patients.33 The Ultraflex colonic stent is composed of nitinol, has a mid-body diameter of 25 mm and is available in lengths of 57–117 mm. The esophageal Z-stent is made of stainless steel and is fully covered with polyethylene. Stents are composed of interconnecting rows of open stainless

steel wires configured in a Z-pattern in long coated cylinders. The stent does not shorten on deployment and some models have a compressible valve that prevents reflux of gastric contents, often called the ‘windsock’ design.22 The colonic GPCR Compound Library concentration Z-stent is an uncovered stent with a mid-body diameter of 25 mm and is available in lengths from 40–120 mm. The stent cannot be deployed through-the-scope. The biliary Zilver stent is a nitinol stent that has recently

been developed in an attempt to overcome the limitations of the Gianturco-Rosch Z-stent which had large spaces between the wires that may have permitted more frequent tumor ingrowth. The entire stent is configured as one wire by cutting a nitinol alloy cylinder in a zigzag shape using a laser. The stent has a narrow delivery system (7 F), minimal shortening and is available in small diameters which

facilitate insertion into intrahepatic ducts. However, the expansile force is weaker than other products, radiopaque markers can be difficult to detect at fluoroscopy and there is limited opportunity to reposition the stent. Niti-S stents (Fig. 1b) are nitinol wires intertwined in a tight net-shaped cylinder with platinum radio-opaque markers at both ends. nearly Esophageal Niti-S stents are available as uncovered, covered and double stents. The latter consists of two layers, an inner polyurethane layer and an outer uncovered layer of nitinol wire. The stents have flares at both ends and have an inner diameter of 18 mm. The Niti-S stents shorten by about 35% upon deployment,34 but can be repositioned or removed. The ComVi-stent (Fig. 1c) is a combination of a covered and uncovered stent that incorporates a layer of polytetrafluoroethylene between two layers of nitinol. This is designed to minimize tumor ingrowth and at the same time to minimize the risk of migration. Various modifications including the D-type, T-type and Y-type have also been developed in order to facilitate the insertion of a second stent in patients with hilar tumors. However, insertion of the second stent is still technically difficult and the expansile force may be insufficient to facilitate bile drainage.35,36 The stents are composed of nitinol and are available for use in the upper esophagus, lower esophagus, stomach, duodenum, colon and bile duct.