Patent Publication Number: US-2023149191-A1

Title: Retrievable stent system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/863,161, filed Apr. 30, 2020, which is a continuation of U.S. patent application Ser. No. 15/936,651, filed Mar. 27, 2018, now U.S. Pat. No. 10,667,930, which claims priority to U.S. Provisional Application Ser. No. 62/477,737, filed Mar. 28, 2017, the entirety of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure pertains to medical devices, methods for manufacturing medical devices, and the use thereof. More particularly, the present disclosure pertains to stents designed to be removed from the body and methods for manufacturing and using such stents. 
     BACKGROUND 
     Implantable medical devices (e.g., expandable stents) may be designed to provide a pathway for digested material, blood, or other fluid to flow therethrough following a medical procedure. Further, some implantable medical devices may incorporate features that aid in fistula treatment, bypass procedures and/or anastomosis treatment. These medical devices may include radially or self-expanding stents which may be implanted transluminally via an endoscope. Additionally, some stents may be implanted in a variety of body lumens such as the esophageal tract, the gastrointestinal tract (including the intestine, stomach and the colon), tracheobronchial tract, urinary tract, biliary tract, vascular system, etc. 
     In some instances it may be desirable to design a stent which includes sufficient radial strength to maintain its positon within a body lumen while also having the ability to function as a passageway for food or other digested material to flow therethrough. However, in some stents, the compressible and flexible properties that assist in stent positioning may also result in a stent that has a tendency to migrate from its originally deployed position. For example, stents that are designed to be positioned in the esophageal or gastrointestinal tract may have a tendency to migrate due to peristalsis (i.e., the involuntary constriction and relaxation of the muscles of the esophagus, intestine, and colon which push the contents of the canal therethrough). Additionally, the generally moist and inherently lubricious environment of the esophagus, intestine, colon, etc. further contributes to a stent&#39;s tendency to migrate when deployed therein. One method to reduce stent migration may include exposing bare metal portions of the stent to the tissue of the body lumen. The stent scaffold may provide a structure that promotes tissue ingrowth into the interstices or openings thereof (e.g., the stent structure may promote a hyperplastic response). The tissue ingrowth may anchor the stent in place and reduce the risk of stent migration. 
     Additionally, while it is important to design stents that reduce the degree to which a stent migrates within a body lumen, it also important to design stents that may be easily removed and/or re-positioned from the body lumen post-deployment. Stents including bare portions (i.e., uncovered portions) designed to promote tissue ingrowth (e.g., to reduce stent migration as described above) may also be more difficult to remove once the tissue has anchored the stent in the body lumen. One method to reduce the force necessary to remove a stent from a body lumen may include positioning a covered, expandable secondary stent within the lumen of the primary (e.g., anchoring) stent. The radial expansion of the secondary stent within the lumen of the primary stent may cause the tissue ingrowth to recede, thereby reducing the force necessary to remove both the primary and secondary stents from the wall of the body lumen. Examples of secondary medical devices which are capable of being utilized with other medical devices are disclosed herein. 
     BRIEF SUMMARY 
     This disclosure provides design, material, manufacturing method, and use alternatives for medical devices. An example system for treating a body lumen includes a first stent. The first stent includes a first tubular scaffold, the first tubular scaffold including an inner surface. The first stent also includes an outer surface and a lumen extending therethrough and a liner disposed within the lumen of the first tubular scaffold, wherein the liner is configured to be radially spaced from the inner surface of the first tubular scaffold to permit tissue ingrowth along a portion of first tubular scaffold. The system also includes a second stent. The second stent includes a second tubular scaffold and a covering disposed on the second tubular scaffold, wherein the second stent is configured to be positioned within the first stent such that expansion of the second stent causes the tissue ingrowth to recede. 
     Alternatively or additionally to any of the embodiments above, wherein the second tubular scaffold is configured to expand radially outward, and wherein the radially outward expansion of the second tubular scaffold causes the tissue ingrowth to recede. 
     Alternatively or additionally to any of the embodiments above, wherein the first stent includes an inner surface having a first profile, and wherein the second stent includes an outer surface having a second profile, and wherein the first profile matches the second profile. 
     Alternatively or additionally to any of the embodiments above, wherein the second stent includes a first end region and a second end region, and wherein the first end region, the second end region, or both the first and second end regions have a flared portion. 
     Alternatively or additionally to any of the embodiments above, wherein the liner is configured to be radially spaced from a medial region of the first tubular scaffold to permit a tissue ingrowth region along the medial region, and wherein the second stent is configured to exert a radially outward expansion force along the tissue ingrowth region, wherein the radially outward expansion force is sufficient to cause the tissue ingrowth to recede. 
     Alternatively or additionally to any of the embodiments above, wherein the radially outward expansion force is 0.15 N or more. 
     Alternatively or additionally to any of the embodiments above, wherein the liner is configured to limit the amount of tissue ingrowth into the medial region of the tubular scaffold due to a hyperplastic response. 
     Alternatively or additionally to any of the embodiments above, wherein the tissue ingrowth region is formed between the inner surface of the tubular scaffold and an outwardly-facing surface of the liner. 
     Alternatively or additionally to any of the embodiments above, wherein the portion of the liner extending along the tissue ingrowth region is configured to deflect radially inward from the inner surface of the tubular scaffold. 
     Alternatively or additionally to any of the embodiments above, wherein the medial portion of the tubular scaffold includes a first inner diameter, and wherein the diameter of the liner along the tissue ingrowth region includes a second inner diameter, and wherein the second inner diameter is greater than 25% of the diameter of the first inner diameter. 
     Alternatively or additionally to any of the embodiments above, wherein the tissue to ingrowth region extends circumferentially around the inner surface of the tubular scaffold. 
     Alternatively or additionally to any of the embodiments above, wherein a medial region of the tubular scaffold of the second stent has an outer diameter in a radially expanded state of the second stent greater than an inner diameter along a medial region of the tubular scaffold of the first stent in a radially expanded state of the first stent. 
     Another system for treating the esophagus includes: 
     a first stent including:
         a first expandable scaffold, the first expandable tubular scaffold including an inner surface, an outer surface and a lumen extending therein; and   a liner disposed within the lumen of the first expandable scaffold, wherein the liner is configured to be radially spaced from a medial region of the first expandable scaffold to define a tissue ingrowth region along a portion of first expandable scaffold; and       

     a second stent including:
         a second expandable scaffold and a covering disposed on the second expandable scaffold;       

     wherein the second stent is configured to be positioned within the first stent such that expansion of the second stent causes the tissue ingrowth to recede along the tissue ingrowth region. 
     Alternatively or additionally to any of the embodiments above, wherein the second expandable scaffold is configured to expand radially outward, and wherein the radially outward expansion of the second expandable scaffold causes the tissue ingrowth to recede. 
     Alternatively or additionally to any of the embodiments above, wherein the second stent is configured to exert a radially outward expansion force along the tissue ingrowth region, wherein the radially outward expansion force is sufficient to cause the tissue ingrowth to recede. 
     Alternatively or additionally to any of the embodiments above, wherein the radially outward expansion force is 0.15 N or more. 
     Alternatively or additionally to any of the embodiments above, wherein the first stent includes an inner surface having a first profile, and wherein the second stent includes an outer surface having a second profile, and wherein the first profile matches the second profile. 
     Alternatively or additionally to any of the embodiments above, wherein the portion of the liner extending along the tissue ingrowth region is configured to deflect radially inward from the inner surface of the tubular scaffold. 
     Alternatively or additionally to any of the embodiments above, wherein the liner extends continuously within the lumen of the first expandable scaffold. 
     An example method of treating a body lumen includes: 
     advancing a retrieval stent into the lumen of an implanted stent disposed along an inner surface of the body lumen, wherein a portion of tissue defining the inner surface of the body lumen has grown into the implanted stent, and wherein the implanted stent includes:
         a liner disposed within the lumen of the implanted stent, wherein the liner is configured to be radially spaced from a medial region of the implanted stent to define a tissue ingrowth region along a portion of the implanted stent;       

     deploying the retrieval stent within the lumen of the implanted stent, wherein an outer surface of the retrieval stent exerts an outward radial force along the ingrown tissue region of the implanted stent, and wherein the retrieval stent causes the ingrown tissue to recede. 
     The above summary of some embodiments is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The Figures and Detailed Description, which follow, more particularly exemplify these embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure may be more completely understood in consideration of the following detailed description in connection with the accompanying drawings, in which: 
         FIG.  1    is an example stent; 
         FIG.  2    is a cross-sectional view of the stent of  FIG.  1    including a liner taken along line  2 - 2  of  FIG.  1   ; 
         FIG.  3    is a cross-sectional view of the stent of  FIG.  1    taken along line  3 - 3  of  FIG.  2   ; 
         FIG.  4    is a cross-sectional view of the stent of  FIG.  1    taken along line  4 - 4  of  FIG.  2   ; 
         FIG.  5    is a cross-sectional view of the stent of  FIG.  1    including a liner; 
         FIG.  6 A  is a cross-sectional view of another example stent including a liner and covered portions; 
         FIG.  6 B  is a cross-sectional view of another example stent including a liner and covered portions; 
         FIG.  7 A  is a cross-sectional view of another example stent including a liner and covered portions; 
         FIG.  7 B  is a cross-sectional view of another example stent including a liner and covered portions; 
         FIG.  8 A  is a plan view of another example stent including a liner and covered portions; 
         FIG.  8 B  is a plan view of another example stent including a liner; 
         FIG.  8 C  is a cross-sectional view of another example stent; 
         FIG.  9    is another example stent; 
         FIG.  10    is a cross-sectional view of the stent of  FIG.  9    taken along line  10 - 10  of  FIG.  9   ; 
         FIGS.  11 - 13    illustrate an example stent positioned in a body lumen undergoing a hyperplastic response; 
         FIGS.  14 - 17    illustrate an example method for deploying an example stent within another example stent; 
         FIG.  18    illustrates the retrieval of the example stent system illustrated in  FIGS.  14 - 17   . 
     
    
    
     While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the disclosure to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure. 
     DETAILED DESCRIPTION 
     For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification. 
     All numeric values are herein assumed to be modified by the term “about”, whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (e.g., having the same function or result). In many instances, the terms “about” may include numbers that are rounded to the nearest significant figure. 
     The recitation of numerical ranges by endpoints includes all numbers within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5). 
     As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise. 
     It is noted that references in the specification to “an embodiment”, “some embodiments”, “other embodiments”, etc., indicate that the embodiment described may include one or more particular features, structures, and/or characteristics. However, such recitations do not necessarily mean that all embodiments include the particular features, structures, and/or characteristics. Additionally, when particular features, structures, and/or characteristics are described in connection with one embodiment, it should be understood that such features, structures, and/or characteristics may also be used connection with other embodiments whether or not explicitly described unless clearly stated to the contrary. 
     The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the disclosure. 
     As discussed above, in some instances it may be designed to provide a pathway for digested material, blood, or other fluid to flow therethrough following a medical procedure. Further, some implantable medical devices may incorporate features that aid in fistula treatment, bypass procedures and/or anastomosis treatment. These medical devices may include radially or self-expanding stents which may be implanted transluminally via an endoscope. Additionally, some stents may be implanted in a variety of body lumens such as the esophageal tract, the gastrointestinal tract (including the intestine, stomach and the colon), tracheobronchial tract, urinary tract, biliary tract, vascular system, etc. 
     In some instances it may be desirable to design a stent which includes sufficient radial strength to maintain its positon within a body lumen while also having the ability to function as a passageway for food or other digested material to flow therethrough. However, in some stents, the compressible and flexible properties that assist in stent positioning may also result in a stent that has a tendency to migrate from its originally deployed position. For example, stents that are designed to be positioned in the esophageal or gastrointestinal tract may have a tendency to migrate due to peristalsis (i.e., the involuntary constriction and relaxation of the muscles of the esophagus, intestine, and colon which push the contents of the canal therethrough). Additionally, the generally moist and inherently lubricious environment of the esophagus, intestine, colon, etc. further contributes to a stent&#39;s tendency to migrate when deployed therein. One method to reduce stent migration may include exposing bare metal portions of the stent to the tissue of the body lumen. The stent scaffold may provide a structure that promotes tissue ingrowth (e.g., a hyperplastic response) into the interstices or openings thereof. The tissue ingrowth may anchor the stent in place and reduce the risk of stent migration. 
     Additionally, while it is important to design stents that reduce the degree to which a stent migrates within a body lumen, it also important to design stents that may be easily removed and/or re-positioned from the body lumen post-deployment. Stents including bare portions (i.e., uncovered portions) designed to promote tissue ingrowth (e.g., to reduce stent migration as described above) may also be more difficult to remove once the tissue has anchored the stent in the body lumen. One method to reduce the force necessary to remove a stent from a body lumen may include positioning a covered, expandable secondary stent within the lumen of the primary (e.g., anchoring) stent. The radial expansion of the secondary stent within the lumen of the primary stent may cause the tissue ingrowth to recede, thereby reducing the force necessary to remove both the primary and secondary stents from the wall of the body lumen. Examples of secondary medical devices which are capable of being utilized with other medical devices are disclosed herein. 
       FIG.  1    shows an example stent  10 . Stent  10  may have a first end  21 , a second end  23  and a lumen extending therein. When positioned in a body lumen (e.g., esophagus) first or proximal end  21  may be defined as the end of stent  10  closest to a patient&#39;s mouth and second or distal end  23  may be defined as the end of stent  10  closest to a patient&#39;s stomach. 
     Additionally, stent  10  may include one or more stent strut members  12  forming a tubular scaffold. Stent strut members  12  may extend helically, longitudinally, circumferentially, or otherwise along stent  10 . While  FIG.  1    shows stent strut members  12  extending along the entire length of stent  10 , in other examples, the stent strut members  12  may extend only along a portion of stent  10 . 
     Additionally,  FIG.  1    shows example stent  10  including a first flared end region  14  proximate the first end  21  and/or a second flared region  16  proximate the second end  23  of stent  10 . In some instances, first flared region  14  and second flared region  16  may be defined as an increase in the outer diameter, the inner diameter or both the inner and outer diameter along one or both of the first end  21  and/or second end  23  of stent  10 . Further,  FIG.  1    illustrates stent  10  including a medial region  18  positioned between first flared region  14  and second flared region  16 . 
     However, it is contemplated that while  FIG.  1    shows stent  10  including both a first flared region  14  and a second flared region  16 , stent  10  may only include one flared region. For example, it is contemplated that stent  10  may include only flared region  14  or flared region  16 . It is further contemplated that all or a portion of first flared region  14  and/or second flared region  16  may flare outwardly (e.g., away from the central, longitudinal axis of stent  10 ). Alternatively, it is further contemplated that all or a portion of first flared region  14  and/or second flared region  16  may flare inwardly (e.g., toward the central, longitudinal axis of stent  10 ). 
     In some instances, stent  10  may be a self-expanding stent or stent  10  may be a balloon expandable stent. Self-expanding stent examples may include stents having one or more struts  12  combined to form a rigid and/or semi-rigid stent structure. For example, stent struts  12  may be wires or filaments which are braided, wrapped, intertwined, interwoven, weaved, knitted, looped (e.g., bobbinet-style) or the like to form the stent structure. For example, while the example stents disclosed herein may resemble a braided stent, this is not intended to limit the possible stent configurations. Rather, the stents depicted in the Figures may be stents that are knitted, braided, wrapped, intertwined, interwoven, weaved, looped (e.g., bobbinet-style) or the like to form the stent structure. Alternatively, stent  10  may be a monolithic structure formed from a cylindrical tubular member, such as a single, cylindrical tubular laser-cut Nitinol tubular member, in which the remaining portions of the tubular member form the stent struts  12 . Openings or interstices through the wall of the stent  10  may be defined between adjacent stent struts  12 . 
     Stent  10  in examples disclosed herein may be constructed from a variety of materials. For example, stent  10  (e.g., self-expanding or balloon expandable) may be constructed from a metal (e.g., Nitinol, Elgiloy, etc.). In other instances, stent  10  may be constructed from a polymeric material (e.g., PET). In yet other instances, stent  10  may be constructed from a combination of metallic and polymeric materials. Additionally, stent  10  may include a bioabsorbable and/or biodegradable material. 
     In some instances, example stent  10  may include one or more layers positioned on and/or adjacent to the inner and/or outer surface of the tubular scaffold of stent  10 . For example,  FIG.  1    shows example stent  10  including an outer layer  22  (depicted as a dotted pattern in  FIG.  1   ) disposed along a portion of the outer surface of stent  10  (e.g., along the first flared portion  14  and/or the second flared portion  16  of stent  10 ). In some instances, outer layer  22  may be an elastomeric or non-elastomeric material. For example, outer layer  22  may be a polymeric material, such as silicone, polyurethane, or the like. 
     Additionally, example stent  10  may include one or more layers positioned on and/or adjacent to the inner surface of stent  10 . While not shown in  FIG.  1    (but shown in  FIG.  2   ), stent  10  may include an inner layer  20  disposed within the lumen of stent  10 . In some instances, inner layer  20  may be an elastomeric or non-elastomeric material. For example, inner layer  20  may be a polymeric material, such as silicone, polyurethane, UE, PVDF, Chronoflex® or similar biocompatible polymeric formulations. 
     It can be appreciated that as inner layer  20  and outer layer  22  extend outwardly and inwardly, respectively, they may touch and/or form an interface region within the spaces (e.g., openings, cells, interstices) in the wall of tubular scaffolding of stent  10 . Further, the inner layer  20  and outer layer  22  may additionally extend between adjacent struts  12 , thereby filling any space between adjacent strut members  12  of the tubular scaffold. Stent  10  may include areas in which one or more filaments  12  are surrounded, encased and/or covered by the outer layer  22  and/or inner layer  20 . For example, some portions of stent  10  may include filaments  12  which are sandwiched between outer layer  22  and inner layer  20 . 
       FIG.  2    shows a cross-section of example stent  10  along line  2 - 2  of  FIG.  1   .  FIG.  2    illustrates that first flared region  14  and/or second flared region  16  may include tapered portion  25  and end portion  27 . While  FIG.  2    shows tapered portions tapering radially outward toward ends of stent  10 , it is contemplated that one or more of tapered portions  25  may, alternatively, taper radially inward. 
       FIG.  2    further illustrates inner layer  20  extending along all or a portion of the inner surface  24  of stent  10 . For example,  FIG.  2    illustrates inner layer  20  extending along an inner surface of end portions  27 , tapered portions  25  and medial portion  18 . For purposes of the discussion herein, inner layer  20  may be interchangeably referred to as a liner, coating and/or covering. Liner  20  may extend circumferentially around the lumen of stent member  10 . In other words, it can be appreciated that liner  20  may be defined as an annular layer that extends continuously around the lumen of stent member  10 . Further, liner  20  may extend continuously (e.g., uninterrupted) around the lumen of stent  10 , from the first end  21  to the second end  23 . 
     As discussed above,  FIG.  2    illustrates stent  10  may include an outer layer  22  disposed along an outer surface  26  of stent  10 . For example, in some instances, stent  10  may include an outer layer  22  disposed along the outer surface of one or more of end portions  27 . 
     In some instances (such as that illustrated in  FIG.  2   ), outer layer  22  may be a continuous extension of inner layer  20 . For example,  FIG.  2    shows inner layer  20  extending along the inner surface  24  of end portions  27 , whereby inner layer  20  “wraps” over the end  28  of the end portion  27  and continues to extend along the outer surface of end portion  27 . It should be noted that, in this example, what has been described above as outer layer  22  may define the portion of the inner layer  20  which has “wrapped over” end  28  of tubular scaffold of stent  10  and further extends along the outer surface of end portion  27 . Further, both the inner layer  20 , and the portion of the inner layer  20  that wraps over end  28  of stent  10  to form outer layer  22  may, together, sandwich filaments  12  therebetween. Further, while  FIG.  2    illustrates inner layer  20  wrapping around (e.g., extending continuously around) both end portions  27  of stent  10  in  FIG.  2   , it is contemplated that inner layer  20  may wrap around only one end portion  27  of stent member  10 . 
       FIG.  2    illustrates that inner layer  20  may be fixedly attached to the inner surface of end portions  27  and/or tapered regions  25 . In other words,  FIG.  2    shows that inner layer  20  may be adhered (e.g., affixed, secured, etc.) to the inner surface of strut members  12  which define end portions  27  and/or tapered regions  25  of stent  10 . 
     Additionally,  FIG.  2    illustrates that, in some examples, a portion of inner layer  20  may be spaced away from (i.e., spaced radially inward of) the inner surface  24  of stent  10 , providing a gap or space therebetween. In particular,  FIG.  2    illustrates that the portion of inner layer  20  extending along the medial portion  18  of stent member  10  may be unattached to medial portion  18  of the tubular scaffold of stent  10  and spaced radially inward from the inner surface  24  of the tubular scaffold of stent  10 . For example,  FIG.  2    shows that liner  20  may be attached (e.g., circumferentially) at a first attachment point  30  and a second attachment point  32 , with the length of liner  20  between attachment points  30 / 32  remaining unattached (i.e., not directly attached) to the tubular scaffold of medial portion  18  of stent  10 .  FIG.  2    shows that inner layer  20  may be unattached to the inner surface  24  of the tubular scaffold (i.e., the struts  12 ) of stent  10  along a portion of stent  10  between first attachment point  30  and second attachment point  32 . It should be noted that the portion of stent  10  shown in  FIG.  2    in which inner layer  20  is unattached to the inner surface  24  of struts  12  of stent  10  may correspond to the medial portion  18  of stent  10  described above. In other words, in some examples, inner layer  20  may be unattached and thereby extend radially inward from the inner surface  24  of the tubular scaffold (i.e., struts  12 ) along the medial portion  18  of stent  10 . 
     As discussed above, stents that are designed to be positioned in a body lumen (e.g., esophageal or gastrointestinal tract) may have a tendency to migrate (due to peristalsis and/or the generally moist and inherently lubricious environment of the body lumens). Therefore, one method to reduce stent migration may include exposing tissue ingrowth promoting regions, such as uncovered and/or bare metal portions of the stent to the tissue of the body lumen. The uncovered or bare stent scaffold may provide a structure that promotes tissue ingrowth into the interstices or openings thereof. The tissue ingrowth may anchor the stent in place and reduce the risk of stent migration. 
     Accordingly, it can be appreciated that the portions of stent  10  discussed above which include an inner and/or outer layer which is attached (e.g., covers) stent struts or filaments  12  may act to prevent tissue from growing into the interstices or openings thereof. For example, the struts or filaments  12  of tapered regions  25  and end portions  27  of stent  10  which include inner layer  20  and/or outer layer  22  attached thereto to thereby span across interstices of the tubular scaffold may prevent tissue ingrowth along their respective surfaces and interstices therebetween. 
     However, it can be appreciated that tissue may be permitted to grow around, between, through, within, etc. those filaments  12  of stent  10  in which inner layer  20  is not attached (e.g., the portion of inner layer  20  extending along medial portion  18  of stent  10 ). In other words,  FIG.  2    illustrates a “tissue ingrowth region”  36  defined along medial region  18  of stent  10 . The detailed view of  FIG.  2    illustrates that tissue ingrowth region  36  may be extend radially inward from the inner surface  24  of stent member  10  to the outer surface  38  of inner liner  20 . The distance between the inner surface  24  of stent member  10  to the outer surface  38  of inner liner  20  may be depicted as “D 1 ” in  FIG.  2   . Distance “D 1 ” may be about 0.5 mm-10 mm, or about 1 mm-6 mm, or about 1.5 mm-4 mm, or about 2 mm. 
       FIG.  2    further illustrates that tissue ingrowth region  36  may be defined as the space between the inner surface  24  of the tubular scaffold of stent  10  and the outer surface  38  of liner  20  extending between attachment points  30 / 32 . Tissue ingrowth region  36  may be positioned between attachment points  30 / 32 . Thus, tissue ingrowth region  36  may be defined as a space between the inner surface  24  of the tubular wall defined by struts or filaments  12  of the stent  10  and the outer surface  38  of the wall of the inner layer  20  between the circumferential attachment points  30 / 32 . Further, tissue ingrowth region  36  may be defined as extending circumferentially within the lumen of the tubular scaffold of stent  10 . In other words, it can be appreciated that tissue ingrowth region  36  may be defined as an annular space that extends continuously around the lumen of the tubular scaffold formed by struts or filaments of stent  10  radially inward of the stent wall. 
     It can further be appreciated that liner  20  may be constructed from an elastic material in some instances. Accordingly, a liner  20  including an elastic material component may be able to stretch radially inward. For example, as tissue grows through the interstices of stent member  10 , it may push radially inward against the outer surface  38  of inner layer  20 . In response, inner layer  20  may deflect, stretch, etc. radially inward in response to inward forces (e.g., tissue ingrowth) acting thereupon. In particular, the space D 1  between the inner surface  24  of stent  10  and the outer surface  38  of liner  20  may increase as the liner  20  deflects radially inward. In other embodiments, the liner  20  may be inelastic and, therefore, may not deflect relative to stent  10 . 
     While liner  20  may include an elastic element permitting it to deflect radially inward from the inner surface  24  of the tubular scaffold of stent  10 , in some instances it may be desirable to limit the amount of deflection of inner layer  20 . For example,  FIG.  2    illustrates that inner layer  20  defines a lumen  40  extending therein. Lumen  40  may be designed to permit food and/or or other digestible material to flow therethrough. Therefore, in some instances it may be desirable to design inner layer  20  to preserve the passageway defined by lumen  40  to permit food and/or other digestible material to flow through stent  10  when implanted in a body lumen. In other words, it may be desirable in some instances to prevent lumen  40  from closing radially inward in on itself. In some instances the inner layer  20  may include reinforcing filaments (e.g., fibers) embedded in the material of the inner layer  20  that may be drawn taut after a threshold amount of stretching of the material of the inner layer  20  to prevent further stretching of the inner layer  20 . In some instances, the reinforcement filaments may be arranged longitudinally, circumferentially, helically, randomly, or otherwise arranged in the inner layer  20 . 
       FIG.  2    depicts an inner diameter of tubular scaffold of stent  10  along medial region  18  as “D 4 .” Further,  FIG.  2    depicts an inner diameter of inner liner  20  along medial region  18  as “D 2 .” Diameter “D 4 ” may be about 10 mm-30 mm, or about 15mm-25 mm, or about 20 mm, in some instances. Further, diameter “D 2 ” may be about 10 mm-30 mm, or about 15 mm-25 mm, or about 18 mm, in some instances. Additionally, in some instances, it may be desirable to design inner liner  20  such that the diameter “D 2 ” is greater than or equal to a given percentage of diameter “D 4 .” For example, in some instances diameter “D 2 ” may be greater than or equal to 10% of “D 4 ”, or greater than or equal to 25% of “D 4 ”, or greater than or equal to 50% of “D 4 ”, or greater than or equal to 60% of “D 4 ”, or greater than or equal to 75% of “D 4 ”,or “D 2 ” may be between 10-20% of “D 4 ”, or “D 2 ” may be between 20-30% of “D 4 ”, or “D 2 ” may be between 30-40% of “D 4 ”, or “D 2 ” may be between 40-50% of “D 4 ”, or “D 2 ” may be between 50-75% of “D 4 ”, or “D 2 ” may be between 75%-90% of “D 4 ”, in some instances. 
     It can be appreciated that limiting the amount of deflection of inner liner  20  may not only assure that lumen  40  remains open, but it also limits that amount of tissue ingrowth occurring along stent  10 . For example, by limiting the degree to which liner  20  may deflect radially inward along medial region  18 , the amount of tissue ingrowth occurring along medial  18  may be controlled. As discussed above, controlling the amount of tissue ingrowth occurring along stent  10  may be desirable because the amount of tissue ingrowth may directly correspond to the force necessary to remove stent  10  from a body lumen. In other words, the stent  10  maybe customized to have a given removal force by limiting the amount of elasticity (e.g., and thereby limiting the amount of radially inward deflection) of liner  20 . 
     As can be appreciated from  FIG.  2   , end portions  27  may include an inner diameter depicted as “D 3 .” Diameter “D 3 ” may be greater than or equal to diameter “D 2 .” Diameter “D 3 ” may be about 15 mm-35 mm, or about 20 mm-30 mm, or about 25 mm, in some instances. In other words, inner layer  20  may be generally shaped to taper longitudinally from the end portion  27  closest to first end  21  to the medial portion  18 . For example, the tapered portion  25  may bear some resemblance to a cone-shaped funnel. Further, as illustrated in  FIG.  2   , stent  10  may taper inwardly toward central longitudinal axis of stent  10  along flared portion  14  and may taper outwardly away from the central longitudinal axis of stent  10  along flared portion  16 . 
       FIG.  3    illustrates a cross-section along line  3 - 3  of  FIG.  2   . As described above, this cross-section is taken through end portion  27  of flared region  14 . As illustrated in  FIG.  3   , the filaments  12  of stent  10  defining end portion  27  may be sandwiched between inner layer  20  and outer layer  22 . In other words,  FIG.  3    illustrates that some portions of stent  10  (e.g., along flared region  14  and/or flared region  16 ), filaments  12  may have both inner layer  20  and outer layer  22  directly attached thereto. In other words, along some portions of stent  10  (e.g., along flared region  14  and/or flared region  16 ) no space may exist between filaments  12  and both inner layer  20  and outer layer  22 . 
       FIG.  4    illustrates a cross-section along line  4 - 4  of  FIG.  2   . As described above, this cross-section is taken through medial portion  18  of stent  10 . As illustrated in  FIG.  4   , the inner layer  20  of stent  10  may be spaced away from (i.e., radially inward of) filaments  12  of stent  10  along medial portion  18 . Further,  FIG.  4    illustrates tissue ingrowth region  36  extending between the inner surface  24  of filaments  12  of stent  10  and the outwardly-facing surface  38  of inner member  20 . Additionally,  FIG.  4    illustrates tissue ingrowth region  36  extending circumferentially around the longitudinal axis of stent  10  radially outward of liner  20  and radially inward of filaments  12  of the tubular scaffold. 
     While the above discussion disclosed examples in which inner layer  20  and outer layer  22  are fixedly attached (e.g., directly secured) to the end portions  27  and/or tapered portions  25 , other configurations are contemplated. For example,  FIG.  5    illustrates an example stent member  110 . Stent  110  may be similar in form and functionality to stent  10  described above. For example, stent  110  may include a liner  120  disposed within a lumen of the tubular scaffold of stent  110 . Further, as illustrated in  FIG.  5   , liner  120  may be circumferentially attached along the inner surface  124  of stent  110  at attachment point  130  and/or attachment point  132 . Attachment points  130 / 132  may be located at opposing end regions of stent  110 , such as in opposing flared end regions of stent  110 . 
     However,  FIG.  5    illustrates that different attachment point locations  130 / 132  are contemplated along stent member  110 . For simplicity purposes, example positions contemplated for attachment points  130 / 132  are depicted in terms of a distance from the end  128  of stent member  110 . For example, the attachment points  130 / 132  are depicted as being a distance “W” (as measured along the outer surface  126  of stent  110 ) from end  128 . In other examples, attachment points  130 / 132  may be positioned at distances depicted as “X,” “Y” and “Z” (as measured longitudinally from end  128  of stent  110 . Distance “Z” may be understood to be the equivalent attachment location of attachment points  30 / 32  along stent  110  described above. Additionally, in some examples distance “W” may be approximately 25% of distance “Z,” distance “X” may be approximately 50% of distance “Z” and distance “Y” may be approximately 75% of distance “Z.” 
     Additionally, it is contemplated that liner  120  may not be attached along the inner surface  124  of stent  110 . For example, attachment points  130 / 132  may be located at the end point  128  of stent  110 . Further, in instances where attachment points  130 / 132  are located at ends  128 , liner  120  may cover and or encapsulate the ends  128  of stent  110 . 
     It can be appreciated from  FIG.  5    that the different attachment point  130 / 132  along stent  110  may correspond to different size tissue ingrowth regions  136 (described above as tissue ingrowth region  36  of stent  10 ). For example, the tissue ingrowth section  136  defined by attachment point  130 / 132  located a distance “W” from end  128  may be larger than a tissue ingrowth region  136  defined by attachment point  130 / 132  located a distance “Y” from end  128 . For reasons discussed above, it can be appreciated that the larger tissue ingrowth regions may create a stent  110  which has increased removal forces. 
     Outer layer  122  may also extend any desired distance from end  128  of stent  110  along the outer surface of the tubular scaffold defined by filaments or struts  112 . For example, outer layer  122  may extend a distance depicted as “W,” “X,” “Y” or “Z” from end  128 . The distance outer layer  122  extends from end  128  of stent  110  may be the same or different than the distance for attachment points  130 / 132 . 
     While the above discussion of stent  10  and stent  110  illustrates a variety of attachment locations along stent  10 , it is contemplated that liner  20  may be attached at any location along the inner surface  24  and/or outer surface of stent member  10 . The different attachment locations may result in stents having different performance characteristics (e.g., different removal forces, different anti-migration properties). It is noted that the attachment distances shown in  FIG.  5    are equally applicable to the attachment point  132  at the opposite end of stent  110  and/or outer layer  122  at the opposite end of stent  110 . 
       FIGS.  6 A- 8 B  illustrate example stents that may be similar in form and function to the stent designs disclosed above. For example, each of the stents shown in  FIGS.  6 A- 8 B  may include an inner liner disposed within the lumen of the tubular scaffold of stent (e.g., as shown in  FIG.  2   ). Further, each of the stents shown in  FIGS.  6 A- 8 B  may also include an outer layer as described above (e.g., as shown in  FIG.  1   ) extending along at least a portion of the flared end regions of the tubular scaffold. However, the stents illustrated in  FIGS.  6 A- 8 B  may further include an additional outer layer (which could be formed separately or in conjunction with the outer layer disposed on the flared end regions and/or the inner layer) disposed along the outer surface of the medial portion of the stent, leaving a remainder of the tubular scaffold uncovered to promote tissue ingrowth therethrough. 
     For example,  FIG.  6 A  shows an example stent  210 . Example stent  210  that may be similar in form and function to the stent designs disclosed above. However, as  FIG.  6 A  illustrates, stent  210  includes additional outer layers  223  disposed along the outer surface  226  of the tubular scaffold of stent  210 .  FIG.  6 A  shows outer layers  223  as circumferential rings of material which may be positioned such that they extend circumferentially around the outer surface  226  of stent  210  (the dashed lines in  FIG.  6 A  depict the outer layers  223  extending circumferentially around the outer surface  226  of stent  210 ) and spaced apart relative to one another. In some examples, outer layers  223  may be oriented such that they extend laterally across stent  210 . As shown in  FIG.  6 A , individual outer layers  223  may be spaced longitudinally apart from one another. It can be appreciated that the configuration of outer layers  223  creates one or more tissue ingrowth regions  236  (similar to in function to those described above) along the medial region of stent  210 . Tissue ingrowth regions  236  may be circumferentially uncovered portions of the tubular scaffold of stent  210 . Inner layer  220  may be located radially inward of tissue ingrowth regions  236  to limit the amount a tissue ingrowth permitted. 
     Alternatively, some stent examples disclosed herein may be designed such that one or more portions of an inner layer extending along the inner surface of the stent may be spaced away from (i.e., spaced radially inward of) the inner surface of the stent, providing a gap or space therebetween. For example,  FIG.  6 B  (which may be similar in form and function to the stent design disclosed above with respect to  FIG.  6 A ) illustrates an alternative example stent having one or more portions of inner layer  220  extending along the inner surface  224  of stent  210  may be unattached to the inner surface of stent  210  and spaced radially inward from the inner surface  224  of the tubular stent  210  while other portions of the inner layer  220  are attached to the inner surface  224  of stent  210 . The space created by the inner layer  220  extending radially inward of the inner surface  224  of the stent  210  may define one or more tissue ingrowth regions  238 . Tissue ingrowth regions  238  may extend circumferentially around the inner surface  224  of stent  210 . 
       FIG.  7    shows another example stent  310 . Example stent  310  may be similar in form and function to the stent designs disclosed above. However, as  FIG.  7    illustrates, stent  310  includes additional outer layer  323  disposed along the outer surface  326  of the tubular scaffold of stent  310 .  FIG.  7    shows outer layer  323  may be positioned such that it extends circumferentially around the outer surface  326  of stent  310  (the dashed lines in  FIG.  7    depict outer layer  323  extending circumferentially around the outer surface  326  of stent  310 ). However,  FIG.  7    shows that outer layer  323  may be oriented such it extends in a helical configuration around the outer surface  326  of stent  310 . It can be appreciated that the configuration of outer layer  323  creates one or more tissue ingrowth regions  336  (similar in form and function to those described above) along stent  310 . Tissue ingrowth regions  336  may be circumferentially uncovered portions of the tubular scaffold of stent  310 . Inner layer  320  may be located radially inward of tissue ingrowth regions  336  to limit the amount a tissue ingrowth permitted. 
     Alternatively, some stent examples disclosed herein may be designed such that one or more portions of an inner layer extending along the inner surface of the stent may be spaced away from (i.e., spaced radially inward of) the inner surface of the stent, providing a gap or space therebetween. For example,  FIG.  7 B  (which may be similar in form and function to the stent design disclosed above with respect to  FIG.  7 A ) illustrates an alternative stent example having one or more portions of inner layer  320  may extend in a helical orientation along and attached to the inner surface  324  of stent  310 . It can be appreciated that the helical configuration of inner layer  320  creates one or more tissue ingrowth regions  338  (similar in form and function to those described above) along stent  310 . Tissue ingrowth regions  338  may be helically oriented uncovered portions of the tubular scaffold of stent  310 . 
       FIG.  8 A  shows an example stent  410 . Example stent  410  that may be similar in form and function to the stent designs disclosed above. However, as  FIG.  8 A  illustrates, stent  410  includes additional outer layers  423  disposed along the outer surface  426  of stent  410 .  FIG.  8 A  shows outer layers  423  may be positioned such that they extend longitudinally along the outer surface  426  of stent  410 . As shown in  FIG.  8 A , individual outer layers  423  may be circumferentially spaced apart from one another. It can be appreciated that the configuration of outer layers  423  creates one or more tissue ingrowth regions  436  (similar to in function to those described above) along the stent  410 . Tissue ingrowth regions  436  may be uncovered portions of the tubular scaffold of stent  410 . Inner layer  420  may be located radially inward of tissue ingrowth regions  436  to limit the amount a tissue ingrowth permitted. 
     Alternatively, some stent examples disclosed herein may be designed such that one or more portions of an inner layer extending along the inner surface of the stent may be spaced away from (i.e., spaced radially inward of) the inner surface of the stent, providing a gap or space therebetween.  FIG.  8 B  illustrates an alternative stent example (which may be similar in form and function to the stent design disclosed above with respect to  FIG.  8 A ) having an inner layer  420  spaced away from an inner surface of stent  410 . As shown in  FIG.  8 B  and  FIG.  8 C  (discussed below), inner layer  420  may include one or more discrete attachment points  425  along the inner surface of stent  410  in which the inner layer  420  is attached to the inner surface of stent  410 . It should be noted that the discrete attachment points of inner layer  420  may extend the full (or partial) longitudinal length (e.g., from the distal end region to the proximal end region) along the inner surface of stent  410 . 
       FIG.  8 C  illustrates an example cross-section along line  8 C- 8 C of example stent  410  shown in  FIG.  8 B .  FIG.  8 C  illustrates that one or more portions of inner layer  420  may be attached along the inner surface of stent  410 . Further, the inner layer  420  may be attached along the inner surface of stent  410  at one or more discrete attachment points  425 . It can be appreciated that the space between the discrete attachment points  425  may create one or more tissue ingrowth regions  436 . 
     Example stents disclosed herein may include one or more anchoring members designed to prevent the tubular member from shifting with respect to a body lumen in which the stent member is implanted. For example, some stents disclosed herein may include anti-migration elements. Anti-migration elements may include hooks, barbs, posts, flares, hoops, fins, quills, tines or the like. Anti-migration features may be beneficial in controlling the amount that a stent moves during and/or after deployment in the body lumen. 
     As discussed above, while medical device  10  is implanted along a body lumen, tissue ingrowth may occur along the tissue ingrowth region, which may reduce migration of implantable medical device  10  within the body lumen. However, in some examples, it may be necessary to remove medical device  10  from the body lumen. In at least some examples contemplated herein, removal of medical device  10  (which is effectively anchored to the body lumen via tissue ingrowth) may include positioning a second medical device (e.g., a second expandable stent) within the lumen of the medical device  10  such the second medical device may exert a radially outward force along the tissue ingrowth region, thereby causing the ingrown tissue to recede. In other words, a second expandable stent may be deployed within the lumen of medical device  10 , whereby the radial outward expansion of the second stent “pushes back” the ingrown tissue, causing it to recede radially outward (toward the vessel wall) and thereby reducing the force necessary to remove medical device  10  and/or the second stent. This method of using a second medical device to remove medical device  10  (e.g., the anchored stent) will be further illustrated and described below. 
       FIG.  9    shows an example second stent  510 . In some instances, second stent  510  may be referred to as an interior stent, removal stent and/or retrieval stent  510  configured to by positioned within a lumen of a previously implanted stent. Stent  510  may have a first end  521 , an opposite second end  523  and a lumen extending therein. When positioned in a body lumen (e.g., esophagus) the first or proximal end  521  may be defined as the end of stent  510  closest to a patient&#39;s mouth and the second or distal end  523  may be defined as the end of stent  510  closest to a patient&#39;s stomach. 
     Additionally, stent  510  may include one or more stent strut members  512  forming a tubular scaffold. Stent strut members  512  may extend helically, longitudinally, circumferentially, or otherwise along stent  510 . While  FIG.  9    shows stent strut members  512  extending along the entire length of stent  510 , in other examples, the stent strut members  512  may extend only along a portion of stent  510 . In some instances, stent struts  512  may be wires or filaments which are braided, wrapped, intertwined, interwoven, weaved, knitted, loops (e.g., bobbinet-style) or the like to form the stent structure. In other instances, the stent struts  512  may be portions of a monolithic structure formed from a cylindrical tubular member, such as a laser-cut Nitinol tube. 
     Additionally,  FIG.  9    shows example stent  510  including a first flared end region  514  proximate the first end  521  and/or a second flared end region  516  proximate the second end  523  of stent  510 . In some instances, first flared region  514  and second flared region  516  may be defined as an increase in the outer diameter, the inner diameter or both the inner and outer diameters along one or both of the first end  521  and/or second end  523  of stent  510 . Further,  FIG.  9    illustrates stent  510  including a medial region  518  positioned between first flared region  514  and second flared region  516 . 
     However, it is contemplated that while  FIG.  9    shows stent  510  including both a first flared region  514  and a second flared region  516 , stent  510  may only include one flared region. For example, it is contemplated that stent  510  may include only flared region  514  or flared region  516 . It is further contemplated that all or a portion of first flared region  514  and/or second flared region  516  may flare outwardly (e.g., away from the central, longitudinal axis of stent  510 ). Alternatively, it is further contemplated that all or a portion of first flared region  514  and/or second flared region  516  may flare inwardly (e.g., toward the central, longitudinal axis of stent  510 ). 
     In some instances, stent  510  may be a self-expanding stent or stent  510  may be a balloon expandable stent. Self-expanding stent examples may include stents having one or more struts  512  combined to form a rigid and/or semi-rigid stent structure. For example, stent struts  512  may be wires or filaments which are braided, wrapped, intertwined, interwoven, weaved, knitted, looped (e.g., bobbinet-style) and combinations thereof to form the stent structure. For example, while the example stents disclosed herein may resemble a braided stent, this is not intended to limit the possible stent configurations. Rather, the stents depicted in the Figures may be stents that are knitted, braided, wrapped, intertwined, interwoven, weaved, looped (e.g., bobbinet-style) or the like to form the stent structure. Alternatively, stent  510  may be a monolithic structure formed from a cylindrical tubular member, such as a single, cylindrical tubular laser-cut Nitinol tubular member, in which the remaining portions of the tubular member form the stent struts  512 . Openings or interstices through the wall of the stent  510  may be defined between adjacent stent struts  512 . 
     Stent  510  in examples disclosed herein may be constructed from a variety of materials. For example, stent  510  (e.g., self-expanding or balloon expandable) may be constructed from a metal (e.g., Nitinol, Elgiloy, etc.). In other instances, stent  510  may be constructed from a polymeric material (e.g., PET). In yet other instances, stent  510  may be constructed from a combination of metallic and polymeric materials. Additionally, stent  510  may include a bioabsorbable and/or biodegradable material. 
     In some instances, example stent  510  may include one or more layers (e.g., coverings) positioned on and/or adjacent to the inner and/or outer surface of the tubular scaffold of stent  510 . For example,  FIG.  9    shows example stent  510  including an outer layer  522  (depicted as a dotted pattern in  FIG.  9   ) disposed along at least a portion of the outer surface of stent  510  (e.g., along the middle portion, along the first flared portion  514  and/or the second flared portion  516  of stent  510 ). In some instances, the outer layer  522  may cover the entire outer surface of the tubular scaffold of stent  510 . In some instances, outer layer  522  may be an elastomeric or non-elastomeric material. For example, outer layer  522  may be a polymeric material, such as silicone, polyurethane, or the like. 
     Additionally, example stent  510  may include one or more layers positioned on and/or adjacent to the inner surface of stent  510 . For example, stent  510  may include an inner layer (not shown in the Figures) disposed within the lumen of stent  510 . In some instances, inner layer may be an elastomeric or non-elastomeric material. For example, inner layer may be a polymeric material, such as silicone, polyurethane, UE, PVDF, Chronoflex® or similar biocompatible polymeric formulations. 
       FIG.  10    shows a cross-section of example stent  510  along line  10 - 10  of  FIG.  9   .  FIG.  10    illustrates that first flared region  514  and/or second flared region  516  may include tapered portion  525  and end portion  527 . While  FIG.  10    shows tapered portions tapering radially outward toward ends of stent  510 , it is contemplated that one or more of tapered portions  525  may, alternatively, taper radially inward. 
     As discussed above,  FIG.  10    illustrates stent  510  may include an outer layer  522  disposed along an outer surface of stent  510 . For example, in some instances, stent  510  may include an outer layer  522  disposed along the outer surface of a middle portion between flared ends  514 ,  516 , one or more of both tapered portions  525  and/or end portions  527 . Further, in some examples, outer layer  522  may extend longitudinally along the entire length and circumferentially around the entire circumference of outer surface of stent  510 . 
     As will be discussed in greater detail below,  FIGS.  11 - 13    illustrate an example stent  10  undergoing a hyperplastic response,  FIGS.  14 - 17    illustrate the deployment and positioning of an example retrieval stent within stent  10  and  FIG.  18    illustrates the removal of both stent  10  and the retrieval stent  510 . 
       FIGS.  11 - 13    illustrate an example stent undergoing a hyperplastic response of tissue within an example body lumen subsequent to implantation of stent  10  within a body lumen  11 .  FIG.  11    shows example stent  10  deployed in body lumen  11 . As illustrated, upon initial deployment in the body lumen  11 , the end portion  27  of the first flared region  14  and the end portion  27  of the second flared region  16  may apply a radially outward force upon the inner surface of body lumen  11  as the expandable scaffold of stent  10  expands to an expanded state in the body lumen  11 . This radially outward force exerted on the inner surface of body lumen  11  may provide a temporary resistance to migration of stent  10  within the body lumen  11 . 
     Additionally, the end portions  27  of stent  10  may contact the tissue on the inner surface of body lumen  11 . This contact of the end portions  27  with the tissue of the inner surface of the body lumen  11  may provide a seal that funnels food or other material through lumen  40  of stent  10 . For example, as food or other material travels down the esophagus, the flared portions  14 / 16  of stent  10  may prevent the food from traveling along the exterior of stent  10  and along the inner surface of body lumen  11 . Rather, flared portions  14 / 16  are designed to provide a circumferential seal around the inner surface of body lumen  11  such that the food is directed through the lumen  40  of stent  10 . As discussed above, the inner layer  20  of stent  10  may create a passageway (e.g., lumen  40 ) through which food and other material may travel (without leaking to the outer surface of stent  10 ). 
     Over time, tissue may grow through interstices of the stent scaffold along medical region  18 .  FIG.  12    illustrates tissue  13  extending through interstices of the stent filaments  12  along the medial region  18  of stent member  10  radially inward of the uncovered portion of the tubular scaffold of stent  10 .  FIG.  12    further illustrates that the tissue  13  is growing into the tissue ingrowth region  36  toward liner  20  (as depicted by the arrows in  FIG.  12   ). Thus, tissue may grow through interstices of the tubular scaffold of stent  10  and around struts or filaments  12  of tubular scaffold of stent  10  throughout the uncovered portion of medial region  18 . 
     Inner layer  20  may limit the amount of tissue in-growth permitted.  FIG.  13    illustrates that tissue  13  has grown radially inward from the wall of example body lumen  11  to a position in which it has contacted inner layer  20  radially inward. However, as shown in  FIG.  13   , inner layer  20  has reached a point at which it will no longer deflect radially inward, and therefore prevents tissue  13  from further collapsing lumen  40  of stent member  10  (as depicted by the double-ended arrow in  FIG.  13   ). Thus, inner layer  20  may be configured to maintain a desired lumen dimeter through stent  10  while stent  10  is implanted in a patient. 
     In some instances, it may be desirable to remove stent  10  subsequent tissue in-growth through interstices of the tubular scaffold. However, the tissue-ingrowth may hinder removal and/or cause undesirable trauma to the body lumen. As discussed above,  FIGS.  14 - 18    illustrate an example methodology for retrieving and/or removing an example stent  10  (or any other devices disclosed herein) from a body lumen (e.g., the esophagus) while reducing the amount of trauma to the body lumen. Example stent  10  shown in  FIGS.  14 - 18    may depict stent  10  illustrated and described with respect to  FIGS.  11 - 13   . However, stent  10  described in the following methodology may also be similar in form and function to stent  10  of  FIGS.  1  and  2    discussed above. Further, while the following figures describe example stent  10  being retrieved and/or removed from the esophagus, it is contemplated that the methodology may be used to retrieve and/or remove stent  10  (or any other devices disclosed herein) from any other body lumen. 
       FIG.  14    shows an example first step in removing stent  10  from body lumen  11 . Specifically, delivery device  50  may be advanced through body lumen  11  to a first end  21  of stent  10 . The end portion  52  of delivery device  50  may then be further advanced through the lumen  40  of the stent  10  such that the end portion  52  is positioned adjacent the second end  23  of the stent  10 . 
       FIG.  15    illustrates an example second step in removing stent  10  from body lumen  11 . Specifically,  FIG.  15    illustrates that a clinician may retract the end portion  52  of the delivery device  50  in a proximal direction depicted by the arrow in  FIG.  15   . Specifically, the delivery device  50  (e.g., an outer sheath of delivery device  50 ) may be retracted in a distal-to-proximal direction within lumen  40  of the stent  10 . In other words, the delivery device may be retracted from second end  23  toward the opposite end of the stent  10 .  FIG.  15    further illustrates that as the delivery device  50  is retracted, the second end  523  of secondary stent  510  (e.g., retrieval stent) is deployed with the lumen  40  of stent  10 . Additionally, it can be appreciated that as retrieval stent  510  is deployed, it radially expands such that the outer covering  522  of the second end  523  of stent  510  contacts the inner liner  20  of stent  10 . Further, as illustrated in  FIG.  15   , it may be desirable that the second end  523  of retrieval stent  510  and the second end  23  of stent  10  be substantially aligned longitudinally along body lumen  11 . 
       FIG.  16    illustrates an example third step in removing stent  10  from body lumen  11 . Specifically,  FIG.  16    illustrates that delivery device  50  may be fully retracted to a position in which retrieval stent  510  has been fully deployed from the end portion  52  of the delivery device  50 . Additionally, it can be appreciated that after retrieval stent  510  is fully deployed from delivery device  50 , it expands radially outward such that the outer covering  522  of stent  510  contacts the inner liner  20  of stent  10  throughout the length of stent  10 , with the expandable scaffold of stent  510  exerting a radially outward force on inner liner  20  of stent  10 . For example, the expandable scaffold of stent  510  can exert a radially outward force throughout the medial region  18  of the inner liner  20 . 
     Further, as illustrated in  FIG.  16   , it may be desirable that the first end  521  of retrieval stent  510  and the first end  21  of stent  10  may be substantially aligned longitudinally along the body lumen  11 . Further,  FIG.  16    illustrates that in some instances it may be desirable that both the first and second ends of retrieval stent  510  substantially align with the first and second ends of stent  10 . 
     Additionally, it can be appreciated that in some instances the retrieval stent  510  may include a profile along its outer surface that matches the profile of the inner surface of stent  10 . In other words, in some instances it may be desirable for stent  10  and retrieval stent  510  to have a similar, or substantially equivalent geometric shape. It can further be appreciated that if the profile of retrieval stent  510  matches the profile of stent  10 , the retrieval stent  510 , when deployed within the lumen  40  of stent  10 , may contact substantially the entire inner surface of stent  10 . 
     As discussed above,  FIG.  16    further illustrates that when retrieval stent  510  is positioned and deployed within the lumen  40  of stent  10 , it may exert a radially outward force (depicted by the double-ended arrows in  FIG.  16   ) that pushes outward against the inner surface of stent  10 . For, example, retrieval stent  510  may be configured to have a deployed, radially expanded outer diameter greater than the inner diameter of the medial region  18  of stent  10  to exert a radial outward force against inner liner  20 . Accordingly, this outward radial force may push the portion of liner  20  that is adjacent the tissue ingrowth region, thereby exerting an outward radial force against the tissue  13 , as shown in  FIG.  16   . It can be appreciated that stent  510  may be designed such that it exerts an outward radial force which is large enough to push both liner  20  and tissue  13  radially outward toward body lumen  11 , thereby causing tissue  13  to retreat and effectively die off. In some examples, the outward radial force exerted by stent  510  may be about 0.10 N to about 2.5 N, or about 0.15 N to about 2.0 N. In some instance, the outward radial force exerted by stent  510  may be about 0.10 N or more, about 0.15 N or more, about 0.5 N or more, about 1.0 N or more, about 1.5 N or more, or about 2.0 N or more. 
       FIG.  17    illustrates stent  10  and retrieval stent  510  of  FIG.  16    after the retrieval stent  510  has been deployed within stent  10  and allowed to exert an outward radial force along the tissue ingrowth region of liner  20 . As can appreciated from  FIG.  17   , the tissue  13  present in  FIG.  16    has effectively died off and liner  20  has relaxed to a position in which it is positioned along the inner surface of the tubular scaffold of stent  10  throughout medial region  18 . As discussed above, because the retrieval stent  510  has reduced the amount of tissue  13  extending through the stent struts  12  of stent  10 , tissue  13  no longer attaches stent  10  to the inner surface of body lumen  11  with as much force as when the tissue  13  is fully ingrown into the stent struts  12 . Accordingly, this reduced attachment force translates into a lower force which is necessary to remove stent  10  and/or stent  510  from body lumen  11 . 
       FIG.  18    illustrates an example step in removing stent  10  from body lumen  11 . Removal of the stent  10  may be performed once tissue in-growth into the interstices of the tubular scaffold of stent  10  has sufficiently receded. For example, removal of stent  10  may be performed approximately 7-14 days after placing retrieval stent  510  within stent  10 . In some instances, removal of stent  10  may be performed within 1 week or less, within 2 weeks or less, or within 3 weeks or less after placing retrieval stent  510  within stent  10 . Specifically,  FIG.  18    illustrates that a clinician may utilize a retrieval device  54  (e.g., forceps, clamp, etc.) to remove both stent  10  and/or retrieval stent  510 . As illustrated in  FIG.  18   , the retrieval device  54  map grasp the first end portions  21 / 521  of stent  10  and retrieval stent  510  and pull them in a direction out of the body (indicated by the arrow in  FIG.  18   ). The force exerted by the retrieval device  54  may be sufficient to remove both the stent  10  and retrieval stent  510  from the inner surface of the body lumen  11  without damaging the inner surface of the body lumen  11 . Alternatively, retrieval device  54  may grasp or hook a retrieval suture extending circumferentially around the end of stent  10 . When pulled proximally, the retrieval suture may collapse the proximal end of stent  10  and/or the proximal end of stent  510  to facilitate withdrawal of the stents  10 ,  510 . Accordingly, stents  10 ,  510  may be removed from the body lumen  11  simultaneously. Alternatively, stents  10 ,  510  may be removed from the body lumen sequentially, if desired. 
     The materials that can be used for the various components of stent  10  and stent  510  (and/or other stents disclosed herein) and the various medical devices disclosed herein may include those commonly associated with medical devices. For simplicity purposes, the following discussion makes reference to stent  10  and stent  510  and other components of stent  10  and stent  510 . However, this is not intended to limit the devices and methods described herein, as the discussion may be applied to other similar medical devices disclosed herein. 
     Stent  10  and stent  510  and other components of stent  10  and stent  510  may be made from a metal, metal alloy, polymer (some examples of which are disclosed below), a metal-polymer composite, ceramics, combinations thereof, and the like, or other suitable material. Some examples of suitable polymers may include polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), polyoxymethylene (POM, for example, DELRIN® available from DuPont), polyether block ester, polyurethane (for example, Polyurethane 85A), polypropylene (PP), polyvinylchloride (PVC), polyether-ester (for example, ARNITEL® available from DSM Engineering Plastics), ether or ester based copolymers (for example, butylene/poly(alkylene ether) phthalate and/or other polyester elastomers such as HYTREL® available from DuPont), polyamide (for example, DURETHAN® available from Bayer or CRISTAMID® available from Elf Atochem), elastomeric polyamides, block polyamide/ethers, polyether block amide (PEBA, for example available under the trade name PEBAX®), ethylene vinyl acetate copolymers (EVA), silicones, polyethylene (PE), Marlex high-density polyethylene, Marlex low-density polyethylene, linear low density polyethylene (for example REXELL®), polyester, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polytrimethylene terephthalate, polyethylene naphthalate (PEN), polyetheretherketone (PEEK), polyimide (PI), polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), poly paraphenylene terephthalamide (for example, KEVLAR®), polysulfone, nylon, nylon-12 (such as GRILAMID® available from EMS American Grilon), perfluoro(propyl vinyl ether) (PFA), ethylene vinyl alcohol, polyolefin, polystyrene, epoxy, polyvinylidene chloride (PVdC), poly(styrene-b-isobutylene-b-styrene) (for example, SIBS and/or SIBS 50A), polycarbonates, ionomers, biocompatible polymers, other suitable materials, or mixtures, combinations, copolymers thereof, polymer/metal composites, and the like. In some embodiments the sheath can be blended with a liquid crystal polymer (LCP). For example, the mixture can contain up to about 6 percent LCP. 
     Some examples of suitable metals and metal alloys include stainless steel, such as 304V, 304L, and 316LV stainless steel; mild steel; nickel-titanium alloy such as linear-elastic and/or super-elastic nitinol; other nickel alloys such as nickel-chromium-molybdenum alloys (e.g., UNS: N06625 such as INCONEL® 625, UNS: N06022 such as HASTELLOY® C-22®, TINS: N10276 such as HASTELLOY® C276®, other HASTELLOY® alloys, and the like), nickel-copper alloys (e.g., UNS: N04400 such as MONEL® 400, NICKELVAC® 400, NICORROS® 400, and the like), nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such as MP35-N® and the like), nickel-molybdenum alloys (e.g., UNS: N10665 such as HASTELLOY® ALLOY B2®), other nickel-chromium alloys, other nickel-molybdenum alloys, other nickel-cobalt alloys, other nickel-iron alloys, other nickel-copper alloys, other nickel-tungsten or tungsten alloys, and the like; cobalt-chromium alloys; cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like); platinum enriched stainless steel; titanium; combinations thereof; and the like; or any other suitable material. 
     In at least some embodiments, portions or all of stents  10 ,  510  and other components of stent  10  and stent  510  may also be doped with, made of, or otherwise include a radiopaque material. Radiopaque materials are understood to be materials capable of producing a relatively bright image on a fluoroscopy screen or another imaging technique during a medical procedure. This relatively bright image aids the user of stent  10  in determining its location. Some examples of radiopaque materials can include, but are not limited to, gold, platinum, palladium, tantalum, tungsten alloy, polymer material loaded with a radiopaque filler, and the like. Additionally, other radiopaque marker bands and/or coils may also be incorporated into the design of guidewire  10  to achieve the same result. 
     In some embodiments, a degree of Magnetic Resonance Imaging (MRI) compatibility is imparted into stent  10 . For example, stents  10 ,  510  and other components of stent  10  and stent  510 , or portions thereof, may be made of a material that does not substantially distort the image and create substantial artifacts (e.g., gaps in the image). Stent  10  and stent  510  and other components of stent  10  and stent  510 , or portions thereof, may also be made from a material that the MRI machine can image. Some materials that exhibit these characteristics include, for example, tungsten, cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like), nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such as MP35-N® and the like), nitinol, and the like, and others. 
     It should be understood that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of steps without exceeding the scope of the disclosure. This may include, to the extent that it is appropriate, the use of any of the features of one example embodiment being used in other embodiments. The disclosure&#39;s scope is, of course, defined in the language in which the appended claims are expressed.