Abstract:
A medical device includes an elongated member and a reinforced retention structure. The device can be used for draining substances from organs or abscessed areas within a body of a patient. The elongated member is made of a flexible material. The reinforced retention structure extends from or is formed integrally with the elongated member and comprises an elastic member and the flexible material. The reinforced retention structure provides retention strength while providing flexibility and patient comfort. The use of the reinforced retention structure also provides increased stability to the device within the patient&#39;s body and combats migration and/or expulsion of the device. The nature of the reinforcement in the retention structure may extend into the elongated member, which allows for larger drainage openings in the device and increases the radiopacity of the device.

Description:
RELATED APPLICATIONS  
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/195,995, filed Apr. 11, 2000. 
     
    
     
       TECHNICAL FIELD  
         [0002]    This invention generally relates to medical devices, such as drainage stents and catheters.  
         BACKGROUND INFORMATION  
         [0003]    Medical devices used for draining fluids from body cavities are generally made of plastic tubing. The tubing is often pre-formed on one or both of its ends to a geometry designed to maintain or anchor the device in position within the body. Medical devices of this type are commonly placed through a ureteroscope, laprascope, or endoscope and into lumens and/or body orifices. In the case of abscess catheters, placement generally occurs percutaneously through a puncture of the external dermis and musculature. In most cases, however, a guidewire is first passed through the orifice or puncture to the desired drainage site, around or through obstacles if required. The medical device is then placed over the guidewire through a lumen running the full length of the device. This straightens the anchoring geometry to ease and allow insertion. After insertion, the guidewire is pulled out through the device&#39;s proximal end. Once the guidewire is removed from the body, the anchoring geometry assumes its natural, pre-formed shape to retain the device in position within the body of the patient.  
           [0004]    Some medical device use coils or pigtails as anchors in an open area of the anatomy, such as the renal pelvis of a kidney or abscessed area within a body cavity. These types of anchors allow the device (such as a ureteral drainage stent) to maintain its position within the body by blocking its migration through thinner tract openings. Another type of anchoring mechanism is commonly known as a malecot. Some other devices, such as biliary stents, use one or more barbs (formed, for example by partially skiving a tube in a longitudinal direction). Some biliary stents use barbs for retention in the biliary tract.  
         SUMMARY OF THE INVENTION  
         [0005]    Known anchoring mechanisms used with medical devices can fail. For example, internal forces from involuntary bodily functions (such as peristalsis and other secretory forces, as well as patient movement) can force the device out of its intended position within the body. In addition, doctors typically recommend catheter and stent anchoring or retention structures fabricated from softer materials to enhance patient comfort. These softer materials generally have lower retention strengths as compared to more rigid materials. Also, the lower strengths of these softer materials limits the size of holes that can be formed in the medical device to help drain fluid from the body of a patient.  
           [0006]    The present invention provides significantly increased strength to retention structures while also maintaining patient comfort. With the invention, softer materials can be used to maximize patient comfort, and reinforcement of these soft materials affords greater retention properties. Examples of devices that can include retention structures according to the present invention include, but are not limited to, a drainage catheter, a ureteral stent, a urethral stent, a biliary stent, and a prostatic stent.  
           [0007]    In general, one aspect of the present invention relates to a medical device comprising an elongated member and a reinforced retention structure. The elongated member comprises a flexible material and defines a lumen extending therethrough. The reinforced retention structure extends from the elongated member and comprises an elastic member and the flexible material.  
           [0008]    The elastic member may be embedded within the flexible material, or bound to a surface of the retention structure such as the inner or outer wall of the retention structure. The retention structure may extend from the distal or proximal portions of the device, lie between the distal and proximal portions in a middle portion, or exist in or on two or more portions of the device.  
           [0009]    As used herein, “distal portion” refers to the portion of the medical device furthest away from the medical operator inserting the device within the open or abscessed area of the anatomy, such as the portion in and/or near the kidney. “Proximal portion” refers to the opposite portion of the device closest to the medical operator, such as the portion in and/or near the urinary bladder. “Middle portion” refers to the portion of the medical device that lies between the distal and proximal portions.  
           [0010]    In some embodiments, at least one large drain hole slot is formed through the wall of the retention structure. The use of the elastic member in the retention structure eliminates the risk that the retention structure will collapse on itself because of the size of the drain holes. Alternatively or additionally, the elastic member may extend into the elongated member. Because of the stability provided by this configuration, a large drain hole slot may be cut into the elongated member in place of typical smaller drain hole configurations. Also, the elastic member increases the radiopacity of at least the retention structure, thereby enhancing the locatability of the device (or at least the retention structure) using flouroscopy.  
           [0011]    The extension of the elastic member into the elongated member also enhances pushability of the device during insertion into a body of a patient. The elastic member prevents the device from kinking as it moves within the body. In one embodiment, the elastic member may be removable from the elongated member after insertion. Under this construction, two separate elastic members reside in the retention structure and the elongated member. The length of the elastic member disposed in the elongated member exceeds the length of the device. After insertion of the device into the body of the patient, the operator proximally pulls the elastic member residing in the elongated member from the patient&#39;s body. The elastic member residing in the retention structure remains in place.  
           [0012]    The shape of the retention structure and its positioning with respect to the elongated member can vary in different embodiments according to the invention. The retention structure may be formed integrally with the elongated member or it may be affixed to the elongated member. A retention structure may be located anywhere along the length of the elongated member. Also, two or more retention structures may be disposed along the length of the elongated member.  
           [0013]    In one embodiment, a elastic member is pre-formed to a curved shape and disposed within the wall of a plastic tubing. The curved shape may be a retention structure with a single turn, a retention structure with two or more turns, or simply a J curl. In another embodiment, a plurality of lengths of a pre-formed elastic material can be positioned longitudinally in the wall of a piece of tubing surrounding a central lumen. Portions of the tubing can then be cut longitudinally in between the superelastic pieces to form the arms of a malecot. In another embodiment, a dual-lumen tube is partially skived at one end into a barbed configuration. A preformed curved piece of elastic material is secured in the skived portion for added strength.  
           [0014]    In other embodiments, one or more elastic rings radially protruding from the elongated member and containing a reinforcing superelastic ring and a flexible material may be formed or disposed along the elongated member as a retention structure. By varying the size of the rings, the device can accommodate body cavities of different shapes and sizes and work in maintaining the lumen of the tube wide open. The elastic ring or rings may be constructed from a variety of flexible materials, such as elastomeric compounds. Materials like these combine rigidity and the softness necessary for patient stability and comfort.  
           [0015]    In all of the above-described embodiments, a plurality of drain holes may be cut into the elongated member and/or retention structure to maximize drainage. Alternatively or additionally, large drain hole slots can be cut into the elongated member and/or retention structure depending on the placement of the elastic member.  
           [0016]    In other aspects, the invention involves methods of placing medical devices, such as the devices previously described. A method of placing a medical device of the invention into the body of a patient comprises providing the device, collapsing the retention structure and inserting the device into a patient&#39;s body to release the retention structure, and thereby deploy the medical device in the body.  
           [0017]    In another aspect, the invention involves methods of making medical devices of the present invention. A method of making such a device comprises extruding an elongated member made of a flexible material and incorporating a pre-formed elastic member to the flexible material by embedding the elastic member within the flexible material or by binding the elastic member to a surface or groove of the flexible material to form a reinforced retention structure.  
           [0018]    The foregoing and other objects, aspects, features, and advantages of the invention will become more apparent from the following description, drawings, and from the claims.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention.  
         [0020]    [0020]FIG. 1. is a schematic side view of one embodiment of the medical device of the invention with an elongated member and a single loop retention structure.  
         [0021]    [0021]FIG. 1A is an enlarged cross sectional view of a cut-out portion of the single loop retention structure of FIG. 1.  
         [0022]    FIGS.  2 A-B show two side views of an insertion catheter with stylet for collapsing a single loop retention structure and inserting the catheter into a body of a patient with the retention structure deployed (A) and collapsed (B).  
         [0023]    FIGS.  3 A-C show transverse cross-sectional views of various embodiments of retention structures of medical devices of the invention.  
         [0024]    FIGS.  4 A-C show additional transverse cross-sectional views of various embodiments of retention structures of medical devices of the invention.  
         [0025]    [0025]FIG. 5 is a schematic longitudinal view of the medical device of the invention with an elongated member and two retention structures.  
         [0026]    [0026]FIG. 6 is a schematic longitudinal view in partial longitudinal cross-section of a portion of an embodiment of the medical device of the invention with an elongated member and a reinforced malecot.  
         [0027]    FIGS.  7 A-B show two side views of an insertion catheter with stylet for inserting embodiments of a medical device of the invention into a body of a patient with the retention structure deployed (A) and collapsed (B).  
         [0028]    [0028]FIG. 8 is a schematic longitudinal view in partial longitudinal cross-section of a portion of an embodiment of the medical device of the invention with an elongated member and a reinforced barb.  
         [0029]    [0029]FIG. 9 shows a longitudinal view of an insertion catheter with stylet and cannula for inserting an embodiment of the medical device of the invention into a body of a patient.  
         [0030]    [0030]FIG. 10 is a schematic longitudinal view in partial longitudinal cross-section of one embodiment of the medical device of the invention with an elongated member and an inward spiral coil.  
         [0031]    [0031]FIG. 11 is a schematic longitudinal view of a portion of an embodiment of the medical device of the invention with an elastic ring retention structure.  
         [0032]    FIGS.  12 A-B are schematic longitudinal views of a portion of two medical devices of the invention with collapsed retention structures illustrating a comparison of a series of holes configuration (FIG. 12A) with the reinforced large drain hole configuration of the present invention (FIG. 12B).  
         [0033]    [0033]FIG. 13 is a schematic diagram illustrating the medical device of the invention implanted within the kidney and ureter of a patient. 
     
    
     DESCRIPTION  
       [0034]    Medical devices of the present invention are generally constructed of an elongated member and a reinforced retention structure. The elongated member includes a flexible material and the reinforced retention structure includes the same or a different flexible material with an elastic member embedded within or bound to a surface or groove of the flexible material. Preferred materials for the flexible material include, but are not limited to plastic, silicone, TEFLON®, and other PTFE polymers, polyurethane polymers and the like. These materials may also be provided with radiopaque portions to assist in the implantation of the devices in a body of a patient under fluoroscopic monitoring.  
         [0035]    The elongated member may be tubular or conical or a combination of both. Generally, the elongated member comprises a lumen extending through the entire length of the elongated member to provide drainage of fluid from a body cavity. Alternatively or additionally, drainage may be provided or enhanced by grooves located on the external surface of the retention structure and/or elongated member.  
         [0036]    The reinforced retention structure is designed to anchor the medical device in place notwithstanding certain forces such as internal forces from involuntary bodily functions such as peristalsis and other secretory forces, or patient movement. The reinforced retention structure may be formed as an extension of the elongated member. Under this construction, an elongated member is molded into a predetermined shape to form a reinforced retention structure such that it can extend from the elongated member. Alternatively, a reinforced retention structure may be fixedly mounted to the elongated member in that both the elongated member and retention structures are pre-formed and thereafter attached to one another. The reinforced retention structure may adopt any geometry that protrudes laterally or radially from the elongated member to provide adequate anchoring. Examples of retention structure geometry include, but are not limited to, a retention coil including one turn, a retention coil including two or more turns, a J curl, an inward spiral coil, a barb, a malecot, and a protruding ring. The retention structure and/or the elongated member itself can have a number of drainage holes disposed along its length. The holes provide drainage areas to allow fluids to drain into the lumen of the elongated member. Alternatively or additionally, a large drain hole slot (FIG. 12 b ) may be cut into the retention structure and/or the elongated member to further facilitate drainage.  
         [0037]    Retention structures according to the invention may be reinforced by a segment made of an elastic member embedded within the flexible material or bound to a surface or groove of the retention structure (such as the inner or outer wall of the retention structure). The elastic member may have a cross-section that can be round, flat, square, crescent or D-shaped. Certain examples of these cross-sectional shapes are illustrated in FIGS.  3 A-C and  4 A-C.  
         [0038]    The elastic member may be fabricated from a material having “superelastic” properties. Materials with superelastic properties, make it possible to configure a segment into a particular advantageous shape of a retention structure, such as a pigtail, a malecot arm, a coil, a barb or a ring and then modify reversibly the geometry of the retention structure by straightening the retention structure through use of guidewires, outer sheaths and the like for easy implantation in the body. For example, the pigtail, malecot, and coil retention structures assume straightened geometries when placed over or within the length of a cannula. After the device is straightened, placement into a body with conventional insertion techniques may occur. After insertion and removal of the straightening device, the elastic member reverts spontaneously to its predetermined configuration thereby regaining its deployed geometry and reforming the retention structure.  
         [0039]    The superelastic material may comprise an alloy of In—Ti, Fe—Mn, Ni—Ti, Ag—Cd, Au—Cd, Au—Cu, Cu—Al—Ni, Cu—Au—Zn, Cu—Zn, Cu—Zn—Al, Cu—Zn—Sn, Cu—Zn—Xe, Fe 3 Be, Fe 3 Pt, Ni—Ti—V, Fe—Ni—Ti—Co, and Cu—Sn. Preferably, the superelastic material comprises a nickel and titanium alloy, known commonly as Nitinol available from Memry Corp of Brookfield, Conn. or SMA Inc. of San Jose, Calif. The ratio of nickel and titanium in Nitinol may be varied. Examples include a ratio of about 50% to about 52% nickel by weight or a ratio of about 47% to about 49% nickel by weight. Nitinol has shape retention properties in its superelastic phase.  
         [0040]    In other embodiments, the elastic member comprises any suitable material that has sufficient elastic properties to allow for straightening of the retention structure during insertion into the body, but provides desired reinforcement strength to the retention structure during use. Such materials include, for example, stainless steel or suitable polymeric materials.  
         [0041]    The elastic member disposed within the retention structure may have a one-dimensional shape, such as a linear wire, a two-dimensional shape, such as a curled wire to form a loop or an inward coil, or a three-dimensional shape, such as a helical coil or a pigtail coil. In two-dimensional embodiments, the wire may be bent along a second axis such that the wire occupies a plane. In three-dimensional embodiments, the wire may be coiled tightly about itself within the retention structure.  
         [0042]    An embodiment of a medical device  10  according to the present invention is shown in FIG. 1. The medical device comprises an elongated member  12  and a reinforced retention structure  14 . The elongated member may be viewed as extending along a first axis  16 . In FIG. 1 the first axis  16  extends in a longitudinal direction. The retention structure  14  extends along the first axis  16  and a second axis  18 . As seen in FIG. 1, the second axis  18  extends laterally from the first axis  16 . The elongated member  12  defines an internal lumen  20 . The internal lumen  20  also extends into and through the retention structure  14 .  
         [0043]    In FIG. 1, the retention structure  14  is shaped into a coil including a single turn. The retention structure comprises a reinforcing structure made of an elastic member  22  embedded within a flexible material  24 . FIG  1 A is an enlarged cross sectional view of an portion of the single loop retention structure of FIG. 1, and depicts the elastic member embedded within the flexible material. Alternatively, the reinforcing elastic member  22  may be bound to an inner or outer wall of the flexible material  24 . The stability provided by the elastic member  22  to the retention structure  14  allows for a large drain hole slot  26  to be cut into the retention structure  14  alongside the reinforcing material  22 . Optionally, the elastic member  22  can extend into the elongated member  12 . A large drain hole slot  28  may be cut into a portion of a wall of the elongated member  12  for increased drainage. To facilitate drainage, both the retention structure  14  and/or the elongated member  12  may, alternatively or additionally, incorporate a plurality of drainage holes  30  disposed along their lengths to permit drainage of fluid into the lumen  20 .  
         [0044]    Insertion of the device  10  into a body of a patient can be accomplished by straightening the retention structure  14  with a rigid elongated member along the first axis  16 , such as inserting a stylet or guidewire within the lumen  20  or a cannula or sheath over the elongated member, inserting the device  10  with the rigid member into the body and removing the rigid member from the device to deploy the retention structure once the device has been inserted and properly positioned within a body cavity. Removal of the rigid member from the device  10  releases the constraint on the elastic member and allows the retention structure to regain its shape. For example, referring to FIGS.  2 A-B, a catheter includes a rigid member  13  connected to a handle  17  manually inserted into the lumen of the device  10 . The catheter  15  comprises an adapter  19  for attaching the medical device  10  to the handle  17 , another catheter, or a collection bag. When the rigid member  13  extends throughout the entire device  10  as in FIG. 2B, the single coil retention structure  14  is straightened along the longitudinal axis  16 . The insertion catheter  15  is then inserted into a body of a patient, and the rigid member  13  is removed from the body proximally. The elastic member allows the retention structure  14  to regain its coiled shape in the body upon removal of the rigid member  13  as in FIG. 2A.  
         [0045]    The elastic member may have a variety of shapes and arrangements within the wall of the flexible material  24  forming the retention structure. For example, FIGS.  3 A-C represent cross-sectional views of retention structures  14  of the present invention, and show a wire made of a elastic core  22  disposed within the wall of the retention structure  14 . This configuration and these shapes may be suitable for coiled reinforced retention structures (e.g. FIGS. 1, 5, and  10 ) or barbed retention structures (e.g. FIG. 8). In cross-section, the inner lumen  20  is surrounded by the walls of the retention structure  14  with the elastic member  22  embedded within the flexible material  24 . The elastic member  22  embedded within the flexible material  24  may be D-shaped as shown in FIG. 3A, round as in FIG. 3B, or flat, rectangular, or ribbonlike as in FIG. 3C. The elastic member may also have more complex shapes such as wires with enlarged or thinner segments along their length, or more intricate shapes such as an arrow head for a barb or the like.  
         [0046]    Alternatively, the retention structure may have more than one elastic core disposed at various intervals (regular or irregular) within the wall of the flexible material. For example, FIGS.  4 A-C show four superelastic cores  22  having various shapes disposed within the wall of the retention structure  14 . In cross-section, within the retention structure  14 , an inner lumen  20 , is surrounded by the flexible material  24 . Elastic member  22  is disposed within the flexible material  24  of the retention structure  14 . In the cross-sectional views of the embodiments displayed in FIGS.  4 A-C, the elastic member  22  is disposed at four different locations within the flexible material  24 . These four locations lie at 0°, 90°, 180°, and 270° angles along the radius of the retention structure  14 . The elastic member may, however, lie at any combination of angles along the radius of the retention structure  14 . These configurations may be suitable to a coil (e.g. FIGS. 1, 5, and  10 ) multiple barbs (e.g. FIG. 8) or multiple arms of a malecot retention structure (e.g. FIG. 6). The elastic member  22  within the flexible material  24  may be D-shaped as in FIG. 4A, round as in FIG. 4B, or flat, rectangular, or ribbonlike as in FIG. 4C.  
         [0047]    Referring now to FIG. 5, another embodiment of a medical device  10 A according to the invention is shown. The device  10 A is suitable for use as a ureteral stent, and is made of a flexible material forming an elongated member  12 A. The elongated member  12 A extends along a longitudinal axis  16 A and forms two retention structures  32  and  34  at its proximal and distal ends defining a longitudinal portion  11  therebetween. The retention structures extend along lateral axes  18 A and  18 A′ relative to the longitudinal axis  16 A. Here, both retention structures  32  and  34  occupy the same plane. But the retention structures  32  and  34  may occupy different planes. The use of dual retention structures provides increased stability to the device within a patient&#39;s body and combats migration and/or expulsion of the device  10 A. The two or more retention structures  32  and  34  may also be positioned anywhere along the length of the elongated member  12 A. The elastic member  22 A embedded within the flexible material  24 A may be positioned in one or both of these retention structures  32  and  34  and may extend along a short segment of the wall in the longitudinal portion  11 .  
         [0048]    The enhanced stability provided to the device  10 A by the elastic member  22 A in the flexible material  24 A allows for a large drain hole slot  26 A or slots to be cut into the side of one or both of the retention structures  32  and  34 . Alternatively or additionally, a large drain hole slot  28 A may be cut into the side of the longitudinal portion of the elongated member  12 A that contains the extension of the elastic member  22 A in the flexible material  24 A. A plurality of drain holes  30 A may be disposed along the elongated member  12 A and/or the retention structures  32  and  34  to permit drainage of fluid into the lumen.  
         [0049]    [0049]FIG. 6 depicts a retention structure  35 , known as a malecot, with two or more laterally bulging arms formed along a portion of a length of an elongated member  12 B. The elongated member  12 B extends along a longitudinal axis  16 B. Two arms  33  and  36  of the retention structure  35  extend along a lateral axis  18 B relative to the longitudinal axis  16 B. The malecot  35  may also comprise a plurality of collapsible bulging arms including, but not limited to, any number of arms from two arms to eight arms, for example, with three to six arms typical. As with other retention structure constructions, the malecot  35  comprises an elastic member  22 B embedded within the flexible material  24 B in each of the malecot&#39;s arms. In their deployed shape, the arms may have a symmetrical omega (Ω) shape or an omega shape tilted proximally or distally as shown in FIG. 6.  
         [0050]    Formation of the malecot  35  can be a multi-step process. A piece of tubing may be first extruded, molded or otherwise shaped into an elongated member  12 B to have a central lumen  20 B surrounded by a series of smaller outer lumens disposed into the wall of the elongated member  12 B and surrounding the lumen  20 B. Lengths of elastic material are shaped into curved geometries formed by a sequence of alternating convex and concave curves of varied length and radii that shape the arms of the malecot. These preformed lengths of elastic material  22 B are then placed into the outer lumens of the flexible material  24 B. The multi-lumen tubing is then cut longitudinally between each of the pieces of elastic material  22 B to separate the arms of the malecot from each other.  
         [0051]    The elastic member  22 B allows the arms of the malecot  35  to protrude laterally from the elongated member  12 B in a natural state, and collapse to lie flat along the length of the elongated member  12 B for insertion of the device  10 B as seen in FIGS.  7 A-B. An insertion catheter  21  comprising a rotatable handle  23  having internal threads, a threaded element  25  that interlocks with the rotatable handle  23 , a molded hub  27 , a rigid member  29 , and a malecot in an expanded state is shown in FIG. 7A. To collapse the malecot  35 , the device  10 B is disposed on the rigid member  29  while holding the molded hub  27  steady. Longitudinal tension exerted on device  10 B by opposing tugs exerted on the hub  27  and distal end of the rigid member  29  pulls opposite ends of the device  10 B apart and collapses the malecot  35 . FIG. 7B shows the malecot  35  in its collapsed state.  
         [0052]    After the malecot has been collapsed, the insertion catheter  21  may be directly inserted into a body of a patient. The rigid member  29  is released from the device  10 B by rotating the handle  23  to release it from the hub  27 . Removal of the rigid member  29  releases tension on the device  10 B and allows the elastic member to resume its expanded shape deploying the malecot and securing the device  10 B within the body.  
         [0053]    [0053]FIG. 8 depicts a retention structure  38  as a barb having two ends. One end  37  of the barb is formed integrally with the elongated member  12 C. The other end  39  of the barb extends laterally from the elongated member  12 C. The elongated member  12 C extends along a longitudinal axis  16 C. The retention structure  38  extends along a lateral axis  18 C relative to the longitudinal axis  16 C. The barb  38  may be disposed anywhere along the length of the elongated member  12 C. The barb comprises a curved elastic member  22 C embedded within a flexible material  24 C. The barb  38  may or may not create an opening in the elongated member  12 C depending on the depth of the cut made in the elongated member  12 C. In the embodiment depicted in FIG. 6, the barbed portion  38  forms an opening  40 .  
         [0054]    To form the barbed retention structure  38  a piece of tubing is extruded to have a central lumen surrounded by a smaller outer lumen in a wall of the elongated member  12 C. Two angled cuts are made into the wall of the elongated member  12 C intersecting to form end  39 . The end  39  of the barb extending laterally from the elongated member  12 C exposes the small lumen. An elastic member  22 C is shaped into a curved geometry that will form to the shape of the barb  38 . The curved length of elastic member is then inserted into the small lumen through end  39 .  
         [0055]    Referring to FIG. 9, insertion of the device  10 C into a body of a patient can be accomplished by placing the device  10 C in a conventional delivery system  41  and inserting the delivery system  41  into a body of a patient. In FIG. 9, the device  10 C is disposed over a rigid member  43  on the delivery system  41 . The delivery system  41  comprises a handle  45 , a threaded hub  47 , the rigid member  43 , and an adapter  51  designed to attach the medical device  10 C. When the device  10 C is disposed over the rigid member  43 , the end  37  of the barb  38  formed integrally with the elongated member  12 C is preferably inserted into the body first so that the barb  38  folds into the opening  40  created in the elongated member  12 C. For applications where end  39  of the barb is to be inserted first, a cannula  53  may be inserted over the elongated member  12 C to cover and collapse the barb  38  therein. Once the device is positioned into the body, the cannula is withdrawn deploying the barb within a body cavity thereby anchoring the device  10 C in the body.  
         [0056]    [0056]FIG. 10 shows a reinforced inward spiral coil retention structure  42 . The inward spiral retention structure may be disposed at either end or at both ends of the elongated member  12 D. The elongated member  12 D extends along a longitudinal axis  16 D. The spiral coil  42  extends along a lateral axis  18 D relative to the longitudinal axis  16 D. The spiral coil  42  anchors the medical device  10 D in place to prevent migration. As with the single and double retention coils (FIGS. 1 and 5), the elastic member  22 D embedded within the flexible material  24 D in the spiral coil retention structure  42  may be disposed along its inner perimeter. Alternatively, the elastic member may be disposed along the outer perimeter of the coil or along its flanks. It may optionally also extend within a portion of the elongated member  12 D itself. The lumen  20 D extends through at least a portion of the spiral coil  42  to facilitate drainage of fluid and other substances and may extend all the way through the spiral coil  42 . The elongated member  12 D and the retention structure  42  may incorporate a plurality of holes  30 D and/or a large drain hole slot  28 D to further facilitate drainage. Insertion of the device  10 D into a body of a patient can be accomplished through use of the insertion catheter shown in FIG. 2.  
         [0057]    To form a J curl retention structure, a single cut between approximately ⅜ and ¾ of a turn along the spiral coil retention structure may be made. As shown in FIG. 10, two examples of suitable cuts  55  and  56  made in the spiral coil retention structure at approximately ⅜ and ¾ of a turn respectively form the J curl retention structure. After the cut is made, the open end of the retention structure may then be tapered on both sides to form a small opening at the distal tip of the device.  
         [0058]    To form the inward spiral retention structure, a dual lumen elongated member of flexible material is provided. An elastic member pre-formed into an inward coil may be inserted into one of the lumens, and the elongated member wound about itself to form the designated structure. Alternatively, the pre-formed elastic member  22  may be bound to an outer wall of the flexible material  24 , and the distal end of the elongated member of flexible material wound about itself.  
         [0059]    Referring to FIG. 11, a reinforced retention structure of the invention can be an elastic ring  44  containing an elastic member  22 E embedded within a flexible material  24 E. The elongated member  12 E extends along a longitudinal axis  16 E. The retention structure  44  extends along a lateral axis  18 E relative to the longitudinal axis  16 E. The reinforced ring may be at a 90° angle transverse from the longitudinal axis  16 E or at a lesser angle designed to adapt to various internal body openings. The elastic ring or rings  44  protrude from the external surface of the elongated member  12 E. The elastic rings  44  are designed to provide rigidity to the device and prevent migration of the device  10 E. Drainage holes or apertures  30 E are disposed along the length of the elongated member  12 E to provide for fluid communication with the lumen  20 E and to facilitate urinary drainage.  
         [0060]    FIGS.  12 A-B show retention structures of the present invention in a straightened configuration. In FIG. 12A, a plurality of holes  46  are cut into a retention structure to increase the drainage rate of fluid passing through the lumen  20 F. In FIG. 12B, use of an elastic member provides stability to the retention structure  14 F to support a large continuous drain hole slot  48  in the surface of the retention structure  14 F. The drain hole slot  48  may also appear in the elongated member (not shown) if the elastic member extends out of the retention structure  14 F into the elongated member. The length and width of the drain hole slot can vary depending on the needs of the particular patient. The width of the drain hole slot can be very narrow to prevent tissue in-growth.  
         [0061]    One medical device of the present invention  10 G placed into a body of a patient is illustrated in FIG. 13. The medical device  10 G comprises an elongated member made of a flexible material and a reinforced retention structure  14 G including an elastic member in the flexible material. The retention structure  14 G featured in FIG. 13 has the geometry of an inward spiral coil, but other retention structures described above may also adequately be employed. The device  10 G is easily inserted into the body through the ureter  50  and into the kidney  52  of the patient, as pictured herein. Insertion is accomplished in any conventional manner, such as collapsing the retention structure of the device  14 G using a guidewire, stylet or cannula and then inserting the device  10 G through the urethra. After insertion and removal of the straightening device, the retention structure  14 G of the medical device reverts to a pre-determined geometry.  
         [0062]    A method of manufacturing the medical devices of the present invention (FIGS. 1, 5,  6 ,  8 ,  10 ,  11 ) comprises providing an elongated member made of a flexible material and affixing a elastic member to the flexible material to form a reinforced retention structure. The elastic member is first shaped by mechanical operation at elevated temperatures, for example 500° C. The elastic member may be shaped into a curl, a coil, a malecot, a ring or a barb. Next, the elastic member may be positioned in the flexible material in a number of ways. For example, the pre-shaped elastic member may be introduced into a lumen of a multi-lumen extrusion tube of flexible material. The elastic member may be fed through one of the lumens of the multi-lumen extrusion by hand or by mechanical operation. The elastic member may also be molded in a thermosetting material, in that the pre-shaped elastic member is placed in a mold cavity and a flexible material poured around it such that it may ultimately bind to an external or internal surface of the flexible material. Also, the elastic member may be bound to an external or internal surface of the flexible material with glue or tape.  
         [0063]    Variations, modifications, and other implementations of what is described herein will occur to those of ordinary skill in the art without departing from the spirit and scope of the invention. Accordingly, the invention is to be defined not only by the preceding illustrative description.  
         [0064]    What is claimed is: