A stent is designed to be placed in a lumen of a patient and extend therethrough. The stent includes a distal end and a proximal end. The distal end includes a distal retention structure and the proximal end includes a plurality of radially extending flexible segments to prevent migration of the stent through the lumen. At least one radially extending flexible segment at the proximal end is able to assume an outwardly everted configuration. The stent of the invention, due to its dimensions, shape, and rigidity, minimizes the force of contact and abrasion to sensitive areas of the patient's body, such as the trigone region of the bladder and the ureteral-vesical junction.

TECHNICAL FIELD

The invention generally relates to medical devices for drainage of fluids, and more specifically to stents.

BACKGROUND INFORMATION

A ureter is a tubular passageway in a body that carries urine from a kidney to a bladder. Ureteral stents are used to assist urinary drainage from the kidney to the urinary bladder in patients with a ureteral obstruction or injury, or to protect the integrity of the ureter during a variety of surgical manipulations. Stents may be used to treat or avoid ureteral obstructions (such as ureteral stones or ureteral tumors), which disrupt the flow of urine from the kidneys to the bladder. Serious obstructions may cause urine to back up into the kidneys, threatening renal function. Ureteral stents may also be used after endoscopic inspection of the ureter to prevent obstruction of the ureter by swelling of the ureteral wall caused by the surgical procedure.

Ureteral stents typically are tubular in shape and terminate in two opposing ends: a kidney-end and a bladder-end. One or both of the ends may be shaped in a way to prevent the upward downward migration of the stent due, for example, to physiological movements. The ends may be coiled in a pigtail or J-shape to retain their position in the ureter. A kidney-end coil resides within a lumen of the kidney, known as the renal pelvis, and is designed to prevent stent migration down the ureter and into the bladder. Similarly, the bladder-end coil resides in the bladder and is designed to prevent stent migration upward toward the kidney. The bladder coil may also be used to aid in retrieval and removal of the stent.

Regions such as the trigone region in the bladder and the region of the ureter near the bladder known as the ureteral-vesical junction are particularly sensitive and thus prone to irritation by foreign objects. Commonly used bladder-end coils contact and irritate these regions causing discomfort to the patient. Moreover, ureteral stents particularly the bladder-end, may produce adverse effects including blood in the urine, a continual urge to urinate, and strangury. Thus, while providing drainage from the kidney to the bladder, stents may also cause or contribute to significant patient discomfort and serious medical problems.

SUMMARY OF THE INVENTION

The invention generally relates to medical devices to provide drainage, more particularly to stents, and more particularly to ureteral stents that reduce patient discomfort by minimizing contact between the stent and regions of the body of the patient, including the trigone region and the ureteral-vesical junction. In particular, the invention relates to a stent with a bladder-end that includes a plurality of radially extending flexible segments, which form the bladder retention structure. The bladder retention structure of the stent reduces patient discomfort by minimizing the contact and abrasion between the retention structure and the trigone region and the ureteral-vesical junction of the patient. The retention structure is generally located within the urinary bladder when the stent is placed within the ureter of a patient. The plurality of radially extending flexible segments at the bladder-end function to maintain a proximal end of the stent within the bladder and thus prevent the stent from migrating towards the kidney.

It is noted initially that the directional terms proximal and distal require a point of reference. As used herein, the point of reference is from the perspective of a medical professional. Therefore, the term distal refers to a direction that points into the body of the patient and away from the medical professional, whereas the term proximal refers to a direction that points out of the patient's body.

The shape and composition of the bladder-end or proximal retention structure reduces patient discomfort. The proximal retention structure is formed in a shape that minimizes contact between the radially extending flexible segments of the proximal retention structure and the trigone region of the bladder, thus reducing patient discomfort. The radially extending flexible segments are also sufficiently thin and flexible to minimize the force of contact and abrasion to the sensitive regions of the urinary tract including the trigone region. The plurality of radially extending flexible segments that form the proximal retention structure are, however, sufficiently resilient such that the shape of the proximal retention structure is generally maintained while the stent is in the body.

In one aspect, the invention is directed to a ureteral stent for facilitating drainage from a kidney to a bladder of a patient including an elongated member that includes a proximal end, a distal end, and a length sufficient to extend substantially along an entire length of a ureter of a patient. The elongated member defines a lumen extending at least partially therethrough. The stent further includes a plurality of radially extending flexible segments extending from the proximal end. At least one of the segments is able to assume an outwardly everted configuration to inhibit movement of the segments from the bladder into the ureter after the stent is placed within the patient. A kidney portion extends from the distal end of the stent for receiving urine after placement of the stent within the patient and for passing at least some of the received urine into the lumen of the elongated member. The kidney portion is able to assume a configuration to inhibit movement of the kidney portion into the ureter once inserted into the patient.

In some embodiments of the foregoing aspect of the invention, an outside dimension of the assumed configuration of the kidney portion is larger than an outside diameter of the elongated member at the distal end. In another embodiment, the kidney portion can include a coiled shape. In yet another embodiment, the coiled shape can be conical, spherical, helical, frusto-conical, or combinations thereof.

In another aspect, the invention relates to a stent including an elongated member including a proximal end and a distal end and defining a lumen extending at least partially through the elongated member. The stent further includes a plurality of radially extending flexible segments disposed adjacent to the proximal end. At least one of the radially extending flexible segments is able to assume an outwardly everted configuration to inhibit movement of the segments into a lumen of a patient after the stent is placed within the patient. A distal retention structure is disposed adjacent to the distal end to inhibit movement of the distal end into the lumen of the patient after inserting the stent within the patient.

In some embodiments of the foregoing aspect of the invention, an outside dimension of the distal retention structure is larger than the an outside diameter of the elongated member in the distal end. In a further embodiment, the distal retention structure can include a coiled shape. In another embodiment, the coiled shape can be conical, spherical, helical, frusto-conical, or combinations of the foregoing. In yet another embodiment, the elongated member can have a length sufficient to extend substantially along an entire length of a ureter of the patient.

In various embodiments of the foregoing aspects of the invention, an outside diameter of the plurality of radially extending flexible segments is larger than an outside diameter of the proximal end of the elongated member. In other embodiments, the outside diameter of the segments can be between about 3 cm to about 5 cm. In yet other embodiments, the plurality of radially extending flexible segments can be resilient. In further embodiments of the foregoing aspects of the invention, at least six radially extending flexible segments can extend from the proximal end.

In yet another aspect, the invention relates to a method of placing a stent in the body of a patient. The method includes the steps of providing a stent, inserting the stent into a lumen of the patient, and positioning the stent in the patient such that a plurality of radially extending flexible segments and a distal retention structure inhibit migration of the stent in the lumen of the patient. The stent includes an elongated member including a proximal end and a distal end and defining a lumen extending at least partially through the elongated member. The plurality of radially extending flexible segments extends from the proximal end in one embodiment. At least one of the radially extending flexible segments is able to assume an outwardly everted configuration to inhibit movement of the segments into the lumen of the patient after placement of the stent within the patient. The distal retention structure extends from the distal end to inhibit movement of the distal end through the lumen of the patient after placing the stent within the patient.

In some embodiments, the method includes the step of disposing a stylet within the lumen of the elongated member to maintain the distal retention structure in a substantially linear configuration prior to inserting the stent. In other embodiments, the method includes the step of disposing the stent within a flexible sheath to maintain the radially extending flexible segments in a substantially linear configuration prior to inserting the stent. In one embodiment, the method includes the step of removing the flexible sheath after positioning the stent within the patient, thereby deploying the radially extending flexible segments. In another embodiment, the method includes the step of removing the stylet after positioning the stent within the patient, thereby deploying the distal retention structure.

In various embodiments of the foregoing aspect of the invention, an outside diameter of the plurality of radially extending flexible segments is larger than an outside diameter of the elongated member at the proximal end, and an outside dimension of the distal retention structure may be larger than an outside diameter of the elongated member at the distal end. Further, the stent can be placed within a ureter of the patient and the plurality of radially extending flexible segments can be disposed within a bladder and the distal retention structure is disposed within a kidney.

In still another aspect, the invention relates to a method of making a stent for maintaining the flow of a bodily fluid in a patient. The method includes the steps of providing an elongated member and sectioning a proximal portion of the elongated member into a plurality of segments oriented substantially parallel to a longitudinal axis of the elongated member. The method also includes the step of shaping at least one of the segments to assume a radial, outwardly everted configuration to inhibit movement of the segments into a lumen of a patient after placement of the stent within the patient. The elongated member includes a lumen.

In one embodiment of the foregoing aspect of the invention, the providing step includes forming the elongated member by injection molding. In another embodiment, the providing step includes forming the elongated member by extrusion. In yet another embodiment, the sectioning step includes securing the elongated member in an indexing fixture and cutting the proximal portion with a blade. In some embodiments of the invention, the shaping step includes bending at least one of the segments around a form mold and fixing the at least one segment in the radial, outwardly everted configuration. The fixing step may include thermosetting the at least one segment at about 140-160° C.

DESCRIPTION

Embodiments of the present invention are described below. It is, however expressly noted that a stent in accordance with the present invention is not limited to use as a ureteral stent, but rather the stent may be used in essentially any lumen within a body.

One embodiment of the invention generally relates to a ureteral stent that minimizes discomfort when positioned within a lumen of a patient. The stent of the present invention includes a proximal retention structure that includes a plurality of radially extending flexible segments, wherein at least one segment is able to assume an outwardly everted configuration. Due to its dimensions, shape, and flexibility, the proximal retention structure minimizes the force of contact and abrasion to sensitive areas outside one end of the lumen. When the stent is used as a ureteral stent, the proximal retention structure minimizes irritation to the trigone region of the bladder and the ureteral-vesical junction.

Referring toFIG. 1, a ureteral stent100includes an elongated member118that includes a proximal portion102, a distal portion106, and a central body108. The proximal portion102includes a plurality of radially extending flexible segments110(six are depicted) that form a proximal retention structure101. The radially extending flexible segments110extend from a proximal end107of the central body108in an outwardly everted configuration. The distal portion106of the stent100also includes a distal or kidney retention structure116extending from a distal end109of the central body108. The stent100further includes the central body108interposed between the proximal end107and the distal end109. A lumen105passes at least partially through the length of the elongated member118and is defined by the elongated member118. In one embodiment, the elongated member118has an opening104at the proximal portion102and at least one opening114in the distal portion106. Openings104and114are in fluid communication with the lumen105. One or more openings may be provided along the length of the central body in fluid communication with the lumen105.

FIG. 2Ais a cross-section of the stent100ofFIG. 1illustrating the lumen105that exists in at least a portion of the elongated member118.FIGS. 2B-2Ddepict alternative cross-sectional views of the elongated member118. In one embodiment of the invention, shown inFIG. 2A, a circular lumen105is defined by the central body108.FIG. 2Bdepicts an alternative embodiment of a stent with an elliptical lumen210defined by a central body208.FIG. 2Cdepicts yet another alternative embodiment, wherein a central body212defines multiple circular lumens214. In some embodiments, the cross-sectional configurations of the multiple lumens214can be circular, elliptical, polygonal wedge-shaped or any combination thereof. In yet another alternative embodiment, as shown inFIG. 2D, a square lumen218is defined by the central body216.

The various configurations may include different numbers of lumens of various sizes. Moreover, a lumen may be shaped specifically to receive or to be compatible with guide wires, cannula, or other devices. The inner diameters or dimensions, the number, and the arrangement of lumen(s) within the stent100may be varied to suit a particular application, for example, to alter physical properties of the stent100and/or the rate of urine flow therethrough. For example, inFIG. 2Athe longitudinal center axis203of the lumen105is arranged coaxially with the longitudinal center axis204of the central body108. Alternatively, the longitudinal center axes203and204can be arranged abaxially to one another.

Referring back toFIG. 2A, the wall202of the lumen105is of sufficient thickness to resist the pressure from adjacent tissue caused by, for example, a tumor, peristalsis, or swelling that would restrict the ureter405(SeeFIG. 4A) if not for the presence of the ureteral stent100. For example, the wall thickness may range from about 2.5×10−3to about 2.0×10−3mm. In a particular embodiment, the ureteral stent100has a wall thickness of about 2.1×10−3μm. In one embodiment, the radially extending flexible segments110are produced by sectioning the proximal portion102of the elongated member118(SeeFIG. 5B). In that case, the thickness of the segments110are determined by the wall thickness of the elongated member118. Where a greater wall thickness is desired, the high degree of flexibility of the segments110may be compromised. In that case, radially extending flexible segments110of lesser thickness may be prepared and later attached to the proximal end107of the central body108(SeeFIGS. 5C and 5D).

The outside diameter170of the central body108may range from about 4 French to about 9 French. Depending on the size of the patient, an acceptable range for the outside diameter170of the central body108is about 4.8 French to about 7.3 French. When a larger diameter is required, such as, for example, when a higher flow or a greater stiffness is desired, a central body108having a larger outside diameter170may be used. An acceptable larger outside diameter170of the central body108may be about 8 French to about 12 French. Where larger diameters are employed, it may be desirable to prepare the proximal retention structure101separately to ensure that the segments110maintain a high degree of flexibility.

The length of the central body108may also vary to suit a particular application, for example, the size of the patient and the particular lumen. Referring toFIG. 4B, an acceptable length of the central body108positions the proximal end107of the central body108at the ureteral-vesical junction408and the distal end109of the central body108adjacent to the renal pelvis403. The length of the central body108may range from about 20 cm to about 30 cm, for example.

The radially extending flexible segments110are of sufficient length to form a proximal retention structure101that is effective in preventing the upward migration of the stent100, for example, towards the renal pelvis403. The length of a single segment may range from about 2 cm to about 5 cm. In a particular embodiment, the length of an individual segment110is about 4.7 cm. The diameter152formed by a single everted segment110(SeeFIG. 1) may range from about 1 cm to about 3 cm and preferably about 2 cm.

To prevent the proximal retention structure101from passing through the ureter405, an outside diameter150formed by the radially extending flexible segments110should exceed the outside diameter170of the proximal end107of the central body108. The outside diameter150of the segments110may range from about 2 cm to about 6 cm. In a particular embodiment, the outside diameter150of the segments110is about 4 cm. Detailed methods of producing the radially extending flexible segments110are depicted inFIGS. 5A-D.

In one embodiment of the invention, a medical professional, such as a physician, advances the ureteral stent100into the patient's body using a pushing device or stylet305, as shown inFIGS. 3A and 3B.FIG. 3Adepicts a longitudinal cross-section of the ureteral stent100showing a stylet305disposed within the lumen105of the elongated member118. The radially extending flexible segments110are shown in a linear configuration, representing the shape assumed when advancing the stent100through the patient's urethra. Due to their high degree of flexibility, the radially extending flexible segments110are able to assume a substantially linear configuration upon insertion into the urethral opening411of the patient.

The stylet305has a distal end307and a proximal end309. The stylet305should be long enough such that the distal end307of the stylet305can contact the distal tip117of the elongated member118, while the proximal end309of the stylet305remains outside of the patient's body when the ureteral stent100is properly positioned within the ureter405of the patient (SeeFIG. 4A). The stylet305is sufficiently rigid to deform the distal retention structure116into a linear conformation, thus facilitating insertion of the stent100into the patient's body.

In an alternative embodiment, a flexible sheath300is disposed around the ureteral stent100to maintain the elongated member118in a linear conformation.FIG. 3Bdepicts a longitudinal cross-section of the flexible sheath300showing the ureteral stent100disposed therein. The flexible sheath300has a linear cavity304defined by an outer wall302. The leading portion306of the flexible sheath300includes a tapered tip308, which facilitates passage through a bodily lumen. A sheath retraction structure303is coupled to the outer wall302for removing the flexible sheath300from the patient after the stent100is inserted into the patient. The sheath retraction structure303can be a thread-like structure that is disposed in the urethra and extends outside of the patient while a medical professional inserts the stent100into the patient's body.

In one embodiment, prior to inserting the ureteral stent100into the patient the stent100is loaded into the flexible sheath300. The ureteral stent100is oriented in the linear cavity304such that the distal retention structure116of the elongated member118is disposed within the leading portion306of the flexible sheath300. The flexible sheath300confines the ureteral stent100within the linear cavity304, causing the elongated member118to assume a substantially linear configuration.

To connect the stylet305to the ureteral stent100, the medical professional passes the stylet305through the lumen105of the elongated member118until the distal end307of the stylet305contacts the distal tip117of the elongated member118. The flexible sheath300may then be disposed over elongated member118to linearize the radially extending flexible segments110. The ureteral stent100, the flexible sheath300and the stylet305are sufficiently flexible to conform to curvatures encountered in the bodily lumen (SeeFIG. 4A).

Referring toFIGS. 1,4A, and4B, the radially extending flexible segments110reduce patient discomfort by minimizing contact with the trigone region409of the bladder407. At least one of the radially extending flexible segments110is able to assume an outwardly everted configuration, such that a portion of the at least one segment110is substantially perpendicular to the longitudinal axis204of the central body108. In a particular embodiment, all of the radially extending flexible segments110are able to assume an outwardly everted configuration, allowing the proximal retention structure101to maintain a relatively compact shape, thus minimizing contact to the trigone region409of the bladder407.

Should the proximal retention structure101contact a bladder wall410abrasion and irritation of the bladder407are further reduced by minimizing the force of contact of the radially extending flexible segments110against the sensitive regions of the bladder407. The radially extending flexible segments110are generally thin, narrow and light in weight. Additionally, the segments110are constructed from a flexible material that readily yields to pressure exerted by the bladder wall410. As such, when the proximal retention structure101contacts the bladder wall410, much of the force of contact is absorbed by the flexible segments110. When absorbing the force of contact the radially extending flexible segments110collapse on an axis substantially perpendicular to the longitudinal axis204of the central body108. Accordingly, the outside diameter150of the proximal retention structure101remains greater than the diameter of the ureter, thus inhibiting migration of the stent100through the ureter405.

Additionally, the force of contact of the proximal retention structure101against the bladder wall410may be further reduced due to the configuration of the radially extending flexible segments110. In one embodiment, as shown inFIG. 1, the radially extending flexible segments110may be outwardly everted such that the distal ends111of the segments110are generally orthogonal to the proximal end107of the central body108. In this configuration, the portion of the radially extending flexible segment110that contacts the bladder wall410is generally planar. Consequently, when the proximal retention structure101contacts the bladder wall410, abrasion and irritation to the sensitive regions of the bladder407is minimized. Moreover, the radially extending flexible segments110are constructed from a resilient material, allowing the segments110to regain their original shape after being deformed.

In operation, the central body108of the stent100is positioned in the urinary tract of a patient between the bladder407and a kidney401and extends along the entire length of the ureter405(SeeFIGS. 4A and 4B). Alternatively, the stent100may be used in other bodily lumens. The proximal retention structure101is positioned within the bladder407and the distal retention structure116is positioned within the renal pelvis403of the kidney401(SeeFIG. 4B). At the proximal portion102, the proximal retention structure101functions as an anchor to inhibit migration of the stent100through the ureteral-vesical junction408. A retraction structure103can be disposed adjacent to the proximal retention structure101to allow the stent100to be removed without using a cytoscope. The retraction structure103can be a thread-like structure that is disposed in the urethra and extends outside of the patient when the stent100is in use.

The distal portion106of the elongated member118is located within the renal pelvis403when the stent100is positioned in the patient. The distal portion106forms a distal retention structure116that functions as an anchor to prevent the migration of the stent100out of the renal pelvis403and down into the ureter. To prevent the distal portion106from passing through the ureter405, an overall outside dimension154of the distal retention structure116should exceed the outside diameter170of the distal end109of the central body108. The shape of the distal retention structure116may be a coil112. Alternatively, the distal retention structure116may assume the configuration of a pigtail, J-shape, or a helical coil, for example.

FIGS. 4A and 4Billustrate a method of inserting the stent100into the ureter405of a patient. The ureteral stent100inFIGS. 4A and 4Bis shown disposed within the flexible sheath300. As shown inFIG. 4A, a medical professional inserts the ureteral stent100and the flexible sheath300into the patient's bladder407by advancing the stylet305through the urethral opening411of the patient. The stylet305is further advanced up into the ureter405, transporting the ureteral stent100and the flexible sheath300into the desired location. So that the physician can confirm the proper placement of the stent100by radiographic techniques, a small amount of metal or other radiopaque material, such as, for example, bismuth, may be embedded within the elongated member118or alternatively at the distal end307of the stylet305.

Once the stent100is properly positioned in the patient's body, the medical professional removes the flexible sheath300by drawing the sheath retraction structure303out of the body. The drawing action causes the ureteral stent100to slip through an opening310in the flexible sheath300and remain positioned in the ureter. When drawing the sheath retraction structure303out of the body, a sufficient amount of counter-force should be applied to the stylet305to maintain the proper position of the ureteral stent100. Removal of the flexible sheath300allows the flexible segments110to regain their original shape, thus inhibiting upward migration of the stent100. After the flexible sheath300is removed from the patient, the stylet305may be retrieved from the patient's body.

To ensure that the stent100maintains its position within the ureter405, the stylet305should be retrieved from the patient at a relatively slow pace to avoid displacing the stent100from its position in the ureter405. As the stylet305is removed from the distal end109, the distal retention structure116is able to assume a configuration that inhibits movement down the ureter405. Thus, the stylet305may be retrieved at a progressively faster pace as the distal retention structure116regains its original shape.

Alternatively, the flexible sheath300, once removed from the stent100, can be used as a pusher for preventing migration of the stent100while withdrawing the stylet305. More particularly, the flexible sheath300is removed from the stent100, but remains in the bladder407, adjacent to the proximal retention structure101. As the stylet305is retrieved from the patient, the flexible sheath300is pushed upward against the proximal retention structure101, thus preventing the stent100from migrating down the ureter405. Indeed, when removing the stylet305from the stent100, a sufficient amount of counter-force should be applied to the proximal retention structure101to maintain the proper position of the stent100within the ureter405. Once the stylet305is removed from the stent100, both the stylet305and the flexible sheath300can be retrieved from the body of the patient.

FIG. 4Bshows the distal retention structure116positioned within the renal pelvis403of the kidney401and the radially extending flexible segments110positioned in the bladder407. After the stent100is properly placed, a medical professional retracts the stylet305through the urethral opening411leaving the stent100in the ureter405of the patient. Once the stylet305is removed from the stent100, the distal retention structure116is deployed, thereby inhibiting migration of the stent100out of the kidney401.

Once inserted into the body, the stent100operates to drain urine from the kidney401to the bladder407. Referring toFIGS. 1 and 4B, drainage of urine occurs by receiving at least some of the urine into the lumen105through at least one opening114disposed in the distal portion106. Thereafter, the urine passes through the lumen105within the central body108and the proximal portion102until reaching the opening104where the urine empties into the bladder407. The urine may then be expelled from the body under the natural control of the patient.

While the stent100is in use, the retraction structure103remains attached to the stent100and extends outside the patient through the urethral opening411. The length of the retraction structure103in the proximal portion102may vary depending on the size of the patient. When use of the ureteral stent100is no longer required, a medical professional removes the stent100by drawing the retraction structure103out of the patient, which causes the stent100to migrate down the ureter405and out of the patient though the urethral opening411.

During retraction, the retention structures101and116assume substantially linear configurations in response to the force exerted by the medical professional. Particular, the distal portion106is linearized as the renal pelvis403exerts force on the distal retention structure116while exiting the kidney401. Similarly, the proximal portion102assumes a substantially linear configuration as the segments110are folded over the proximal end107of the central body108. In this configuration, the distal ends111of the radially extending segments110are generally parallel to the longitudinal axis204of the central body108. Once removed from the body, the stent100regains its original shape.

Various methods may be used to produce the stent100.FIGS. 5A-5Dillustrate various methods of making the radially extending flexible segments110. As shown inFIG. 5A, the radially extending flexible segments110may be formed by securing the elongated member118in an indexing fixture501and longitudinally sectioning the proximal portion102into segments110(one shown) using a cutting tool505.

In one embodiment, the segments110have widths156that are substantially uniform. In that embodiment, the slices130(SeeFIG. 5B) formed by the cutting tool505are equally spaced around the proximal portion102of the stent100to produce a particular number of segments110. The width156of an individual segment110is dependent on a diameter158of the proximal portion102and the number of segments110produced from the proximal portion102. For example, a proximal portion102with a 9 French diameter may produce six segments110, where each segment110has a width156of about 1.5 mm. The number and width156of the segments110can vary to suit a particular application.

After the proximal portion102is sectioned, the segments110can be form molded and fixed into an outwardly everted configuration, as illustrated inFIG. 5B. In one embodiment, the segments110at the proximal portion102can be conformed to a mold507and fixed by methods commonly known in the art. For example, fixation can occur by thermosetting the formed segments110at about 140 to about 170° C.

The ureteral stent100may be constructed of a biocompatible plastic, such as but not limited to, polyester, nylon based biocompatible polymers, polytetrafluoroethylene polymers, silicone polymers, polyurethane polymers polyethylene polymers, and thermoplastic polymers. In a particular embodiment, the stent100is constructed of ethylene vinyl acetate. The elongated member118may be formed by extrusion or injection molding techniques commonly known in the art.

FIG. 5Cshows an alternative embodiment of the invention where the proximal retention structure101is manufactured separately to include the radially extending flexible segments110and later attached to the stent100.FIG. 5Dillustrates another alternative embodiment where each radially extending flexible segment110is individually manufactured and separately attached to the proximal portion102of stent100. Attachment of the components may be carried out using biocompatible adhesives or various bonding techniques, such as ultrasonic and radio frequency bonding.

Bonding of the components may be performed by heat bonding. Heat bonding functions by partially melting the plastic of a structure, allowing the melted plastic to adhere to a contacting surface or other component, and allowing the plastic to cool and harden, thus forming a bond. Heat bonding methods that include radio frequency bonding, induction heating, and conduction heating may be used. The plastic of a first component may be selected to melt at a similar temperature as a second component so that both components are melted during the heat bonding process. Alternatively, either the first or second component may be constructed from a plastic with a lower melting temperature than the other component in order that only the component with the lower melting temperature may melt during the bonding process.

Alternatively, the components may be bonded by the use of a solvent, such as cyclohexanone and methylethylketone. The solvent acts by dissolving and swelling the plastic of the components. As the plastic of the components dissolve and swell, the components adhere to each other. The solvent is then removed allowing for the dissolved and swollen plastic to harden and thus complete the bonding process.

Having thus described certain embodiments of the present invention, various alterations, modifications, and improvements will be apparent to those of ordinary skill. Such alterations, modifications, and improvements are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description of embodiments of the invention is not intended to be limiting.