Ureteral stent with anti-migration features

Ureteral stents include a tubular body defining a lumen and have (i) a distal kidney section to be placed in or near a patient's kidney, (ii) a proximal bladder section to be placed within or near the patient's bladder, and (iii) a ureter section between the distal and proximal sections to be placed within the patient's ureter. A first anti-migration feature may be provided at the proximal bladder section and may include one or more projections extending outward from the tubular body. The first anti-migration feature may extend less than a total length of the proximal bladder section, and may be configured to not enter the patient's bladder. Furthermore, a second anti-migration feature may be provided at the distal kidney section, the proximal bladder section, or both.

BACKGROUND

The invention relates to ureteral stents.

A ureter is a tubular passageway in the body that conveys urine from a kidney to a bladder. Ureteral stents are used to facilitate urinary drainage from the kidney to the bladder in patients having a ureteral obstruction or injury, or to protect the integrity of the ureter in a variety of surgical manipulations. Ureteral stents are typically about 30 cm long, hollow catheter-like devices made from a polymer and placed within the ureter with the distal end residing in the kidney and the proximal end residing in the bladder. Ureteral stents function by channeling the flow of urine from the kidney to the bladder. One or both ends of a ureteral stent may be coiled in a pigtail shape to prevent the upward and/or downward migration of the stent due to patient movement. For example, the ureter may stretch up to 5 cm in either direction during a patient's normal bodily movements, such as movement during breathing. If the stent is not sufficiently anchored, this may result in stent migration and displacement.

Another factor to be considered relates to tissue irritation caused by the stent. A stent may cause tissue irritation due to the relative movement between the stent and the ureter during natural stretching of the ureter, even when the stent is properly anchored. A typical semi-rigid, anchored stent is unable to adjust for the natural extension and contraction of the ureter during bodily movements, resulting in pressure and irritation of the ureter and surrounding tissue.

Regions of tissue most vulnerable to stent-induced irritation include the kidney, the renal pelvis, the sensitive bladder tissue in the trigonal region, and tissue of the ureteral vesicle junction leading into the bladder. Irritation may be caused by the static or dynamic contact of the semi-rigid stent with sensitive tissues of the body, such as the kidney and the renal pelvis. Chronic trigonal tissue irritation may result from contact of tissue by the bladder-anchoring features of the stent, for example, pigtails at the stent ends. Irritation problems are of concern regardless of the duration of use of the stent. Irritation is of particular concern, however, when use of a stent is required over a long time period.

Another problem associated with ureteral stents is urine reflux and pain during urine voiding. On the initiation of voiding, the bladder wall muscles contract causing the pressure inside the bladder to increase. Because a typical ureteral stent holds the ureteral orifice open, increased bladder pressure during voiding is transmitted to the kidney through the stent, causing urine reflux and flank pain.

SUMMARY

Many factors thus should be considered when designing a ureteral stent. Such factors include the function to be performed by different parts of the stent, such as anchoring, maintenance of an open-flow condition, etc., and comfort. In particular, it is desirable to make a ureteral stent that is easy to insert, comfortable at all times, exhibits good coil recovery (the tendency of the stent ends to return to the originally-designed coiled state after having been straightened, for example, during insertion), remains anchored during normal bodily movements, provides for suitable flow of urine, is easily removable and avoids fracture during insertion, use and removal. The invention relates to various designs for a ureteral stent that facilitate some or all of the above goals.

Ureteral stents according to embodiments of the invention may include a tubular body defining a lumen and having (i) a distal kidney section to be placed in or near a patient's kidney, (ii) a proximal bladder section to be placed within or near the patient's bladder, and (iii) a ureter section between the distal and proximal sections to be placed within the patient's ureter. A first anti-migration feature may be provided at the proximal bladder section and may include one or more projections extending outward from the tubular body. The first anti-migration feature may extend less than a total length of the proximal bladder section, and may be configured to not enter the patient's bladder. Furthermore, a second anti-migration feature may be provided at the distal kidney section, the proximal bladder section, or both.

The invention also relates to methods for providing drainage from a kidney to a bladder within a patient in a ureteral stent. The methods may include deploying the ureteral stent from an outer sheath within a ureter of a patient and sliding an outer layer of the ureteral stent from a first position to a second position to expose one or more projections on the ureteral stent such that the one or more projections move from a delivery position in which the projections do not protrude beyond an outer circumference of the tubular body, to a deployment position in which the projections protrude beyond the outer circumference of the tubular body and contact a ureteral wall of the patient. Additionally, the methods may include locking the position of the outer layer with regard to the tubular body to lock the projections in the deployment position.

DETAILED DESCRIPTION OF EMBODIMENTS

The disclosure relates to ureteral stents configured to reduce movement of the stent when deployed within a patient. As shown inFIG. 1A, ureteral stent10may include a tubular body12having a proximal bladder section20, a distal kidney section15, and a ureter section25. The proximal bladder section20may be disposed at the proximal end50of tubular body12, and may be configured to be disposed in or near a patient's bladder. The distal kidney section15may be disposed at the distal end60of tubular body12, and may be configured to be disposed in or near the patient's kidney. As further shown inFIG. 1A, the ureter section25may be disposed between the proximal bladder section20and the distal kidney section15, and may be configured to be disposed within a patient's ureter.

Tubular body12may define a lumen14configured for the flow of fluid from the distal end60to the proximal end50. The lumen14may be of constant diameter throughout the length of tubular body12(FIG. 1B). However, it is further contemplated that the lumen14may have varying diameters along the length of tubular body12. For example, the lumen14may have a relatively larger diameter at distal end60and a relatively smaller diameter at proximal end50. Alternatively, the lumen14may have a relatively larger diameter at proximal end50and a relatively smaller diameter at distal end60. Furthermore, the lumen14may include various cross-sectional configurations, for example, such as circular, square, etc. As is well known in the art, distal and proximal ends60,50can he open. Alternatively or additionally, the distal and proximal ends60,50can include perforations. Proximal end50may not extend through the ureteral orifice, and it may be made of a soft, flexible material like silicone or other flexible, bacterial-resistant material to reduce transverse forces on the bladder anatomy when the patient bends.

A first anti-migration feature30may be provided at the proximal bladder section20, and a second anti-migration feature40may be provided at the distal kidney section15, the proximal bladder section20, or both. The first anti-migration feature30may be located at a portion of the longitudinal length of the tubular body such that the first anti-migration feature30is configured to not enter a patient's bladder when the ureteral stent10is deployed with the patient. Therefore, for example, the first anti-migration feature30may be configured to not enter the patient's bladder when the proximal end50of the proximal bladder section20is positioned within or near the patient's bladder. In some embodiments, the first anti-migration feature30may extend less than an entirety of a longitudinal length of the proximal bladder section20, as shown inFIG. 1A. For example, the first anti-migration feature30may extend for ¾, ⅔, ½, or ⅓ the length of the proximal bladder section20. Preferably, the proximal-most end of the first anti-migration feature30is spaced from (distally spaced from) the proximal end50of the proximal bladder section20. As shown in the embodiment ofFIG. 1A, the first anti-migration feature extends a length L1and the proximal bladder section20extends a length L2, wherein L1is approximately ½ the length of L2. The length of L2within the proximal bladder section is selected to provide sufficient anti-migration friction to counteract the natural peristaltic action of the ureter. In a preferred embodiment, the anti-migration feature30locally increases the effective outer diameter of proximal bladder section20by at least 20-50% over a length of approximately 3 cm. A more substantial increase in diameter (i.e. 50-70%) can support a shorter anti-migration length (L1). In some embodiments, the first anti-migration feature30extends approximately the entire length of the proximal bladder section20such that L1is approximately equal to L2.

The first and second anti-migration features30,40may collectively reduce substantial migration of the ureteral stent10. For example, the first anti-migration feature30may reduce retrograde movement of the ureteral stent10(i.e., movement distally and away from the patient's bladder), when the ureteral stent10is disposed within a patient. Additionally, the second anti-migration feature40may reduce antegrade movement of the ureteral stent10(i.e. movement proximally and toward the patient's bladder). In some embodiments, the first and second anti-migration features30,40may prevent such movement of the ureteral stent10. It is further contemplated that the ureteral stent10may include only the first anti-migration feature30or the second anti-migration feature40to reduce and/or prevent such movement of the ureteral stent10.

In some embodiments, the ureteral stent10may include the second anti-migration feature40at both the proximal end50and distal end60(FIG. 1C). In this embodiment, the second anti-migration feature40at the proximal end50may further reduce and/or prevent retrograde movement of the ureteral stent10. For example, the second anti-migration feature40at the proximal end50may be configured to extend into the patient's bladder. In some embodiments, the second anti-migration feature40may be provided at only the proximal end50of the ureteral stent10.

The second anti-migration feature40, as described in further detail below, may alternatively refer to one or more features selected from a list including: a mesh structure configured to expand outward when released from an outer sheath and a cross-sectional contouring provided to the first anti-migration feature30.

The first anti-migration features30may be one or more projections35extending radially outward away from an outermost surface of the tubular body12. As shown inFIG. 2A, the protrusions35may include a radially outermost leading edge37. An outermost diameter D1of the tubular body12may be less than an outermost diameter D2of the radially outermost leading edge37. The diameter D2may be, for example, 1.0-3.0 times larger than the diameter D1. In some embodiments, the diameter D2may be 1.2 to 1.5 times larger than diameter D1, and for example, 1.3 times larger.

As shown inFIG. 2A, the projections35may extend a distance T1from a top surface of the tubular body12, and the projections35may extend a distance T2from a bottom surface of the tubular body12. Distance T1may be equal to, larger than, or smaller than T2such that the radially outermost leading edge37may be constant or of varying dimensions along tubular body12. As shown inFIG. 2A, T1and T2are approximately equal. It is further contemplated that the radially outermost leading edge37may comprise varying shapes. For example, when viewed in cross-section, leading edge37may form a rounded configuration (FIG. 2B), a square configuration (FIG. 2C), a triangular configuration (FIG. 2D), a U-shape configuration (FIG. 2E), and/or a wave configuration (FIG. 2F). Additionally or alternatively, the leading edge37may include a chamfered surface. One or more projections35may include a leading edge37with configurations different from one or more other projections35on tubular body12. For example, half of the projections35closer to proximal end50may comprise a leading edge37with a square configuration (FIG. 2C) and half of the projections35closer to the distal end60may comprise a leading edge37with a rounded configuration (FIG. 2B). In some embodiments, the second anti-migration feature40may be provided as a shape contouring to the first anti-migration feature30. For example, the second anti-migration feature40may include shapes as shown inFIGS. 2B-2Fthat contour to the first anti-migration feature30.

The projections35may form a spiral70, as shown inFIG. 2A, such that the spiral70forms one continuous helical structure along a predefined length of tubular body12. In some embodiments, spiral70may include two or more helical segments, wherein each helical segment forms a continuous structure along a predefined length of tubular body12. The spiral70may be oriented at an angle θ with regard to the outermost surface of the tubular body, and may include a pitch P. The angle θ and/or pitch P may be constant or may vary along the length of tubular body12. For example, the angle θ may be relatively larger and the pitch P may be relatively smaller closer to the proximal end50.

In some embodiments, as shown inFIG. 3, the projections35may be one or more rings80, wherein each ring80is separated from an adjacent ring80by distance S. The distance S between each ring may be constant or may vary along the length of tubular body12. For example, S may be smaller closer to the proximal end50.

In other embodiments, the projections35may be one or more pads (protrusions)90. For example, as shown inFIG. 4, each pad90may include a raised structure that is separated from each adjacent pad90. A plane traversing each pad90in a longitudinal direction may traverse at least one other pad, and a plane traversing each pad in a crosswise direction, perpendicular to the longitudinal direction, may traverse at least one other pad. The pads90may each comprise approximately equal surface areas, or the pads90may comprise varying surface areas. For example, the pads90closer to the proximal end50may comprise relatively larger surface areas. Additionally, the pads90may be rigid, and they may be made of the same or of a different material than tubular body12. In some embodiments, the pads90may be made from a different material than the tubular body and include a tacky character such as polyurethane, silicone, or PEBAX (polyether block amide). The pads90may be made from the same base material as the tubular body12, but may be altered to be more tacky. It is contemplated that the pads90may further comprise shape contouring as a second anti-migration feature40, for example as shown inFIGS. 2B-2F. It is further contemplated that the tubular body12may include a coating, for example a hydrophilic coating, but that the pads90preferably are not coated. This improves the anti-migration function of the pads90.

According to some embodiments, the first anti-migration feature30may be one or more protrusions100configured to move from a retracted delivery position (FIG. 5), in which the protrusions100do not protrude radially beyond an outer circumference of the tubular body12, to a protracted deployment position (FIG. 6), in which the protrusions100protrude radially outward beyond the outer circumference of the tubular body12. For example, a slideable outer tube110(e.g., outer layer) may be disposed co-axial and outward of the tubular body12, The outer tube110may include one or more apertures120through which the protrusions100protrude when in the deployment position.

As shown inFIG. 5, when in the delivery position, the protrusions100may be disposed between the outer tube110and the tubular body12, The protrusions100may be substantially co-axial with the outer tube110and tubular body12when the protrusions100are in the delivery configuration. The protrusions100may be of a spring-like material such that a radially inward force (e.g., toward the tubular body12) exerted by the outer tube110prevents the protrusions from projecting outward when in this delivery position. Movement of the outer tube110relative to the protrusions100may align the protrusions100with apertures120, disposed on the outer tube110, such that the protrusions100may project through the apertures120and assume their delivery position. Therefore, the radially inward force from the outer tube110may be removed and the protrusions100may assume their delivery position. It is further contemplated that the protrusions100may move relative to the outer tube110to align the protrusions with the apertures120.

As shown inFIG. 6, when in the deployment position, a portion of the protrusions100may remain disposed between the tubular body12and the outer tube110. This portion of the protrusions100may remain secured to the outer tube12through any suitable attachment means, such as, for example, a clip, adhesive, screw, thermal coupling, etc.

The protrusions100may be deployed and assume their delivery configuration only after the ureteral stent10has been delivered to the deployment site within the patient. Therefore, for example, the protrusions100may project into ureteral wall tissue of the patient when the protrusions100project through apertures120. This may facilitate securing the ureteral stent10within the patient and reducing/preventing retrograde movement of the ureteral stent10. After the ureteral stent10is no longer needed and with the protrusions100still deployed, the ureteral stent10may be removed from the patient without retracting the protrusions100within the outer tube110due to the angle at which the deployed protrusions100extend, Therefore, the protrusions100may remain deployed, and thus in their deployment position, when the ureteral stent10is removed from the patient. In other embodiments, the outer tube110may be moved relative to the protrusions100to fully retract the protrusions100within the outer tube110(FIG. 5) before the ureteral stent10is removed from the patient.

FIG. 7shows the ureteral stent ofFIGS. 5 and 6used with an insertion/extraction tool130. When the ureteral stent10is to be inserted into a patient, the insertion/extraction tool130is inserted into the proximal end50of the stent such that a button (a locking mechanism)135that is spring-biased radially outward fits into an opening (hole)145in the outer tube110. The insertion/extraction tool130can be used to push and/or pull the ureteral stent10into position. For example, when it is desired to deploy the protrusions100, the insertion/extraction tool130may be pulled proximally, which causes the outer tube110to move proximally relative to the tubular member12and to the protrusions100. This causes the protrusions100to become aligned with the apertures120of the outer tube110, and thereby move from the delivery position to the deployment position shown inFIG. 7. As the outer tube110is moved proximally, a slide-lock140, which is part of the outer tube110, may move radially inward to the position shown inFIG. 7. Because the slide-lock140has moved radially inward, the outer tube110cannot be moved distally relative to the tubular body12. The protrusions100thus remain in the deployed position shown inFIG. 7. The button135can be moved radially inward so that it no longer extends into the hole145, and then the insertion/extraction tool130can be removed from the ureteral stent10.

The second anti-migration feature40may include one or more features suitable to reduce and/or prevent antegrade movement of the ureteral stent10. For example, as shown inFIG. 8, the second anti-Migration feature40may include a coiled structure160. As shown inFIGS. 8 and 14, the coiled structure160may be configured to longitudinally extend from a tightly coiled state (FIG. 8) to a loosely coiled state (FIG. 14). This extension may be due to movement of the patient, for example when the patient is breathing.

One or more holes170may be disposed on the coiled structure160, and the holes170may be of sufficient size for fluid flowing within lumen14to exit the tubular body12. It is further contemplated that the holes170are disposed along at least a portion of the proximal bladder section20and/or the ureter section25. For example, the holes170may be disposed along the entire length of tubular body12.

The proximal end50of the tubular body12may include valve180. As shown inFIG. 9Athe valve180may be disposed centrally with regard to a central axis C of the tubular body12. In other embodiments, as shown inFIG. 9B, the valve may180may be disposed lateral to the central axis C of the tubular body12. The valve180may be a one-way valve such that fluid within lumen14may only flow out of the lumen14via the valve180, and not into lumen14via the valve180.

In some embodiments, the second anti-migration feature40may include a mesh structure190configured to expand outward when released from an outer sheath220. As shown inFIG. 10, the mesh structure190may include a middle mesh layer200surrounded by an outer layer205and an inner layer210. The middle mesh layer200may be biased to assume an expanded configuration when released from the sheath220, and the middle mesh layer200may be comprised of a network of interlocking struts. The middle mesh layer200may include for example, a superelastic alloy such as Nitinol. The outer layer205may provide a coating on the mesh layer200to reduce friction between the outer sheath220and the mesh layer200. Additionally, the inner layer210may provide a coating on the middle mesh layer200to facilitate the flow of fluid within the lumen14. In some embodiments, the outer layer205and inner layer210may include, for example, a polymeric material. For example, the outer layer205may comprise polyurethane, PEBAX (polyether block amide), a low friction polymer including TEFLON (PTFE), FILM (Viton, Fluorel, Aflas), or mixtures thereof. The inner layer210may comprise a hydrophilic or polar polymer including, for example, polyurethane or PEBAX (polyether block amide) or mixtures thereof.

Movement of the outer sheath220relative to the mesh structure190may allow the ureteral stent10to move from a delivery position, in which the mesh structure190is disposed within the sheath220, to a deployment position, in which the mesh structure190is removed from the sheath220. As shown inFIG. 10, the mesh structure190may expand to a diameter larger than an outer diameter of the remainder of the tubular body20when in the deployed position. For example, a mesh coated with a flexible material like silicone may be permitted to expand as shown inFIG. 10. This mesh may be restricted to the distal kidney section15of the stent and may have a different cross section than the remainder of the tubular body12. In another embodiment, mesh structure190may be fabricated of the same material as the remainder of the tubular body12, but with a smaller wall thickness so as to be more flexible to more readily form the second anti-migration feature40.

The tubular body12may include one or more fold lines230such that the tubular body12is configured to collapse upon the fold lines230when in a delivery configuration, for example as shown inFIG. 11. The fold lines230may include preformed grooves, indentations, or slits to enable the tubular body12to collapse and fold upon the fold lines230. The fold lines230in tubular body12may be formed into a super-elastic metal mesh, such as one made of nitinol wire, or formed into a polymeric material with self-expanding capabilities. The fold lines230cut into tubular body12may include multiple layers of mesh, with an outer mesh layer being capable of greater expansion diameters than an inner mesh layer. The inner mesh layer may provide additional anchoring support to the outer mesh layer in the deployment position and may contribute to a superior anchoring capability, The elastic restoring force of the inner mesh layer may provide additional force to secure the ureteral stent10in position during deployment. The mesh may be woven or non-woven, collapsible, and self-expanding. The self-expansion may arise from an elastic restoring force to engage the mesh with the surrounding tissue. In some embodiments, the outer mesh layer may expand into a contoured outer shape, being formed into different cross sectional profiles, such as rounded, triangular, square shaped, U-shaped, or wave shaped. It is contemplated that individual wires within the mesh may be shaped with a rounded, triangular, square shaped, U-shaped or wave shaped configuration as illustrated in FIGS.2B-2F to provide additional anchoring support. As shown inFIGS. 11 and 12, the tubular body12may expand radially outward from the fold lines230upon removal of the outer sheath220.

The tubular body12may comprise a material suitable to withstand multiple compression and relaxation cycles of a patient's bladder without breaking. Suitable materials include, for example, polymeric materials, such as polyurethane, silicone, PEBAX (polyether block amide), or any biocompatible thermoplastic elastomer. In some embodiments, the distal kidney section15of the tubular body12may be comprised of a different material than the ureter section25and/or the proximal bladder section20. For example, the distal kidney section15may comprise a relatively more flexible material than the ureter section25and/or the proximal bladder section20. A more flexible distal kidney section15may allow the distal kidney section15to bend and collapse under pressure from a patient's kidney (for example, during urine voiding), and therefore reduce discomfort that is typically associated with a traditional ureteral stent. In some embodiments, the distal kidney section15may be thinner and may comprise a relatively stiffer material than the proximal bladder section20in order to reduce such discomfort. Additionally or alternatively, the distal kidney section15may comprise one or more depressions240, as shown inFIG. 13. The depressions240may provide adequate flexibility to the distal kidney section15of tubular body12to reduce such discomfort. The depressions240may include slits, holes, or indentations in the distal kidney section15. Alternatively or additionally, the depressions140may include a material sufficient to provide such flexibility to the distal kidney section15. This material may be the same or different from the material of the remainder of the tubular body12.

The inner and/or outer surfaces of the tubular body12may be coated. For example, the inner surface may be coated with a lubricious coating to facilitate the flow of fluid within lumen14. In some embodiments, the inner surface coating may substantially prevent the growth of biofilm. The outer surface may be coated with, for example, a hydrophilic coating to promote the attachment of the ureteral stent10to the ureter wall of a patient.

As shown inFIG. 14, the ureteral stent10may be delivered to the ureter300of a patient with, for example, outer sheath220. In this example, the ureteral stent10may be positioned within a patient such that the distal end60is disposed within the patient's kidney310and the proximal bladder section20does not enter the patient's bladder320. The distal kidney section15is thus secured within the kidney310to prevent and/or reduce antegrade movement of the ureteral stent10. Furthermore, the proximal bladder section20is positioned such that it does not enter the bladder320but still provides a secure attachment to the wall of the ureter300to prevent and/or reduce retrograde movement of the ureteral stent10. Thus, ureteral stent10may not contact the sensitive bladder tissue in the trigonal region of a patient and thereby reduce pain and discomfort for the patient. In some embodiments, the ureteral stent10may be positioned such that the proximal end50does not enter the patient's bladder320. The first and second anti-migration features30,40allow the ureteral stent to remain fixed in place within the patient while the ureteral stent10reduces such pain and discomfort. Thus, ureteral stent10advantageously provides increased patient comfort.