Abstract
A stent having an elongated tubular configuration consisting of at least one anchor section to inhibit migration. Said anchor section is fabricated by an expandable mesh of woven metallic or polymeric elements. The anchor is configured to minimize contact abrasion and irritation to the entrance of the lumen being stented, as well as to enervated tissue surrounding that entrance, as well as to better absorb forces and increase retention as the lumen is stretched.
Claims
1. A method for deploying a ureteral stent, said method comprising: Advancing the distal anchoring device at the distal end of the ureteral stent into a patient's kidney; Expanding the proximal anchoring device in the bladder wherein a surface of the anchoring device is at risk of engaging the ureteral orifice or immediately adjacent tissue when the anchor is fully deployed; Pre-shaping or deforming the expanded anchoring device to reduce the risk of the expanded anchoring device engaging the ureteral orifice or immediately adjacent tissue when the stent is fully deployed.
2. A method as in claim 1 wherein the bladder-end anchor is fabricated from a woven mesh that acts as a shock absorber.
3. A method as in claim 1 wherein expanding the proximal anchoring device comprises releasing the proximal anchoring device from constraint so that said proximal anchoring device self-expands in the bladder.
4. A method as in claim 2 wherein the woven mesh material has antibacterial properties or coating to avoid encrustation
5. A method as in claim 4 wherein the antibacterial mesh material is a silver alloy or silver coating.
6. A method as in claim 1 wherein pre-shaping and deforming comprises everting a distal surface of the expanded proximal anchoring device into a cup-shaped form to create a contact region with the bladder wall spaced radially outwardly from the shaft of the ureteral stent to create a non-contact region surrounding the ureteral orifice.
7. A method as in claim 6 wherein the contact region is an annular ring surrounding the ureteral stent shaft, with an inner non-contact diameter at least three times the outer diameter of the stent shaft.
8. A method as in claim 6 wherein the contact region of the cup-shaped form is softer and more flexible than the balance of the anchor.
9. A method as in claim 1 wherein there is a second proximal anchor on the stent having higher retention force and located proximal to a softer anchor in normal contact with the tissue.
10. A method as in claim 1 and claim 6 wherein retention force of the proximal anchor in the bladder may be made variable by use of an stretchable internal resistance member
11. A method as in claim 10 wherein the stretchable internal resistance element increases anchor stiffness and retention force as the stent is pulled harder up the ureter.
12. A ureteral stent having a proximal anchor in the bladder with reduced tissue irritation and improved shock-absorbing characteristics, said ureteral stent comprising: a stent body or shaft; a proximal anchor in the bladder formed from a woven mesh at the proximal end of the stent body or shaft, wherein the proximal anchor can be stretched axially to reduce diameter during placement, and radially expand after placement; wherein the proximal anchor is configured to have an initial self-expanded conformation pre-shaped or everted into a flexible concave cone or cup-shape having an annular contact region shaped to avoid contact pressure against the ureteral orifice or bladder tissue immediately adjacent to the ureteral orifice when the stent is placed therethrough.
13. A bladder-end anchor as in claim 12, wherein the woven mesh has different physical characteristics in the bladder tissue contact area than in the balance of the anchor.
14. The woven mesh of the anchor in claim 13, wherein the mesh in tissue contact is softer than the balance of the anchor.
15. The woven mesh of the anchor in claim 13, wherein the wires of the mesh in tissue contact are flat, while the remaining mesh wires are round.
16. The woven mesh of the anchor in claim 13, wherein the mesh in contact with the tissue has a more open weave than the remaining mesh.
17. The bladder-end anchor as in claim 12, wherein the flexible cone or cup shape in contact with the bladder tissue has an inner diameter of at least three times the diameter of the stent shaft where there is no contact with the ureteral orifice or bladder tissue.
18. A bladder-end anchor as in claim 12, wherein the strands of the mesh are made from Nitinol, stainless steel, or a silver alloy.
19. A bladder-end anchor as in claim 12, wherein the strands of the mesh are made of a polymeric material such as a fluoropolymer, polyethylene or polyester.
20. A bladder-end anchor as in claim 12, wherein there is an internal resistance member that increases anchor stiffness as the anchor is pulled towards the ureteral opening.
21. An internal resistance member for a bladder-end anchor as in claim 20 consisting of an elastic cord or spring between the most proximal end of the anchor and the attachment of the anchor to the body of the stent.
22. A multi-part anchor where a second stiffer anchor is formed proximally to the anchor in claim 12, this anchor not typically in direct tissue contact, and having higher retention force than the anchor in typical tissue contact.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a typical self-expanding mesh stent designed to keep a blood vessel or other body lumen patent and constructed of woven metallic wires without anchoring structures.
[0017] FIG. 2 is the stent which has been stretched axially to reduce its diameter for placement.
[0018] FIG. 3 is a ureteral stent with an ellipsoidal self-expanding anchor as described in U.S. Pat. No. 6,395,021
[0019] FIG. 4 is a ureteral stent with ellipsoidal self-expanding anchor placed in the kidney, ureter, and bladder.
[0020] FIG. 5 is an enlarged view of an ellipsoid mesh anchor adjacent to the bladder tissue and UO.
[0021] FIG. 6 is an enlarged view of a cup or conical shaped mesh anchor of the present invention.
[0022] FIG. 7 is an enlarged view of a truncated cup or conical mesh anchor of the present invention.
[0023] FIG. 8 is a stent of the present invention with a pigtail coil anchor for the renal pelvis of the kidney and a cup or conical shaped mesh anchor for the bladder.
[0024] FIG. 9 is an enlarged view of the anchor placed in the renal pelvis end of the stent.
[0025] FIG. 10 is an enlarged sectional view of a cup or conical shaped mesh anchor at the bladder end of the stent of the present invention.
[0026] FIG. 11 is a stent of the present invention in position in the ureter
[0027] FIG. 12 is an enlarged sectional view of a truncated cup or conical shaped mesh anchor at the bladder end of the stent of the present invention showing clearance between the anchor and the bladder wall BW and the ureteral orifice UO.
[0028] FIG. 13 is an enlarged sectional view of a truncated cup or conical shaped mesh anchor at the bladder end of the stent of the present invention. This also shows the embodiment having an internal elastic band or member connecting the bond between anchor and shaft to the most distal and stiffer portion of the anchor.
[0029] FIG. 14 is a stent of the present invention having multiple mesh anchors at the bladder end. The two anchors having differing characteristics to each optimize either comfort or retention force.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
[0030] Some embodiments of the present invention are illustrated as an example and embodiments are not limited by the figures of accompanying drawings:
[0031] FIG. 1 FIG. 1 illustrates the braid construction of a flexible, self-expanding stent such as the Wallstent manufactured by Boston Scientific Corporation WS. The braid is made out of a flexible small diameter metal wire such as shape memory Nitinol. The combination makes this particular braid very soft and flexible. In this particular braid construction, the braid is created on a slightly larger mandrel than the desired final outer diameter. The wire size is in the range of outer diameter 0.001 to 0.007. The pick count of the braid is selected between 20 PPI to 80 PPI. The braid configuration and wire parameters are selected to make sure the braid will form a desired cylindrical shape having a diameter sufficient to slightly dilate a target lumen and, to attempt to maintain its position in the lumen despite fluid flow, patient movement, and, with most difficulty, peristalsis.
[0032] FIG. 2 illustrates the braid's (from FIG. 1) ability to be stretched axially to form a lower profile for placement that is significantly less than its expanded diameter. This allows delivery of the stent through compatible accessories such as a delivery catheter, an endoscope or a sheath (not shown). The braid pick count will be reduced during the stretching of the braid, but a minimum, typically 5 PPI, is selected to ensure self-expansion after the braid is stretched to its lowest desired profile.
[0033] FIG. 3 illustrates a device using the braid in FIG. 1 which has been shape-set to cause it to increase its diameter to a pre-set configuration when no longer stretched axially or constrained by a lumen. Depending on the shape that was set previously, this increase in diameter may form a sphere or ellipsoid as shown in the prior art. A complete assembly of a ureteral stent US is shown with a traditional pigtail kidney anchor 01 at one end, a soft polymer shaft 02 and an ellipsoidal bladder B anchor 03 made out of the same type of braid described above in FIG. 1 and FIG. 2
[0034] FIG. 4 illustrates the ureteral stent US of FIG. 3 in place in the ureter U. The proximal end of the stent having the mesh bladder anchor 03 is shown slightly compressed against the bladder wall BW as if there is some positional stretching of the ureter occurring.
[0035] FIG. 5 illustrates an enlarged view of the ellipsoidal mesh anchor 03 of FIG. 3 and FIG. 4, shown in contact with the ureteral orifice UO and the bladder wall BW adjacent to the ureteral orifice. If the mesh in this construction is soft, it can extrude into the UO when under tension by the shaft 02, then pull back when tension is relieved, thus abrading the delicate mucosa inside the ureter. If stiff enough for good retention and to avoid extrusion, the mesh can abrade the sensitive mucosa and enervated tissue of the bladder wall BW directly adjacent to the UO
[0036] FIG. 6 illustrates an enlarged view of a cup or conical shaped mesh anchor of the present invention 04, with its concave surface 05 facing the bladder wall BW and UO. As stretching of the ureter puts tension on the shaft and pulls the anchor against the bladder wall BW, the circular bearing surface of the anchor is separated from the ureteral orifice UO and the enervated bladder wall BW adjacent to the UO. Some of the protruding shaft 02 may be pulled into the UO, but not the mesh portion of the anchor 04. The internal diameter of the bearing surface NC, which defines the non-contact area, should be at a minimum 3X the diameter of the stent shaft 02.
[0037] FIG. 7 illustrates an enlarged view of an alternative embodiment of a cup or conical shaped mesh anchor 06 which has been shortened or compressed to provide increased bearing surface against the bladder wall BW. This will distribute the force on the bladder wall by the anchor over a wider area and thus reduce trauma to the tissue. Increased surface contact will decrease the non-contact area adjacent to the enervated bladder wall BW so it is important to adjust the diameter of the anchor to maintain a minimum non-contact area of approximately 3 times the diameter of the UO by adjusting the OD of the anchor. Anchor 06 also illustrates the use of varying the weave of the mesh to change the physical properties in different portions of the anchor. A low pick count in the region contacting the bladder wall 07 results in an open, softer, more compressible mesh, which acts as a shock absorber. A relatively high pick count in the proximal area of the anchor 08 results in a denser weave, and a stiffer mesh which provides high compressive force and retention when needed.
[0038] FIG. 8 illustrates a ureteral stent of the present invention 09 having a pigtail anchor 01, a polymer shaft 02, and a cone shaped mesh anchor 04.
[0039] FIG. 9 illustrates an enlarged sectional view of the pigtail anchor 01.
[0040] FIG. 10 and FIG. 12 illustrate an enlarged sectional view of the cone shaped mesh anchor 04. FIG. 12 shows that anchor when deployed in the bladder B. Note how the tissue contact surface of the anchor avoids contact with the ureteral orifice UO or the immediate surrounding bladder wall BW when deployed as illustrated.
[0041] FIG. 11 illustrates a ureteral stent of the present invention 09 in position in the ureter U, having a deployed pigtail anchor 01 in the renal pelvis of the kidney K and a view of the cone shaped mesh anchor 04 as deployed in the bladder B.
[0042] FIG. 13 illustrates an enlarged sectional view of an additional embodiment of the cone shaped mesh anchor 04. This embodiment additionally incorporates an elastic member E internally connecting the distal end of the anchor to the proximal end of the shaft. This pre-loads the compression of the mesh, increasing its retention force, while also helping to maintain the cup or cone shape.
[0043] FIG. 14 illustrates an additional embodiment of the present invention, consisting of two individual mesh anchors 10 and 11 mounted congruently at the bladder end of a ureteral stent 12. Similar to the anchor of FIG. 7, the mesh anchor 11 closest to the ureteral orifice UO and typically in contact with bladder wall BW is formed of a softer, better shock absorbing braid, and the mesh anchor 10, which is not typically in contact, is formed of a stiffer braid and provides a higher level of retention force. With two separate anchors, one has additional means such as different wire diameters, wire profiles, and materials to provide different properties, rather than only adjusting the pitch/density of the mesh. Differing wire profiles (not shown) could provide additional advantages such as use of flattened profile wire in the contact anchor 11 to increase surface area in tissue contact and/or to enhance flexibility in one direction, and decrease flexibility in another.
[0044] Although a number of exemplary embodiments of the invention have been shown and described, many other changes, modifications, substitutions will now be apparent to those of ordinary skill in the art, without necessarily departing from the spirit and scope of this invention as set forth in the following claims.
