Compressible ureteral stent for comfort

[0001] This application claims priority to and the benefit of the U.S. provisional patent application Ser. No. 60/295,465, filed on Jun. 1, 2001, the entirety of which is incorporated herein by reference.

[0002] This invention generally relates to ureteral stents. More particularly in one embodiment, the invention is directed to a ureteral stent having a bladder end adapted to reduce patient discomfort.

[0003] A stent is a medical device provided for propping open an obstructed passage within the body, such as a blocked ureter. In general, ureteral blockage is a medical condition requiring treatment. A ureteral blockage can occur for a number of reasons, including the passage of a kidney stone and/or other material into the ureter where it becomes entrapped. Also, a tumor growing against the outer wall of the ureter can force compression or constriction of the ureter. A tumor on the internal ureteral wall can also cause blockage of the ureter. Ureteral stents are often used to correct such problems. A ureteral stent may be placed inside the ureter on a temporary basis to allow proper drainage of fluids from the kidney to the bladder. A ureteral stent usually comprises a straight length of hollow tubing with each end having a hook or a curl or other configuration for preventing migration or expulsion of the stent from its placed position within the ureter. One end of a typical ureteral stent is placed in the kidney and the other end is placed in the bladder. The end positioned in the kidney is typically configured to retain the stent within the renal pelvis and to prevent the downward migration of the stent into the ureter. The bladder end of the stent is typically configured to prevent upward migration of the stent towards the kidney.

[0004] FIG. 1 is a conceptual background drawing showing a portion of the human urinary tract. Referring to FIG. 1, in a human urinary tract 100, the ureters 102 and 104 transport urine from the kidneys 106 and 108 to the bladder 110. The trigone region of the bladder 112 is located between the urethral opening 114 and the two ureteral orifices 116 and 118. The pain associated with an in-dwelling ureteral stent is attributable in-part to contact between the stent and the bladder mucosa 120 in the trigone region 112. The trigone region 112 is believed to be particularly innervated and sensitive to the presence of any foreign bodies such as the bladder end of a ureteral stent. The intramural tunnel regions 122 and 124 of the ureters 102 and 104, respectively, act like valves, shutting off to prevent back flow of urine from the bladder 112 to the kidneys 106 and 108. The intramural tunnel regions 122 and 124 are also believed to be particularly innervated and sensitive to the presence of any foreign bodies. In addition, further discomfort due to in-dwelling stents can be caused by flank pain due to urine shooting from the bladder 110 back up the ureters 102 and 104 intra-luminally via the stent, and/or extra-luminally around the stent.

[0005] The invention generally relates to ureteral stents, particularly those that reduce (compared with conventional ureteral stents) patient discomfort when the stent is placed within the patient's body. One object of the invention is to keep the ureteral passage open to allow the flow of fluids from the kidney to the bladder. Another object of the invention is to reduce, minimize or avoid patient discomfort associated with conventional in-dwelling ureteral stents by reducing irritation of the trigone region of the bladder mucosa.

[0006] In one embodiment, the invention is directed to a ureteral stent including an elongated portion, a retention portion for placement substantially within a kidney, and a collapsible portion for placement substantially within the intramural tunnel portion of a ureter and extending into the bladder. The elongated portion of the stent has a lumen which extends along the length of the ureter from the kidney to the bladder. According to one feature, the retention portion extends from a first end of the elongated portion and is configured to be retained within the kidney. According to another feature, the collapsible portion extends from a second end of the elongated portion, and it is collapsible under radial compression from the intramural tunnel region to inhibit back flow of urine to the kidney.

[0007] In one embodiment, the collapsible portion is fabricated from a mesh material. In another embodiment, the collapsible portion is fabricated from a wound coil. According to one feature, the collapsible portion includes an outer coating of a biocompatible material adapted to avoid tissue ingrowth. According to another feature, the collapsible portion includes an inner lining adapted to avoid urine encrustation on an inner surface of a lumen formed by the collapsible portion which extends from the lumen formed by the elongated portion of the stent.

[0008] In another aspect, the invention relates to methods of inserting into a patient one of the ureteral stents mentioned above. One method includes the step of passing a guide wire through the ureter and into the kidney, and thereafter coaxially sliding a stent over the guide wire and into the ureter by using a tubular stent pusher. One alternate method includes placing a stent with a closed kidney end over a guide wire, and then advancing the stent into the ureter by pushing the guide wire. According to another embodiment, the stent is inserted from the kidney downward through the ureter and into the bladder.

[0009] In yet other aspects, the invention features methods of manufacturing stents such as the ureteral stents mentioned above.

[0010] The foregoing and other objects, aspects, features and advantages of the invention will become more apparent from the following description and from the claims.

[0034] As discussed above in summary, in one embodiment, the invention is directed to a ureteral stent having a bladder end adapted to reduce patient discomfort. FIG. 2 depicts a ureteral stent 200 in accordance with an illustrative embodiment of the invention. FIGS. 3A and 3B depict the ureteral stent 200 placed inside a human urinary tract 100. A skilled artisan will appreciate that a ureteral stent of the invention can be placed in either ureter 102 or 104. However, for simplicity, the following discussion is limited to placement of the ureteral stent 200 within the ureter 102. As depicted, the illustrative ureteral stent 200 includes an elongated portion 202, a retention portion 204, and a collapsible portion 206. The elongated portion 202 has a length 208 that is sufficient to extend through the ureter 102 from the kidney 106 to the bladder 110. The elongated portion 202 of the ureteral stent 200 defines a lumen (shown in FIGS. 4A and 4B at 400) extending from a kidney end 212 to a bladder end 214. According to the illustrative embodiment, the ureteral stent 200 also includes one or more through apertures or eye ports 210 located along the length of the elongated portion 202 for providing fluid communication between an outer wall (shown in FIGS. 4A and 4B at 412) and an inner lumen wall (shown in FIG. 4B at 410) to further enable drainage through the internal lumen 400 of the ureteral stent 200. According to one feature, the elongated portion 202 is made of a physiologically compatible material such as, for example, polyvinyl alcohol, polyethylene oxide, hydroxy ethyl cellulose, stainless steel, or the like.

[0035] The retention portion 204 extends from the kidney end 212 of the ureteral stent 200, and is adapted for placement substantially within the kidney 106, and for retention of the placement. According to one feature, the retention portion 204 includes one or more through apertures or eye ports 211 for providing fluid communication between an outer wall (shown at FIG. 4A at 414) and an inner lumen (shown in FIG. 4A at 402) to further enable drainage through the internal lumens 400 and 402.

[0036] The collapsible portion 206 extends from the bladder end 214 of the ureteral stent 200, and is adapted for residing substantially within the intramural tunnel region 122 of the ureter 102 and for extending into the bladder 110. According to an illustrative embodiment, the invention addresses reflex prevention and intramural tunnel irritation via the collapsible portion 206 of the ureteral stent 200.

[0037] FIG. 3A depicts the intramural tunnel region 122 in a relaxed state and the collapsible portion 206 of the ureteral stent 200 in an expanded and open state. As shown in FIG. 3B, as the intramural tunnel region 122 contracts radially, the collapsible portion 206 collapses to restrict urine back flow from bladder 110 to the kidney 106.

[0038] FIG. 4A is a schematic of a longitudinal, cross-sectional view of the ureteral stent 200. FIG. 4B is a lateral cross-sectional view of the length 208 of the elongated portion 202 taken along the view A-A′. As mentioned above, and as shown in FIGS. 4A and 4B, the elongated portion 202 of the ureteral stent 200 defines an internal lumen 400 that extends through the elongated portion 202 between the kidney end 212 and the bladder end 214. The retention portion 204 also defines an internal lumen 402 which extends from the lumen 400 of the elongated portion 202. The retention portion 204 includes at least one through aperture 404 adapted for providing fluid communication between the internal lumen 402 and the kidney 106.

[0039] The collapsible portion 206 also defines an inner lumen 406 which extends from the internal lumen 400 of the elongated portion 202. The inner lumen 406 terminates in at least one through aperture 408. As shown in FIGS. 3A and 3B, when placed in a patient, the through aperture 408 resides within the bladder 110 and is adapted for providing urine flow from the lumen 406 into the bladder 110.

[0040] FIG. 5A depicts one illustrative embodiment in which the collapsible portion 206 of a ureteral stent 200 of the invention includes a mesh portion 500. Illustratively, the mesh portion 500 extends from the bladder end 214 of the elongated portion 202. In FIG. 5A, the mesh portion 500 is depicted in an expanded and open state. FIG. 5B is a longitudinal, cross-sectional view of the collapsible portion 206 of the stent of FIG. 5A in the expanded and open state. As shown, the mesh portion 500 forms an inner lumen 502 which extends from the internal lumen 400 of the elongated portion 202. The lumen 502 ends in at least one opening 504 which resides in the bladder 110 to allow fluid communication between the lumen 502 and the bladder 110. FIG. 5C is a longitudinal, cross-sectional view of the collapsible mesh portion 500, shown in a collapsed state. As discussed above, the collapsible portion 206 collapses, for example, due to a radial force exerted on the exterior of the mesh portion 500, and inhibits through fluid flow. In one illustrative embodiment, the mesh portion 500 is manufactured from polymeric or metallic materials such as, for example, stainless steel, tantalum, gold, titanium, nitinol, polytetrafluoroethylene (PTFE) or any suitable material that collapses under an exerted force of the type exerted by the intramural tunnel region 122 of the ureter 102, and returns to an expanded state upon removal of such a force. One advantage of the invention is that the collapsible mesh portion 500 of the ureteral stent 200 prevents fluid flow in response to radial force exerted by the intramural tunnel region 122 by collapsing to inhibit vesicourinal reflux, back flow of urine and flank pain in a patient.

[0041] FIGS. 6A-6C depict enlarged longitudinal, cross-sectional views, further illustrating embodiments of the mesh portion 500. As shown in FIG. 6A, in one illustrative embodiment, the collapsible mesh portion 500 has an outer covering 600. In the illustrative embodiment, the outer covering 600 is formed from a flexible polymer such as, for example, polyurethane, polyamide, silicone, polyvinyl chloride, or the like. As shown in FIG. 6B, in a further illustrative embodiment, collapsible mesh portion 500 has an inner lining 602 such as, for example, a jacket or a sleeve. In one embodiment, the inner lining 602 encases the interior of the mesh portion 500. The inner lining 602 functions to substantially prevent internal mesh encrustation due to urine contact. In the illustrative embodiment, the inner lining 602 is fabricated from a polymer such as, for example, polyurethane, polyamide, silicone, polyvinyl chloride, or the like.

[0042] In one preferred embodiment, the collapsible mesh portion 500 includes both an outer covering 600 as well as an inner lining 602. In the illustrative embodiment, the mesh portion 500 is sandwiched between an outer covering 600 and an inner lining 602, which encase the exterior and the interior of the mesh portion 500 respectively. In another embodiment, a polymer is interspersed within the mesh.

[0043] FIGS. 7A-7C depict an alternative embodiment in which the collapsible portion 206 of the ureteral stent 200 includes a wound coil 700 instead of a mesh portion 500. The wound coil 700 behaves similarly to the mesh portion 500, in that under radial force from the intramural tunnel region 122 of the ureter 102, the wound coil 700 flattens out to close off the lower portion of the ureter 102 and thus prevent urine back flow to the kidney 106. FIG. 7A depicts one illustrative embodiment in which the wound coil 700 extends from the bladder end 214 of the elongated portion 202. In FIG. 7A, the wound coil 700 is depicted in an open and expanded state. FIG. 7B is a longitudinal, cross-sectional view of the collapsible portion 206 of the ureteral stent of FIG. 7A in an open and expanded state. As shown, the wound coil 700 forms a lumen 702 which extends from the internal lumen 400 of the elongated portion 202. FIG. 7C is an illustrative embodiment featuring the wound coil 700 in a collapsed state. As discussed above, the wound coil 700 collapses, for example, due to radial force exerted on the exterior of the wound coil 700 and inhibits fluid flow through the lumen 702. In response to the radial force being removed, the radial wound coil 700 returns to the expanded and open state.

[0044] FIGS. 8A-8C depict enlarged longitudinal cross-sectional views, further illustrating embodiments of the wound coil 700. As shown in FIG. 8A, the collapsible wound coil 700 has an outer covering 800. In an illustrative embodiment, the outer covering 800 is formed from a flexible polymer such as, for example, polyurethane, polyamide, silicone, polyvinyl chloride, or the like. As shown in FIG. 8B, in a further illustrative embodiment, the wound coil 700 has an inner lining 802, such as, for example, a jacket or a sleeve. In one embodiment, the inner lining 802 encases the interior of the lumen 702 of the wound coil 700. In the illustrative embodiment, the inner lining 802 is fabricated from a polymer such as, for example, polyurethane, polyamide, silicone, polyvinyl chloride, or the like.

[0045] In one preferred embodiment of the invention, the wound coil 700 includes both an outer covering 800 as well as an inner lining 802. In the illustrative embodiment, the wound coil 700 is sandwiched between an outer covering 800 and an inner lining 802, which encase the exterior and the interior portions of the wound coil 700 respectively.

[0046] FIG. 9 is an enlarged, transverse cross sectional end view of the terminal end 416 of the collapsible portion 206 taken along view B-B′. In one preferred embodiment, the collapsible portion 206 has a polymeric ring 900 extending circumferentially around its terminal end 416. According to the illustrative embodiment, the polymeric 900 ring protects, for example, the jagged edges of the mesh portion 500 or wound coil 700 and helps to maintain the shape of the mesh portion 500 or wound coil portion 700 after the ureteral stent 200 is placed within a patient. Preferably, the polymeric ring 900 is made from a thermoplastic polymer. In yet another embodiment, a retention flange is used instead of a polymeric ring.

[0047] FIGS. 10A-10C are conceptual drawings depicting various illustrative embodiments of the retention portion 204. The retention portion 204 of the ureteral stent 200 may be shaped, for example, as a hook, a coil or a malecot, or the like, to facilitate its retention in the kidney 106. In one illustrative embodiment, shown in FIG. 10A, the retention portion 204 of the ureteral stent 200 is shaped like a J hook 1000. In another illustrative embodiment, shown in FIG. 10B, the retention portion 204 of the ureteral stent 200 has a single loop configuration 1002. In a preferred illustrative embodiment of the invention, depicted in FIG. 10C, the retention portion 204 has a multi-loop configuration 1004. In this illustrative embodiment, the multi-loop configuration 1004 allows the ureteral stent 200 to compensate for any changes in the length of the ureter 102 caused by peristalsis in the urinary tract 100. The multi-loop configuration 1004 also enables the accommodation of different ureteral sizes in different size patients.

[0048] Various methods are used for inserting the ureteral stent 200 into a patient. In one embodiment of the invention, the retention portion 204 of the ureteral stent 200 is inserted though the urethral opening 114 of a patient, advanced through the bladder 110 and the ureter 102, and subsequently placed in the kidney 106 of the patient. Prior to insertion, the collapsible portion 206 is temporarily collapsed to facilitate insertion into the patient's body. The retention portion 204 is also straightened out prior to insertion.

[0049] In yet another embodiment of the invention, a cytoscope is used for inserting the ureteral stent 200 of the invention into a patient. In this embodiment, the ureteral stent 200 is inserted within the cytoscope prior to insertion into the urinary tract 100 and the cytoscope is removed subsequent to proper positioning of the ureteral stent 200 within the patient.

[0050] In yet another embodiment, the mesh portion 500 of the ureteral stent 200 is maintained to have a sufficiently large inner diameter, so as to allow passage over a guide wire.

[0051] In one aspect of the invention, a method of manufacturing the collapsible mesh portion 500 of the ureteral stent is 200 described. The mesh portion 500 is fabricated from polymeric or metallic materials, such as, for example, stainless steel, tantalum, gold, titanium, nitinol, polytetrafluoroethylene (PTFE) or any suitable plastic material that is collapsible when formed and radially expandable.

[0052] The mesh portion 500 can be of any design or configuration and is made in any manner described in the art. In one embodiment of the invention, the mesh is braided in a “2 over-2 under” helical pattern. The mesh braid is then laminated over the bladder end 214 of the elongated portion 202 of the ureteral stent 200.

[0053] In another embodiment, individual mesh strands are attached to each other via thermal bonding, in the case of polymeric materials, or via resistance welding or use of an adhesive in the case where metallic elements are utilized.

[0054] In yet another embodiment, the braided mesh is braided directly over the bladder end 214 of the ureteral stent 200 using a pre-heat step to embed the braid onto the bladder end 214. In another aspect of the invention, ureteral stent 200 is prepared by hollowing out a metal pipe to leave a stent skeleton. Exemplary processes known in the art for preparation of the ureteral stent 200, include an etching process, also known as photo-fabrication; processes that employ masks and chemicals; electric discharge machining processes; and mechanical machining processes or stamping an open-cell pattern into a solid tube which is usually made of a polymeric material.

[0055] A ureteral stent 200 is used to treat ureteral blockage for proper drainage of fluids between the kidney 106 and the bladder 110. Treatment of ureteral blockage is provided, for example, by inserting a ureteral stent 200 over a guide wire with a pusher through the urethral opening 114 and into the bladder 110. The guide wire or a cannula is used temporarily to straighten out the retention portion 204 of the ureteral stent 200. The retention portion 204 of the uretral stent 200 is typically made from material that is able to regain its structure after distortion which allows for the retention portion 204 to be straightened out prior to placement within the body.

[0056] In one aspect of the invention, a method for treating ureteral blockage in a patient includes sliding the ureteral stent 200 over a guide wire. The guidewire is inserted into the body of a patient through the bladder 110 and into the ureter 102. A ureteral stent 200 is subsequently slid over the guide wire, such that one end of the guide wire is inserted through the kidney end 212 of the ureteral stent 200. The ureteral stent 200 is moved along the length of the guide wire by the use of a pusher which includes a lumen to accept a guide wire.

[0057] In a preferred embodiment of the invention, the collapsible mesh portion 500 maintains a sufficiently large inner diameter so as to allow passage over a 0.035″/0.038″ guide wire. In one embodiment, the ureteral stent 200 is tracked over the wire for positioning inside the body using conventional methods of placement such as a pusher to abut the retention portion 204 of the ureteral stent 200.

[0058] 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 the scope of the invention. This invention is not limited to the preceding illustrative description.