Abstract:
A stent delivery system for the placement of non-expandable stents in the urethra is described. The delivery system is generally composed of a catheter with a stent mounted near the distal end of the catheter. The stent is held in place by a balloon or mechanical mechanism.

Description:
FIELD OF THE INVENTION 
     This invention relates to stent delivery systems to facilitate the temporary relief of urinary retention caused by enlargement of the prostate gland or severe lower urinary tract symptoms. 
     BACKGROUND OF THE INVENTION 
     The prostate gland surrounds the prostatic urethra, and enlargement of the prostate gland prevents passage of urine from the bladder. Enlargement of the prostate gland can result from the following etiologies: 1) benign prostatic hyperplasia (BPH); 2) carcinoma of the prostrate; 3) prostatitis; 4) post-procedural edema; 5) prostatic trauma; as well as others. Prostatic enlargement, is a common affliction among men. Prostatic enlargement is uncomfortable because it makes urination difficult or impossible. The condition is also dangerous because it can lead to infection of the bladder and kidneys, and severe cases may lead to death. 
     Lower urinary tract symptoms (LUTS), also common among older men, comprise a variety of conditions which can also lead to urinary retention and other complications resulting from retention. Some of the conditions falling under LUTS diagnosis include an enlarged prostate, BPH, and bladder outlet obstruction. 
     Prostatic enlargement can be treated with the implantation of a prostatic urethral stent. The stent serves to hold open the prostatic urethra to facilitate fluid flow during urination. A stent may be implanted, or delivered, as an interim solution to hold open the prostatic urethra while the patient awaits corrective treatment A stent may be implanted after thermal therapy or cryosurgery to keep the urethra open while post-treatment edema subsides. A stent may be implanted after radiation to keep the urethra open as the radiation effects on the prostatic tissue subside. Finally, a stent may be implanted as a primary treatment. 
     There are many different types of urethral stents. Generally, they are tubular in shape, and may be composed of solid tubes, coiled wire or ribbon, mesh, or braided filaments. Many stents are inserted, or delivered, into the urethra in a radially compressed form by a stent delivery system. After being properly positioned, these types of stents are radially expanded into their final shape, typically by thermal or mechanical means. 
     There are also non-expandable stents that are inserted into the urethra in their final form by a stent delivery system. These stents have an advantage over expandable stents in that the final configuration of the stent is known at the time of stent insertion. 
     During the first steps of the stent deployment process, the stent must be held in place on the stent delivery system during insertion. For expandable stents, this is typically accomplished by placing the stent inside a sheath, by crimping onto a catheter balloon, or by using a mechanical retainer or stopper. 
     Non-expandable stents are held in place on the stent delivery system by means of flexible tether strings (see U.S. Pat. No. 5,322,501 to Mahmud-Durrani) or a coiled wire fastening element (see U.S. Pat. No. 5,098,374 to Orthel-Jacobsen, et al.). 
     In the case of the Mahmud-Durrani delivery system, the stent is retained within the prostatic urethra by the same flexible tether strings, connected to a locating member. The locating member remains in the bladder as an anchoring means after the stent is delivered. 
     In the Orthel-Jacobsen delivery system, the coiled wire fastening element must be rotated by over 900 degrees in a screwing movement to release the stent from the fastening element. 
     Another consideration for urethral stent delivery is that it is usually better to deliver the stent to a location which allows uncompromised function of the bladder neck sphincter and the external sphincter. These sphincters control the flow of urine through the urethra. Obstruction of these sphincters leads to incontinence. To ensure the proper positioning of the stent, a number of prior art stent delivery systems provide position systems including visualization of the bladder and prostatic urethra during placement, mechanically locating off of the bladder neck, and anchoring of the stent delivery system in place during insertion. 
     In summary, prostatic enlargement is a common affliction among men. The symptoms of prostatic enlargement can be treated with the implantation of a urethral stent, which holds open the urethra to facilitate fluid flow during urination. Both expandable and non-expandable urethral stents have been used. The known final dimension of the non-expandable stents is a desirable feature. However, simple means for holding the non-expandable stent on the stent delivery system, and a simple method of deployment of non-expandable stents is desired. 
     SUMMARY OF THE INVENTION 
     The stent delivery system described below permits placement of stents in the prostatic urethra. The delivery system is intended to deploy a non-expandable stent into the urethra. This is accomplished by disposing the stent delivery system in the urethra such that the non-expandable stent is located in the prostatic urethra, releasing the non-expandable stent from the stent delivery system, and removing the stent delivery system from the urethra. 
     The device may be provided as a disposable item that is generally composed of a catheter with a stent mounted near the distal end of the catheter. The stent is held in place by a balloon or mechanical mechanism. 
     In a preferred embodiment, surgeons who use the disclosed stent delivery system can also be sure that the stent does not block the bladder neck sphincter. This is accomplished by disposing the stent delivery system in the urethra, temporarily anchoring the stent delivery system within the bladder neck such that the non-expandable stent is located in the prostatic urethra, releasing the non-expandable stent from the stent delivery system, releasing the stent delivery system anchor from the bladder neck, and removing the stent delivery system from the urethra. 
     The preferred embodiment device may be provided as a disposable item which is generally composed of a catheter with a locating balloon or mechanical mechanism attached at its distal end which serves to anchor the device in place and locate the bladder neck, and a stent mounted proximal to the locating balloon or mechanical mechanism. The stent is held in place by a separate retention balloon or mechanical mechanism. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The novel features of the present invention will be more readily apparent upon reading the following description in conjunction with the drawings in which like elements in different figures are identified by the same reference numeral and wherein: 
         FIG. 1  is a cross-sectional view of the lower abdominal portion of the human male anatomy with a stent delivery system in place; 
         FIG. 2  shows an exploded view of a first embodiment of the inventive stent delivery system; 
         FIG. 3  shows a perspective view of the distal tip of the first embodiment of the stent delivery system; 
         FIG. 4  shows a perspective view of the proximal end of the catheter of the first embodiment of the stent delivery system; 
         FIG. 5  shows a perspective assembly view of the first embodiment of the stent delivery system; 
         FIG. 6  shows a perspective view of the first embodiment of the stent delivery system with the stent retention balloon inflated; 
         FIG. 7  shows a view of the lower abdominal portion of the human male anatomy with the first embodiment of the stent delivery system in place; 
         FIG. 8  shows an exploded view of a second embodiment of the stent delivery system; 
         FIG. 9  shows an end view of the proximal end of the catheter of the second embodiment of the stent delivery system; 
         FIG. 10  shows a perspective view of the distal tip of the second embodiment of the stent delivery system; 
         FIG. 11  shows a perspective assembly view of the second embodiment of the stent delivery system; 
         FIG. 12  shows a perspective assembly view of the second embodiment of the stent delivery system with the stent retention balloon inflated; 
         FIG. 13  shows a view of the lower abdominal portion of the human male anatomy with the second embodiment of the stent delivery system in place; 
         FIG. 14  shows a view of the lower abdominal portion of the human male anatomy with the second embodiment of the stent delivery system in place with the locating balloon inflated; 
         FIG. 15  shows a perspective view of the catheter of a third embodiment of the stent delivery system; 
         FIG. 16  shows an end view of the proximal end of the catheter of the third embodiment of the stent delivery system; 
         FIG. 17  shows a perspective view of the distal tip of the third embodiment of the stent delivery system; 
         FIG. 18  shows an exploded view of a fourth embodiment of the stent delivery system; 
         FIG. 19  shows a perspective assembly view of the fourth embodiment of the stent delivery system; 
         FIG. 20  shows a view of the lower abdominal portion of the human male anatomy with the fourth embodiment of the stent delivery system in place; 
         FIG. 21  shows a view of the lower abdominal portion of the human male anatomy with the fourth embodiment of the stent delivery system in place with the locating balloon inflated; 
         FIG. 22  shows an exploded view of a fifth embodiment of the stent delivery system; 
         FIG. 23  shows a perspective assembly view of the fifth embodiment of the stent delivery system; and 
         FIG. 24  shows an exploded view of the retaining mechanism of the fifth embodiment of the stent delivery system. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a schematic representation of the stent delivery system  20  designed for use in the treatment of benign prostate hyperplasia, prostate cancer, or LUTS in place within the human male anatomy. The details of the local anatomy shown in  FIG. 1  include the prostate gland  2 , the penile urethra  4 , the prostatic urethra  6 , and the bladder  8 . The penile urethra  4  is the channel that conducts urine from the bladder  8  through the penis  10  for discharge from the body. The prostatic urethra  6  is the portion of the urethra located within the prostate gland  2 . The bladder neck sphincter  12  controls flow of urine from the bladder  8  through the bladder neck  16 . The external sphincter  14  controls flow of urine or ejaculate from the prostatic urethra  6  to the penile urethra  4 . The inside diameter of penile urethra  4  is typically about 2 cm, and the prostatic urethra  6  varies in length from about 15 to 75 mm. 
     Stent  150  is placed in prostatic urethra  6  to hold open prostatic urethra  6  to facilitate fluid flow during urination. Stent  150  is shown throughout this document as a device with generally cylindrical geometry. More specifically, stent  150  is shown as the coiled wire structure reported in U.S. Pat. No. 6,338,739, issued Jan. 15, 2002 from U.S. patent application Ser. No. 09/470,619, entitled “Biodegradable stent”, assigned to Ethicon Incorporated and incorporated herein by reference. However, one trained in the art could see that other stent constructs could also be used with the stent delivery system of the current invention. 
     Stent  150  is delivered to the prostatic urethra  6  by the stent delivery system  20  illustrated in the following figures. A first embodiment of the present invention is shown on  FIGS. 2–7 . The stent delivery system  20  generally includes catheter  22 , distal tip  40 , and stent retention balloon  35 . 
     Catheter  22  is a tubular structure with proximal  24  and distal  26  ends, through-lumen  28 , stent retention balloon lumen  30 , and stent retention balloon port  32 . Distal tip  40 , disposed on catheter distal end  26 , has tip lumen seal protrusion  42  and tip through-hole  44 . Distal tip  40  is disposed on catheter distal end  26  so that tip lumen seal protrusion  42  is disposed in stent retention balloon lumen  30  to seal the lumen, and tip through-hole  44  is aligned with through-lumen  28 . In practice, tip through-hole  44  and through-lumen  28  allow passage of either a guide wire, or a visualization means to facilitate delivery system placement, through catheter  22  to allow for accurate placement of stent  150  in prostatic urethra  6 . 
     Alternatively, distal tip blunting and lumen sealing to seal stent retention balloon lumen  30  can also be accomplished by thermal/RF forming and lumen potting. 
     Stent retention balloon  35  is disposed on catheter  22  so that stent retention balloon port  32  is covered by stent retention balloon  35  approximately centered with respect to one another. Tip lumen seal protrusion  42  seals stent retention balloon lumen  30  so that when pressurized gas, such as air, or a fluid such as saline, is introduced into stent retention balloon lumen  30 , the gas or fluid passes through stent retention balloon port  32  and stent retention balloon  35  is inflated.  FIGS. 5 and 6  show stent retention balloon  35  in both deflated and inflated states, respectively. 
     The procedure for using stent delivery system  20  to implant stent  150  into the prostatic urethra  6  to maintain urethral patency is initiated by disposing stent  150  over a deflated stent retention balloon  35 . Stent retention balloon  35  is then inflated as discussed above to hold stent  150  on stent delivery system  20 . Stent delivery system  20  is inserted through the penile urethra  4  until stent  150  is located in the prostatic urethra  6  as shown in  FIG. 7 . Stent retention balloon  35  is then deflated. This releases stent  150  from stent delivery system  20  without changing the dimensions of stent  150 . Stent delivery system  20  is removed from the prostatic  6  and penile  4  urethrae, leaving stent  150  in prostatic urethra  6 . 
     As previously mentioned, tip through-hole  44  and through-lumen  28  allow passage of either a guide wire, or a visualization means to facilitate delivery system placement, through catheter  22  to allow for accurate placement of stent  150  in prostatic urethra  6 . A second embodiment stent delivery system  50 , as shown in  FIGS. 8 to 14 , could also be used to accurately place stent  150  in prostatic urethra  6 . Stent delivery system  50  generally includes catheter  52 , distal tip  70 , stent retention balloon  35 , and locating balloon  66 . 
     Catheter  52  is a tubular structure with proximal  54  and distal  56  ends, stent retention balloon lumen  58 , locating balloon lumen  60 , stent retention balloon port  32 , and locating balloon port  64 . Distal tip  70 , disposed on catheter distal end  56 , has tip lumen seal protrusions  74 ,  76 . Distal tip  70  is disposed on catheter distal end  56  so that tip lumen seal protrusions  74 ,  76  are disposed in stent retention balloon lumen  58  and locating balloon lumen  60 , respectively, to seal these lumen. Distal tip blunting or lumen sealing may also be used to seal these lumens. 
     Stent retention balloon  35  is disposed on catheter  52  so that stent retention balloon port  32  is covered by stent retention balloon  35 . Tip lumen seal protrusion  74  seals stent retention balloon lumen  58  so that when pressurized gas, such as air, or a fluid such as saline, is introduced into stent retention balloon lumen  58 , the gas or fluid will pass through stent retention balloon port  32  to inflate stent retention balloon  35 .  FIGS. 11 and 12  show stent retention balloon  35  in both deflated and inflated states, respectively. 
     Locating balloon  66  is disposed on catheter  52  so that locating balloon port  64  is covered by locating balloon  66  roughly centered with respect to one another. Tip lumen seal protrusion  76  seals locating balloon lumen  60  so that when pressurized gas is introduced into locating balloon lumen  60 , the gas or fluid will pass through locating balloon port  64  to inflate locating balloon  66 . 
     The procedure for using stent delivery system  50  to implant stent  150  into the prostatic urethra  6  to maintain urethral patency is initiated by disposing stent  150  over a deflated stent retention balloon  35 . Stent retention balloon  35  is then inflated to hold stent  150  on stent delivery system  50 . Stent delivery system  50  is inserted through the penile urethra  4  until stent  150  is located in the prostatic urethra  6 , and locating balloon  66  is located in bladder  8 . This is shown in  FIG. 13 . 
     Locating balloon  66  is then inflated, and stent delivery system  50  is withdrawn and disposed so that locating balloon  66  is seated at bladder neck  16 , as shown in  FIG. 14 . The locating balloon  66  is affixed to catheter  52  at an appropriate distance from stent retention balloon  35  so that the seating of locating balloon  66  at bladder neck  16  assures proper placement of stent  150  in prostatic urethra  6 . Stent retention balloon  35  is then deflated. This releases stent  150  from stent delivery system  50  without changing the dimensions of stent  150 . Locating balloon  66  is then deflated. Stent delivery system  50  is removed from the prostatic  6  and penile  4  urethra, leaving stent  150  in prostatic urethra  6 . 
     Alternatively, stent retention balloon  35 , as well as locating balloon  66  may be deflated simultaneously. This would also release stent  150  from stent delivery system  50  without changing the dimensions of stent  150 . Stent delivery system  50  is then removed from the prostatic  6  and penile  4  urethra, leaving stent  150  in prostatic urethra  6 . 
     Although this embodiment of the stent delivery system of the current invention allows for accurate placement of stent  150  in prostatic urethra  6 , the user of the stent delivery system of the current invention may still wish to exercise an over-the-wire guidewire placement technique or direct visualization to place stent  150 . A third embodiment of a catheter  82  and distal tip  100 , shown in  FIGS. 15 to 17 , will allow for this capability. 
     Catheter  82  is a tubular structure with proximal  84  and distal  86  ends, stent retention balloon lumen  87 , locating balloon lumen  89 , through-lumen  88 , stent retention balloon port  91 , and locating balloon port  92 . Distal tip  100 , disposed on catheter distal end  86 , has tip lumen seal protrusions  102 ,  104 , and tip through-hole  106 . Distal tip  100  is disposed on catheter distal end  86  so that tip lumen seal protrusions  102 ,  104  are respectively disposed in stent retention balloon lumen  87  and locating balloon lumen  89  to seal, and tip through-hole  106  is aligned with through-lumen  88 . In practice, tip through-hole  106  and through-lumen  88  allow passage of either a guide wire, or a visualization means to facilitate delivery system placement, through catheter  82  to allow for accurate placement of stent  150  in prostatic urethra  6 . 
     In each of the stent delivery system embodiments shown so far, stent  150  is held onto the delivery system by radial pressure and a frictional fit between stent  150  and stent retention balloon  35 . In a fourth embodiment of the stent delivery system, shown in  FIGS. 18 to 21 , stent  150  is held on to delivery system by all or a portion of stent  150  captured between retention balloons at each end of stent  150 . This stent delivery system  120  generally includes catheter  122 , distal tip  70 , proximal stent retention balloon  142 , and distal balloon  144 . 
     Catheter  122  is a tubular structure with proximal  124  and distal  126  ends, stent retention balloon ports  32 ,  134 , and, as seen on  FIG. 9 , stent retention balloon lumen  58 , locating balloon lumen  60 , and locating balloon port  64 . Distal tip  70 , shown on  FIG. 10 , is disposed on catheter distal end  126 , and has tip lumen seal protrusions  74 ,  76 . Distal tip  70  is disposed on catheter distal end  126  so that tip lumen seal protrusions  74 ,  76  are respectively disposed in stent retention balloon lumen  58  and locating balloon lumen  60  to seal. 
     Distal balloon  144  has two balloon chambers, distal stent retention balloon  146 , and locating balloon  148 , and is affixed to catheter  122  at both ends and between the two chambers. 
     Proximal stent retention balloon  142  and distal balloon  144  are disposed on catheter  122  so that stent retention balloon port  32  is covered by proximal stent retention balloon  142 , and stent retention balloon port  134  is covered by distal stent retention balloon  146 . Tip lumen seal protrusion  74  seals stent retention balloon lumen  58  so that when pressurized gas, such as air, or a fluid such as saline, is introduced into stent retention balloon lumen  58 , the gas or fluid will pass through stent retention balloon ports  32  and  134  to inflate proximal  142  and distal  146  stent retention balloons. 
       FIG. 19  shows stent delivery system  120  when assembled, with stent  150  disposed on stent delivery system  120  between proximal  142  and distal  146  stent retention balloons. 
     Locating balloon  148  is disposed on catheter  122  so that locating balloon port  64  is covered by locating balloon  148 . Tip lumen seal protrusion  76  seals locating balloon lumen  60  so that when pressurized gas, such as air, or a fluid such as saline, is introduced into locating balloon lumen  60 , the gas or fluid will pass through locating balloon port  64  to inflate locating balloon  148 . 
     The procedure for using stent delivery system  120  to implant stent  150  into the prostatic urethra  6  to maintain urethral patency is initiated by disposing stent  150  on catheter  122 , with all, or a portion of stent  150  located between proximal  142  and distal  146  stent retention balloons. Proximal  142  and distal  146  stent retention balloons are then inflated to hold stent  150  on stent delivery system  120 . Stent delivery system  120  is inserted through the penile urethra  4  until stent  150  is located in the prostatic urethra  6 , and locating balloon  148  is located in bladder  8 . This is shown on  FIG. 20 . 
     Locating balloon  148  is then inflated, and stent delivery system  120  is withdrawn and disposed so that locating balloon  148  is seated at bladder neck  16 , as shown in  FIG. 21 . The locating balloon  148  is affixed to catheter  122  at an appropriate distance from distal stent retention balloon  146  so that the seating of locating balloon  148  in bladder neck  16  assures proper placement of stent  150  in prostatic urethra  6 . Proximal  142  and distal  146  stent retention balloons are then deflated. This releases stent  150  from stent delivery system  120  without changing the dimensions of stent  150 . Locating balloon  148  is then deflated. Stent delivery system  120  is removed from the prostatic  6  and penile  4  urethra, leaving stent  150  in prostatic urethra  6 . 
     Alternatively, proximal  142  and distal  146  stent retention balloons, as well as locating balloon  148  may be deflated simultaneously. This would also release stent  150  from stent delivery system  120  without changing dimensions of stent  150 . Stent delivery system  120  is then removed from the prostatic  6  and penile  4  urethra, leaving stent  150  in prostatic urethra  6 . 
     In each delivery system discussed to this point, balloons have been used as the means for holding the sent on the delivery system. As previously discussed, these means may also be mechanical. Such an embodiment is shown on  FIGS. 22 to 24 , where stent  150  is held on to delivery system by all or a portion of stent  150  captured between retaining mechanisms at each end of stent  150 . This stent delivery system  200  generally includes catheter proximal portion  202 , catheter central portion  204 , catheter distal portion  206 , and mechanical retaining mechanisms  220 . 
     Catheter portions  202 ,  204 ,  206  are tubular structures which are connected by mechanical retaining mechanisms  220 . Mechanical retaining mechanisms  220  comprise proximal  222  and distal  224  couplers with through-holes  226 ,  228 , respectively, and radial retention members  230 . Each radial retention member  230  has a deployment ramp  232 . When a deployment rod, a catheter, or a scope passes through through-holes  226 ,  228  of proximal  222  and distal  224  couplers, the rod will contact the deployment ramps  232 , and radially displace the radial retention members  230 . 
       FIG. 23  shows stent delivery system  200  when assembled, with stent  150  disposed on stent delivery system  200  between mechanical retaining mechanisms  220 . 
     The procedure for using stent delivery system  200  to implant stent  150  to maintain urethral patency is initiated by disposing stent  150  on catheter central portion  204 , with all, or a portion of stent  150  located between mechanical retaining mechanisms  220 . Mechanical retaining mechanisms  220  are then radially expanded to hold stent  150  on stent delivery system  200 . After stent delivery system  200  is inserted into, and properly located in the prostatic urethra, the deployment catheter, rod, or scope is removed, which allows mechanical retaining mechanisms  220  to radially collapse to release stent  150  from stent delivery system  200  without changing the dimensions of stent  150 . Stent delivery system  200  is then removed. 
     In regard to each embodiment illustrated above, the mechanisms which enable holding the stent to the stent delivery system, and anchoring the stent delivery system in the proper position before stent deployment, may be beneficially employed with any type of non-expanding stent. 
     Thus, while preferred embodiments of the devices and methods have been described in reference to the environment in which they were developed, they are merely illustrative of the principles of the invention. Other embodiments and configurations may be devised without departing from the spirit of the invention and the scope of the appended claims.