WO1988005317A1

WO1988005317A1 - Urethral stent

Info

Publication number: WO1988005317A1
Application number: PCT/US1987/000032
Authority: WO
Inventors: David H. Kuntz
Original assignee: Kuntz David H
Priority date: 1987-01-13
Filing date: 1987-01-13
Publication date: 1988-07-28

Abstract

A urethral stent (10) comprises an elongated, flexible tubular member which has a distal end (12) which is magnetically attractable. The proximal and distal ends (11, 12) are preferably set in the form of hooks (13, 14). A method of removing the stent from the urethra comprises introducing a retrieving catheter with a magnet at its tip into the urethra, catching the magnetically attractable distal end of the stent with the magnet and removing the stent by withdrawing the catheter with the distal end of the stent magnetically held by the magnet of the catheter.

Description

URETERAL STENT

Field of the Invention The present invention relates to ureteral stents. More particularly, it relates to a novel εtent which can be more easily removed than existing stents.

Background of the Invention Indwelling ureteral catheter stents or drainage tubes have been used to bypass ureteral obstructions or uretero- vaginal fistulas and maintain urinary drainage. In the past, stents made of straight lengths of open end tubing have been used for this purpose and have provided good drainage for sustained periods of time. However, the use of such open end tubing has not been completely satisfactory. For example, in some instances, the tubing has migrated and in others it has been expelled.

Various attempts have been made to produce stents which do not have the problems which accompany the use of such tubing. For example, stents have been designed which are closed at one end to facilitate passage into a body passage and which have at the other end a flange to make upward migration of the stent less likely. Another approach has been to provide the body of the stent with sharply pointed barbs which are designed to prevent downward migration and expulsion. However, such barbs increase the diameter of the εtent making it more difficult to insert and in some instances can cause the stent to migrate outside the bladder.

In U.S. Patent No. 4,212,304 issued July 15, 1979 and U.S. Patent No. 4,307,723 issued December 29, 1981, ureteral stents are disclosed which have hooks at each end which are _ _

surprisingly effective in preventing migration and expulsion. The patented stents are widely accepted because they can be easily introduced both endoscopically and during open surgery. All the commercially available stents have one diεadvan- tage in common; they are difficult to remove, especially from male patients. The usual method for removal of an indwelling εtent from the ureter of a male is a complex and painful procedure which can require a general anesthetic.

Summary of the Invention It is an object of the present invention to discloεe a novel ureteral εtent which can be readily removed from the ureter of male or female patients.

It is another object to disclose a unique method of removing the novel stent from the ureter and a kit for practicing the method.

The ureteral catheter εtent of the present invention can take many forms but preferably it comprises an elongated, flexible tubular member of subεtantially uniform outεide εurf ce throughout its length having proximal and distal ends which are set in the form of hooks and a distal end which is, at least in part, of a magnetically attractable material.

The main body of the εtent is preferably made of a soft, flexible, radiopague material and may be provided with indicating means which can be seen through a cyεtoscope and which will show the direction the proximal hook will extend when the εtent is in place. In the preferred embodiment, the terminal portion of the distal end is closed by a rod of magnetic material. The rod is permanently affixed to the main body of the stent and may be covered with a εoft outer la er of biocom atible material if deε . The εtent is generally put in place by inserting a guide wire through the most diεtal opening and i o the lumen. The preferred guide wire used for this purpose has a yielding leading end which is smaller than the proximal end opening so that if an obstruction is encountered the guide wire can be maneuvered paεt the obεtruction and the ureteral stent advanced over the guide wire and past the obεtruction. Because the guide wire is relatively stiff both of the hooks are straightened in the process. Next, a stent pusher is threaded over the free end of the guide wire behind the εtent to aid the paεεage of the εtent through a cyεtoεcope. If a guide wire is used which has a proximal leading end that is larger than the proximal opening in the ureteral εtent it can be used to position the stent and a stent pusher need not be used.

When for some reason it is desired to remove the indwel¬ ling εtent, a retrieving catheter with a magnetic tip is inεerted through the urethra into proximity with the magneti¬ cally attractable rod at the proximal end of the εtent. The catheter iε maneuvered until the magnetic tip catches the magnetically attractable rod at the diεtal end of the εtent. • The catheter with the stent attached iε then completely removed from the patient. Alternatively, the catheter and εtent combination can be withdrawn to a poεition at which the distal end of the εtent can be caught with a retraction device, εuch aε forcepε, as opposed to completely removed with the catheter.

The method of removing an indwelling ureteral εtent of the present invention can be done without εurgical interven- tion or general aneεthetic. Furthermore, it can be uεually accompliεhed without even viεualizing the εtent. —

The above stated and other objects and advantages of the invention will be apparent from the description which follows:

Description of the Drawingε Fig. 1 iε an elevational view of the preferred embodi¬ ment of the stent, the stent puεher, the retrieving catheter and the guide wire of the preεent invention;

Fig. 2 iε an enlarged view partly in section of the diεtal end of the εtent of Fig. 1; Fig. 3 iε an enlarged εectional view of the proximal end of the retrieving catheter; and

Fig. 4 is an enlarged view εhowing the proximal end of the retrieving catheter magnetically attached to the diεtal end of the εtent of Fig. 1. Description of the Preferred Embodiment

In the preferred embodiment shown in Fig. 1, the stent 10 is εeen to be an elongated tubular member having a proxi¬ mal end 11 and a diεtal end 12. Portions adjacent each of the endε 11 and 12 are formed and εet in the shape of gently curved hooks 13 and 14 which extend in opposite directions.

The two gently formed opposed hooks 13, 14 of the εtent • prevent it from migrating either upwardly or downwardly once it iε in place. A suitable material may be incorporated into the hooks 13 and 14 to make them less flexible and therefore make the εtent more reεiεtant to migration. The hooks 13 and 14 extend in opposite directions so that when the εtent 10 iε uεed aε an indwelling ureteral εtent the proximal end 11 can hook into the lower calix or renal pelviε while the distal end 12 curves out into the bladder. This design also preventε the tip of the stent from impinging directly into the bladder mucosa thereby decreaεing discom¬ fort and inflammation.

The stent 10 includes a relatively straight intermediate section 15 which extends between the proximal hook 13 and the diεtal hook 14.

The main body of the εtent 10 iε made of a εuitable flexible material such as nylon which is soft and stiff enough for the intended purpoεe and which preferably con¬ tains a radiopague material. The εtent may be εupplied in 7 French and 8.5 French sizes in 16, 24, 26, 28 and 30 cm lengths. The listed length of the εtent 10 iε the length of the εection 15 and doeε not include the hooked ends 13 and 14. This allows the user to radiographically estimate the ureteral length and select the proper εtent for passage. Still referring to Fig. 1, it can be seen that the stent 10 has radial drainage passages 16 which connect the lumen 17 of the εtent 10 to the outside and permit inside/ outside drainage. The drainage pasεages 16 are located about 5 centimeters apart on both sides of the straight section 15. The passages 16 of both sides are preferably aligned. There are similar but larger openings 18 in the inside wall of proximal hook 13 and an opening D adjacent the tip of the diεtal end 12.

In Fig. 1, there also can be seen a εtent puεher 19, a retrieving catheter 20 and a guide wire 21 which iε uεed to poεition the εtent 10 in a body passage such as a ureter.

The stent 10 iε normally εupplied with the proximal and distal ends 11 and 12 closed. However, if desired both or only one end may be open. When normal endoscopic insertion iε employed, the guide wire 21 iε introduced into the lumen 17 of the stent 10 via the opening D to straighten both hooks 13 and 14. The preferred guide wire 21 has a yielding proximal tip 21a which can be pasεed through the proximal opening of the εtent when an obεtruction iε encountered and used to maneuver the εtent: paεt the obεtruction.

Aε εeen in Fig. 2, the diεtal end 12 of the εtent 10 includes a portion 22 which is magnetically attractable. Preferably, portion 22 iε a rod 23 of magnetic ceramic or gold plated εteel permanently attached to the remainder of the stent 10. The rod 23 may be covered with a protective" coat of biocompatible material, such aε εilicone, if deεired. The rod 23 iε preferably force fit and/or glued to the main plaεtic body of the εtent but other methods of attachment may be uεed. To aεεiεt in properly poεitioning the εtent 10 in a ureter uεing a cyεtoεcope, the εtent pusher 19 is threaded over the free end of the guide wire 21. The εtent puεher 19 iε then uεed to advance the εtent 10 into poεition. Once the εtent 10 is properly positioned, the guide wire 21 and the stent pusher 19 are removed by withdrawing the guide wire 21 while holding the εtent puεher 19 thuε cauεing the stent 10 and εtent pusher 19 to separate after which the guide wire 21 and then the stent pusher 19 are withdrawn. The εtent 10 may also be positioned in an unobεtructed ureter without employing a εtent puεher by uεing a guide wire (not εhown) with a leading end^* which iε larger than the proximal opening in the ureteral εtent 10.

Aε εeen in Fig. 3, the proximal end 20a of the retrieving catheter 20 is bent to form an obtuse angle. When it is desired to remove the preferred stent of the present inven- tion, the retrieving catheter 20 with a magnet 24 m its proximal end 20a iε introduced into the urethra until the magnet 24 iε near the magnetically attractable distal end 12 of the εtent 10. The end 20a can be rotated in an arc when the catheter is inεerted into proximity with the stent until the magnet 24 catches the magnetically attractable rod 23 of the stent (as seen in Fig. 4). The catheter may be marked with a stripe 25 as seen in Fig. 1 or a εpot or dimple to indicate the direction of the bent proximal end 20a. The catheter 20 and εtent 10 combination may then be completely withdrawn by withdrawing the catheter 20. Alternatively, the catheter 20 can be withdrawn just enough for the distal end 12 of the stent 10 to be reached with a forceps or other graεping device. The deεcribed method of removing an in- dwelling stent iε εurpriεingly εucceεεful even though it iε accomplished without any visualization of the εtent.

The ureteral stent 10 of the present invention iε preferably made of εilicone rubber. If a stiffer εtent iε preferred it may be made of a polymer which has a durometer between about 70 Shore 'A' and about 55 Shore 'D' to which 10% barium sulfate has been added aε the radiopague agent. Stents made of the latter material have been found to be soft enough not to cause undue discomfort to the patient and stiff enough to bypass obstructionε in the ureter. Other plastic materials εuch as polyurethane which possess the desired properties and resist encrustation with urine εaltε can alεo be uεed.

The εtent 10 is preferably formed by extruding a length of tubing of the desired size and durometer. The proximal end 11 of the tubing is then placed in a mold to close the lumen. The length of tubing iε then placed in a form to εhape the hookε 13 and 14. The drainage openingε D, 16 and 18 may be formed at any εtep of the process by piercing the wall of the tubing with a flattened, sharpened hole cutter of the desired size or by use of a laser or any other conven¬ tional means. The magnetically attractable rod 22 iε then glued, force fit or otherwiεe permanently attached to the remainder of the stent 10.

The ureteral εtent 10 of the preεent invention may be εupplied aε a εeparate item or aε a component of a kit. A kit might contain a εtent 10 of the deεired εize, a εtent puεher 19, a suitable guide wire 20 and a retrieving catheter 20 as seen in Fig. 1.

The εtent puεher 19 may be supplied aε a ready made component of the kit or a εatiεfactory εtent puεher 19 may be made from a half length of a relatively εtiff εtandard ureteral catheter, preferably 5 French.

The retrieving catheter 20 which iε approximately 16 Fr. or .215" in diameter iε preferably of a relatively εtiffer material then the εtent 10 and it haε a proximal end 20a which iε bent at an obtuεe angle of about 150°. The main body of the retrieving catheter iε preferably hollow and there iε a fluid drainage paεεage 26 near the proximal end 20a so that fluid can drain out through the catheter 21. In the preferred embodiment described and shown in the drawing, the proximal and distal end portions of the catheter stent are both in the form of gently curved hookε. However, it iε to be underεtood that the term "hook" iε intended to include other functionally equivalent εhapes which prevent migration and do not increase the effective outer diameter -?-

It will be readily apparent to those skilled in the art that a number of modifications and changes can be made without departing from the spirit of the invention. For example, although in the preferred embodiment the agnetic- ally attractable rod 23 and the magnet 24 are both of metal, one or both could be of magnetic ceramic, if desired. In addition, if a stronger magnet 24 is deεired, a small electro¬ magnet could be uεed. Furthermore, if desired, the rod 23 could be replaced with a magnetically attractable tube. Finally, it should be understood that it is within the scope of the invention to have the magnet on the distal end of the εtent and the magnetically attractable material at the proximal end of the retrieving catheter; however, such an arrangement may not be as desirable. Therefore, it is to be understood that the scope of the invention iε not to be limited by the foregoing description, but only by the claimε.

Claims

- AC ¬CLAIMS

1. A ureteral catheter εtent compriεing an elongated flexible tubular member of εubεtantially uniform outεide diameter throughout itε length, having a proximal end in the form of a hook and a magnetically attractable distal end.

2. The εtent of claim 1 in which the diεtal end iε also in the form of a hook.

3. The stent of claim 1 which has at least one radial drainage paεεage to allow inεide/outside drainage.

4. The εtent of claim 1 in which the magnetically attractable diεtal end iε of εteel.

5. The stent of claim 1 in which the remainder of the εtent other than the diεtal end iε of a non-magnetically attractable material.

6. A retrieving catheter for removing an ureteral εtent with a magnetically attractable diεtal end, εaid catheter being of a εize which can be introduced into the urethra of a patient and having meanε at itε proximal end for magnetically attracting the diεtal end of the stent.

7. A retrieving catheter of claim 7 in which a proximal portion including the proximal end iε bent to form an obtuεe angle with the rest of the catheter.

8. A method of retrieving a ureteral εtent of claim 1 from a patient which compriεeε introducing into the urethra of the patient a catheter with means for magnetically attract¬ ing the diεtal end of the stent, bringing said means into contact with the magnetically attractable diεtal end of the εtent and then withdrawing the catheter and the εtent.