GB2464765A

GB2464765A - A ureteral stent having a sheath which retains a plurality of objects

Info

Publication number: GB2464765A
Application number: GB0819893A
Authority: GB
Inventors: Vinod Nargund
Original assignee: HOMERTON UNIVERSITY HOSPITAL N
Current assignee: HOMERTON UNIVERSITY HOSPITAL N
Priority date: 2008-10-30
Filing date: 2008-10-30
Publication date: 2010-05-05
Also published as: GB0819893D0

Abstract

The present invention relates to a ureteral stent comprising an elongate member 401 configured to be disposed within a urinary tract of a subject. The elongate member 401 defines a lumen, configured to convey urine from the renal pelvis to the bladder. The elongate member 401 has a distal end portion, a proximal end portion, and a medial portion disposed between the distal end portion and the proximal end portion. The distal and proximal end portions each have at least one opening for urine drainage. The elongate member 401 further comprises a sheath 402 in contact with a surface of the elongate member 401, configured to retain a plurality of objects 403 against said surface of the elongate member 401. In a preferred embodiment, said objects 403 are packages of radiation. The stent may be configured for use in brachytherapy of the ureter and/or surrounding tissue.

Description

Catheter The present invention relates to self-retaining catheters for continuous drainage of urine from the kidney and into the bladder. This function is normally performed by the ureter, a long narrow muscular tube that connects the kidneys to the bladder.

Ureteric cancers can occur at any point along the ureter, in the lower third (iv-Figure 2), middle third (ii and iii-Figure 2) or upper third (i-Figure 2) or at a specific point along the ureter (U, Figure 2, v and vi). The main type of cancer affecting the ureter is transitional cell carcinoma (TOO). This type of cancer develops in the epithelial cells that line the ureter. The current treatment for upper urinary tract cancers is total excision of the ureter, kidney and possibly part of the bladder (nephro-ureterectomy) (as shown on figure 1, dotted line). This drastic operation is carried out to ensure that any local undiagnosed cancerous tissue is removed. Patients can generally cope with a first nephro-ureterectomy, however, after a second they will clearly require dialysis or subsequent renal transplant. There is thus a clinical need for a treatment for upper urinary tract cancers which maintains the presence of the ureter whenever possible.

Brachytherapy or sealed source radiation therapy is the clinical application of radioactive compounds in close proximity to an area requiring irradiation, for example a tumour. If the tumour requiring treatment is near the surface of the body then the radioactive source can simply be placed on the body surface, near the offending tissue. Localised tumours further into the body can be treated with brachytherapy by "seeding" the cancerous tissue with a radioactive source. This can be achieved with insertion of Iridium-i 92 wire or, more commonly, titanium capsules encasing an Iodine-i 25 source (also known as seeds). These seeds are approximately one millimetre in diameter and several millimetres long. Brachytherapy is commonly used to treat localised prostate cancer, cervical cancer and cancers of the head and neck. When treating prostate cancer, seeds are inserted into the prostate gland through a fine needle, which is capable of delivering 2 to 6 seeds.

Generally the radioactive isotope Iodine125 is used in titanium seeds. The seeds are left in position permanently, they are biologically active for about 9 months, after which they are effectively inert. Bracytherapy allows a high dose of radiation to be delivered directly to the tissue of interest. The dose is focused and substantially greater than can be delivered with conventional external beam radiotherapy. Cancers of the bladder may be treated with brachytherapy using devices known in the art as TCC of the bladder is sensitive to radiotherapy. However, such devices do not service cancers of the ureter, and thus there is no way of targeting brachytherapy to this section of the urinary tract (ureter). There is thus a great unmet need in the treatment of upper urinary tract cancers, given that the current treatment protocol (nephro-ureterectomy) is so drastic, and whilst therapies such as brachytherapy remain unavailable to this part of the urinary tract. The present invention meets this unmet need.

Catheter stents are commonly used to promote drainage of urine when the ureter has been damaged or occluded. Ureteric stenting is a commonplace procedure to treat strictures of the ureter. The ureteric narrowings could be due, amongst other causes, to congenital defects, direct ureteric cancers or indirect local cancers pressing on the ureter. Stenting may also be performed if the ureter has been physically damaged (i.e. during an accident), during infection, to manage post-operative swelling, and in conjunction with kidney stone operations to allow the safe passage of stone remnants into the bladder. The ureteral stent may stay in place on a short term (days to weeks) or long term (weeks to months), but will always be removed as it may get encrusted through use.

In order to insert the stent, a cystoscope is inserted into the bladder through the urethra, and the ureteric opening to be stented is identified. A guide wire is inserted into the ureter under fluoroscopic guidance. The guide wire provides a path for the placement of the stent, which is advanced over the wire with the help of a pusher. Once the stent is in place, the guide wire and cystoscope are removed. Patients who fail this method of ureteral stenting may have the stent placed percutaneously (through the skin), into the kidney, and subsequently into the ureter and bladder. Once treatment is finished and the indwelling stent is no longer required, a further cystoscopy can be performed for retrieval of the stent. Alternatively, a suture (string) is attached to the bladder end of the stent, which is run from the bladder through the urethra, to the outside of the body. The stent can thus be removed by grasping and pulling the string.

The size, shape and material of the ureteral stent to be used depends on the patient's height and the reason why the stent is to be placed. The majority of stents are 12 to 32cm in length, and have a diameter of 1.5-7mm.

Generally, one or both ends of the stent may be coiled to prevent it moving out of place; alternatively open-ended (no coils) stents are used in some circumstances on a short term basis An ideal stent material must be flexible, durable, non-reactive and visible on X-ray or a fluoroscope. The most common form of stent is the double j (JJ) stent or a double pigtail stent (Figure 3). This tube (1) has a curl at both ends. The distal end (2) is designed to fit into the bladder whilst proximal end (3) is designed to fit into renal pelvis. On the curls there are small holes (not shown) which allow urine to pass from the renal cavity, down the catheter and into the bladder. The stent is resilient enough to maintain patency through the stricture, ensuring urine can pass from the kidney to the bladder.

There is no current ureteral stent that would permit brachytherapy for ureteral cancers, and it is thus an object of the invention to provide such a stent.

The present invention relates to a ureteral stent comprising: an elongate member configured to be disposed within a urinary tract of a subject, the elongate member defining a lumen configured to convey urine from the renal pelvis to the bladder, the elongate member having a distal end portion, a proximal end portion, and a medial portion disposed between the distal end portion and the proximal end portion, the distal and proximal end portions each having at least one opening for urine drainage, the elongate member having a sheath in contact with a surface of the elongate member, configured to retain a plurality of objects against said surface of the elongate member.

In some embodiments, said sheath is in contact with the external surface of the elongate member. In these embodiments, said sheath is preferably an elastic sheath, which is tensed in a radial direction around the elongate member. Once an object is inserted between the sheath and the elongate member, the tension in the sheath acts to hold the object against the surface of the elongate member.

In other embodiments, said sheath is in contact with the internal surface of the elongate member. In these embodiments, said sheath is compressed against the internal surface of the elongate member. Once an object is inserted between the sheath and the elongate member, the compression action of the sheath acts to hold the object against the surface of the elongate member.

The ureteral stent of the invention is configured to hold objects between the sheath and the elongate member. In some preferred embodiments, the objects are packages of radioactivity. In such embodiments, the ureteral stent may be used for brachytherapy. This is an advantage of the invention, since it is not currently possible to deliver brachytherapy to this part of the urinary system.

Figure 1 shows the physiological location of the kidney (K), ureter (U) and bladder (B). The dotted area represents the tissue removed in a nephro-ureterectomy.

Figure 2 shows the kidney (K) and ureter (U) and various possible locations for ureteric cancer along the ureter (i to vi) although the cancer can be located at any point.

Figure 3 shows a ureteric stent (1). The stent shown is a double j (JJ) or pigtail stent, as it has a coil at both the distal end portion (2) and the proximal end portion (3), whilst it is substantially straight in the medial portion (4).

Figure 4 shows (in cross section) one embodiment of the invention.

Figure 4A shows the ureteric stent comprising an elongate member (401) with a sheath (402) in contact with the external surface. Figure 4B shows the same stent as figure 4A, with an inserted object (403). The pocket formed between the elongate member (401) and the sheath (402) is shown (405).

Figure 5 shows (in cross section) the ureteric stent previously depicted in figure 4A, together with one embodiment of the method for inserting the object between the elongate member and the sheath. A needle insertion assembly, comprised of a hollow delivery tube (501) with an internal separate needle (502) is used. The assembly is used together to pierce a hole in the sheath (402) -Figure 5A and SB. The needle (502) is withdrawn from the hollow tube (501) -Figure 50. An object (403) can then be inserted between the sheath (402) and the elongate member (401)-Figure SD. Figure SE shows the section of the stent once the procedure is complete and the hollow delivery tube is removed, the sheath (401) closes around the insertion hole and holds the object (403) against the elongate member (401).

Figures 6 and 7 shows two embodiments of the invention in cross section, comprising a ureteric stent with a sheath (402) in contact with the external surface of the elongate member (401). A plurality of objects (403) have been placed between the sheath (402) and elongate member (401).

The distal end portion (2) and proximal end portions (3) are shown, and in these embodiments are curled.

Figure 8 shows an alternative embodiment of the invention in cross section. In this embodiment, the sheath (402) is in contact with the inner surface of the elongate member (401). In this embodiment, an aperture (404) is present in the elongate member (401) to allow the insertion of the object (403) between the sheath (402) and the elongate member (401). Figure 8A shows the ureteric stent without an inserted object, and figure 8B shows the same stent with an inserted object (403).

Figure 9 shows one embodiment of the invention (in cross section) placed in the ureter (U) and kidney (K) of a subject, more particularly; the distal end portion (2) forms a large coil in the renal pelvis (F). In this embodiment, the sheath (402) is in contact with the outer surface of the elongate member (401) including the distal end portion (2). Objects (403) have been inserted between the sheath (402) and the elongate member (401).

The ureteric stent of the present invention may be used to hold objects (403) against specific points in the ureter once the stent has been inserted in the ureter. As such, the stents are configured to hold radioactive packages against tissues in the ureter or surrounding area that are cancerous. Thus, the stent of the invention may be used to deliver radiation to the ureter and surrounding tissues, namely brachytherapy.

The elongate member (401) of the stent of the present invention is configured to be disposed within the urinary tract of a subject, more particularly within the ureter of a subject. The elongate member defines a lumen which is configured to convey urine from the kidney to the bladder. The stent and thus the elongate member has a length sufficient to extend within the ureter from the subject's kidney, in particular the renal pelvis to the subject's bladder. It will be understood by the person skilled in the art that the length of the stent can thus be variable. Moreover, the skilled person will understand that the stent can be used in either ureter. According to one feature, the elongated member is made of a physiologically compatible material such as, for example, polyvinyl alcohol, polyethylene oxide, hydroxy ethyl cellulose, or the like. An ideal material must be flexible, durable, non-reactive and visible on an x-ray or fluoroscope. The elongate member may be resilient and maintain the flow of urine from the kidney to the bladder.

The surface of the elongate member (401) in contact with the sheath may be textured in order to provide an enhanced hold on the object (403).

The elongate member (401) has a distal end portion (2), a proximal end portion (3) and a medial portion (4) which is between the distal and proximal end portions.

Each of the distal end portion (2) and the proximal end portion (3) have at least one opening to allow the flow of urine. In some embodiments, the opening may be an open end to the lumen of the elongate member (401). In other embodiments, the opening may be one or more, or a plurality of holes in the wall of the elongate member, through to the lumen of the elongate member. Those skilled in the art will be aware of appropriate openings to allow the flow of urine. The lumen of the elongate member is thus in fluid communication with the urine that passes out of the kidney and into the bladder.

The proximal end portion (3) is adapted for use at the top of the ureter, in order to collect urine from the kidney, in particular the renal pelvis. In some embodiments, the proximal end portion may be open-ended, particularly if the stent is intended for short-term use. In other embodiments, the proximal end portion retains the position of the ureteral stent when placed substantially within the kidney. Any suitable means for retaining the stent in position is encompassed, including curls (shown on figure 3) The proximal end portion of the ureteral stent is typically made from material that is able to regain its structure after distortion which allows for the distal end portion to be straightened out prior to placement within the subject.

In a preferred embodiment, the proximal end portion (3) is adapted such that it forms a curl which sits close to the renal pelvis (F) , which would allow radiotherapy and the like to be administered directly to this area of the kidney, should this be desirable (Figure 9).

The distal end portion (2) is adapted for use at the bladder end of the ureter in order to deliver the urine to the bladder. In some embodiments, the distal end portion may be open-ended, particularly if the stent is intended for short-term use. In other embodiments, the distal end portion retains the position of the ureteral stent when placed substantially within the bladder.

Any suitable means for retaining the stent in position is encompassed, including curls (shown on figure 3) The distal end portion of the ureteral stent is typically made from material that is able to regain its structure after distortion which allows for the proximal end portion to be straightened out prior to placement within the subject.

In a preferred embodiment, both the proximal end portion (3) and the distal end portion (2) form curls, which enable the stent to be held in place (a double J stent format).

A sheath (402) is in contact with a surface of the elongate member (401). Said sheath may be in contact with the external or internal surface of the elongate member, or any part or portion thereof. The sheath may be in contact with the entirety of one surface of the elongate sheath (for example the external or internal surface), or a section thereof, particularly the medial section (4) thereof. It is preferred that the sheath is contiguous to the surface of the elongate member. In a preferred embodiment, the sheath is fixed to the elongate member only at the proximal and distal end portions of the elongate member. In an alternative embodiment, the sheath is fixed in discrete sections to the elongate sheath, allowing the formation of pockets wherein the sheath is not fixed to the elongate member.

The sheath (402) is configured to allow the insertion and retention of an object (403) against the surface of the elongate member (401). Thus, the sheath is applying a force to the surface of the elongate member in order to hold the object in place.

In one embodiment, the sheath (402) is in contact with the external surface of the elongate member (401) as depicted in Figure 4. As depicted herein, the sheath is fixedly attached to the elongate member at each end, whilst the remainder is in contact with the elongate member. In this embodiment, the sheath preferably an elastic sheath, which is tensed in a radial direction around the elongate member. Once an object (403) is inserted between the sheath and the elongate member, the tension in the sheath acts to hold the object against the surface of the elongate member, and prevent the object from moving. In this embodiment, a plurality of objects may be placed along the length of the catheter, at any location (Figures 6 and 7). In a modified aspect, the sheath has been fixedly attached at points to the elongate member. This allows the formation of pockets, in which an object can be inserted.

The sheath is formed of any suitable elastic material known to those skilled in the art. Preferably, the sheath is resilient and once punctured in order to insert the object, closes around the site of insertion. An example of a suitable sheath to be in contact with the external surface of the elongate member is a membrane, particularly an elastic membrane.

In an alternative embodiment, the sheath (402) is in contact with the internal surface of the elongate member (401) as depicted in Figure 8. In this embodiment, the sheath is pushing against the inner surface of the elongate member, it could be said to be compressed against the inside of the elongate member. The force in this embodiment is against the internal surface of the elongate member. In order to allow the insertion of an object (403) between the sheath and the elongate member, the elongate member comprises a plurality of apertures (403) through which the object may be inserted. These apertures are configured to allow the entry of the object, whilst preventing the object from escaping once put in place. They are thus angled appropriately.

The tension in the sheath holds the object against the inner surface of the elongate member, preventing movement of the object. In one aspect, the sheath is fixedly attached to both ends of the elongate member or part thereof (for example the medial portion). In an alternative aspect, the sheath is fixedly attached at points to the elongate member. This allows the formation of pockets, in which an object can be inserted. It is preferred that these pockets are in communication with the apertures (403).

The sheath may be formed of any suitable material which allows the compression of the sheath against the internal surface of the sheath. Suitable materials are known to those skilled in the art, but include wire meshes, membranes and the like.

It is preferred that the sheath (402) for any aspect of this invention is physiologically acceptable and inert in the urinary tract.

It is preferred that the sheath (402) is in contact with the substantially the entirety of one surface of the elongate member (401), for example substantially the entire external surface. This would result in a stent wherein the distal end portion (2) and proximal end portion (3) are in contact with the sheath. This would allow for delivery of the object to the renal cavity or the neck of the ureter in the bladder.

The ureteral stent of the present invention allows for the insertion of one or more, or a plurality of objects (403) between the sheath (402) and the elongate member (401). It is preferred that these objects are packages of radiation, more particularly, radioactive seeds. An example of a suitable radioactive seed is ProstaSeed� from Core Oncology. This seed is an 1-125 brachytherapy source consisting of a welded titanium capsule containing Iodine 1-125 adsorbed onto five silver spheres which also serve as radiographic markers. The seed has the dimensions 4.5 mm long, 0.8 mm outside diameter, 0.05 mm wall. Any suitable packages of radiation may be used, with any suitable radiation source.

In an alternative embodiment, the objects may be drug compounds or the like.

The objects (403) may be inserted into the stent just prior to the insertion of the stent into the subject by the clinician, particularly when those objects are packages of radioactivity. In this manner, the stent may have a longer shelf-life than one with previously inserted packages of radioactivity, geiven the relatively short half-life of the radioactive sources used for brachytherapy. Suitable precautions should be taken by the skilled person in charge of inserting the packages of radiation into the stent to prevent exposure of clinical staff to radiation.

Figure 5 shows one in vitro technique for the insertion of an object between the sheath (402) and the elongate member (401). A needle insertion assembly, comprised of a hollow delivery tube (501) with an internal separate needle (502) is used. The assembly is used together to pierce a hole in the sheath (402) -Figure 5A and 5B. The needle (502) is withdrawn from the hollow tube (501)-Figure 5C. An object (403) can then be inserted between the sheath (402) and the elongate member (401)-Figure SD. Figure SE shows the section of the stent once the procedure is complete and the hollow delivery tube is removed, the sheath (401) closes around the insertion hole and holds the object (403) against the elongate member (401). A similar method may be used when the sheath is in contact with the internal surface of the elongate member, a hollow tube could be inserted in the apertures (404) in order to place the object between the sheath and the elongate member.

Generally, a normal ureter has a diameter size that may extend up to between about 2 millimeters and 6 millimeters. After dilation of the ureter, the ureter's diameter size may be further increased up to about 8 millimeters.

Dilation of the ureter may be required prior to the insertion of the ureteric stent of the invention. This may be achieved by any standard means, preferably by the insertion of an ordinary ureteric stent for 2-3 weeks. Thus, it is preferred that the stent has a diameter between 2 and 8 millimeters. The majority of stents are 1 2 to 32cm in length, and it is preferred that the stent of the present invention has a length between 12 and 32cm.

The subject as used herein may be any human or animal subject in need of treatment of the ureter. It is preferred that the subject is human.

By using the stent of the present invention to hold packages of radioactivity, the stent may be placed into the urinary tract of a subject with packages in multiple and different positions which correspond to the areas that require radiotherapy. This allows for tailored and targeted radiation exposure, specific to the site against which the stent will sit. This will thus reduce the need for nephro-ureterectomy particularly in solitary renal unit, which is an object of the invention.

The stent of the present invention can be used in the treatment of ureteric cancers, and/or selected cancers of the kidney and bladder.

The stent of the present invention may be inserted by any means known in the art to insert a ureteral stent. It is preferred that the insertion of the stent is monitored using fluoroscopy. A portion or substantially all of the stent should therefore be opaque, such that it may be viewed during insertion.

Claims

Claims: 1. A ureteral stent comprising: an elongate member configured to be disposed within a urinary tract of a subject, the elongate member defining a lumen configured to convey urine from the renal pelvis to the bladder, the elongate member having a distal end portion, a proximal end portion, and a medial portion disposed between the distal end portion and the proximal end portion, the distal and proximal end portions each having at least one opening for urine drainage, the elongate member having a sheath in contact with a surface of the elongate member, configured to retain a plurality of objects against said surface of the elongate member.
2. A ureteral stent as claimed in claim 1 wherein said sheath is in contact with the external surface of the elongate member.
3. A ureteral stent as claimed in claim 1 wherein said sheath is in contact with the internal surface of the elongate member.
4. A ureteral stent as claimed in any previous claim, wherein said object is a package of radioactivity.
5. A ureteral stent as claimed in any previous claim, which is adapted for use in brachytherapy of the ureter and/or surrounding tissues.