URETERIC STENT
The invention relates to stents, and particularly to ureteric stents.
Stents are medical devices which are inserted into tubes in the body, for example an artery, to maintain a specified width for the artery. Ureteric stents are inserted into the ureter, the tube that joins the kidney to the bladder.
Ureteric stents are used to prevent or treat obstruction of the ureter resulting from many causes, includes stones and tumours.
Conventional ureteric stents extend all the way from the kidney to the bladder and are left in place for long periods of time, or even permanently.. Encrustations may build up on the stents and the conventional stents also cause side effects.
I have developed new stents which have the potential to cause fewer side effects.
The invention provides a ureteric stent having a length which is less than half that of the ureter.
Preferably the stent has a length substantially equal to one third of the length of the ureter.
Preferably the stent has means to retain the stent in a predetermined position within the ureter.
The means to retain the stent in position may comprise a portion of the stent which exerts sideways pressure on the wall of the ureter, so that the stent is maintained in position by frictional forces.
The said portion of the stent may comprise a spiral coil.
Preferably the spiral coil is arranged at one end of the stent.
One embodiment of stent, for use in the upper or middle third of the ureter may have a spiral coil at each end.
Each coil may have a maximum diameter of from 1cm to 2cm and a length of from 1cm to 2cm.
A preferred diameter is 6 French and a preferred length is 1cm. The stent may have a substantially straight central region.
The central region may have a length of from 3 to 6cms.
The lower end of the stent may have one or more threads attached thereto.
The threads may be of Nylon.
Each end of the central region may be provided with a radio-opaque marker.
The stent may be manufactured from PTFE or other biocompatible polymer material.
By way of example, two specific embodiments of the invention will now be described, with reference to the accompanying drawings in which:
Figure 1 is a perspective view of one embodiment of stent according to the invention; and
Figure 2 is a perspective view of a second embodiment of stent according to the invention.
The embodiment of ureteric stent shown in Figure 1 comprises two spiral coils 10, 11 separated by a central straight section 12.
At each end of the straight section 12 is a radio opaque marker 13.
Nylon threads 14 are attached to the lower end of the stent.
The stent is manufactured from PTFE (e.g. Percuflex) and is self-supporting with the configuration shown in Figure 1.
The stent shown in Figure 1 can be inserted into the ureter and in use this embodiment of stent will be positioned in the upper or middle third of the ureter.
In use, the larger diameter portions of the stent maintain the ureter with a given width.
The spiral coils 10 and 11 apply fight pressure against the walls or the ureter and the stent is thus maintained in position, at the desired location, by frict πal forces.
The stent can be inserted in a conventional manner, for example over a conventional 0.038 inch diameter guide wire, using a conventional pusher. The radio opaque markers 13 enable the location of the stent within the body to be tracked with conventional equipment
The nylon threads 14 facilitate extraction of the stent, for example using a flexible cystoscope.
The embodiment of stent shown in Figure 2 has a single spiral coil 10 attached to a central region 12. Radio opaque markers 13 are again present.
At the lower end of the stent shown in Figure 2 there is a bladder segment 15 to which is attached nylon threads 14.
The embodiment of stent shown in Figure 2 is designed for use in the lower third of the ureter. The bladder segment 15 comprises a pigtail shape as used on conventional ureteric stents. The retention effect of the spiral coils is only exhibited within the ureter, where the light pressure can be applied against the wall of the ureter. With the embodiment of the invention shown in Figure 2, the lower end of the stent is to lie within the bladder so there is no advantage in using a spiral coil. It is sufficient to use the conventional pigtail which resists movement of the lower end of the stent out of the bladder.
Each spiral coil has a length of 1cm and a maximum diameter of 1cm.
Each central region 12 has a length of from 3 to 6 cms.
Conventional stents always protrude into the bladder from the lower end and into the kidney from the upper end. This can cause irritation and infection. They can also cause backflow of urine with attendant problems.
The stents according to the invention occupy only the obstructed segment of the ureter and this reduces the risk of irritation and side effects.
Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.
All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive,
Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.
The invention is not restricted to the details of the foregoing embodiments). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.