Ureteral stent-catheter having varying internal diameter and method of use

A tubular flexible stent, a combination of stent-catheter, and method thereof, comprises a flexible tubular drain passage segment and a flexible tubular ureteral catheter receiving segment which is collinearly integral with the passage segment. The stent is formed with a curl at each end of the drain passage segment and the catheter receiving segment. The outer width of the catheter receiving segment is same or slightly larger than that of the drain passage segment. The inner width of the catheter receiving segment is larger than that of the drain passage segment. The length of the drain passage segment is substantially longer than that of the catheter receiving segment. A rigid ureteral catheter is inserted into the receiving segment to straighten the preformed curl formed therein and a stiffening wire is passed through the catheter and the stent to straighten the curl formed in the drain passage segment. A rigid tube is slid over the catheter and abutted against the free end of the receiving segment to pull the catheter out of the stent.

BACKGROUND 
Ureteral stents are fundamental to the practice of Urology. These devices 
allow one to bypass and drain an obstructed ureter, determine urine output 
from a particular renal unit, and inject contrast to study the upper 
urinary tract. With the advent of newer methods to manage upper urinary 
tract stones, such as extracorporeal shock wave lithotropsy (ESWL) 
disclosed in U.S. Pat. No. 4,913,683 issued to Gregory, and urethroscopy, 
the use of ureteral stents will continue to grow. 
The ideal ureteral stent should allow one to measure urine output from a 
particular renal unit, drain even tenaciously purulent material, allow 
injection of contrast for imaging and finally remain indwelling and self 
contained if longterm ureteral stenting or drainage is required. 
The presently available devices consist of external or internal ureteral 
stents. Both types are usually passed through the ureteral meatus via a 
cystoscope, though they can be placed openly through different sites in 
the urinary tract. 
Externalized ureteral stents drain the upper urinary tract and pass through 
the bladder, exiting the urethra and draining into an external collecting 
device. They allow drainage through ports and a central lumen or channel, 
and can be irrigated as needed to drain tenacious and obstructing 
material. By draining externally, the output from the involved renal unit 
can be carefully monitored. Contrast can be injected as needed to evaluate 
the upper tract. 
Unfortunately, these devices are not self contained and must be secured or 
they will migrate and be extruded by ureteral peristalsis. They therefore 
are not suitable for longterm outpatient care. 
With this objective in mind, internalized ureteral stents were developed. 
The most commonly used type is a plastic stent with a curl at both the 
proximal and distal ends, i.e., a "double-J" stent. The curls are 
straightened over a central stiffening wire in order to pass the stent, 
but are reformed when the stiffening wire is removed. The proximal curl 
prevents distal migration and thereby keeps the device in the renal 
pelvis. The distal curl is positioned in the bladder to allow completely 
internalized drainage. No urethral catheter is needed to secure this type 
of stent, making it ideal for outpatient management. 
U.S. Pat. No. 4,957,479 issued to Roemer; U.S. Pat. No. 4,931,037 to 
Wetterman; U.S. Pat. No. 4,913,683 to Gregory; U.S. Pat. Nos. 4,820,262 
and 4,307,723 to Finney U.S. Pat. No. 4,790,810 to Pugh, Jr. et al.; U.S. 
Pat. No. 4,790,809 to Kuntz; U.S. Pat. No. 4,787,884 to Goldberg; U.S. 
Pat. No. 4,713,049 to Carter; U.S. Pat. No. 4,671,795 to Mulchin; and U.S. 
Pat. No. 4,610,657 to Densaw all show this general approach, while U.S. 
Pat. No. 4,813,925 to Anderson, Jr. et al., and U.S. Pat. No. 4,531,933 to 
Norton et al. show a variation of this concept by using helixes to replace 
hooks. 
The devices shown by these patents, however, have disadvantages. The urine 
output from the involved renal unit cannot be recorded as only total 
urethral urine output can be recorded and this would include both kidneys. 
Also, since the distal end of the stent is internalized, it is not 
possible to irrigate the tube should it become obstructed. Under these 
circumstances the obstructed stent could be more detrimental than 
beneficial as it would occlude an already narrow ureteral lumen. Since the 
ureteral stent can become obstructed without any external indication, the 
situation can become dramatically acute before it is realized that the 
internalized stent is no longer serving its purpose. Lastly, as the stent 
is not externalized, contrast cannot be injected if needed to image the 
upper tract. 
U.S. Pat. No. 4,913,683 to Gregory allows injection of contrast via a small 
lumen in the stiffening wire. This lumen, however, is too small to allow 
reliable and accurate monitoring of urine output or drainage and 
irrigation of tenacious debris from the involved kidney. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the present invention is to provide a universal 
stent which, once in place, functions as an external ureteral stent which 
can be easily converted into an internalized ureteral stent. 
Another object of the present invention to provide a combination 
catheter-stent that improves on the known prior art devices in that it has 
the advantages of both an externalized ureteral stent and the advantage of 
an internalizable ureteral stent once the necessity of externalized 
drainage or access is overcome. 
The above-identified objects and other readily apparent advantages are 
realized in the present invention by providing a double-J stent with side 
openings along two-third of its proximal length. The proximal end is 
preferably closed. The distal one-third of the double-J stent has a wider 
lumen (inside diameter) to accept the insertion of a rigid open-ended 
ureteral catheter, but may still have a substantially the same diameter 
throughout the stent. The wider lumen in the distal one-third of the stent 
permits the catheter itself to have a lumen that is substantially the same 
size as the lumen of the proximal two-third of the stent so as to not 
restrict fluid communication. As previously mentioned, the outer diameter 
of the proximal two-third may have substantially the same outer diameter 
as the distal one-third so that the stent has a substantially uniform 
diameter throughout. In another embodiment, the outer diameter of the 
distal one-third of the stent may have a slight taper, with the widest 
diameter at the free end thereof. 
To provide for an abutting surface in which an immobilizing abutting open 
tube can abut thereagainst, the inner diameter of the immobilizing 
abutting open tube and the outer diameter of the catheter is substantially 
similar, with sufficient clearance to permit the immobilizing abutting 
open tube to slide relative to the catheter, so that the end of the 
immobilizing open tube abuts against the distal end of the stent. 
The rigid ureteral catheter is long enough to exit the urethra and can be 
drained by an external drainage system. When the necessity of outside 
drainage, contrast injection, or monitoring no longer exists, the rigid 
catheter can be disconnected from the flexible ureteral stent. This allows 
the part of the stent in the bladder to return to its preformed curl to 
function as a normal double J shaped stent.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
Two specific embodiments of the present invention are shown in the drawings 
for merely purposes of illustrating the principles of the present 
invention. Accordingly, the present invention is not to be limited solely 
to the exact configuration and construction as illustrated and set forth 
herein. 
For convenience, the same or equivalent elements of the preferred 
embodiments of the present invention illustrated in the drawings have been 
identified with same reference numerals. 
The ureteral stent 1 comprises a flexible plastic tube 2 having apertures 3 
along the proximal segment 4, defined by length L.sub.1 and a wider 
catheter receiving segment provided at the distal segment 12, defined by 
length L.sub.2. Although any length proportion may be selected, the 
embodiment contemplated in the drawings show the length L.sub.1 being 
preferably about twice the length of L.sub.2. The apertures 3 communicate 
between the outside of the stent and the longitudinally extending lumen or 
channel 5. The lumen 5 extends substantially the entire length of the 
stent. The stent 1 may be constructed from any suitable durable plastic 
material, preferably of a flexible material. The proximal segment 4 is 
preferable provided with conventional length identification or position 
indicator 6 to indicate the stent's position, i.e, conventional centimeter 
markings. More preferably, the proximal segment 4 of the ureteral is made 
of radiopaque silicone or silastic material. 
The distal segment 12 in both embodiments of FIGS. 2 and 3 has an inside 
diameter (lumen) wider than that of the proximal segment 4, as apparent 
from the dash lines of FIG. 1 and the cross-sectional view thereof in 
FIGS. 2 and 3. The junction between the distal segment 12 and the proximal 
segment 4 is tapered as shown by a gradual taper 12t to form a non-abrupt 
contour to minimize stress points. In the embodiment of FIG. 2, the outer 
diameter of the proximal segment 4 is substantially identical to the outer 
diameter of the distal segment 12. In the embodiment of FIG. 3, the outer 
diameter of the distal segment becomes gradually larger toward the free 
end 12e, forming a largest diameter at the free end 12e. This provides a 
larger end abutment surface for the pusher 16. 
As previously indicated the lumen 5 extends substantially the entire length 
of the stent with the distal end thereof being opened. A rigid open ended 
catheter 8 having substantially the same diameter as the constant inner 
diameter portion 12a of the proximal segment of the stent is fitted into 
the distal end of the stent. The rigid catheter need only be inserted far 
enough into the flexible tube to assure a secure engagement of the 
flexible tube. The rigid catheter is held in place by reason of its close 
or interference fit with the flexible tube. 
The free end 12e functions to allow the pusher or the immobilizing abutting 
open tube 16 to disengage the rigid catheter 8 from the stent 1 by 
abutting thereagainst and immobilizing the stent while the catheter 8 is 
pulled from the stent. To provide for an abutting surface in which the 
pusher can abut thereagainst, the inner diameter of the pusher and the 
outer diameter of the catheter 8 is substantially similar, with the inner 
diameter of the pusher having a sufficient clearance to be able to slide 
relative to the catheter, so that the end 16e of the immobilizing open 
tube abuts against the distal end 12e of the stent. The wall in the distal 
end 12e of the stent should have a sufficient thickness and strength to 
prevent the wall from buckling or substantially stretching under the 
pulling force during the removal of the catheter abutting the pusher so as 
to not displace or dislodge the proximal segment of stent from the renal 
cavity during the catheter removal. 
As shown in FIG. 1, a stiffening wire 9 is used to uncurl the curl 13 
formed in the proximal segment and to keep the flexible tube relatively 
straight while the stent is inserted. The stiffening wire can be passed 
through a rubber stopper 10 within the distal end of the rigid catheter 8. 
The stopper prevents the wire from receding from the distal end of the 
catheter during insertion. When the stent has been properly placed in the 
renal cavity, the stiffening wire is withdrawn along with the stopper. 
The ends of the stent are formed and set in the shape of gentle curls 13 
and 14 as shown in FIG. 5. The insertion of the rigid ureteral catheter 8 
into the distal segment of the stent straightens the curl 14 formed 
thereat and holds it in a straight alignment as shown in FIGS. 2 and 3. 
A thread or suture 15 is preferably attached adjacent to the distal end in 
order to allow easy removal of the stent by pulling on the suture. 
The catheter 8 is formed of material conventionally used for such catheters 
and stents and is preferably a stiff polymeric material with a hard smooth 
surface that glides such as polytetrafluorethylene or nylon. 
The catheter is marked near its distal end. With the catheter inserted in 
the distal segment of the stent, the length markings 17 of the catheter 
can be used in conjunction with the pusher 16 as a visual guide for 
determining when the pusher 16 abuts against the distal end of the stent. 
Specifically, prior to the insertion of the stent, when the catheter is 
properly inserted into the stent, the marking nearest the distal end 12e 
is noted. Thereafter, the stent-catheter combination are inserted into a 
ureteral meatus. Since the length of the pusher 16 can be readily measured 
or is known and the markings 17 can be used to indicate when the pusher 
abuts against the distal end of the stent prior to pulling out the 
catheter from the stent. 
Different sizes and diameters can be made available with component sizes 
scaled appropriately. The sizes, lengths and diameters of the various 
elements are those conventionally used in the art. The precise dimensions 
of the stent may vary based on the dimensional characteristics of 
particular patient, as disclosed in U.S. Pat. No. 4,913,683 issued to 
Gregory, which also disclose a range of sizes of the stent, the disclosure 
of which is incorporated herein by reference. 
In operation, a rigid catheter 8 is first inserted into the distal segment 
12 of the stent. The outer diameter of the catheter is designed to fit in 
the lumen of the distal segment, held therein by friction or interference. 
A conventional stiff guide wire having a diameter of about 0.038 mm is 
introduced through the catheter and inserted all the way to the end of the 
distal segment to straighten and stiffen the proximal curl 13. The wire 
extends further out from the distal part of the catheter and is held in 
place securely by the detachable rubber stopper 10. 
With the wire in place, the proximal curl 13 of the stent is straightened 
and can be inserted through a cystoscope, and passed up in the ureteral 
orifice to the renal cavity. The wire then is removed along with the 
rubber stopper, allowing the proximal end 11 to curl. The rigid catheter 
is long enough to extend out through the urethra and the system can be 
used for an immediate imaging study if needed. To continuously drain the 
kidney (i.e. to monitor urine output, drain purulent debris, or irrigate 
to free the system of purulent material) one can secure the rigid ureteral 
catheter to an indwelling urethral catheter and attach the rigid ureteral 
catheter to an external drainage bag. 
Once the patient is stable and there is no more need for external drainage, 
the stent can be internalized. The rigid catheter is then completely 
cleansed with a topical disinfectant and sterile gloves are donned. A 
sterile pusher 16 is lubricated and passed over the rigid ureteral 
catheter until resistance is met as it abuts the distal end 12e of the 
stent. The operator will also know that the distal end of the stent has 
been abutted because the marking on the rigid ureteral catheter can be 
visualized. Then the rigid catheter is gently pulled through the pusher, 
holding the pusher in place against the distal end 12e. Then the pusher is 
then gently extracted from the urethra. The removal of the catheter will 
allow the distal segment of the stent to form a curl 14 in the bladder and 
thereby leave a completely internalized stent, as disclosed, for example, 
in U.S. Pat. No. 4,913,683 to Gregory. The thread or suture can be left 
attached to the distal end of the stent to allow easy extraction through 
the urethra. 
If desired, the stiffening wire can be inserted first using conventional 
means. After cutting off the proximal tip of the stent, the stent-ureteral 
catheter device is passed over the wire in order to insert the catheter 
combination. 
Also if desired, various adapters can be secured to the external end of the 
rigid ureteral catheter in order to permit irrigation, application of 
contrast solutions to the renal cavity etc. 
The thread or suture is preferably of a synthetic polymer with opaque 
characteristics. It is attached to the stent at any convenient location. 
The advantages of the above described device are many. The materials of 
construction are conventional. The device can be packaged intact and ready 
to insert. The various elements can be formed in a variety of sizes, 
lengths and diameters with component sizes scaled appropriately. 
The device obviates the need for separate externalized and internalized 
ureteral catheters. Further, the device is simple in operation and makes 
use of concepts and designs proven to be effective and reliable. 
It is to be noted that the rigid catheter need only be inserted into the 
distal segment of the stent to the extend necessary to securely attach to 
the stent. Accordingly, the rigid catheter does not have to be inserted 
fully into the distal segment. Further, it can be seen that the specific 
type of connection described is not critical. Any method of connection 
that allows the catheter to function as described is contemplated herein. 
Given the disclosure of the present invention, one versed in the art would 
readily appreciate the fact that there can be many modifications of the 
present invention not specifically depicted and described, but that are 
well within the scope and spirit of the disclosure set forth herein. 
Accordingly, all expedient modifications readily attainable by one versed 
in the art from the disclosure set forth herein that are within the scope 
and essence of the present invention, are to be included as further 
embodiments of the present invention.