Medical device with tail(s)

Details Medical device with tail(s) Medical device with tail(s)

1999-04-27

2003-12-02

Casler, Brian L. (Department: 3763)

Surgery

Devices transferring fluids from within one area of body to...

C604S544000, C623S023640, C623S023660

Reexamination Certificate

active

06656146

ABSTRACT:

FIELD OF THE INVENTION
This application relates to ureteral stents.
BACKGROUND OF THE INVENTION
Ureteral stents are used to assist urinary drainage from the kidney to the bladder in patients with ureteral obstruction or injury, or to protect the integrity of the ureter in a variety of surgical manipulations. More specifically, stents may be used to treat or avoid ureter obstructions (such as ureteral stones or ureteral tumors) which disrupt the flow of urine from the kidneys to the bladder. Serious obstructions may cause urine to back up into the kidneys, threatening renal function. Ureteral stents may also be used after endoscopic inspection of the ureter.
Ureteral stents typically are tubular in shape, terminating in two opposing ends: a kidney (upper) end and a bladder (lower) end. The ends may be coiled in a pigtail or J-shape to prevent the upward or downward migration of the stent, e.g., with physiological movements. The kidney coil is designed to retain the stent within the renal pelvis of the kidney and to prevent stent migration down the ureter. The bladder coil sits in the bladder and is designed to prevent stent migration upwards toward the kidney. The bladder coil is also used to aid in retrieval and removal of the stent.
Ureteral stents, particularly the portion positioned in the ureter near the bladder and inside the bladder, may produce adverse effects including blood in the urine, a continual urge to urinate, strangury, and flank pain accompanying reflux of urine up the stent (e.g., when voiding) as pressure within the bladder is transmitted to the kidney. In short, stents may cause or contribute to significant patient discomfort and serious medical problems.
FIG. 10
is a schematic drawing of the human urinary tract without a stent, showing the renal pelvis, the kidney, the ureter, and the ureteral orifices opening into the bladder.
FIG. 11
depicts a typical double-J stent
10
which comprises a small tube
12
which sits inside the urinary system and assists the flow of urine from the kidney (renal pelvis) to the bladder.
FIG. 12
depicts prior art indwelling ureteral stent
10
in position. Such stents are typically made of biocompatible plastic, coated plastic, or silicone material. Tube
12
typically varies in size from 4-8 fr. (mm in circumference), and it has multiple small holes throughout its length. A coiled shape pre-formed at each end
14
and
16
is designed to confine its movement within the urinary system, so that it will be maintained in the desired position. The upper (kidney) end
14
of the stent may be closed or tapered, depending on the method of insertion (e.g., the use of a guidewire). The tubular stent extends through the ureteral orifice
18
a
and into the bladder, fixing orifice
18
a
open, and thereby enhancing the opportunity for reflux. For clarity, the ureter entering bladder
20
through orifice
18
b
is not shown. A monofilament thread
22
may be attached to the bladder end of the stent for removal, usually without cystoendoscopy.
U.S. Pat. No. 4,531,933 (“the '933 patent”) discloses a ureteral stent having helical coils at each end which are provided for preventing migration and expulsion.
SUMMARY OF THE INVENTION
We have discovered a ureteral stent design that avoids patient discomfort and urine reflux upward toward the kidney. Rather than rely on a tubular structure to contain and facilitate all (or, in some embodiments, any) urine flow along the ureter, the invention features a thin flexible elongated tail member having an elongated external urine-transport surface. Urine flows along the outside surface of the structure, between that surface and the inside wall of the ureter. Without limiting ourselves to a specific mechanism, it appears that urine may remain attached to, and flow along, the external urine transport surface. The use of a foreign body that is as small as possible in the lower (bladder) end of the ureter and in the bladder itself decreases patient discomfort. Typically, the external urine transport surface is sized and configured to extend along at least part of the ureter near the bladder, across the ureter/bladder junction, and from there through the ureteral opening into the bladder.
While most or all of the length of the stent may rely on such an external surface to assist flow, more typically the stent will also include an upper elongated tubular segment to transport urine along a significant portion of the upper ureter. The upper tubular segment is connected at its lower end to an elongated tail which has the above described external urine-transport surface. The upper tubular segment comprises: a) an upper region having at least a first opening; b) a lower region having at least a second opening to be positioned in the ureter outside the bladder, and c) a central lumen connecting the first opening to the second opening. The elongated tail is a thin flexible tail member or filament(s) extending from the lower region of the tubular segment at a point outside the bladder so as to receive urine from the second opening of the tubular segment and to transport urine along the ureter from the lower region of the tubular segment across the ureter/bladder junction and into the bladder. Typically, but not exclusively, the upper region of the tubular segment is configured and sized for placement in the renal cavity.
Typically the elongated tail member comprises at least one (and more preferably at least two) thread filament(s). Two or more of the filaments may be configured in at least one filament loop, and, advantageously, the tail comprises no unlooped filaments, so that the tail is free from loose ends. The loop(s) can be made by joining the ends of a single filament, in which case the filament loop comprises a junction of individual filament ends, which junction typically is positioned at the point where tail joins to the elongated tubular segment. Preferably, the tail is long enough to effectively prevent migration of the entire tail into the ureter, and the tail has a smaller outer diameter than the outer diameter of the tubular segment.
The tubular stent segment is stiff enough to avoid crimping during insertion through the ureter, so that it can be inserted by typical procedures. The tail, on the other hand, is extremely flexible (soft) in comparison to the tubular segment, and it has a much smaller diameter than the tubular segment to avoid discomfort. Even quite thin structures will provide urine transport, and the thinner and more flexible the tail is, the less likely it is to cause patient discomfort. On the other hand, the tail (and its connection to the rest of the stent) should have sufficient strength so the stent can be retrieved by locating the tail in the bladder and pulling on the tail to retrieve the stent from the kidney and ureter. Details of the tail size are discussed below. The use of reinforcing materials (e.g., sutures as described below) permits the use of thinner tails while still providing the ability to locate the tail in the bladder and to retrieve the stent. The tail may be a suture, and the suture may be coated to avoid encrusting.
The external urine-transport surface of the tail can be convex (circular or oval in section), concave or flat. The tail filament may be fluted. The tail may, but need not, include an accurately shaped anchor segment to control migration up the ureter. The tail may be either solid or hollow; even when hollow, it is not designed to transport a significant amount of urine internally. The tail may also be tapered.
The upper region of the tubular segment may have a portion designed for placement in the renal cavity, which portion has enlarged diameter and/or straight sides and corners. The stent may include an extractor thread attached to the lower end of the elongated tail member.
To make the stent, the tail may be molded in one piece with the tubular segment, or it may be made separately and attached to the bladder end region of the tubular segment at a point toward the kidney from the bladder end of the lower region of the tubular segment. I

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