Abstract:
A tool for removing non-visually, urinary tract stents placed within the urinary tract of a patient, comprising a distal end, a longitudinally-extending stem, and a handle. The distal end has a conical head with a groove for hooking a stent, stent string or similar stent configuration. The snare head may have a channel for advancing the tool through a urethra over a guide wire. The snare head has a narrow conical front end for dilating urethral strictures. The stem connects the snare head to the snare handle and is made to be flexible or bend on encountering resistance.

Description:
FIELD OF INVENTION 
       [0001]    The present invention is in the field of stent removal. More particularly, the present invention is in the field of the nonvisual removal of ureteral stents. 
       BACKGROUND OF INVENTION 
       [0002]    The urinary tract is susceptible to the obstruction of urine flow either by endogenous causes such as the formation of stones, external compression by anatomic abnormalities, or neoplastic growth. Obstruction can also be iatrogenic, induced by manipulation or surgery. Ureteral stents have been developed to bypass such urinary tract obstructions. Typically, ureteral stents are made of biocompatible plastic materials. During a typical surgical procedure to bypass a urinary tract obstruction, the ureteral stent is passed over a guide wire. The stent is tubular to allow for the flow of urine, just large enough to fit over a guide wire, but of several diameters within a small range (2-3 mm) and with “S” shaped ends which act as anchors that prevent the stent&#39;s migration. The ureteral stents are often placed at the end of an operation or by themselves, when no other procedure is indicated, but the relief of the obstruction. 
         [0003]    Typically, ureteral stents are introduced through the urethra via a fiberoptic endoscopic instrument, such as for example, a cystoscope. The set-up for an endoscopic procedure typically includes light and water sources, and local anesthesia or sedation. Stent removal is also typically performed using fiberoptic endoscopic instruments. Fiberoptic endoscopic instruments are generally guided through a urethra visually, with a doctor manually guiding the endoscope based on the images observed through the fiberscope. The endoscopic instrument is typically guided to the stent at which point it is removed with a “foreign body” grasper. 
         [0004]    Visually guiding endoscopes through the urinary tract in this manner is often labor intensive, and requires special set-up and assistant time. Moreover, some endoscopes are large enough to allow for the passage foreign body graspers, causing discomfort for patients. Fluid flow and local anesthetics are also frequently used during removal procedures, however discomfort is not completely eliminated. Attempts have been made to remove stents without relying on visual instruments such as a cystoscope by attaching a string to the stent. However, the strings tend to retract and reside within the urethra still requiring the use of a cystoscope for their retrieval. 
         [0005]    Other drawbacks exist. 
       SUMMARY OF THE INVENTION 
       [0006]    Embodiments of a tool and method for removing urinary tract stents without a visual aid are disclosed. In one embodiment of the stent snare, the stent snare for removing stents includes a conical head for hooking a ureteral stent, a handle for controlling the passage of the conical head through the urethra and a stem extending from the head to the handle. In embodiments of the invention, the conical head has a front end for dilating a urethra as the stent snare passes through the urethra, and a base end having a snare. Embodiments of the invention may also include a channel for guiding the snare head over a guide wire. The tool&#39;s ability to slide over a guide wire gives it better accuracy to travel through distorted, narrowed, scarred portions of the urethra, and prevents the formation of false passages, which can occur with blind dilation. Embodiments of the invention allow for easier removal of indwelling ureteral stents without the need for visual aids, and for the dilation of urethral strictures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1A  is a diagram of a side view of a stent snare head according to one embodiment of the invention. 
           [0008]      FIG. 1B  is a diagram of a front view of a stent snare head according to one embodiment of the invention. 
           [0009]      FIG. 2A  is a diagram of a side view of a stent snare stem according to one embodiment of the invention. 
           [0010]      FIG. 2B  is a diagram of a side and front view of a stent snare handle according to one embodiment of the invention. 
           [0011]      FIG. 3  is an illustration of a stent snare removal tool removing a stent from a urethra according to one embodiment of the invention. 
           [0012]      FIG. 4  is an illustration of a stent snare removal tool removing a stent from a urethra according to another embodiment of the invention. 
           [0013]      FIG. 5  is an illustration of a plane view of the stent snare removal tool according to one embodiment of the invention. 
           [0014]      FIG. 6  is an illustration of a plane view of the stent from the handle end. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    Referring to  FIGS. 1A and 1B , a stent snare head according to one embodiment of the invention is depicted. A stent snare head may have a conical shape, with a front end  105 , base end  114 , bottom exterior surface  106 , and top exterior surface  104 . The front dilating end  105  may be conical or leveled as depicted in  FIG. 1A . The base end  114  may have a snare formed by a snare hook having interior surface  102  and exterior surface  103  and snare base having interior surface  101  and exterior surface  107 . The snare hook and snare base may form a groove across a portion of the base end, having length  108 . The bottom exterior surface  106  may be straight, diagonal, or arcuated as depicted in the  FIGS. 1A and 1B . According to some embodiments, the snare head may have a channel  115  running from the front dilating end  105  through to the base end  114 . 
         [0016]    According to some embodiments of the invention, the top exterior surface  104  of the exterior of the head extends beyond the base, forming the exterior surface of the snare hook  103 . The bottom surface  106  may also extend beyond the base, forming the exterior of the snare base  107 .  FIG. 1A  depicts a side view of the first surface  102 .  FIG. 1B  illustrates a cross-sectional view of the snare hook and snare base according to one embodiment of the invention. The snare hook and snare base may be flat or rounded as  FIG. 1B  illustrates. For example, as  FIG. 1B  illustrates, the snare hook and snare base are rounded in the same annular shape as the snare head. 
         [0017]    In another aspect of the invention, the snare may include a longitudinal channel  105 . The longitudinal channel  115  may extend from the tip of the snare head  105  through the base of the snare head  114 . The longitudinal channel  105  guides the snare head over a guide wire (not pictured), through a urethra. 
         [0018]    The groove formed by the snare hook and base are used to hook the “S” configuration of a bladder curl residing inside the bladder, or of a stent string lodged in the urethra. The bladder curl of a stent is generally characterized as a flexible curl in the shape of an “S” at one end of the stent. Generally, the bladder curls keep the stent positioned between the kidney and the bladder and prevents migration. According to one embodiment, the snare hook may remove the stent by attaching to the bladder curl. Specifically, the stent may be removed by inserting the snare into the bladder, hooking the curl of the stent lodged in the bladder, and pulling the snare from the bladder with a sliding motion. 
         [0019]    According to further embodiments, the snare hook may also be used to remove stents of other shapes and configurations. For example, the stent snare may also be used to trap the string portion of a stent usually found in the urethra. Stent strings may have a tail made of nylon thread, which can hang into the urethra, and have a loop configuration at the end. In some embodiments, the strings may also have a lasso configuration. In further embodiments, the loop or lasso may be created at the time of insertion. The snare hook may attach to the string and remove the snare by pulling on the string, as described above. However, when removing a stent by its nylon thread, the snare does not have to advance into the bladder as when being removed by the bladder curl. 
         [0020]    According to other embodiments, the snare may be advanced into a bladder over a guide wire. A guide wire may be first passed through the meatus of the urethra manually. The guide wire may then be threaded through the channel  115  of the snare head. The snare may then be advanced into the bladder over a guide wire passing through channel  115 . As the snare head advances over the guide wire, the dilating front end dilates and disrupts scar tissue inside the urethra, if present. Once the snare is in the bladder, the stent may be trapped manually and removed according to the pulling motions described above. The guide wire thereby allows the tool to be accurately advanced through distorted, narrowed, scarred portions of a urethra, and also prevents the formation of false passages, which can occur with blind dilation. 
         [0021]    According to some embodiments of the invention, the snare base may further include a hole  116  for affixing a stem and handle.  FIG. 1B  illustrates the cross sectional view of the hole  112 . Affixing the stem and handle to the snare head with hole  116 ,  112  provides greater control over the snare head and improved durability of the snare and stem. 
         [0022]    In one aspect of the invention, the dilating front end  105  of the snare has a height between the bottom surface  106  and top surface  103  that gradually increases from the front of the head  105  to the base  114 , to dilate the urethra as the snare is inserted through a urethra stricture. For example, in one embodiment, the head has a diameter between 2.5 mm and 6 mm at its widest circumference. Snare heads of this size allows for dilation of between 8 F and 18 F. Other sizes can increase the dilation to 22 F, 24 F or 28 F. 
         [0023]      FIG. 2A  depicts a stem  228  according to one embodiment of the invention. The stem  228  longitudinally extends from the snare head to the handle  221 . The stem is attached to the snare head by hole  116  (also depicted as  227 ). The stem is inserted off center on the head as not to interfere with the channel  115 . In one aspect of the invention, the stem has a springing action that allows the snare head to slide through the distal urethra and the proximal tortuous urethra, without undue trauma. The spring quality provides tactile feedback to the operator in case of meeting resistance. The spring quality comes from the quality of the material, which is drawn thin enough to be flexible and “give” upon meeting resistance. 
         [0024]    In one aspect of the invention, the stem may also have markings to indicate the distance from the handle, which in turn, indicates the distance the snare head has been inserted into the urethra. The markings may include an indication of the diameter of the tool.  FIG. 2B  illustrates a handle attachment according to one embodiment of the invention. The handle attachment  221  controls the stem  228  and snare head as they advance through the urethra. The handle has a hole  214 ,  222  for attaching to a stem, and aligning the handle in the transverse plane of the head. The handle may have a width  216 , and height  219 . As the cross-section illustration of the handle shows, the handle  221  may be trapezoidal, allowing for convenient and ergonomic manipulation of the tool. However, in other embodiments, the handle may be square, round, or triangular. In one aspect of the invention, the handle may include an identification of the manufacturer on the flat surface of the handle. 
         [0025]      FIG. 3  depicts a method of removing a stent from a female urethra with a stent snare removal tool removing according to one embodiment of the invention.  FIG. 3  shows a female urethra  303  having a bladder wall  301 , right ureter  302  and stent  304 . The stent has a bladder curl  305 . The handle  307  is used to advance the snare head  306  through the urethra. The groove of the snare head may hook onto a bladder curl  305 . Once the snare groove has attached to the snare head, the stent may be removed by gently pulling on the stent curl with the snare head. 
         [0026]      FIG. 4  depicts a method of removing a stent from a male urethra with a stent snare removal tool according to another embodiment of the invention. A stent  401  has a stent bladder curl  402  has a stent string  403 , which has been configured with a lasso or loop  404 . The groove of the snare head  405  hooks onto the lasso or loop of the stent string outside the bladder, before the stent head  405  advances through the prostate  408 . The snare head  405  may be advanced through the urethra by manipulating the handle  407  and stem  406 . 
         [0027]      FIG. 5  illustrates a plane view of the snare head according to one embodiment of the invention. The snare head has a front dilating end  501 , groove  502 , exterior surface  503 , snare hook  504 , channel  505  and stem  506 . 
         [0028]    In a preferred embodiment, the snare head has 10 mm in length and has a radius of 6 mm at the widest dimension. The channel  115  has a radius of 0.5 mm to allow travel over a guide wire, and a groove 3 mm wide. 
         [0029]    According to some embodiments, the snare head may be constructed out of surgical steel, plastic or hard polymers. The snare head may be finished with a smooth surface, to allow for non-traumatic travel through the urethra. In a different embodiment the snare head may have the shape of a coil with the “hook” element being the space between the coils. In another embodiment the groove may be placed horizontal (or 90 degrees) to the longitudinal axis of the tool. In a preferred embodiment, the snare head, stem and handle are made from a biologically inert material, such as surgical-quality stainless steel. In other embodiments, the head is made from metal and the remainder of the body is made from a plastic material.