Abstract:
A method for identifying a ureter during a medical procedure, the method comprising: providing an electrical stimulator comprising: a shaft having at least one electrode; and a power supply connected to the at least one electrode for providing an electrical signal to the at least one electrode; advancing the shaft so that the at least one electrode contacts tissue; operating the power supply so that the electrical signal is applied to the tissue; and visually observing the tissue to determine the presence of a ureter in the tissue.

Description:
REFERENCE TO PENDING PRIOR PATENT APPLICATION 
       [0001]    This patent application claims benefit of pending prior U.S. Provisional Patent Application Ser. No. 61/938,767, filed Feb. 12, 2014 by The Methodist Hospital and Albert Yung-Hsiang Huang for MINIMALLY INVASIVE URETER IDENTIFICATION DEVICE (Attorney&#39;s Docket No. METHODIST-11 PROV), which patent application is hereby incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to medical procedures and apparatus in general, and more particularly to methods and apparatus for identifying the ureter. 
       BACKGROUND OF THE INVENTION 
       [0003]    In minimally-invasive surgery, the identification of anatomical structures must be done through knowledge of the anatomy and knowledge of anatomical landmarks, given the lack of true tactile feedback for the surgeon. When operating in the lower abdomen and pelvis, surgeons of many specialties (e.g., general surgery, colorectal surgery, transplant surgery, urology, obstetrics, gynecology, etc.) are acutely aware of the need for accurate identification of the ureter in order to prevent potentially catastrophic injury to the ureter. Although identification of the ureter may appear to be a simple and routine visual task, difficulties lie in “hostile” abdomens where there have been prior surgeries, inflammation and/or scarring, or if tissue planes are not well defined. 
         [0004]    It has been reported that the incidence of ureteral injuries in gynecological procedures is upwards of 3.2%, with 70% of the ureteral injuries not being discovered until after completion of the procedure. 
         [0005]    A ureteral injury can result in significant morbidity to the patient. In addition, a ureteral injury can also lead to longer operating room (OR) times (due to the need for ureteral repairs), the involvement of specialists, the potential need for long term ureteral stent placements, and long term effects (such as scarring) that may lead to kidney damage. All of these are costly, both to the patient as well as the hospital, inasmuch as medical insurance generally does not cover costs related to complications from an operation. 
         [0006]    Several different approaches are currently used to identify the ureter during a minimally-invasive procedure. 
         [0007]    Where the ureter is easily identified visually, the surgeon generally confirms ureter identification by lightly compressing the ureter with an instrument (e.g., graspers, forceps, etc.) and observing the resulting visible contractions of the ureter up and down its length as a response to the instrument stimulus. However, as noted above, the ureter is frequently difficult to identify visually and, even where it is relatively easily identifiable, the ureter does not always generate visually-detectable contractions as a result of an instrument stimulus. Furthermore, care must be taken with this approach to avoid injuring to the ureter. 
         [0008]    For these reasons, surgeons have turned to the pre-operative (but post-anesthesia) placement of ureteral stents via cystoscopy. Where the surgery is an “open” procedure, the surgeon can detect the ureteral stent by manual sensation. Where the surgery is a “closed” procedure (e.g., a minimally-invasive procedure), light-emitting stents may be utilized, with the light-emitting stents being detected visually during the minimally-invasive procedure. 
         [0009]    However, with ureteral stents, a urologist must generally be available to deploy the ureteral stents up each ureter from the bladder. This process may be time-consuming, which leads to a longer OR time (and thus longer anesthesia time) and comes with its own risks of ureter injury and infection, due to the need to place a foreign object in the ureter. Furthermore, the average cost of the ureteral stent placement procedure is approximately $1500, with studies demonstrating a significant decrease (e.g., up to 85%) in procedural profit margin where prophylactic ureteral stenting is utilized. In addition, even where a ureteral stent is used, ureter injury can still occur. Many experienced surgeons have noted that, at times, the ureteral stent only serves to notify them that they have injured the ureter, i.e., when the surgeons see the ureteral stent exposed inside the abdomen. 
         [0010]    Even with these drawbacks, pre-operative ureteral stent placement is quickly becoming routine in hospitals nationwide due to the need to reliably identify the ureter during surgery. 
         [0011]    Thus there is a need for a new method and apparatus for reliably identifying the ureter in both open and closed procedures and which eliminates the need for pre-operative ureteral stent placement, whereby to avoid the risks and costs associated with pre-operative ureteral stent placement. 
       SUMMARY OF THE INVENTION 
       [0012]    The present invention provides a new method and apparatus for reliably identifying the ureter in both open and closed procedures and which eliminates the need for pre-operative ureteral stent placement, whereby to avoid the risks and costs associated with pre-operative ureteral stent placement. 
         [0013]    In accordance with the present invention, there is provided a novel electrical stimulator which generates a low-level electrical current (preferably but not necessarily in a pulsatile form), such that when the tip of the electrical stimulator is positioned near the ureter, the low-level electrical current provided by the electrical stimulator will cause the ureteral muscles to contract up and down the length of the ureter. This results in movement of the anatomy that can be visualized by the surgeon, even if the ureter is obscured by other tissues (e.g., scar tissue). In this way, the location of the ureter can be identified (or confirmed) so that the ureter may be avoided during the surgical procedure. 
         [0014]    In one preferred form of the present invention, there is provided a method for identifying a ureter during a medical procedure, said method comprising: 
         [0015]    providing an electrical stimulator comprising:
       a shaft having at least one electrode; and   a power supply connected to said at least one electrode for providing an electrical signal to said at least one electrode;       
 
         [0018]    advancing said shaft so that said at least one electrode contacts tissue; 
         [0019]    operating said power supply so that said electrical signal is applied to the tissue; and 
         [0020]    visually observing the tissue to determine the presence of a ureter in the tissue. 
         [0021]    In another preferred form of the present invention, there is provided an electrical stimulator for identifying a ureter during a medical procedure, said electrical stimulator comprising: 
         [0022]    a shaft having a distal end, a proximal end and at least one electrode disposed at said distal end, said shaft having a diameter sized for insertion through an intervening device during a minimally-invasive procedure, and said shaft having a length so that said at least one electrode can contact tissue located at a remote internal site while said proximal end of said shaft remains outside the body of a patient; and 
         [0023]    a power supply connected to said at least one electrode for providing an electrical signal to said at least one electrode, wherein said electrical signal is configured to elicit a peristaltic response from a ureter when said at least one electrode is positioned so as to deliver said electrical signal to the ureter. 
         [0024]    In another preferred form of the present invention, there is provided a method for identifying an anatomical structure during a medical procedure, said method comprising: 
         [0025]    providing an electrical stimulator comprising:
       a shaft having at least one electrode; and   a power supply connected to said at least one electrode for providing an electrical signal to said at least one electrode;       
 
         [0028]    advancing said shaft so that said at least one electrode contacts tissue; 
         [0029]    operating said power supply so that said electrical signal is applied to the tissue; and 
         [0030]    visually observing the tissue to determine the presence of the anatomical structure in the tissue. 
         [0031]    In another preferred form of the present invention, there is provided an electrical stimulator for identifying an anatomical structure during a medical procedure, said electrical stimulator comprising: 
         [0032]    a shaft having a distal end, a proximal end and at least one electrode disposed at said distal end, said shaft having a diameter sized for insertion through an intervening device during a minimally-invasive procedure, and said shaft having a length so that said at least one electrode can contact tissue located at a remote internal site while said proximal end of said shaft remains outside the body of a patient; and 
         [0033]    a power supply connected to said at least one electrode for providing an electrical signal to said at least one electrode, wherein said electrical signal is configured to elicit a visible response from the anatomical structure when said at least one electrode is positioned so as to deliver said electrical signal to the anatomical structure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]    These and other objects and features of the present invention will be more fully disclosed or rendered obvious by the following detailed description of the preferred embodiments of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts, and further wherein: 
           [0035]      FIG. 1  is a schematic view showing a novel electrical stimulator formed in accordance with the present invention; 
           [0036]      FIG. 2  is a schematic view showing the distal end of the probe of the novel electrical stimulator shown in  FIG. 1 ; 
           [0037]      FIG. 3  is a schematic view showing the probe advanced through a cannula so that its distal end is positioned adjacent a surgical site; 
           [0038]      FIGS. 4-6  are schematic views showing electrical stimulation of a ureter using the novel electrical stimulator shown in  FIG. 1 ; 
           [0039]      FIG. 7  is a schematic view showing another novel electrical stimulator formed in accordance with the present invention; 
           [0040]      FIGS. 8-10  are schematic views showing construction details of the novel electrical stimulator shown in  FIG. 7 ; and 
           [0041]      FIG. 11  is a schematic view showing an electromyogram (EMG) probe which may be used in conjunction with the novel electrical stimulator of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0042]    The present invention provides a new method and apparatus for reliably identifying the ureter in both open and closed procedures and which eliminates the need for pre-operative ureteral stent placement, whereby to avoid the risks and costs associated with pre-operative ureteral stent placement. 
         [0043]    In one form of the present invention, there is provided an inexpensive, simple-to-use device that is handheld, disposable and which can be advanced to the surgical site through a cannula during a minimally-invasive procedure so as to electrically stimulate tissue, whereby to identify the ureter from surrounding anatomy. Note that the device can also be advanced to the surgical site through the working channel of an endoscope, or through a working channel of any other device leading to an internal surgical site. 
         [0044]    More particularly, when a patient is under general anesthesia and paralyzed for an intraabdominal operation, the “skeletal muscles” of the patient are unable to respond to electrical nerve stimulation. However, “smooth muscles” (which include structures such as the ureter) are able to respond (e.g., contract and peristalse) when electrically stimulated. The present invention utilizes this fact to identify the ureter during a surgical procedure. 
         [0045]    In accordance with the present invention, there is provided a novel electrical stimulator which generates a low-level electrical current (preferably but not necessarily in a pulsatile form), such that when the tip of the electrical stimulator is positioned on or near the ureter, the low-level electrical current provided by the electrical stimulator will cause the ureteral muscles to contract up and down the length of the ureter. This results in movement of the anatomy that can then be visualized by the surgeon, even if the ureter is obscured by other tissues (e.g., scar tissue). In this way, the location of the ureter can be identified (or confirmed) so that it may be avoided during the surgical procedure. Note that the electrical stimulator does not need to be positioned directly on the ureter in order to achieve ureter stimulation, it simply needs to be placed close enough to the ureter that the low-level electrical current reaches the ureter. 
         [0046]    In one form of the present invention, the electrical stimulator comprises a probe component comprising electrodes and a power supply component housed in a base unit, with the probe component being connected to the power supply component with an external cable (i.e., a “modular construction”). 
         [0047]    In another form of the present invention, the power supply component is carried by the probe component and the external cabling can be omitted (i.e., an “integrated construction”). 
       Modular Construction 
       [0048]    More particularly, in one preferred form of the present invention, and looking now at  FIGS. 1 and 2 , there is provided a novel electrical stimulator  5  which generally comprises a probe  10  and a power supply  15 . A cable  20  connects power supply  15  to probe  10 . 
         [0049]    Probe  10  generally comprises a shaft  25  having a distal end  30  and a proximal end  35 . In one preferred form of the invention, shaft  25  has a length of approximately 330 mm and a diameter of approximately 5 mm. Note that the diameter of probe  10  may be larger or smaller so as to fit through cannulas of different diameters. Note also that the length of shaft  25  may be longer or shorter depending upon the distance to the internal surgical site (e.g., shaft  25  may be longer where novel electrical stimulator  5  is to be used in conjunction with robotic surgical equipment). 
         [0050]    A pair of leads  40 A,  40 B extend through shaft  25  from distal end  30  to proximal end  35 . Lead  40 A terminates distally in an electrode tip  45 A and lead  40 B terminates distally in an electrode tip  45 B, with electrode tip  45 A acting as one of the anode and cathode and electrode tip  45 B acting as the other of the anode and cathode. If desired, electrode tip  45 A and electrode tip  45 B may be separated by an insulating mass which physically separates the anode and cathode from one another so as to ensure that the electrical signal must pass through tissue in contact with the device. If desired, the insulating mass may form part of a blunt tip for shaft  25 , with the blunt tip being designed for blunt dissection in the minimally-invasive setting. Lead  40 A terminates proximally in an electrical connector  50 A and lead  40 B terminates proximally in an electrical connector  50 B. 
         [0051]    Power supply  15  provides the energy source for probe  10 . Power supply  15  comprises a base unit  55  housing an internal power supply (not shown) capable of providing a desired electrical signal. In one preferred form of the invention, the electrical signal provided by power supply  15  is a pulsatile signal of variable pulse width (e.g., 25-300 milliseconds), variable pulse frequency (e.g., 1-5 Hz), variable pulse intensity (e.g., 60 mV-500 V) and variable pulse amperage (e.g., 5-200 mA, preferably adjustable in 20 mA increments, although it is preferred that the amperage be limited to 60 mA to minimize patient discomfort and avoid cardiac arrhythmias). To this end, power supply  15  preferably comprises a power on/off switch  60 , an associated power on/off indicator  65 , a pulse width control  70 , a pulse frequency control  75 , a pulse intensity control  80  and an activate button  85 . Power supply  15  also comprises an electrical connector  90 . 
         [0052]    Cable  20  connects the output of power supply  15  to electrical connector  50 A and electrical connector  50 B of probe  10 , so that the output of power supply  15  can be applied to electrode tip  45 A and electrode tip  45 B of probe  10 . 
         [0053]    In use, cable  20  is connected to probe  10  and power supply  15 , power supply  15  is turned on via power on/off switch  60 , and pulse width control  70 , pulse frequency control  75  and pulse intensity control  80  are all set to appropriate levels. Next, and looking now at  FIG. 3 , probe  10  is advanced to the surgical site (e.g., through a cannula  95  extending through the skin  100  of a patient). Then probe  10  is advanced to the region where the ureter is believed to lie, electrode tips  45 A and  45 B are placed against the tissue, and then activate button  85  is depressed so as to apply a low-level pulsatile electrical current to the tissue. When electrode tips  45 A and  45 B are located in the vicinity of the ureter, the electrical signal will cause the ureter to generate a rhythmic twitch as the ureteral muscles contract up and down the length of the ureter. The surgeon can observe this muscular response of the ureter, whereby to confirm ureter presence as well as the ureter path. 
         [0054]    It should be appreciated that the characteristic response of the ureter “smooth muscle” is a propagation of contractile movement that begins at the focus of stimulation. This contraction travels retrograde and antegrade along the length of the ureter. This contraction is easily visualized on the video monitor use in minimally-invasive procedures (e.g., laparoscopic procedures, robotic procedures, etc.) as well as with direct visualization in open surgery settings. The ureter does not need to be fully dissected out from nearby tissue inasmuch as the contraction movements can be seen even with the ureter “smooth muscle” being beneath other tissues such as scar tissue, thin layers of fat or connective tissues. 
         [0055]    See  FIGS. 4-6 , which show (i) the natural path of a ureter in an unstimulated condition ( FIG. 4 ); (ii) the probe  10  positioned against the ureter but before the electrical signal is applied to the tissue ( FIG. 5 ); and (iii) the path of the ureter a few moments after electrical stimulation has been applied to the tissue ( FIG. 6 ). 
         [0056]    If at any time during the procedure, re-confirmation of ureter positioning needs to performed, the surgeon simply re-inserts probe  10  to the surgical site and repeats the foregoing procedure. 
         [0057]    Once the surgical procedure is complete, probe  10  may be disconnected from power supply  15  and disposed of. 
         [0058]    In another preferred form of the present invention, the electrical signal provided by power supply  15  has a preset pulse width (e.g., 100 milliseconds), a preset pulse frequency (e.g., 1 Hz) and a preset pulse intensity (e.g., 200 V). Using a “preset” electrical signal can have certain advantages, e.g., depending on target tissue(s), safety concerns, etc. 
         [0059]    And in another preferred form of the present invention, the electrical signal provided by power supply  15  can be produced at a preset interval and for a preset duration (i.e., a preset pulse rate and a preset pulse width) of milliseconds, microseconds or seconds when active, so as to generate a rhythmic twitch in the target tissue. 
         [0060]    Alternatively, power supply  15  can be configured to provide a single continuous signal when active so as to generate a sustained contraction in the target tissue. 
       Integrated Construction 
       [0061]    In another preferred form of the present invention, and looking now at  FIGS. 7-10 , novel electrical stimulator  5  may incorporate power supply  15  into probe  10  so that the entire device is lightweight and handheld and fully disposable. In this case cable  20  may be omitted. More particularly, in this form of the invention, probe  10  may include an enlarged handle  105  carrying power supply  15  therein. By way of example but not limitation, power supply  15  may comprise a 9 V battery  110  and appropriate control electronics  115  for providing the desired electrical signal at electrode tips  45 A,  45 B. 
         [0062]    In this form of the invention, the electrical signal provided by power supply  15  preferably has a preset pulse width (e.g., 100 milliseconds), a preset pulse frequency (e.g., 1 Hz) and a preset pulse intensity (e.g., 200 V), so that the only actions required of the user are (i) turning the device on or off via on/off switch  60 , (ii) contacting the target tissue with electrode tips  45 A,  45 B, and (iii) pressing activate button  85  when the electrical signal is to be delivered to the tissue. 
         [0063]    However, if desired, electrical stimulator  5  may also be constructed so that the electrical signal provided by power supply  15  has a variable pulse width, variable pulse frequency, variable pulse intensity and variable pulse amperage, in which case electrical stimulator  5  includes an appropriate pulse width control  70 , an appropriate pulse frequency control  75  and an appropriate pulse intensity control  80 . 
         [0064]    In this form of the invention, the entire electrical stimulator  5  (including probe  10  and power supply  15 ) may be disposed of at the conclusion of the procedure. 
       Additional Constructions 
       [0065]    In the foregoing disclosure, electrical stimulator  5  is described as comprising two electrodes, i.e., electrode tips  45 A,  45 B. In general, such a “bipolar” construction is preferred since it provides a more specific localization and a more localized current when attempting to target a smaller field and tissue. However, it is also anticipated that electrical stimulator  5  may comprise a “monopolar” construction having only one electrode tip, with the “return” being provided by a grounding pad. 
         [0066]    In another form of the present invention, electrical stimulator  5  may comprise a relatively short probe  10  which is connected to an independent power supply  15  via cable  20 . In this construction, probe  10  may be inserted into the abdominal cavity through a 5 mm trocar port using graspers (including robotic graspers) and may be thereafter manipulated by those graspers so as to apply electrical stimulation to the tissue which is believed to be the ureter so as to confirm ureter presence as well as the ureter path. 
         [0067]    And in another form of the present invention, electrical stimulator  5  may be used in conjunction with an electromyogram (EMG) probe which detects electrical signals from a ureter&#39;s peristalsis and converts them into an audio signal. More particularly, in this form of the invention, and looking now at  FIG. 11 , there is provided an electromyogram (EMG) probe  120  which comprises an electromyogram (EMG) sensor  125  on the distal tip of electromyogram (EMG) probe  120 . Signals detected by electromyogram (EMG) sensor  125  are relayed (via a cable  130 ) to a base unit  135  which converts those signals into an audio signal. Thus, in this form of the invention, electrical stimulator  5  is used to apply an electrical signal to the tissue which is believed to be the ureter, and the surgeon can then (i) visually observe the muscular response of the ureter, whereby to confirm ureter presence as well as the ureter path, and/or (ii) listen to the output of base unit  130 , whereby to confirm ureter presence. 
       Additional Applications 
       [0068]    The novel electrical stimulator of the present invention may also be used for purposes other than identifying the ureter. 
         [0069]    By way of example but not limitation, the electrical stimulator may be incorporated on the end of a catheter or endoscope for use in other fields of “smooth muscle” stimulation or non-cauterizing electrical energy delivery. In one exemplary use, the electrical stimulator may be passed through the working channel of an endoscope and used to stimulate target tissues to confirm visual findings of the smooth muscle sphincter of the bile and pancreatic ducts. 
         [0070]    Inasmuch as the electrical stimulator is able to stimulate both “skeletal muscle” and “smooth muscle”, the electrical stimulator may also be used to determine muscle viability and reactivity in both minimally-invasive and open surgical settings. At the same time, the electrical stimulator can be used in these situations to assist in tissue/muscle identification and delineation, especially in unclear settings. 
       Modifications 
       [0071]    While the present invention has been described in terms of certain exemplary preferred embodiments, it will be readily understood and appreciated by those skilled in the art that it is not so limited, and that many additions, deletions and modifications may be made to the preferred embodiments discussed herein without departing from the scope of the invention.