Abstract:
An expandable access sheath. In one embodiment, the sheath includes a lumen defining an inner passage and an outer surface, and a balloon that is provided on the lumen outer surface, wherein when the balloon is inflated the balloon expands the lumen to increase the size of the inner passage.

Description:
BACKGROUND 
       [0001]    Ureteral access sheaths are used to form a channel along a patient&#39;s urinary tract that provides access to a location along the tract, such as the ureter. With an established channel to the ureter, a surgeon can insert and withdraw a ureteroscope or other instrument more rapidly and with less trauma to the patient&#39;s urinary system. 
         [0002]    Typical ureteral access sheaths include two subassemblies: a dilator and a sheath. The dilator is placed within the sheath, and the dilator and sheath are advanced together through the urethra, through the bladder, and into the ureter. The dilator is then withdrawn, leaving the sheath in place. A ureteroscope can then be advanced through the sheath to access the ureter. 
         [0003]    One problem with conventional ureteral access sheaths is that it is difficult to pass the sheath and dilator through the urinary tract given that the outer diameter of the sheath is significantly larger than the inner diameter of the passageways of the urinary tract. This is particularly true with respect to the intramural ureter, which typically comprises the narrowest section of the urinary tract. In addition, it is possible to damage the urinary tract during the insertion process by, for example, perforating a vessel of the tract, such as the urethra or the ureter. 
         [0004]    Although a simple solution to the above-described problems would be to reduce the diameter of the access sheath to a point at which the sheath can be easily inserted, such a measure would reduce the inner diameter of the sheath to a point at which a typical ureteroscope may not fit within the access sheath, thereby defeating the purpose of using the access sheath. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0005]    The disclosed access sheath can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. 
           [0006]      FIG. 1  is a perspective view of an embodiment of an access sheath and means for expanding the access sheath. 
           [0007]      FIG. 2  is a cross-sectional view of a portion of a first embodiment of a tube of the access sheath shown in  FIG. 1 . 
           [0008]      FIG. 3  is a cross-sectional view of a portion of a second embodiment of a tube of the access sheath shown in  FIG. 1 . 
           [0009]      FIG. 4  is an end view of an embodiment of a tube of the access sheath shown in  FIG. 1  prior to expansion. 
           [0010]      FIG. 5  is an end view of the tube of  FIG. 4 , shown after expansion. 
           [0011]      FIG. 6  is an end view of an alternative embodiment of an access sheath, shown after expansion. 
           [0012]      FIG. 7  is an end view of the sheath of  FIG. 6 , shown prior to expansion. 
       
    
    
     DETAILED DESCRIPTION  
       [0013]      FIG. 1  illustrates an example embodiment of a ureteral access sheath  10  in an expanded state. As is described in greater detail below, the sheath  10  can be inserted into the urinary tract in an unexpanded state in which it has a small diameter, and can then be expanded while within the urinary tract to provide a passageway for a surgical instrument, such as a ureteroscope. 
         [0014]    As is indicated in  FIG. 1 , the sheath  10  comprises an elongated lumen  12  having a proximal end  14  and a distal end  16 . Positioned at the proximal end  14  of the lumen  12  is a lug  18  that forms an entrance to a working channel of the lumen. 
         [0015]    The lumen  12  is made of a non-elastomeric material, such as polyethylene terephthalate (PET) or another suitable polymeric material, such as nylon. The walls of the lumen  12  are relatively thin. By way of example, the lumen walls are about 0.1 to about 2 millimeters (mm) thick. In its unexpanded state, the lumen  12  has an outer diameter (or French) that permits the lumen to be easily passed through the urinary tract of a patient. By way of example, the lumen  12  has an outer dimension of about 3 French (Fr.) in the unexpanded state. The lumen  12  has a length that, when the lumen is inserted in the urinary tract, is long enough to provide access to the upper ureter. By way of example, the lumen  12  is about 35 to about 55 centimeters (cm) long. 
         [0016]    The lug  18  is formed of a rigid material, such as a plastic material or metal material, and, in some embodiments, can be used to couple the sheath  10  to other objects, such as a surgical instrument. 
         [0017]    Formed around the lumen  12  is a balloon  20 . In the embodiment shown in  FIG. 1 , the balloon  20  is formed as a continuous, elongated coil that is helically wrapped around the lumen  12 . The balloon  20  defines a continuous interior chamber into which fluid can be introduced to inflate the balloon. Suitable fluids include gases, such as air, and liquids, such as saline-based solutions (e.g., that contain contrast media). Irrespective of the fluid that is used to inflate the balloon  20 , such inflation causes the balloon to expand such that the inner and outer diameters defined by the coils of the balloon increase in size. Because the balloon  20  is attached (e.g., adhered or welded) to the outer surface of the lumen  12 , expansion of the balloon results in similar expansion of the lumen, thereby enlarging the inner diameter of the lumen to provide space for an instrument, such as a ureteroscope, to pass. 
         [0018]      FIGS. 2 and 3  illustrate example embodiments for the balloon  20  shown in  FIG. 1 . Beginning with  FIG. 2 , illustrated is a balloon  20 ′ that has a rectangular cross-section that is defined by opposed square corners  22 . The balloon  20 ′ defines an interior chamber  24  that, as is indicated by hidden lines, spirals around the lumen  12 . 
         [0019]    Turning to  FIG. 3 , illustrated is a balloon  20 ″ that has a rounded outer surface that is defined by a curved outer wall  26 . Like balloon  20 ′, the balloon  20 ″ defines an interior chamber  28  that spirals around the lumen  12 . 
         [0020]    Irrespective of the particular configuration that is used for the balloon  20 , the balloon is constructed of a non-elastomeric material that, although flexible, will not stretch as the balloon is pressurized. By way of example, the balloon  20  is constructed of PET or another suitable polymeric material. When such a material is used, the walls of the balloon  20  can be very thin. By way of example, the walls of the balloon  20  are about 0.003 inches (in) thick. 
         [0021]    As is noted above, the sheath  10  is inserted into the urinary tract when the sheath is in an uninflated state in which the sheath has a relatively small outer diameter. In order to minimize that diameter, both the lumen  12  and the balloon  20  can be configured in an initial collapsed orientation.  FIG. 4  illustrates an example collapsed orientation for the lumen  12  and the balloon  20 . As is indicated in  FIG. 4 , the lumen is radially folded such than an inner passage  29  remains that is sized and configured to be passed over a guidewire. By way of example, the passage  29  has a diameter of about 0.016 in. to about 0.045 in. The balloon  20  is wrapped around the lumen  12  by forming a plurality of longitudinal creases  30  in the balloon. With such creases, the balloon  20  can be tightly wrapped around the lumen  12  in a selected direction (clockwise in  FIG. 4 ). Once wrapped in this manner, the sheath  10  has a small effective outer dimension, for example about 3 Fr. to about 6 Fr. 
         [0022]    A guidewire (not shown) may be used to facilitate insertion of the sheath  10 . In such a case, the guidewire is first introduced into the urinary tract and is extended into the ureter. Once the guidewire has been so positioned, the sheath  10  can be passed over the guidewire to position the catheter within urinary tract and, typically, within the ureter. 
         [0023]    Once the sheath  10  has been placed in the desired position along the urinary tract, a pathway has been established that protects the walls of the patient&#39;s urinary system. Given that the inner diameter of the lumen  12  is so small, however, the lumen must be expanded in order to provide a passageway that is large enough for an instrument, such as a ureteroscope, to pass. By way of example, such a ureteroscope may have an outer dimension of about 10 Fr. 
         [0024]    As is described above, the lumen  12  is expanded by inflating the balloon  20 . Referring back to  FIG. 1 , such inflation can be achieved using a syringe  15  or other appropriate inflation mechanism. In cases in which a syringe  15  is used, the inflation fluid can be delivered from the syringe through a supply tube  17  that connects to an inlet  19  of the balloon  20  that provides access to the balloon&#39;s interior chamber. Optionally, the syringe  15  can comprise a threaded plunger that enables precise dilation pressures to be reached and maintained. 
         [0025]    When the balloon  20  is fully inflated and the sheath  10  is placed in the fully expanded state, the lumen  12  has an inner dimension of about 10 Fr. to about 14 Fr.  FIG. 5  illustrates the fully expanded state. Due to the helical or spiral shape of the balloon  20 , the balloon has good radial integrity that prevents the lumen  12  from collapsing or kinking, yet is still flexible such that the sheath  10  can follow the contours of the patient&#39;s urinary tract. 
         [0026]    At this point, a passageway to the patient ureter has been formed that is large enough to pass instruments, such as a ureteroscope, through to the ureter. Given that the sheath  10  is inserted prior to expansion, insertion is easier to achieve and is less likely to cause damage to the patient&#39;s urinary system. 
         [0027]      FIGS. 6 and 7  illustrate an alternative embodiment of an access sheath  32 . As is indicated in  FIG. 6 , the access sheath  32 , like access sheath  10 , includes a lumen  34  and a balloon  36  that is helically wrapped around the lumen. In addition, however, the sheath  32  comprises an auxiliary lumen  38 . With such an arrangement, the sheath  32  includes a main channel  40  that can be used as a passageway for a tool, such as a ureteroscope, and an auxiliary channel  42  can be used to receive a guidewire, to facilitate irrigation, or for another purpose. Notably, multiple auxiliary channels could be provided, if desired. 
         [0028]    With reference to  FIG. 7 , the lumen  34  and balloon  36  can be wrapped around the auxiliary lumen  38  when the sheath  32  is in the unexpanded state. In such a case, the auxiliary channel  42  is sized to configured to receive the guidewire during insertion of the sheath  32 . 
         [0029]    While particular embodiments of the disclosed ureteral access sheath have been disclosed in detail in the foregoing description and drawings for purposes of example, variations and modifications thereof can be made. All such variations and modifications are considered to fall within the scope of the present disclosure.