fig1 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 . as is indicated in fig1 , 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 . 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 . 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 . formed around the lumen 12 is a balloon 20 . in the embodiment shown in fig1 , 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 . fig2 and 3 illustrate example embodiments for the balloon 20 shown in fig1 . beginning with fig2 , 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 . turning to fig3 , 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 . 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 . 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 . fig4 illustrates an example collapsed orientation for the lumen 12 and the balloon 20 . as is indicated in fig4 , 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 fig4 ). once wrapped in this manner , the sheath 10 has a small effective outer dimension , for example about 3 fr . to about 6 fr . 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 . 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 . as is described above , the lumen 12 is expanded by inflating the balloon 20 . referring back to fig1 , 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 . 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 . fig5 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 . 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 . fig6 and 7 illustrate an alternative embodiment of an access sheath 32 . as is indicated in fig6 , 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 . with reference to fig7 , 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 . 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 .
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 .