Abstract:
A sheath and a method of operating the sheath are provided for assisting movement of an endoscope within a cavity of a patient&#39;s body. The sheath includes an everting shaft having an internal and external lining with an inflatable lumen between them, proximal and distal regions and a lumen for receiving the endoscope. An expandable member is positioned along the distal region, which is expandable from a first diameter, at which the expandable member grips the endoscope to a second, larger diameter at which the expandable member engages a wall of the cavity.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to medical devices and more particularly to endoscopes for performing colonoscopy and other medical procedures.  
       BACKGROUND OF THE INVENTION  
       [0002]     Flexible colonoscopy has been performed for more than 30 years. While significant advances have been made during that time, the procedure is still relatively unpleasant for most patients, and quite painful for others requiring not insignificant amounts of pain sedation. During the procedure, the physician advances a flexible endoscope through the soft and winding colon. During advancement, the physician pushes one end of the endoscope while trying to direct the distal tip (that can be up to four feet away from the physician) through the colon. Since the endoscope is flexible, the force applied to the endoscope at the proximal end is not necessarily transferred to the distal end. Rather, the endoscope tends to form bends and loops as it is being pushed through the colon.  
         [0003]     This inevitably leads to stretching of the colon and of the various points where the colon is tethered inside the body causing discomfort for the patient. As a result, physicians typically need to administer sedation to the patient in order for the patient to remain comfortable through the procedure and reduce the pain created by the stretch. Sedation carries significant risks, particularly when higher doses are used, including depressing the respiratory and cardiac function.  
         [0004]     Recent technical advances in colonoscopies over the past several years include thinner endoscopes, better optics and adjustable stiffness of the scope shaft, which assists in advancing the scope more easily into the colon. However, the basic technique is unchanged and problems of overstretching the colon remain. The procedure still remains unpleasant for the patient and most often requires considerable sedation.  
         [0005]     Improved endoscopes and colonoscopy procedures are therefore desired.  
       SUMMARY OF THE INVENTION  
       [0006]     One embodiment of the present invention is directed to a sheath for assisting movement of an endoscope within a cavity of a patient&#39;s body. The sheath includes an everting shaft having proximal and distal regions and a lumen for receiving the endoscope. An expandable member is positioned along the distal region, which is expandable from a first diameter to a second, larger diameter for engaging a wall of the cavity.  
         [0007]     Another embodiment of the present invention is directed to an endoscope apparatus. The apparatus includes an everting shaft having inner and outer layers and a lumen defined by the inner layer. An endoscope extends along the lumen and is engaged with the inner layer. An expandable member is positioned along a distal region of the outer layer and is expandable from a first diameter at which the expandable member grips the endoscope to a second, larger diameter at which the expandable member releases the endoscope and allows the endoscope to move relative to the expandable member.  
         [0008]     Another embodiment of the present invention is directed to a method of moving an endoscope along an elongated body cavity. The method includes: (a) inserting an endoscope apparatus into the body cavity, the apparatus comprising an endoscope and an everting shaft, which includes inner and outer layers, a lumen through which the endoscope extends, and an expandable member; (b) advancing the apparatus to a curved portion of the body cavity with the expandable member contracted to a first diameter at which the expandable member grips the endoscope; (c) expanding the expandable member from the first diameter toward a second, larger diameter at which the expandable member releases the endoscope and anchors to a wall of the body cavity; (d) applying a withdrawing force on the outer layer when the expandable member is anchored to the wall of the body cavity to thereby reduce curvature of the curved portion of the body cavity; and (e) advancing the endoscope relative to the expandable member such that engagement between the endoscope and the inner layer causes a distal portion of the inner layer to evert to the outer layer during advancement.  
         [0009]     Another embodiment of the present invention is directed to a medical device for insertion into a body cavity. The device includes an elongated sheath. The expandable member is expandable from a first diameter to a second, larger diameter and is mounted to the elongated sheath such that the elongated sheath has an angular position that is rotatable relative to the expandable member. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIGS. 1-1  through  1 - 14  illustrate a colonoscopy procedure according to one embodiment of the present invention.  
         [0011]      FIG. 2  is a side view of an endoscope apparatus in a deflated state according to one embodiment of the present invention.  
         [0012]      FIG. 3  is a side view of the endoscope apparatus in an inflated state according to one embodiment of the present invention.  
         [0013]      FIG. 4  is an enlarged, cross-sectional view of the distal end of the apparatus shown in  FIGS. 2-3  within a patient&#39;s colon.  
         [0014]      FIG. 5  is an enlarged view of the distal end showing an expandable member in an inflated state.  
         [0015]      FIG. 6  is an enlarged view of the distal end showing the expandable member in a deflated state.  
         [0016]      FIG. 7  is a side view of an endoscope apparatus according to an alternative embodiment of the present invention.  
         [0017]      FIG. 8  is a cross-sectional view of an endoscope apparatus having the inflation cavity of an expandable member coupled to the inflation cavity of an everting sheath according to an alternative embodiment of the present invention.  
         [0018]      FIG. 9  is a cross-sectional view of an endoscope apparatus having a rotatable balloon according to an alternative embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]      FIGS. 1-1  through  1 - 14  illustrate a colonoscopy procedure according to one embodiment of the present invention. During the procedure, an endoscope apparatus  10  is advanced into the colon  12  of a patient. The endoscope apparatus  10  is inserted into the bottom  14  of colon  12  and advanced through each segment to reach the end  16 . For simplicity, the full length of endoscope apparatus  10  is not shown beyond the bottom  14  of colon  12  in  FIGS. 1-1  through  1 - 14 .  
         [0020]     As described in more detail below, apparatus  10  includes an endoscope  17 , which extends through an outer everting sheath  18  and has a distal end  17   a  and a proximal portion  17   b . Sheath  18  assists in advancing endoscope  17  through colon  12 . In one embodiment, everting sheath  18  has an inner layer that frictionally engages the outer diameter surface of endoscope  17  and an outer layer that carries an expandable member  20 . In one embodiment, expandable member  20  forms a balloon, which can be inflated and deflated. When sheath  18  and expandable member  20  are inflated, the outer layer of the sheath becomes separated from the inner layer. The inner layer is connected to the outer layer at the distal end of sheath  18  to allow the inner layer to evert to the outer layer at the distal end of sheath  18 .  
         [0021]     In  FIG. 1-1 , the endoscope apparatus  10  is shown inserted into colon  12 , within the everting sheath  18 , which is fully deflated. When deflated, one or more elastic elements or bands  26 , grip the expandable member  20  and sheath  18  to the outer diameter of endoscope  17  such that the endoscope and sheath can be advanced together along colon  12 .  
         [0022]     At this point in the procedure, the endoscope is used in a normal manner. As the endoscope is advanced further within the colon, the shaft of the endoscope begins to form bends and loops, causing discomfort due to stretching of the colon from its normal configuration. This is usually the first point in the procedure when the patient experiences significant discomfort. As the physician pushes proximal portion  17   b  in order to advance distal end  17   a , the bend in endoscope  17  can cause the colon  12  to stretch along area  30  causing pain.  
         [0023]      FIG. 1-2  illustrates everting sheath  18  and expandable member  20  inflated with a fluid such as water. However, any suitable fluid (liquid or gas) can be used for inflating sheath  18  and/or expandable member  20 . Sheath  18  and expandable member  20  can be inflated through a common passage or lumen or can be inflated through separate passages or lumens. When expandable member  20  and sheath are inflated, the water pressure overcomes the grip of the small elastic bands  26  (shown in  FIG. 1-1 ) such that expandable member  20  and the outer layer of sheath  18  no longer grip the outer diameter of endoscope  17 . Expandable member  20  is sized and shaped such that, when inflated, the outer diameter surface of expandable member  20  engages the interior surface of colon  12  and can serve to anchor sheath  18  in position relative to the colon. Various shapes and textures of the expandable member can be used to anchor the sheath and expandable member to the colon without applying excessive radial force on the colon, as excessive radial force could cause discomfort in and of itself. When the sheath and expandable member are anchored in position, endoscope  17  is free to move in an axial direction relative to expandable member  20 .  
         [0024]     In  FIG. 1-3 , with expandable member  20  anchored to colon  12 , the physician pulls endoscope  17  and sheath  18  from proximal portion  17   b  to withdraw slightly the endoscope and sheath from the colon and thereby straighten that section of the colon.  
         [0025]     In  FIG. 1-4 , the bottom of colon  12  begins to shorten and the stretch along area  30  is reduced as endoscope  17  and sheath  18  are withdrawn further. Eventually, the curve formed by endoscope  17  is reduced with further withdrawal of endoscope  17  and sheath  18 , creating a relatively straight section of colon  12  for advancement of the endoscope along the colon.  
         [0026]     Referring to  FIG. 1-5 , expandable member  20  remains inflated and is fixed against the wall of colon  12 . Endoscope  17  is able to move independently from expandable member  20  because of the action of everting sheath  18  underneath the expandable member. The physician can then push the proximal portion  17   b  of the endoscope while maintaining a pulling force on the outer layer of sheath  18 . As shown in  FIG. 1-6 , the frictional engagement between the outer diameter surface of endoscope  17  with the inner layer of sheath  18  causes the inner layer of the sheath to evert out of the distal end of the sheath (as shown by everted section  32 ). As sheath  18  everts, more of the distal end  17   a  of the endoscope becomes exposed.  
         [0027]     As shown and described in more detail below, everted section  32  represents material along the inner layer of sheath  18  that has advanced relative to the outer layer of the sheath and is therefore exposed out of the distal end of the sheath.  
         [0028]     At this point in the procedure, the distal end  17   a  of endoscope  17  has reached a relatively straight section of colon  12  due to the everting action of sheath  18  and the straightening of the bottom portion of the colon. Expandable member  20  and sheath  18  can then be deflated, as shown in  FIG. 1-7 . This causes elastic bands  26  to re-grip endoscope  17  at a distance further back from distal end  17   a . Endoscope  17  and sheath  18  can then be advanced together once again in the usual manner, as shown in  FIG. 1-8 .  
         [0029]     When the patient starts to feel pain or the endoscope begins to form exaggerated bends once again, expandable member  20  can be re-inflated, as shown in  FIG. 1-9 . As shown in  FIG. 1-10 , the everting sheath  18  can be withdrawn slightly thereby straightening endoscope  17  between expandable member  20  (which is fixed against colon  12 ) and the rectum. This allows the endoscope  17  to be advanced in a relatively straight line between the rectum and expandable member  20 . Now, most of the force applied by pushing endoscope  17  from proximal portion  17   b  is transferred to the level of expandable member  20 . This has the effect of pushing the flexible endoscope  17  from the midshaft rather than at the proximal portion  17   b , providing some mechanical advantage.  
         [0030]     Once endoscope  17  has then been advanced beyond a difficult section and the colon is straightened, expandable member  20  can be deflated as shown in  FIG. 1-11 . Note that as sheath  18  becomes further everted, more of endoscope  17  becomes exposed out of the distal end of the sheath, along everted section  32 . When expandable member  20  is deflated, the expandable member re-grips endoscope  17 , this time even further back from distal end  17   a . In  FIG. 1-12 , endoscope  17  and sheath  18  are advanced further until another difficult point is reached. In  FIG. 1-13 , expandable member  20  can be inflated once again. In  FIG. 1-14 , endoscope  17  is advanced to the end  16  of colon  12 . At this point in the procedure, endoscope  17  can image the end  16  of colon  12 .  
         [0031]     If during the procedure the physician wishes to “reload” expandable member  20  to the distal end  17   a  of endoscope  17 , the physician can advance endoscope  17  and deflated expandable member  20  to an straight section of colon  12  such that shown in  FIG. 1-7 , for example. The expandable member  20  can be inflated to engage the surface of colon  12  and hold the expandable member and sheath in a fixed position relative to the colon. The physician can then pull back and withdraw the endoscope  17  relative to sheath  18  and expandable member  20  until the distal end  17   a  of endoscope  17  reaches expandable member  20 . Expandable member  20  and sheath  18  can then be deflated causing elastic bands  26  to re-grip the distal end  17   a  of endoscope  17 . The endoscope  17 , sheath  18  and expandable member  20  can then be advanced together through the straight section of colon  12 .  
         [0032]     The everting sheath and expandable member described above can be used with any type of endoscope for any medical procedure. In addition to endoscopes used for colonoscopy, the everting sheath and expandable member can be used with endoscopes for performing an upper endoscopy procedure through the esophagus, for example, to facilitate deeper passage into the small intestine. In addition, the sheath and expandable member can be used in other elongated medical instruments or devices for advancement along a human or other animal body cavity.  
         [0033]      FIG. 2  is a side view of endoscope  17  and sheath  18 , with sheath  18  and expandable member  20  in a deflated state according to one embodiment of the present invention.  FIG. 3  is a side view of endoscope  17  and sheath  18 , with sheath  18  and expandable member  20  in an inflated state according to one embodiment of the present invention.  
         [0034]     Referring to  FIG. 2 , endoscope  17  has an elongated shaft with a distal end  17   a , a proximal portion  17   b  and a handle  17   c . Endoscope  17  is shown inserted within everting sheath  18 . Everting sheath  18  has a distal end  18   a  and a proximal end  18   b . Endoscope  17  extends through an internal lumen of sheath  18 , from proximal end  18   b  to distal end  18   a . In one embodiment, expandable member  20  is a separate element that is attached to the outer layer of sheath  18 . In another embodiment, expandable member  20  is formed as a single, continuous piece of material with the outer layer of sheath  18 . For example, expandable member  20  can be defined by one or more areas of reduced material thickness relative to the thickness of sheath  18 , or by one or more areas where the sheath material elasticity is increased relative to the elasticity of sheath  18 . The areas of reduced material thickness or increased material elasticity expand to a greater degree than sheath  18  when sheath  18  is inflated. Expandable member  20  can have any number of sections  28  defined by elastic bands  26 .  
         [0035]     Elastic bands  26  extend around the periphery of expandable member  20  and are sized to grip the outer diameter of endoscope  17  when sheath  18  and expandable member  20  are deflated. Similar to expandable member  20 , elastic bands  26  can be formed of any suitable elastic material, which can be separate from expandable member  20  or integral with the expandable member material. For example, bands  26  can be separate rubber bands that are mounted over expandable member  20 . In an alternative embodiment, elastic bands  26  are formed within the material of expandable member  20 , such as one or more bands having increased material thickness than expandable member  20 . Any number of bands can be used. Sheath  18 , expandable member  20 , and bands  26  can be formed of any suitable elastic material, such as elastic polymers.  
         [0036]     Sheath  18  includes an inflation valve or port  40  for inflating sheath  18  through a lumen  42 . In this embodiment, sheath  18  further includes a separate inflation valve or port  44  for inflating expandable member  20  through a separate lumen  46 . Again, sheath  18  and expandable member  20  can be inflated through a common lumen or through separate lumens. As described in more detail below, sheath  18  is formed as a cylindrical tube with sidewalls formed by two layers of material with a space between them. When a fluid is introduced within the space between the two layers, the fluid pressure expands the space, thereby inflating the sheath, as shown in  FIG. 3 . The expandable member  20  is attached to the outer layer of material and can be inflated with sheath  18  or separately from sheath  18  in alternative embodiments.  
         [0037]     Inflation valve  40  can include a fitting for attaching a syringe that can be used for inflating the sheath and/or expandable member. In addition, inflation valve  40  can include a chamber for storing extra material of sheath  18  that can be used during eversion.  
         [0038]     In one embodiment, the inner layer of sheath  18  is frictionally attached to the outer diameter of endoscope  17  when sheath  18  is inflated and deflated. This allows the inner layer of sheath  18  to evert out the distal end of the sheath when sheath  18  and expandable member  20  are inflated and endoscope  17  is advanced relative to expandable member  20 . Inflation of sheath  18  provides an area of lubrication between the inner and outer layers of the sheath material to allow expandable member  20  to slide back and forth relative to endoscope  17 , as shown in more detail in  FIGS. 4 and 5 .  
         [0039]      FIG. 4  is an enlarged, cross-sectional view of the distal end  18   a  of everting sheath  18  when inflated. Endoscope  17  extends through an internal lumen  60  of sheath  18 . Sheath  18  has a cylindrical inner layer  62  and a cylindrical outer layer  64 , which together form an elongated, annular tube. At distal end  18   a , inner layer  62  is attached to outer layer  64 , forming a continuous material, for example. Cavity  66  between inner layer  62  and outer layer  64  is inflated by introducing a pressurized fluid (such as water) within the cavity. Inflation of the space between the inner and outer layers of sheath  18  separates elastic bands  26  and expandable member  20  from endoscope  17  and allows the endoscope to move independently from expandable member  20 .  
         [0040]     When sheath  18  and expandable member  20  are inflated and endoscope  17  is advanced relative to expandable member  20 , as shown by arrow  68 , the frictional engagement between inner layer  62  and the outer diameter of endoscope  17  causes the inner layer  62  to travel with endoscope  17  relative to expandable member  20  and outer layer  64 . As endoscope  17  continues to advance, more of the inner layer material gets everted out of distal end  18   a , as shown by arrows  69 , thereby forming additional outer layer material. This eversion action increases the length of everted section  32  that extends forward beyond expandable member  20  (not shown in  FIG. 4 ). As mentioned above, the movement of inner layer  62  relative to outer layer  64  about the fluid in cavity  66  provides an area of lubrication to allow expandable member  20  to slide back and forth relative to endoscope  17 , and the inner layer  62  is able to pass freely under expandable member  20 .  
         [0041]      FIG. 5  is an expanded view of the distal end  18   a  of sheath  18  according to one embodiment of the present invention. When sheath  18  and expandable member  20  are inflated, fluid pressure inside the expandable member and the sheath overcomes the grip of elastic bands  26  and allows expandable member  20  to expand from a first diameter to a second, larger diameter. When elastic bands  26  are released from endoscope  17 , the endoscope is free to move relative to the fixed expandable member  20 . Expandable member  20  can have any number of sections. In the embodiment shown in  FIG. 5 , expandable member  20  has three sections separated by two elastic bands  26 . When inflated, expandable member  20  engages the inner surface of colon  12 . This allows the location of expandable member  20  and the outer layer  64  of sheath  18  to remain fixed relative to colon  12 .  
         [0042]     As mentioned above, expandable member  20  can be inflated and deflated either separately or with sheath  18 . In the embodiment shown in  FIG. 5 , expandable member  20  has an internal cavity  80 , which is coupled to lumen  46  for inflating expandable member  20  separately from sheath  18 .  
         [0043]      FIG. 6  cross-sectional view of the distal end  18   a  of sheath  18  when sheath  18  and expandable member  20  are deflated. When deflated, elastic bands  26  collapse expandable member  20  until the bands grip the outer diameter of endoscope  17  through outer layer  64  and inner layer  62  of sheath  18 . In this state, endoscope  17  and sheath  18  can be advanced or withdrawn together through colon  12 .  
         [0044]      FIG. 7  is a side view of endoscope  17  and sheath  18  showing sheath  18  in a partially everted state, relative to  FIG. 3 . As endoscope  17  is advanced relative to inflated expandable member  20 , the length of everted section  32  forward of expandable member  20  increases, as can be seen with a comparison to  FIG. 3 . Also, more of endoscope  17  becomes exposed beyond the distal end  18   a  of sheath  18 .  
         [0045]      FIG. 7  also illustrates an alternative embodiment in which extra sheath material  70  is stored in a housing  72  containing inflation valve  40 . The extra sheath material can be stored in a housing separate from inflation valve  40  in a further alternative embodiment. In one embodiment, the inner layer of sheath  18  forms a continuous piece of material with the outer layer at proximal end  18   b , similar to distal end  18   a . However, the inner and outer layers can be disconnected from one another at proximal end  18   b  in an alternative embodiment of the present invention.  
         [0046]      FIG. 7  further illustrates an abutment device  92  fastened to the ridges  56  along the outer layer of sheath  18 . Abutment device  92  can be used to anchor the axial position of the outer layer of sheath  18  relative to the patient&#39;s rectum as endoscope  17  is advanced. As described with reference to  FIGS. 1-1  through  1 - 14 , the colon can be straightened by inflating expandable member  20  and then pulling back on endoscope  17  and sheath  18 . If the physician desires not to withdraw endoscope  17  while straightening the colon, the physician can pull back on sheath  18  while pushing endoscope  17  forward. This may require the physician to pull back on sheath  18  with one hand while pushing forward on endoscope  17  with the other hand. Abutment device  90  can help to free one of the physician&#39;s hands while advancing the endoscope  18 . As sheath  18  is being pulled backward, abutment device  90  can be slid forward along sheath  18  toward the patient&#39;s rectum. Abutment device  90  can therefore act as a stopper, which holds the position of sheath  18  relative to the colon to prevent forward movement of the sheath when pushing endoscope  17  forward. This keeps the outer diameter of sheath  18  in place and tension between the sheath and expandable member  20 , thereby maintaining a straightened section of the colon.  
         [0047]      FIG. 8  is a cross-sectional view of the distal end of an endoscope apparatus  100  according to an alternative embodiment of the present invention. The same reference numerals are used in  FIG. 8  as were used in the preceding figures for the same or similar elements. In this embodiment, the internal cavity  80  of expandable member  20  is coupled to the cavity  66  between the inner and outer layers  62  and  64  of sheath  18  through one or more openings  102 . Inflation lumen  46  is coupled to cavity  80  of expandable member  20 , but could alternatively be coupled to cavity  66  of sheath  18 . When a pressurized fluid is inserted into cavity  80  through inflation lumen  46  in order to inflate expandable member  20 , excess fluid enters cavity  66  through openings  102  causing sheath  18  also to inflate.  
         [0048]      FIG. 9  is a cross-sectional view of the distal end of an endoscope apparatus  200  according to another alternative embodiment of the present invention. Again, the same reference numerals are used for the same or similar elements. In  FIG. 9 , endoscope apparatus  200  has an angular position that is rotatable relative to expandable member  20 , as indicated by arrow  201 . Expandable member  20  is mounted to the outer layer  64  of sheath  18  through a sliding interface or fitting  202 . In this example, expandable member  20  has a base  204 , which is mounted in a channel  206  on outer layer  64  to form the sliding interface  202 . Channel  206  has an annular shape, which extends around the circumference of outer layer  64 . Other methods and structures for mounting expandable member  20  to apparatus  10  that allow for relative rotational movement can be used in alternative embodiments of the present invention.  
         [0049]     During some procedures, it may be desirable to apply a rotational torque on the endoscope  17  in order to direct the endoscope  17  around difficult turns or to fine-tune the position of the endoscope  17  when taking a biopsy or removing a polyp, for example. By making exapandable member  20  completely separate from sheath  18 , endoscope  17  can rotate while expandable member  20  remains anchored to the colon in a fixed position.  
         [0050]     A rotatable expandable member or balloon, as shown in  FIG. 9  can be implemented on any elongated medical device, such as an endoscope, endoscope sheath or catheter, for example. If a sheath is used, the sheath can be everting or non-everting.  
         [0051]     Various shapes and configurations of the expandable member can be used to improve the longitudinal traction between the colon and the expandable member without creating excessive radial force against the colon. One such configuration is shown in  FIG. 10 . Endoscope apparatus  250  includes an endoscope  17  and an everting sheath  18 , which are similar to the embodiments discussed above. In this embodiment, sheath  18  includes an expandable member  252  having a shape that allows for the expandable member to catch or grab on to areas of the colon when withdrawn as in the action of an anchor, but would not require excessive inflation and over-expand the colon. When expanded, expandable member  252  forms three anchor fins  254 , which project radially outward from sheath  18  for engaging the colon wall. Fins  254  can extend around all or part of the circumference and can have any suitable cross-sectional shape, such as triangular.  
         [0052]      FIG. 11  illustrates a further embodiment of an endoscope apparatus  275  having an expandable member  280  attached to everting sheath  18 . In this embodiment, expandable member  280  has a conical shape. Elastic band  26  biases expandable member  280  to the smaller diameter when not inflated.  
         [0053]     In a further embodiment, the expandable member can be formed of a mechanical anchor attached to the sheath, which could be made of plastic or other suitable material. The mechanical anchor could be activated (expanded and/or contracted) by means of a wire-triggered (or other) mechanism, rather than by inflation with a fluid or gas.  
         [0054]     With the embodiments shown in the above-described figures, an everting sheath can be preloaded on any standard or specialized endoscope. The sheath carries an expandable member, which can either be fixed to the endoscope by elastic bands (for example) when deflated, or detached from the endoscope when inflated and anchored to the colon. This allows the endoscope and expandable member to be moved either together as a single unit or independently. This device also may remove the need to invest in complicated and expensive endoscopes with special features to allow the endoscope to be advanced easily through the colon. Rather, a standard endoscope can be preloaded with an everting sheath as described above. This can significantly reduce the expense associated with colonoscopy procedures.  
         [0055]     Also, the use of this device may allow the endoscope to be advanced to the end of the colon much faster than endoscopes of the prior art. This significantly reduces the time required for a colonoscopy procedure and reduces the duration of patient discomfort. In addition, the ability to straighten certain difficult sections of the colon allows the endoscope to be advanced with reduced pain to the patient. As a result, physicians may find that colonoscopy procedures can be performed more safely and with less sedation.  
         [0056]     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the scope of the invention.