Patent Publication Number: US-2019174995-A1

Title: Treatment tool for endoscope

Description:
FIELD OF THE INVENTION 
     The present invention relates to a treatment tool for an endoscope used in expansion treatment of a stenosis site or an obstruction site in a lumen of a living body. This application is a continuation application based on PCT Patent Application No. PCT/JP2016/069988, filed Jul. 6, 2016, the content of which is incorporated herein by reference. 
     DESCRIPTION OF RELATED ART 
     Conventionally, in combination with an endoscope, a procedure for performing dilation treatment or the like of a stenosis site or an obstruction site (hereinafter referred to as “stenosis site or the like”) of a digestive tract is performed. In such a procedure, for example, a treatment tool for an endoscope equipped with a balloon is used. Specifically, the treatment tool for an endoscope is inserted into a lumen of a living body along with the endoscope, and the balloon inflated while the balloon is inserted into the stenosis site or the like to dilate the stenosis site or the like. When the treatment tool for an endoscope is disposed to dilate the stenosis site or the like in the lumen of the living body, the balloon may slip against the stenosis site or the like while the balloon is inflated, and the balloon may be removed from a site to be dilated. In this case, since an operator needs to temporarily deflect the balloon first, and to perform positioning of the balloon again, manipulation is complicated. 
     Therefore, to prevent the balloon from slipping on and being displaced from the stenosis site or the like during inflation of the balloon, a treatment tool for an endoscope using a balloon in which a small-diameter portion is formed between a distal portion and a proximal portion when the balloon inflates has been proposed (for example, Published Japanese Translation No. 2003-507906 of the PCT International Publication). 
     In the treatment tools for an endoscope of Published Japanese Translation No. 2003-507906 of the PCT International Publication, Published Japanese Translation No. 2008-528236 of the PCT International Publication, and Japanese Unexamined Patent Application, First Publication No. 2001-190678, a radiopaque marker is provided on a guide member such as a tube inserted into the balloon in order to dispose the small-diameter portion in the stenosis site or the like. In these treatment tools for an endoscope, a position of the placed balloon is specified under observation of radioscopy while checking a position of the marker. 
     SUMMARY OF THE INVENTION 
     A treatment tool for an endoscope according to a first aspect of the present invention includes: a sheath; a balloon provided at a distal end of the sheath, and configured to be expandable from a folded initial shape to an unfolded inflated shape; an inner shaft elongated along a longitudinal axis of the balloon, and passes through an inside of the balloon; and at least one or more positioning markers provided on the inner shaft and configured to be visible through the balloon, wherein the balloon has: a proximal end-side region including a proximal end part of the balloon; a distal end-side region including a distal end part of the balloon; and a middle part that is provided between the proximal end-side region and the distal end-side region, wherein when the internal pressure of the balloon is a first internal pressure value, outer diameters of the proximal end-side region and the distal end-side region are larger than an outer diameter of the middle part, and when the internal pressure of the balloon is a second internal pressure value greater than the first internal pressure value, the proximal end-side region, the distal end-side region, and the middle part are deformed to the inflated shape , and the outer diameter of the middle part is configured to be substantially the same as the outer diameters of the proximal end-side region and the distal end-side region, and wherein at least one of the positioning markers is positioned on the inner shaft at same a longitudinal position as the proximal end-side region. 
     A second aspect of the present invention according to the first aspect, may further including a middle marker provided on the inner shaft at a position located inside the middle part, and configured to be visible through the balloon. 
     A third aspect of the present invention according to the first aspect, the positioning marker may be visible via an imager provided at a distal end of an endoscope insertion part through which the sheath is inserted. 
     A fourth aspect of the present invention according to the third aspect, the positioning marker may be visible by the imager in a state in which the balloon is folded. 
     A fifth aspect of the present invention according to the first aspect, when the balloon is folded in the initial shape, the balloon may have a plurality of wings being formed by folding the balloon, and the plurality of wings being wound around the inner shaft. 
     A sixth aspect of the present invention according to the first aspect, the balloon may be formed of a film of a transparent material. 
     A seventh aspect of the present invention is a treatment tool for an endoscope, including; a sheath; a balloon provided at a distal end of the sheath, and configured to be expandable from a folded initial shape to an unfolded inflated shape; an inner shaft configured to pass through an inside of the balloon; and at least one or more positioning markers provided on the inner shaft and configured to be visible through a film of the balloon, wherein the balloon has: a proximal end-side region including a proximal end part of the balloon; a distal end-side region including a distal end part of the balloon; and a middle part provided between the proximal end-side region and the distal end-side region, and wherein in a state that the balloon is folded by winding around a longitudinal axis of the balloon, outer diameters of the proximal end-side region and the distal end-side region are larger than that of the middle part, and wherein at least one of the positioning markers is positioned on the inner shaft at same a longitudinal position as the proximal end-side region. 
     A eighth aspect of the present invention is a method for dilating a stenosis site, including: a positioning step of disposing a distal end region of a balloon at a position more distal than the stenosis site while observing the stenosis site through an endoscope, and locating a proximal end region of the balloon at a position more proximal than a target site, the distal end region and the proximal region of the balloon being projected from the endoscope; a first inflating step of inflating the distal end region and the proximal end region such that outer diameters of the distal end region and the proximal end region are larger than that of a middle part of the balloon which is disposed between the distal end region and the proximal end region; and a second inflating step of inflating the middle part such that the outer diameter of the middle part is almost the same as those of the distal end region and the proximal end region. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a sectional view illustrating a treatment tool for an endoscope according to an embodiment of the present invention. 
         FIG. 2  is a view illustrating a state of a balloon in an initial shape in the treatment tool for an endoscope according to the embodiment of the present invention. 
         FIG. 3  is a view schematically illustrating a cross section of the initial shape of the balloon in a direction orthogonal to a longitudinal axis. 
         FIG. 4  is a view illustrating a use state of the treatment tool for an endoscope according to the embodiment of the present invention. 
         FIG. 5  is a view illustrating an operation of the treatment tool for an endoscope according to the embodiment of the present invention when the treatment tool for an endoscope is used. 
         FIG. 6  is a view illustrating an image example of an imager of an endoscope when the treatment tool for an endoscope according to the embodiment of the present invention is used. 
         FIG. 7  is a view illustrating an operation of the treatment tool for an endoscope according to the embodiment of the present invention when the treatment tool for an endoscope is used. 
         FIG. 8  is a view illustrating an operation of the treatment tool for an endoscope according to the embodiment of the present invention when the treatment tool for an endoscope is used. 
         FIG. 9  is a view illustrating an operation of the treatment tool for an endoscope according to the embodiment of the present invention when the treatment tool for an endoscope is used. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An embodiment of the present invention will be described with reference to  FIGS. 1 to 9 .  FIG. 1  is a sectional view illustrating a treatment tool  1  for an endoscope of the present embodiment. The treatment tool  1  for an endoscope includes a sheath  2 , a balloon  3 , a connector  4 , a distal end tip  5 , a stylet (an inner shaft)  6 , a positioning marker  7 , and a middle marker  8 . 
     The sheath  2  is a long, flexible member that has a lumen  21  and extends in a direction of a longitudinal axis L. A proximal portion of the balloon  3  is airtightly connected to a distal portion of the sheath  2 . The connector  4  is provided at a proximal portion of the sheath  2 . A communication passage  41  that communicates from a distal end to a proximal end along the longitudinal axis L is formed in the connector  4 . The lumen  21  of the sheath  2  communicates with an inside of the balloon  3  and the communication passage  41  of the connector  4 . Therefore, the balloon  3  is capable of being enlarged in a diameter by supplying a fluid to the balloon  3  via the communication passage  41  and the lumen  21  by a syringe or the like connected to the connector  4 . 
     A marker  22  being capable of being checked under radioscopy is provided at the distal portion of the sheath  2  in order to facilitate the check of a position of a terminal portion of the proximal portion of the balloon. 
     The balloon  3  is a bag-shaped member formed of, for example, a transparent film made of a polyamide resin (for example, PEBAX (registered trademark) manufactured by ARKEMA Inc.). 
     An initial shape that is a shape of the balloon  3  prior to inflation is illustrated in  FIG. 2 . A cross section of the balloon  3  having the initial shape in the direction orthogonal to the longitudinal axis L is schematically illustrated in  FIG. 3 . The balloon  3  is folded by molding a material in an approximately cylindrical shape and then forming folds such that a plurality of wings  36  extending in the direction of the longitudinal axis L are formed. In this case, a plurality of valleys  37  (see  FIG. 3 ) formed to protrude inward in a radial direction at root sides of the wings  36  are formed. A shape of the balloon in which a diameter is reduced by this folding is referred to as an initial shape. Details of the initial shape will be described below. 
     When a fluid is injected to the balloon  3 , the wings are spread, and thereby the balloon  3  opens while being unfolded, and inflates to be in an approximately columnar shape. In this way, a shape that is nearly inflated only by unfolding is referred to as an inflated shape. The balloon  3  is reduced in internal volume so that a size thereof in a radial direction is capable of being contracted, and ideally returns to a shape close to the initial state by removing the fluid injected into the balloon  3  of the inflated shape. When an internal pressure in the balloon  3  of the inflated shape reaches or exceeds a predetermined value, the balloon  3  is expanded and enlarged in diameter while the constituted film is stretched. That is, the balloon  3  is a so-called semi-compliant type balloon. 
     As illustrated in  FIG. 2 , the balloon  3  has a distal end-side region  31  adjacent to the distal end tip  5 , a proximal end-side region  32  adjacent to the sheath  2 , and a middle part  33  between the distal end-side region  31  and the proximal end-side region  32 . As illustrated in  FIG. 3 , in the initial shape, the balloon  3  is folded such that the balloon  3  is bent to form the plurality of wings  36  that protrude outward in a radial direction and the plurality of wings  36  is wound around an axis of the balloon  3 . Outer diameters D 2  of the distal end-side region  31  and the proximal end-side region  32  that are located at opposite ends of the balloon  3  in a longitudinal direction (that is the same as an axial direction of the balloon  3 ) are larger than an outer diameter D 1  of the middle part  33 . 
     In the balloon  3  of the initial shape, an amount of residual strain in the distal end-side region  31  and the proximal end-side region  32  is different from that at the middle part  33  due to a difference of an amount of deformation of a film generated by a folding process. In this specification, “amount of residual strain” refers to the total sum of the amounts of residual strain within a range of a predetermined unit length in the axial direction of the balloon. In the case where a certain region has a length larger than or equal to the unit length in the axial direction, the amount of residual strain per unit length calculated by averaging the amounts of residual strain of the parts is set as the amount of residual strain of the region. 
     In the balloon  3  of the initial shape, residual strain is exclusively generated at portions of folding lines  35  that are tops of the wings  36 , and at the valleys  37  that are bent in the middle between pairs of neighboring wings  36  to be convexedly bent toward the stylet  6 . In the balloon  3  of the present embodiment, an amount of deformation of the middle part  33  is made larger than those of the distal end-side region  31  and the proximal end-side region  32 . As an amount of deformation generated at the film of which the balloon  3  is formed by the folding process increases, the residual strain generated at the folding lines  35  and the valleys  37  becomes larger. Thus, in the balloon  3  of the present embodiment, the amount of residual strain at the middle part  33  is configured to become larger than that in the distal end-side region  31  and the proximal end-side region  32 . 
     As illustrated in  FIG. 2 , the distal end tip  5  is provided at a distal end of the treatment tool  1  for an endoscope. The distal end tip  5  is a member that extends in the direction of the longitudinal axis L and has an approximately conical shape, and a distal portion of the distal end tip  5  is formed in a spherical shape to prevent damage to tissue when the distal end tip  5  is inserted into a body cavity. 
     A distal portion of the balloon  3  is closely fixed to a proximal portion of the distal end tip  5 . 
     The stylet  6  is a shaft member. The stylet  6  is inserted into the balloon  3 , and runs from a distal end to a proximal end of the balloon  3  along the longitudinal axis L. A distal portion of the stylet  6  is connected to a proximal end of the distal end tip  5 . The stylet  6  extends through the inside of the balloon  3 , the lumen  21  of the sheath  2 , and the communication passage  41  of the connector  4 , and is fixed to an inner wall of the communication passage  41  of the connector  4 . The stylet  6  is formed of, for example, stainless steel, a nickel-titanium alloy, or the like. 
     The positioning marker  7  (hereinafter, sometimes simply referred to as “marker  7 ”) is visible through the film of the balloon  3 , and a plurality of markers  7  are provided on the stylet  6 . In the present embodiment, the positioning marker  7  is made up of a first marker  7   a,  a second marker  7   b,  and a third marker  7   c  that are provided at intervals in order from the vicinity of the distal end. 
     The number of positioning markers  7  is not limited to the above, and at least one or more may be provided. For example, the number of positioning markers  7  may be increased/decreased depending on an effective length of the balloon or a position of a boundary between the middle part  33  and the proximal end-side region  32 . For example, the number of positioning markers  7  may be only one. 
     At a side more proximally than the middle part in the direction of the longitudinal axis L of the stylet  6 , the first marker  7   a  located at a most distal end among the three positioning markers  7  is positioned on the stylet  6  at a predetermined range that is a same longitudinal positon as the proximal end-side region  32 . For example, in a case in which an effective length of the balloon is 80 millimeters (mm), the predetermined range is a range which is a same longitudinal position as the boundary between the middle part  33  and the proximal end-side region  32  and is a range of about 2 to 3 mm from the boundary. Therefore, a distal end of the first marker  7   a  may be located at a same longitudinal position as the boundary between the middle part  33  and the proximal end-side region  32  (at a proximal end of the middle part  33 ), or may be located at a same longitudinal position as a proximal side of the balloon where is more proximal than the boundary between the middle part  33  and the proximal end-side region  32 . This range is not limited to the above, and the range may be changed depending on the effective length of the balloon or a position of the boundary between the middle part  33  and the proximal end-side region  32 . 
     In the present embodiment, the second marker  7   b  and the third marker  7   c  are provided at a proximal side from the first marker  7   a  at a pitch of 10 mm. The plurality of markers  7  are disposed at a distal side from at a position at which the proximal end of the balloon  3  is joined with the stylet  6  in consideration of a depth of a field of view of the imager  153 . The first marker  7   a  is positioned on the stylet at same longitudinal position as around the boundary between the middle part  33  and the proximal end-side region  32 , and the three markers  7   a,    7   b  and  7   c  are provided at a regular pitch. 
     The second marker  7   b  and the third marker  7   c  are provided so that an amount of advancing/retracting of the stylet  6  and a position of the first marker  7   a  is capable of being easily seen. The three markers  7   a,    7   b  and  7   c  are intermittently provided, and thereby a user is capable of easily seeing an amount of advancing/retracting of the balloon  3 . 
     The positioning marker  7  may be provided, for example, by painting an outer surface of the stylet  6  with paint or putting a tape on the stylet  6 . In addition, the positioning marker may be provided by inserting a tubular member around the stylet  6 , thermally contracting the tubular member, and externally fitting the tubular member. In the case where the tubular member is mounted, a proximal end face of the positioning marker formed by a thickness of the tubular member becomes a reflecting surface of illumination light  154  of the endoscope  150 , and visibility is capable of being improved more than with the positioning marker of paint or tape. 
     When colors of the markers  7  are selected from colors that are complementary colors to a color of a surface of tissue T, this is preferred because a contrast with the tissue T that is a background within the field of view of the endoscope  150  is high, and visibility of the markers  7  is relatively improved. The colors of the markers  7  need only be visible via the imager  153  of the endoscope  150 , and may be selected within a range overlapping the color of the surface of the tissue in addition to the colors different from the color of the surface of the tissue T. 
     The middle marker  8  is a marker that indicates a position of the middle part  33  and is provided at a position corresponding to the middle part  33  on the stylet  6  in the direction of the longitudinal axis L. Therefore, the middle marker  8  and the three positioning markers  7   a,    7   b  and  7   c  are provided on the stylet  6  from the vicinity of the distal end in turn. Like the positioning marker  7 , the middle marker  8  is visible under observation of the endoscope. The middle marker  8  may also be the same color as the positioning marker  7 . However, the middle marker  8  may have a different color or shape from the positioning marker  7  in order to be easily distinguished from the positioning marker  7  during manipulation. In addition, the middle marker may be provided on a surface of the middle part  33  of the balloon  3 . 
     The middle marker  8  is visible until the middle part  33  enters a stenosis site or the like, and is not visible after the middle part  33  enters the stenosis site or the like. However, an operator is capable of easily seeing the relative positional relationship between the middle part of the balloon and a middle part of the stenosis with the help of a position, a moving direction, and an amount of movement of the positioning marker  7  within the field of view of the endoscope according to an interval distance between the middle marker  8  and the positioning marker  7 . Even in this case, the positioning marker  7  at the most distal end is the first marker  7   a.    
     An operation of the treatment tool  1  for an endoscope configured in this way when the treatment tool  1  is used will be described. 
     As illustrated in  FIG. 4 , the treatment tool  1  for an endoscope is introduced into the body of a patient via a channel provided in an insertion part of the endoscope. As illustrated in  FIG. 4 , a user connects an inflator  200  to the connector  4 , and inserts the treatment tool  1  for an endoscope into an insertion part  151  from a forceps opening  152  of the endoscope  150 . Afterward, the endoscope  150  is inserted into the body of the patient P. The distal end of the endoscope  150  is advanced to the vicinity of a site on which an expansion procedure is performed, for example, a predetermined site of the esophagus. The connection between the treatment tool  1  for an endoscope and the inflator  200  or the insertion of the treatment tool  1  for an endoscope into the endoscope  150  may be performed after the endoscope  150  is inserted into the body of the patient P. 
     The user causes the treatment tool  1  for an endoscope to protrude from the endoscope  150  while observing the target site on which the expansion procedure is performed by the endoscope  150  while using a display unit  155  of the endoscope  150 , and inserts the distal end tip  5  into the target site. As illustrated in  FIG. 7 , a versatile imager  153  disposed close to the proximal portion of the balloon  3  images an inlet of the stenosis site or the like located far from the field of view. In this case, a distal end of the endoscope insertion part is essentially located in a direction that intersects the longitudinal axis L, and the imager  153  faces the stylet  6 . 
     The user further advances the treatment tool  1  for an endoscope until the middle marker  8  enters the target site and is not seen by the display unit  155  of the endoscope  150 . In this case, the user checks the three markers  7   a,    7   b  and  7   c  through the display unit  155 , and can see the amount of advancing/retracting of the balloon  3 . 
       FIG. 6  is a view illustrating an image example of the imager  153  of the endoscope  150  when the treatment tool  1  for an endoscope is used. As illustrated in  FIGS. 5 and 6 , a farthest visible area which viewed by an image through the imager  153  is an opening end positioned at a proximal side of the target site St of the stenosis site or the like, and an area more distal than the stenosis site or the like is not visible. For this reason, after the middle marker  8  enters the target site St, the middle marker  8  is not visible. However, since the first marker  7   a  is provided at more proximally in a longitudinal positon than the boundary between the middle part  33  and the proximal end-side region  32  of the balloon  3 , the user is capable of recognizing the position of the middle part  33  relative to the target site St by means of a position of the first marker  7   a.    
     As illustrated in  FIG. 7 , the imager  153  picks up the image of the inlet of the stenosis site or the like located far in the field of view from the vicinity of the proximal portion of the balloon  3 . For this reason, as illustrated in  FIG. 6 , it is difficult to see a distance around the inlet of the stenosis site or the like in a two-dimensional image of the imager  153 . However, because the three markers  7   a,    7   b  and  7   c  are intermittently provided, the amount and the distance of advancing/retracting of the balloon  3  is easily seen. 
     For example, in the case where the distance of the field of view of the endoscope  150  is about 30 mm, when the first marker  7   a  is separated from the imager  153  of the endoscope  150 , which is disposed close to the proximal end of the balloon  3 , to the distal side by 55 mm or more at the imager  153  of the endoscope  150 , it is difficult to see the position of the first marker  7   a  through the image obtained by the imager  153 . In this way, even when the position of the first marker  7   a  in a depth direction is difficult to see, the position of the middle part  33  is easily adjusted in the direction of the longitudinal axis L by the positions of the second and third markers  7   b  and  7   c  that are intermittently disposed at more proximal than the first marker  7   a.    
     Due to the above manipulation, the treatment tool  1  for an endoscope is held such that the distal end-side region  31  of the balloon  3  is located at more distal than the target site and the proximal end-side region  32  of the balloon  3  is located at more proximal than the target site (the positioning step). 
     Next, the user operates the inflator  200  to supply a fluid such as water or air to the balloon  3 . The balloon  3  is inflated while raising an internal pressure due to the supplied fluid, but the middle part  33  has a larger amount of residual strain than the distal end-side region  31  and the proximal end-side region  32 . Thus, a great force is required such that the wings  36  are inflated by straightening the folding lines  35  and the valleys  37  in a linear shape (the first inflating step). 
     In the state in which the internal pressure of the balloon  3  reaches a predetermined first internal pressure value P1 due to the supply of the fluid, the distal end-side region  31  and the proximal end-side region  32  undergo faster progress of unfolding than the middle part  33 . Even in a semi-inflated state in which the unfolding of the balloon  3  is in progress, the user can adjust a position of the middle of the balloon  3  while checking the positions of the markers  7 . Since the progress of the unfolding is slow, the middle part  33  is smaller in diameter than the distal end-side region  31  and the proximal end-side region  32  (the distal end-side region  31  and the proximal end-side region  32  getting larger in diameter than the middle part  33 ), and the balloon  3  is deformed to a dumbbell shape as a whole as illustrated in  FIG. 8 . Therefore, even if the balloon  3  slips due to mucus or the like of a surface of a lumen organ, the distal end-side region  31  and the proximal end-side region  32  serve as anchors, and are inhibited from moving, and a situation, for example, in which the balloon  3  is removed from the target site St is adequately prevented. 
     When the internal pressure of the balloon  3  reaches a second internal pressure value P2 that is higher than the first internal pressure value P1, all of the distal end-side region  31 , the proximal end-side region  32 , and the middle part  33  are unfolded, and the balloon  3  is nearly returned to the approximately cylindrical shape from before the folding process was performed as illustrated in  FIG. 9  (the second inflating step, the inflated shape). In this case, the distal end-side region  31  and the proximal end-side region  32  have the same dimension or substantially the same dimension in a radial direction as the middle part  33 . The middle part  33  is inflated to substantially the same diameter as the distal end-side region  31  and the proximal end-side region  32 , and thereby the target site St is capable of being sufficiently dilated. 
     The film of which the balloon  3  is formed is hardly stretched at the second internal pressure value P2. However, since the balloon  3  is a semi-compliant type, if the internal pressure is increased above a third internal pressure value P3 higher than the second internal pressure value as needed, the entire balloon  3  is further inflated while stretching the material, and a great expansion force is also capable of being applied by the target site St. 
     In more detail, since the material of which the balloon  3  is formed is hardly stretched until the internal pressure of the balloon  3  reaches the second internal pressure value P2, the balloon  3  is inflated depending exclusively on the progress of the unfolding, and outer diameters of the distal end-side region  31 , the proximal end-side region  32 , and the middle part  33  increase. 
     Since the folding is nearly released after the internal pressure of the balloon  3  reaches the second internal pressure value P2, an increase in outer diameter hardly occurs even if the internal pressure rises. When the internal pressure of the balloon  3  further rises and is increased above the third internal pressure value P3, although the film material of which the balloon  3  is formed starts stretching but the expansion caused by the progress of the unfolding hardly occurs. Therefore, the outer diameters of the distal end-side region  31 , the proximal end-side region  32 , and the middle part  33  increase depending exclusively on the stretching of the film material. The balloon  3  is formed in an inflated shape, and thereby the stenosis site is spread. 
     As described above, according to the treatment tool  1  for an endoscope of the present embodiment, since the positioning marker  7  is provided on the stylet  6  at the position corresponding to the proximal end-side region  32  of the balloon  3 , the position of the middle part  33  of the balloon  3  is capable of being easily seen even after the middle part  33  of the balloon  3  enters the stenosis site or the like. It is possible to prevent the balloon  3  from being inflated in the state in which the balloon  3  is excessively advanced to the distal side and the middle part  33  is disposed at more distal than the stenosis site or the like. Therefore, the middle part  33  is capable of being disposed at a suitable position of the stenosis site or the like by smooth manipulation. As a result, the balloon  3  is possible to hardly slip on the stenosis site or the like during the inflation of the balloon  3 . 
     According to the treatment tool  1  for an endoscope of the present embodiment, since the position of the balloon  3  is capable of being seen by using the positioning marker  7  that is visible via the imager  153  of the endoscope  150 , the treatment tool is excellent in terms of user convenience. 
     According to the treatment tool  1  for an endoscope of the present embodiment, the balloon is capable of being disposed at a more suitable position with respect to the target site, and an effect of preventing position displacement is capable of being positively exhibited. 
     The treatment tool  1  for an endoscope according to the present embodiment is particularly effective, for example, in the case where the length of the stenosis site is long. 
     Since the positioning marker  7  is visible through the film in the initial shape in which the balloon  3  is folded, there is no need to inflate the balloon  3  prior to performing the positioning, and positioning manipulation is capable of being smoothly performed. 
     According to the treatment tool  1  for an endoscope of the present embodiment, the amount of residual strain of the middle part  33  in the balloon  3  is set to be greater than those of the distal end-side region  31  and the proximal end-side region  32  that are disposed to sandwich the middle part  33 . As a result, the balloon  3  is formed in the dumbbell shape in which the distal end-side region  31  and the proximal end-side region  32  are inflated to have the outer diameters larger than that of the middle part  33  at the first internal pressure value P1, and the balloon is capable of being appropriately prevented from being removed or displaced from the target site St in a process of treatment at the target site St. 
     The middle part  33  is capable of being inflated to substantially the same diameter as the distal end-side region  31  and the proximal end-side region  32  at the second internal pressure value P2, and the target site St is capable of being sufficiently dilated. 
     As a result, the prevention of position displacement against the target site and the sufficient expansion of the target site are compatible, and expansion treatment can be suitably performed on the target site of the stenosis site or the like. 
     In the present embodiment, no marker is provided at the position corresponding to the distal end-side region  31  in the direction of the longitudinal axis L of the stylet  6 . For the purpose of disposing the middle part  33  at the stenosis site or the like, since the more distal end side than the middle part  33  is not visible by the imager  153  after the middle part  33  enters the stenosis site or the like, no marker is required. No marker is provided in the distal end-side region  31  in order to prevent confusion with the positioning marker  7  by providing an unnecessary marker. 
     In the present embodiment, the first internal pressure value and the second internal pressure value may be set to desired values by appropriately setting the amounts of residual strain of the distal end-side region  31 , the proximal end-side region  32 , and the middle part  33 . The second internal pressure value need only be set on the basis of a pressure that is desired to be applied to the target site, and the second internal pressure may be set to, for example, three atmospheres (atm.). The first internal pressure value is preferably set to be sufficiently lower than the second internal pressure value such that the effect of preventing position displacement is exerted early, and the first internal pressure may be set to, for example, 0.5 atm. 
     In the above example, an example in which the amounts of residual strain of the distal end-side region  31  and the proximal end-side region  32  are made different from that of the proximal end-side region  32  by making the outer diameters of the distal end-side region  31  and the proximal end-side region  32  in the initial shape to be different from that of the middle part  33  has been described, but a method of making both of the amounts of residual strain different from each other is not limited thereto. For example, it is possible that the amount of residual strain of the middle part  33  is also relatively increased while making the outer diameters of the distal end-side region  31 , the proximal end-side region  32 , and the middle part  33  in the initial shape the same or substantially the same. 
     Although an embodiment of the present invention has been described in detail with reference to the drawings, the specific constitution is not limited to this embodiment, and also includes a change in design or the like without departing from the gist of the present invention. 
     The components represented in the embodiment and modification can be configured in appropriate combinations. 
     For example, in the present embodiment, an example in which the markers  7  are provided on the stylet  6  has been described, but the markers may be provided on the film of the balloon  3 . For example, the markers may be provided in the proximal end-side region  32  of the balloon  3  of the initial shape by painting. In this case, since the markers are provided only around the wings  36  of the balloon  3 , and are separated in the state in which the balloon is inflated, the field of view is hardly obstructed by the markers when the tissue T is observed through the balloon  3 . 
     The lengths of the markers  7   a,    7   b  and  7   c  in the direction of the longitudinal axis L may be the same in all, or be gradually changed. 
     Each of the markers  7   a,    7   b  and  7   c  may be formed on the outer circumferential surface of the stylet  6  in an X shape, and in this case, movement thereof in a direction in which the balloon  3  rotates around the longitudinal axis L is visible. 
     In the present embodiment, an example in which the stylet  6  is inserted through the balloon  3  has been described, but a sheath having a guide wire lumen and a fluid supply lumen instead of the stylet may be configured to be inserted through the balloon. In this case, a guide wire inserted through the guide wire lumen is made to protrude to further distal side of the balloon, and thereby the balloon is capable of being used for a guide for breaking through either a site where strong stenosis occurs or an obstruction site. 
     In the present embodiment, an example in which the three markers  7  are provided has been described, but two or more markers  7  may be intermittently provided. However, when there are too many markers, the pitch for the markers is essentially made fine. When the pitch for the markers is made excessively fine in the case where the marker is observed at a shallow angle with respect to the balloon  3 , it is difficult to find out the advance/retract and the position of the marker. Thus, for example, a sufficient number to dispose the markers having a length of 2 mm to 4 mm in the direction of the longitudinal axis L at a pitch of 10 mm need only be provided according to the length of the proximal end-side region. 
     In the aforementioned embodiment, an example in which the balloon is the semi-compliant type has been described, but a so-called non-compliant type balloon in which the material of which the balloon is formed is not substantially stretched even if the internal pressure is greater than or equal to the second internal pressure value may be used. 
     In the present embodiment, an example in which the shape of the middle part  33  is the same as the initial shape has been described. However, this is only one example, and a case where the middle part starts expansion is also possible. 
     Although an embodiment of the present invention has been described in detail with reference to the drawings, the specific constitution is not limited to this embodiment, and also includes a change in design or the like without departing from the gist of the present invention. 
     The components represented in the embodiment and modification can be configured in appropriate combinations.