Abstract:
A snare for an endoscope includes a flexible sheath, a control wire movable within the flexible sheath, and a snare loop connected to an end of the control wire, wherein when the control wire is axially advanced, the snare loop projects from the flexible sheath and expands into a loop shape, whereas when the control wire is axially retracted, the snare loop retracts into the flexible sheath and is folded into a closed shape. A resilient wire which forms the snare loop includes a hook portion protruding in a lateral direction of the snare loop. The resilient wire includes a biasing portion which biases the distal end of the resilient wire from a tip end to a base end of the hook portion to press the distal end of the resilient wire against an inner surface of the flexible sheath when the resilient wire is retracted.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an endoscopic high-frequency snare for mucosal resection, and the like, via a passage of electric current through the snare, which is used by being introduced into a body through a treatment tool insertion channel of an endoscope. 
   2. Description of the Related Art 
   A typical endoscopic high-frequency snare is provided with an insulating flexible sheath, a conductive control wire which is inserted into the flexible sheath to be freely movable therein along the axis of the flexible sheath, and a snare loop made of a resilient wire which is fixed to the distal end of the control wire. The snare loop moves in and out of the distal end of the flexible sheath when the control wire is operated to retract and advance in the flexible sheath, respectively. The snare loop expands by its resiliency when positioned outside the flexible sheath, and becomes narrow when retracted into the flexible sheath. This type of endoscopic high-frequency snare is disclosed in, e.g., Japanese Patent Application Laid-open No.2000-83963. 
   In a typical endoscopic surgical operation for removing mucosa with an endoscopic high-frequency snare, firstly a mark or marks for indicating the area of a target affected part which is to be removed are made on a surface of the mucosa on the outline of the target affected part, subsequently the surface of the mucosa is dissected annularly along the mark or marks, and thereafter the target affected part of the mucosa surrounded by the annular cut is excised. 
   Among these three procedures, any conventional endoscopic high-frequency snare alone can perform only the procedure of excising mucosa such as the aforementioned target affected part of the mucosa surrounded by the annular cut. Namely, in addition to an endoscopic high-frequency snare, it is necessary to prepare a special marking tool, and another tool for dissecting mucosa. Therefore, each treatment tools, i.e., the endoscopic high-frequency snare, the marking tool and the dissecting tool, must be interchanged with another treatment tool thereof in order to be used, which makes the endoscopic surgical operation troublesome and complicated, and raises the possibility of contaminated water being scattered each time such treatment tools are interchanged; moreover, the disinfecting operation for the treatment tools becomes troublesome. 
   To prevent this problem from occurring, if the resilient wire that forms the snare loop is provided at a distal end of the resilient wire with a hook portion, which is formed by bending a portion of the resilient wire in the vicinity of the distal end thereof so that the hook portion projects in a lateral direction of the snare loop, both the aforementioned marking and mucosa dissection procedures can be carried out with the hook portion before the aforementioned mucosa excision procedure with the snare loop. 
   However, if such a hook portion is formed simply by bending a portion of the resilient wire of the snare loop laterally in the vicinity of the distal end thereof, there is a possibility of the hook portion largely protruding in a lateral direction (radial direction) of the flexible sheath from the distal end of the flexible sheath to such an extend as to get caught by an inner peripheral surface of a channel (e.g., treatment tool insertion channel) of an endoscope, thus making it difficult for the endoscopic high-frequency snare to travel in the channel or damaging the snare loop, when the endoscopic high-frequency snare is inserted and withdrawn into and from the channel. 
   SUMMARY OF THE INVENTION 
   The present invention provides an endoscopic high-frequency snare, with which the marking procedure, the mucosa dissection procedure and the mucosa excision procedure can be easily performed successively without the use of any other treatment tool, and which can travel smoothly in a channel of an endoscope when a mucosa is removed trans-endoscopically with the endoscopic high-frequency snare. 
   According to an aspect of the present invention, a snare for an endoscope is provided, including a flexible sheath, a control wire axially movable within the flexible sheath; and a snare loop connected to a distal end of the control wire, wherein when the control wire is axially advanced, the snare loop projects from a distal end of the flexible sheath and expands into a loop shape due to resiliency of the snare loop, whereas when the control wire is axially retracted, the snare loop retracts into the distal end of the flexible sheath and is folded into a closed shape. A resilient wire which forms the snare loop includes a hook portion at a distal end of the resilient wire, the hook portion protruding in a lateral direction of the snare loop. The resilient wire includes a biasing portion which biases the distal end of the resilient wire in a direction from a tip end to a base end of the hook portion to press the distal end of the resilient wire against an inner peripheral surface of the flexible sheath in a state where the resilient wire is retracted into the distal end of the flexible sheath. 
   It is desirable for the hook portion to be formed by bending a portion of the resilient wire in a vicinity of the distal end thereof so that the hook portion protrudes in the lateral direction of the snare loop. 
   It is desirable for the biasing portion to be formed by bending a portion of the resilient wire in a vicinity of the distal end of the resilient wire so that the biasing portion is resiliently in pressing contact with an inner peripheral surface of the flexible sheath to bias the distal end of the resilient wire in the direction from the tip end to the base end of the hook portion in a state where the resilient wire is retracted into the distal end of the flexible sheath. 
   It is desirable for the biasing portion to be formed by forming the resilient wire in an arc shape as a whole so that the biasing portion is resiliently in pressing contact with an inner peripheral surface of the flexible sheath to bias the distal end of the resilient wire in the direction from the tip end to the base end of the hook portion in a state where the resilient wire is retracted into the distal end of the flexible sheath. 
   It is desirable for a length of the hook portion to be determined so that the tip end of the hook portion is positioned in a close vicinity of an outer edge of the flexible sheath in a state where the resilient wire is retracted into the distal end of the flexible sheath. 
   It is desirable for the flexible sheath and the control cable to be made of an insulating material and a conductive material, respectively. 
   It is desirable for the length of the hook portion to substantially correspond to an outside diameter of the flexible sheath minus a wall thickness of the flexible sheath. 
   It is desirable for the resilient wire to include two resilient wires extending between two mutually secured portions, wherein the hook portion and the biasing portion are formed on one and the other of the two resilient wires, respectively. 
   The hook portion can be formed by bending the portion of the resilient wire in a substantially L shape. 
   In another embodiment, a snare for an endoscope is provided, including a flexible sheath; a control wire axially movable within the flexible sheath; a snare loop made of at least one resilient wire and fixed to a distal end of the control wire, the snare loop expanding and becoming narrow when the control wire is advanced and retracted to make the snare loop project and retract from and into a distal end of the flexible sheath, respectively; a hook portion formed on the resilient wire at a distal end thereof; and a biasing portion, formed on the resilient wire between the hook portion and another end of the resilient wire which is connected to the distal end of the control wire, for biasing the distal end of the resilient wire in a direction from a tip end to a base end of the hook portion to press the distal end of the resilient wire against an inner peripheral surface of the flexible sheath in a state where the resilient wire is retracted into the distal end of the flexible sheath. 
   The present disclosure relates to subject matter contained in Japanese Patent Application No. 2003-411373 (filed on Dec. 10, 2003) which is expressly incorporated herein by reference in its entirety. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be discussed below in detail with reference to the accompanying drawings, in which: 
       FIG. 1  is a perspective view of a first embodiment of an endoscopic high-frequency snare according to the present invention, showing a state where a snare loop formed at the distal end of the endoscopic high-frequency snare expands by its resiliency when positioned outside a distal end of flexible sheath; 
       FIG. 2  is a longitudinal sectional view of the endoscopic high-frequency snare shown in  FIG. 1 , showing a state where the snare loop becomes narrow when withdrawn into the distal end of the flexible sheath; 
       FIG. 3  is a perspective view of a distal end of an insertion tube of an endoscope from which the distal end of the endoscopic high-frequency snare shown in  FIGS. 1 and 2  protrudes, and a target affected part of a mucosa, around which spot marks are made with the first embodiment of the endoscopic high-frequency snare; 
       FIG. 4  is a view similar to that of  FIG. 3 , showing a mucosa dissection procedure with the first embodiment of the endoscopic high-frequency snare; 
       FIG. 5  is a view similar to that of  FIG. 3 , showing another mucosa dissection procedure with the first embodiment of the endoscopic high-frequency snare; 
       FIG. 6  is a view similar to that of  FIG. 3 , showing a mucosa excision procedure with the first embodiment of the endoscopic high-frequency snare; and 
       FIG. 7  is a longitudinal sectional view of a second embodiment of the endoscopic high-frequency snare, showing a state where the snare loop becomes narrow when withdrawn into the distal end of the flexible sheath. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 and 2  show a distal end portion of a first embodiment of an endoscopic high-frequency snare according to the present invention.  FIG. 1  shows a state where a snare loop  3  formed at the distal end of the endoscopic high-frequency snare expands by its resiliency when positioned outside a distal end of a flexible sheath  1 , and  FIG. 2  shows a state where the snare loop  3  becomes narrow when withdrawn into the distal end of the flexible sheath  1 . 
   The first embodiment of the endoscopic high-frequency snare is provided with the aforementioned flexible sheath  1 , a control wire  2  and a snare loop  3 . In this particular embodiment of the endoscopic high-frequency snare, the flexible sheath  1  is formed from an insulating flexible tube such as a tetrafluoroethylene resin tube, while the control wire  2  is formed from an electrically conductive flexible wire such as a stranded stainless steel wire. 
   The snare loop  3  is formed by a pair of electrically conductive resilient wires  4  and  5 . The rear ends of the pair of resilient wires  4  and  5  are fixed to each other and joined to the distal end of the control wire  2  via a metal connection pipe  9 . The control wire  2  is axially movably inserted in the flexible sheath  1 . The control wire  2  is actuated to advance or retract as desired at a control portion (not shown) connected to the proximal end (not shown) of the flexible sheath  1 , so that the snare loop  3  moves in and out of the distal end of the flexible sheath  1  when the control wire  2  is operated to retract and advance axially, respectively, in the flexible sheath  1 . 
   When the snare loop  3  is positioned outside the flexible sheath  1  in a state where no external force is applied thereto, the snare loop  3  forms a curved loop by its resiliency as shown in  FIG. 1 . The snare loop  3  is deformed resiliently to become narrow when drawn into the flexible sheath  1  as shown in  FIG. 2 . 
   Since each of the pair of resilient wires  4  and  5  form the snare loop  3 , for example, a single or stranded stainless steel wire can be used. A high-frequency electric current can be supplied to the snare loop  3  through the control wire  2 . 
   Rear ends of the pair of resilient wires  4  and  5  are positioned side by side in the connection pipe  9 , while front ends of the pair of resilient wires  4  and  5  are positioned side by side and joined to each other by a known fixing method such as silver brazing, gold brazing or laser spot welding. 
   One of the pair of resilient wires  4  and  5 , specifically the resilient wire  4  in this particular embodiment, is provided at a distal end thereof with a hook portion  6  which is formed by bending a portion of the resilient wire  4  in the vicinity of the distal end thereof in a substantially L shape so that the hook portion  6  protrudes in a lateral direction of the snare loop  3  (upwards as viewed in  FIG. 1 ). The length of the hook portion  6  (shown by “e” in  FIG. 2 : a length from a bottom (side) surface of the resilient wire  4  to the upper end of the hook portion  6  as viewed in  FIG. 2 ) is set to a length substantially equal to an outside diameter D (shown in  FIG. 2 ) of the flexible sheath  1  minus a wall thickness t (shown in  FIG. 2 ) of the flexible sheath  1 , i.e., e≈D−t. 
   By determining the length of the hook portion  6  in this manner, the length of the hook portion  6  can be provided as long as possible so as to be easily engaged with a streak fiber tissue of a mucosa, or the like, to resect the same with a high-frequency current. 
   The other of the pair of resilient wires  4  and  5 , specifically the resilient wire  5  in this particular embodiment, is provided in the vicinity of the distal thereof with a biasing portion (bend portion)  7 , which is shaped to bias the joined distal ends of the pair of resilient wires  4  and  5  in a direction (shown by an arrow A in  FIG. 2 ) from the tip end to the base end (from the upper end to the lower end as viewed in  FIG. 2 ) of the hook portion  6  to press the joined distal ends of the pair of resilient wires  4  and  5  against an inner peripheral surface of the flexible sheath  1  when the pair of resilient wires  4  and  5  that form the snare loop  3  are positioned inside the flexible sheath  1 . 
   The biasing portion  7  is formed by bending a portion of the resilient wire  5 , in the vicinity of the distal end thereof, so as to protrude in a direction generally parallel to the protruding direction of the hook portion  6  as shown in  FIG. 2 , with the snare loop  3  retracted into the flexible sheath  1 . In the state shown in  FIG. 2 , the biasing portion  7  is resiliently in pressing contact with an inner peripheral surface of the flexible sheath  1  to bias the joined distal ends of the pair of resilient wires  4  and  5  in a lateral direction thereof (downwards as viewed in  FIG. 2 ), thereby pressing at least a portion of the resilient wire  4 , in the close vicinity of the base end (lower end as viewed in  FIG. 2 ) of the hook portion  6 , against an inner peripheral surface of the flexible sheath  1  that is opposite to the inner peripheral surface of the flexible sheath  1  to which the biasing portion  7  is in pressing contact with. 
   Due to such a structure, the tip of the hook portion  6  is positioned immediately in front of the distal end of the flexible sheath  1  in the close vicinity of an outer edge (upper edge as viewed in  FIG. 2 ) of the flexible sheath  1  in a state shown in  FIG. 2  where the pair of resilient wires  4  and  5  are retracted into the distal end of the flexible sheath  1 , and accordingly the hook portion  6  is not positioned to largely protrude in a lateral direction of the flexible sheath  1  from on outer edge thereof as shown by a two-dot chain line in  FIG. 2 . Consequently, there is little possibility of the hook portion  6  getting snagged on an inner peripheral surface of a channel (e.g., a treatment tool insertion channel) of an endoscope, so that the flexible sheath  1  can be made to pass through the channel smoothly. 
   As shown in  FIG. 3 , the first embodiment of the endoscopic high-frequency snare that has the above described arrangement is inserted into a treatment tool insertion channel  51  of an insertion tube of an endoscope  50  to make the distal end of the endoscopic high-frequency snare extend out of the distal end (open end) of the treatment tool insertion channel  51  to be capable of performing a marking procedure, mucosa dissection procedure and a mucosa excision procedure successively, while the distal end of the endoscopic high-frequency snare is seen through an objective window  52  located at the distal end of the insertion tube of the endoscope  50 . 
     FIG. 3  shows a state where a plurality of spot marks  101  are made on a surface of a mucosa around a target affected part  100  thereof with the use of the first embodiment of the endoscopic high-frequency snare. Each spot mark  101  is made as a burn mark by passing a high frequency current through the snare loop  3  for a short period of time with the tip of the hook portion  6  contacting a surface of the mucosa on the periphery of the target affected part  100 . 
     FIG. 4  shows a mucosa dissection procedure with the first embodiment of the endoscopic high-frequency snare, which is carried out after completion of the marking procedure shown in  FIG. 3 . The mucosa is dissected along the outline of the target affected part  100  by moving the hook portion  6  while penetrating into the mucosa and passing a high frequency current through the snare loop  3  in a manner so that the hook portion  6  traces the spot marks  101 . It is also possible for a side surface of the target affected part  100  be dissected easily with the first embodiment of the endoscopic high-frequency snare in a manner shown in  FIG. 5 . 
     FIG. 6  shows a mucosa excision procedure with the first embodiment of the endoscopic high-frequency snare, which is carried out lastly. The target affected part  100  can be excised easily by firstly surrounding the target affected part  100  (the mucosa of which on the outer edge of the target affected part  100  has been dissected) with the snare loop  3  and subsequently passing a high frequency current through the snare loop  3  while gradually narrowing the snare loop  3  by retracting the snare loop  3  into the flexible sheath  1 . 
   The present invention is not limited solely to the above described particular embodiment. Although the biasing portion  7  is formed on the resilient wire  5 , on which the hook portion  6  is not formed, in the above illustrated embodiment of the endoscopic high-frequency snare, the biasing portion  7  can be formed on the other resilient wire  4 , on which the hook portion  6  is formed, rather than on the resilient wire  5 . 
   Additionally, a biasing portion corresponding to the biasing portion  7  can be formed on the snare loop  3  by forming one or each of the pair of resilient wires  4  and  5  in an arc shape as a whole as shown in  FIG. 7 . In this case, the biasing portion corresponding to the biasing portion  7  only needs to be pressed against an inner peripheral surface of the flexible sheath to be deformed resiliently so that a small portion of the snare portion  3  in the close vicinity of the base end of the hook portion  6  is pressed against an inner peripheral surface of the flexible sheath  1  that is opposite to the inner peripheral surface of the flexible sheath  1  to which this biasing portion is in pressing contact with. 
   According to the present invention, firstly the marking procedure and the mucosa dissection procedure, and subsequently the mucosa excision procedure, can be carried out with the endoscopic high-frequency snare by virtue of the hook portion that is provided at a distal end of the resilient wire and protrudes in a lateral direction of the snare loop. Accordingly, the marking procedure, the mucosa dissection procedure and the mucosa excision procedure can be easily performed successively with a single treatment tool, i.e., the endoscopic high-frequency snare according to the present invention. Moreover, since the biasing portion, which biases the distal end of the resilient wire in a direction from the tip end to the base end of the hook portion (to press the distal end of the resilient wire against an inner peripheral surface of the flexible sheath in a state where the resilient wire is retracted into the distal end of the flexible sheath), is formed on the resilient wire, the endoscopic high-frequency snare can travel smoothly in a channel of an endoscope. 
   Obvious changes may be made in the specific embodiments of the present invention described herein, such  20  modifications being within the spirit and scope of the invention claimed. It is indicated that all matter contained herein is illustrative and does not limit the scope of the present invention.