Patent Publication Number: US-2022225862-A1

Title: Endoscope and overtube

Description:
TECHNICAL FIELD 
     The present invention relates to an endoscope and an overtube. 
     BACKGROUND ART 
     An endoscope is used to observe the state of the digestive tract and the like inside the body. Observation of an extra-fine tract such as a lung requires an extra-fine endoscope that can be inserted into the extra-fine tract. In order to guide such an extra-fine endoscope to a part to be observed inside the body, an endoscope with a larger diameter (for example, an ordinary endoscope) may be used as a base endoscope together with the extra-fine endoscope. 
     The base endoscope is provided with a channel that allows passage of the extra-fine endoscope. The extra-fine endoscope having the function of an image sensor of the base endoscope is disposed inside the channel and inserted into a body lumen together with the base endoscope. After reaching an extra-fine tract such as a lung, the extra-fine endoscope is moved forward inside the channel and is protruded out of the base endoscope. Then, the extra-fine endoscope is further inserted into the periphery of the extra-fine tract. Extra-fine tracts are observed in this manner. 
     Patent Literature 1 discloses an example of an extra-fine endoscope system including these two endoscopes. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP 2009-530051 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, a base endoscope in an extra-fine endoscope system in the related art is designed to be reused, and using the base endoscope as a single-use (disposable) device is costly. 
     More specifically, despite the fact that the base endoscope is used only for guiding the extra-fine endoscope to a lesion area, one that has the function of an ordinary endoscope is used. Therefore, part of the function is wasted and the base endoscope becomes relatively expensive. 
     In addition, since configurations of the base endoscope and the extra-fine endoscope partially overlap each other (for example, image sensor, image processor, and light source), there is also a problem that the entire system increases in size. 
     Furthermore, reuse of the base endoscope as in the related art requires cleaning and sterilization after each use and requires labor and cost. 
     The present invention has been made to solve such problems. An object of the present invention is to provide an endoscope capable of guiding an extra-fine endoscope at low cost using an overtube. 
     Solution to Problem 
     An endoscope system according to the present invention includes: an endoscope; and an overtube, 
     in which the overtube includes an endoscope channel that allows passage of the endoscope, the overtube being bendable according to an operation, and 
     the endoscope includes a light irradiation unit and an imaging unit. 
     This specification is based on and claims priority pursuant to Japanese Patent Application No. 2019-178345, the entire disclosure of which is hereby incorporated by reference herein. 
     Advantageous Effects of Invention 
     An endoscope and an overtube according to an embodiment of the present invention makes it possible to inexpensively guide an extra-fine endoscope using the overtube. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram illustrating a partial configuration of an endoscope system according to a first embodiment. 
         FIG. 2  specifically illustrates a configuration of an insertion portion in  FIG. 1 . 
         FIG. 3  more specifically illustrates the configuration of the insertion portion in  FIG. 1 . 
         FIG. 4  illustrates a specific example of a configuration of an operation unit in  FIG. 1 . 
         FIG. 5  is a cross-sectional view of a connection taken along line V-V in  FIG. 4 . 
         FIG. 6  illustrates another example of a connection structure between an overtube operation unit and an endoscope operation unit in  FIG. 4 . 
         FIG. 7  is an enlarged view of a fixation between the overtube operation unit and the endoscope operation unit in  FIG. 6 . 
         FIG. 8  illustrates a state where the overtube operation unit and the endoscope operation unit in  FIG. 6  are fixed to each other. 
         FIG. 9  illustrates still another example of the connection structure between the overtube operation unit and the endoscope operation unit in  FIG. 4 . 
         FIG. 10  illustrates a modification of a light irradiation unit in an overtube. 
         FIG. 11  illustrates a modification where the light irradiation unit of the overtube is omitted. 
         FIG. 12  illustrates another modification of the light irradiation unit in the overtube. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. 
     First Embodiment 
       FIG. 1  is a block diagram illustrating a configuration of an endoscope system  1  used in this embodiment. The endoscope system  1  may be what is called an electronic endoscope. As illustrated in  FIG. 1 , the endoscope system  1  is, for example, a dedicated system for medical use and includes an endoscope unit  10  and a processor  20  (endoscope processor). 
     As illustrated in  FIG. 1 , the endoscope unit  10  includes an insertion portion  11  and an operation unit  12 . Note that  FIG. 1  conceptually illustrates the outline of functions of the operation unit  12  and does not necessarily accord with the actual configuration. A specific example of the configuration of the operation unit  12  will be described later with reference to  FIGS. 6 to 9 . 
     A user of the endoscope system  1  operates the operation unit  12  to control a movement of the insertion portion  11 . For example, the insertion portion  11  is bent or curved according to an operation of the operation unit  12 . Such a bending mechanism is a known mechanism incorporated in a typical electronic scope. For example, a knob included in the operation unit  12  is rotated, and in conjunction with the rotation, an operation wire is pulled, thereby bending a bendable portion of the insertion portion  11 . 
     In the insertion portion  11 , a part including the distal end can be inserted into any body lumen in a living organism. For example, the part is inserted into a bronchus, a biliary tract, a pancreas, a hepatic duct region, or a urinary organ region. 
     The processor  20  integrally includes a signal processing device that processes an image signal from the endoscope unit  10  and a light source device that applies light via the endoscope unit  10  to a body lumen which has no access to natural light. In another embodiment, the signal processing device and the light source device may be separated. 
     The proximal end of the endoscope unit  10  is provided with a connector unit  13 , and the processor  20  is provided with a connector unit  21 . The connector unit  13  and the connector unit  21  each have a coupling structure corresponding to each other. Coupling of these structures electrically and optically connects the endoscope unit  10  and the processor  20 . 
     The processor  20  functions as a controller that controls the entire endoscope system  1  and includes, for example, a computer provided with an arithmetic unit and a storage unit. Other functions and configurations of the endoscope unit  10  and the processor  20  (for example, the function of acquiring an image inside a body lumen or the like) are appropriately designed by those skilled in the art based on known techniques. For example, the processor  20  performs various calculations based on specific information of the endoscope unit  10  and generates a control signal. Furthermore, the processor  20  uses the generated control signal to control operations and operation timings of various circuits inside the processor  20 , thereby causing the endoscope unit  10  to move appropriately. 
     Note that the endoscope system  1  does not necessarily include the processor  20 . Assuming that the endoscope unit  10  is connected to another appropriate processor, the endoscope unit  10  may be provided as an independent device. 
       FIG. 2  specifically illustrates a configuration of the insertion portion  11 .  FIG. 2( a )  illustrates a structure of the insertion portion  11 , and  FIG. 2( b )  illustrates a state where the insertion portion  11  is bent. The endoscope system  1  includes an overtube  30  and an endoscope  40 . The overtube  30  covers the outer periphery of the endoscope  40 . The overtube  30  includes an endoscope channel  31 . The endoscope channel  31  is, for example, disposed inside the overtube  30  as a cylindrical tubular space extending in the longitudinal direction (axial direction) of the overtube  30 . The endoscope channel  31  may be what is called an endoscope tube and can be used as a channel that allows passage of the endoscope  40 . 
     The overtube  30  and the endoscope  40  may be designed to have any size (such as diameter). However, using an endoscope with a smaller diameter (such as an extra-fine endoscope) as the endoscope  40  reduces the diameter of the entire insertion portion  11 . For example, the overtube  30  has a diameter of 3 mm to 5 mm, and the endoscope  40  has a diameter of 1 mm. 
     The overtube  30  is bendable as illustrated in  FIG. 2( b )  according to a user&#39;s operation. The user operates the overtube  30 , for example, by the operation unit  12 . Although a specific configuration for bending the overtube  30  will not be described, those skilled in the art, for example, can determine an appropriate configuration based on known techniques using an operation wire or the like. Note that the overtube  30  and the endoscope  40  may include a non-bendable rigid portion. In this case, a bendable portion other than the rigid portion is bent. 
     As illustrated in  FIG. 2( b ) , since the endoscope  40  is disposed inside the endoscope channel  31 , the endoscope  40  is bent when the overtube  30  bends. In other words, the overtube  30  is actively bendable while the endoscope  40  is passively bendable. 
     As a modification, for example, in a case where the endoscope  40  is allowed to increase in diameter, the endoscope  40  is bent or curved according to an operation of the operation unit  12 . In this case, the overtube  30  may be passively bent or curved. The endoscope  40  may be bent in one direction (for example, in the horizontal direction or the vertical direction) or may be bent in a plurality of directions (for example, the vertical direction and the horizontal direction similarly to the overtube  30 ). 
       FIG. 3  more specifically illustrates the configuration of the insertion portion  11 .  FIG. 3( a )  is an end view of the distal tip (distal end) of the insertion portion  11 , and  FIG. 3( b )  is a partial cross-sectional view taken along line b-b of  FIG. 3( a ) . 
     The overtube  30  may include a forceps channel  32 . The forceps channel  32  may be what is called a forceps tube and can be used as a channel that allows passage of a forceps (including treatment tools and other required devices). Furthermore, the forceps channel  32  may be used to allow passage of an endoscope different from the endoscope  40 . Still further, the forceps channel  32  can also be used for suction in order to remove minute obstacles or the like from the inside of a living organism. The forceps channel  32  is, for example, disposed inside the overtube  30  as a cylindrical tubular space extending in the longitudinal direction of the overtube  30 . 
     The overtube  30  may include an air/water supply channel  33 . The air/water supply channel  33  is used as a passage for carrying a fluid (for example, air or other gases, or water or other liquids). The air/water supply channel  33  is, for example, disposed inside the overtube  30  as a cylindrical tubular space extending in the longitudinal direction of the overtube  30 . The fluid is carried toward the distal end through the air/water supply channel  33 . 
     The fluid carried by the air/water supply channel  33  may be used to clean the distal surface of the endoscope  40 . For this purpose, the distal tip of the air/water supply channel  33  may be provided with a nozzle, and the nozzle may be configured to eject a fluid toward the endoscope  40 . 
     The overtube  30  may include a water jet channel  34 . The water jet channel  34  is used as a passage for carrying a liquid (water or other liquids). The water jet channel  34  is, for example, disposed inside the overtube  30  as a cylindrical tubular space extending in the longitudinal direction of the overtube  30 . The liquid is carried through this water jet channel  34  towards the distal end. 
     The liquid carried by the water jet channel  34  may be used to clean a living organism. For example, minute obstacles or the like inside a body lumen can be cleaned away and removed by the liquid. 
     The overtube  30  may include a light irradiation unit  35 . In this embodiment, the light irradiation unit  35  includes a light emitting diode (LED). The light irradiation unit  35  provides illumination light necessary for capturing an image by the endoscope unit  10 . The light irradiation unit  35  is placed at or near the distal tip of the overtube  30 . 
     The endoscope  40  is disposed inside the endoscope channel  31  of the overtube  30 . The endoscope  40  includes an imaging unit  41 . The imaging unit  41  may be configured as an imaging unit of a known endoscope, but an example of the configuration will be described with reference to  FIG. 3( b ) . 
     The imaging unit  41  includes a transparent cover  411 , an aperture  412 , an objective optical system including a lens  413  (for example, a convex lens) and one or more spacers  414 , a cover glass  415 , and an image sensor  416  (for example, a CMOS sensor). These components are arranged in a hollow cylindrical rod  417 . These structures including the rod  417  are disposed inside a hollow cylindrical outer tube  418 . 
     The endoscope  40  includes a light irradiation unit  42 . The light irradiation unit  42  is placed at or near the distal tip of the endoscope  40 . The light irradiation unit  42  is, for example, a light guide and includes an optical fiber in this embodiment. In an example illustrated in  FIG. 3 , the optical fiber is supported by a light guide holder fixed to the distal tip (distal end) of the endoscope  40 . In the light irradiation unit  42  illustrated in  FIG. 3 , the optical fiber and the light guide holder are not distinguished from each other. 
     Although not illustrated in  FIG. 3 , the endoscope  40  may include wires as appropriate. For example, along the outer circumference of the rod  417 , the optical fiber extends into the inside of the endoscope channel  31  or the endoscope  40  and provides light from the light source inside the processor  20  to the distal tip. Furthermore, for example, a sensor cable for transmitting a signal may be connected to the image sensor  416 . The sensor cable may extend into the inside of the endoscope channel  31  or the endoscope  40  and transmit a signal that represents an image to the processor  20 . 
     In this embodiment, the overtube  30  does not include an imaging unit. Accordingly, the overtube  30  can be produced relatively inexpensively and produced to have a configuration preferable as a single-use device. 
     The overtube  30  protects and guides the endoscope  40  until the endoscope unit  10  reaches an extra-fine tract inside the body, providing the function that the endoscope  40  does not have. In other words, the overtube  30  provides a function obtained by subtracting the function of the endoscope  40  according to this embodiment from the function of an endoscope in the related art. Therefore, the endoscope  40  does not necessarily have all the functions that an endoscope in the related art standardly has. 
     The endoscope system  1  includes an endoscope fixation  50  for releasably fixing the overtube  30  and the endoscope  40 . In this embodiment, the endoscope  40  is disposed inside the overtube  30 , and the overtube  30  prevents the movement of the endoscope  40  in the radial direction. Accordingly, the endoscope fixation  50  may be one that fixes the overtube  30  and the endoscope  40  in the longitudinal direction. 
     The endoscope fixation  50  is placed, for example, within a range of 3 mm to 15 mm from the distal tip of the endoscope unit  10 . In a case where the non-bendable rigid portion is disposed close to the distal tip of the endoscope unit  10 , the endoscope fixation  50  may be disposed in the rigid portion. However, the endoscope fixation  50  is not limited to the position. 
     In this embodiment, the endoscope fixation  50  includes a permanent magnet. The endoscope fixation  50  includes an N-pole magnet  51  fixed to the overtube  30  and an S-pole magnet  52  fixed to the endoscope  40 . At least one N-pole magnet  51  and at least one S-pole magnet  52  are disposed to face each other, thereby fixing the overtube  30  and the endoscope  40  to each other by a magnetic attractive force. 
     Relative positions of the overtube  30  and the endoscope fixation  50  are fixed by the endoscope fixation  50 . Particularly, the positional relation between the distal surface of the overtube  30  and the distal surface of the endoscope fixation  50  is fixed. When the endoscope fixation  50  is configured to align the longitudinal positions of the distal surfaces (for example, to make the distal surfaces coplanar), it is possible to provide the functions of the overtube  30  and the endoscope  40  in a complementary manner. For example, it is possible to operate a treatment tool via the overtube  30  or supply air or water while capturing and checking an image by the endoscope  40 . Accordingly, the insertion portion  11  including the overtube  30  and the endoscope  40  can be operated similarly to an insertion portion of an endoscope in the related art, which makes it possible to provide functions similar to endoscopes in the related art. 
     When a force that exceeds the magnetic attractive force and separates the N-pole magnet  51  and the S-pole magnet  52  acts between the N-pole magnet  51  and the S-pole magnet  52 , the correlative fixing between the overtube  30  and the endoscope  40  is unfixed. For example, when a force exceeding a predetermined threshold acts to push the endoscope  40  toward the distal tip, the endoscope  40  is disengaged from the overtube  30  and moves toward the distal tip. Such a force may be generated according to a specific operation of the operation unit  12 . 
     In this embodiment, after disengagement of the overtube  30  and the endoscope  40 , it is possible to fix the overtube  30  and the endoscope  40  again. In other words, pulling back the endoscope  40  to the fixed position causes a magnetic attractive force of the N-pole magnet  51  and the S-pole magnet  52 , thereby fixing the overtube  30  and the endoscope  40  again. 
       FIG. 4  illustrates a specific example of the configuration of the operation unit  12 . The operation unit  12  includes an overtube operation unit  60  and an endoscope operation unit  70 . The overtube operation unit  60  is for operating the overtube  30 , and the endoscope operation unit  70  is for operating the endoscope  40 . The overtube operation unit  60  and the endoscope operation unit  70  are connected to each other in a connection  80 . The connection  80  may be a part of the overtube operation unit  60 , a part of the endoscope operation unit  70 , or a combination of both parts. 
     The overtube  30  and the endoscope  40  are connected in the overtube operation unit  60 , the endoscope operation unit  70 , or the connection  80 . For example, inside the overtube operation unit  60 , the endoscope operation unit  70 , or the connection  80 , the endoscope channel  31  of the overtube  30  opens toward the outer periphery of the overtube  30  to form an insertion port for allowing insertion of the endoscope  40 . The endoscope  40  is integrated with the overtube  30  by being inserted into the insertion port. Accordingly, the endoscope  40  can be inserted into the body. 
     The overtube operation unit  60  includes an operational tool for operating the overtube  30 . Although a specific structure of the operational tool is not particularly described in relation to each part illustrated in  FIG. 4 , for example, the overtube operation unit  60  includes a knob for bending the overtube  30  vertically and a knob for bending the overtube  30  horizontally. In addition, the overtube operation unit  60  may include, for example, an air/water supply button for supplying a fluid through the air/water supply channel  33 , a water jet button for supplying a liquid through the water jet channel  34 , and a suction button for suctioning through the forceps channel  32 . 
     Although not particularly illustrated, the operation unit  12  may include an operation panel for inputting information or instructions. The operation panel may include a hardware key, a touch panel GUI, or a combination of a hardware key and a touch panel GUI. 
     The overtube operation unit  60  also includes a forceps channel inlet  62 . The forceps channel inlet  62  is included in the proximal end of the forceps channel  32  and is configured to allow insertion of treatment tools, necessary devices, and the like. 
     The endoscope operation unit  70  includes an operational tool for operating the endoscope  40 . Although a specific structure of the operational tool is not particularly described in relation to each part illustrated in  FIG. 4 , for example, the endoscope operation unit  70  includes an imaging button for controlling imaging by the imaging unit  41  and a light control button for controlling light irradiation by the light irradiation unit  42 . Furthermore, the endoscope operation unit  70  may include a disengagement button for unfixing the fixing by the endoscope fixation  50 . Still further, in a case where the endoscope  40  has the bending function, the endoscope operation unit  70  may include, for example, a knob for bending the endoscope  40  vertically and a knob for bending the endoscope  40  horizontally. 
     Note that  FIG. 4  mainly illustrates the function of the operation unit  12  and does not necessarily accurately represent the actual shape. For example, connection angles of the forceps channel inlet  62  and the endoscope operation unit  70  relative to the overtube operation unit  60  can be appropriately designed depending on the strength, flexibility, and the like of the overtube  30  and the endoscope  40 . 
       FIG. 5  is a cross-sectional view of the connection  80  taken along line V-V in  FIG. 4 . In this example, the connection  80  is configured by combining a connecting member  61  of the overtube operation unit  60  and a connecting member  71  of the endoscope operation unit  70 . The overtube operation unit  60  and the endoscope operation unit  70  are connected by inserting and fitting the connecting member  71  into the connecting member  61 . 
     In this example, a flat portion  61   a  is formed on the inner periphery of the outer connecting member  61 , and a flat portion  71   a  is formed on the outer periphery of the inner connecting member  71 . As described above, in the connecting members  61  and  71 , at least a part of each structure is not cylindrical. Accordingly, while the connecting member  71  is fitted into the connecting member  61 , it is possible to prevent relative rotation. 
     Another example of the connection structure between the overtube operation unit  60  and the endoscope operation unit  70  will be described with reference to  FIGS. 6 to 8 .  FIG. 6  illustrates a state where the overtube operation unit  60  and the endoscope operation unit  70  are not fixed to each other.  FIG. 7  is an enlarged view of an operation unit fixation  90 .  FIG. 8  illustrates a state where the overtube operation unit  60  and the endoscope operation unit  70  are fixed to each other. 
     As illustrated in  FIG. 6 , the overtube operation unit  60  includes a fixing member  63 , and the endoscope operation unit  70  includes a fixing member  73 . The fixing member  63  is fixed to, for example, a cover tube  64  that covers the overtube  30 . The fixing member  73  is fixed to, for example, the endoscope operation unit  70 . 
     In this manner, when the fixing members  63  and  73  are not engaged with each other, the overtube operation unit  60  and the endoscope operation unit  70  are not fixed to each other. Within a range allowed by the overtube  30  and the endoscope  40 , it is possible to change relative positions and postures freely. 
     The fixing members  63  and  73  can be engaged as illustrated in  FIG. 7 . A recess  63   a  of the fixing member  63  and a protrusion  73   a  of the fixing member  73  are slid in the depth direction of  FIG. 7  (from this side of the paper to the other side) and engaged with each other. Accordingly, the fixing members  63  and  73  in  FIG. 7  are prevented from moving in a relative manner and are fixed.  FIG. 8  illustrates the overtube operation unit  60  and the endoscope operation unit  70  fixed in this manner. In order to unfix the fixing members  63  and  73 , the fixing members  63  and  73  may be slid and disengaged in the depth direction of  FIG. 7 . 
     According to the configuration as illustrated in  FIGS. 6 to 8 , since the endoscope operation unit  70  can be releasably fixed to the overtube operation unit  60 , the endoscope operation unit  70  can be appropriately held when the operation by the endoscope operation unit  70  is not necessary. For example, while the endoscope operation unit  70  is fixed to the overtube operation unit  60 , it is possible to operate the overtube operation unit  60  to insert the overtube  30  into a lesion area, and then, detach the endoscope operation unit  70  from the overtube operation unit  60 , and operate the endoscope operation unit  70  to control the endoscope  40 . 
     Still another example of the connection structure between the overtube operation unit  60  and the endoscope operation unit  70  will be described with reference to  FIG. 9  (note that the endoscope operation unit  70  is not illustrated in  FIG. 9 ). The overtube operation unit  60  includes a connection  81  for connecting the endoscope operation unit  70 . The connection  81  includes an adjuster  81   a . A length of the adjuster  81   a  is adjustable and is achieved by, for example, a screw structure. The adjuster  81   a  can be used to adjust an insertion length of the endoscope  40  with respect to the endoscope channel  31  of the overtube  30 . 
     Using such an adjuster  81   a  enables adjustment of the insertion length even when the endoscope unit  10  is inserted into the body. Accordingly, the distal tip of the overtube  30  and the distal tip of the endoscope  40  can be easily aligned at any time point. More specifically, for example, in a case where the distal tip of the overtube  30  and the distal tip of the endoscope unit  10  are misaligned after inserting or bending the endoscope  40 , it is possible to align these distal tips again by operating the adjuster  81   a  at that time. With the adjuster  81   a , note that the endoscope fixation  50  may be omitted. 
     In an example illustrated in  FIG. 9 , the adjuster  81   a  is disposed in the overtube operation unit  60 , but the adjuster  81   a  is not limited to the position, and the adjuster  81   a  can be placed at any position along the endoscope  40 . In the example of  FIG. 9 , an insertion length of the endoscope  40  with respect to the endoscope channel  31  changes along with the change in length of the adjuster  81   a . However, the adjuster  81   a  does not necessarily change in length. 
     As described above, the overtube  30  and the endoscope system  1  according to the first embodiment of the present invention enables configuration of the overtube  30  at a relatively low cost, thereby providing the overtube  30  as a single-use device. 
     In addition, providing the overtube  30  as a single-use device removes the need for cleaning and sterilization after each use, which saves labor and cost. Particularly, sterilization before shipping the overtube  30  removes the need for sterilization at the site of use. 
     In addition, since the overtube  30  includes the endoscope channel  31  and the forceps channel  32  separately, the endoscope  40  and another treatment tool or the like can be used simultaneously. 
     The first embodiment can be modified in the following manner. 
     The overtube  30  can be provided as an independent member without being combined with the endoscope  40 . In this case, the overtube  30  can be used together with an endoscope in the related art. 
     The light irradiation unit in the overtube  30  is not limited to an LED as the light irradiation unit  35  in  FIG. 3 . In a modification illustrated in  FIG. 10 , a light guide  351  is provided as the light irradiation unit. The light guide  351  is, for example, an optical fiber and emits light supplied from a separately provided light source (for example, the light source disposed inside the processor  20 ) at the distal tip of the overtube  30 . 
     In a modification illustrated in  FIG. 11 , the light irradiation unit of the overtube  30  is omitted. Even in this case, it is possible to capture an image using illumination light since the endoscope  40  includes the light irradiation unit  42 . 
     In a modification illustrated in  FIG. 12 , an annular light source  352  as the light irradiation unit of the overtube  30  is disposed along the outer periphery of the distal tip of the overtube  30 . An example of the light source  352  includes a surface emitting type light source, and a more specific example is an organic light emitting diode (OLED). 
     Other components of the overtube  30  can also be omitted depending on the intended use. For example, one or all of the forceps channel  32 , the air/water supply channel  33 , and the water jet channel  34  may be omitted. The overtube  30  does not necessarily have all the configurations or functions that an endoscope in the related art standardly has. 
     The light irradiation unit in the endoscope  40  is not limited to a light guide as the light irradiation unit  42  in  FIG. 3 . An LED or OLED may be used. 
     Furthermore, the endoscope  40  may include a channel having the function similar to that of the forceps channel  32 , the air/water supply channel  33 , or the water jet channel  34 . 
     The endoscope fixation  50  does not necessarily include a permanent magnet as illustrated in  FIG. 3 . It is possible to employ any known configuration capable of releasable fixing. For example, an electromagnet may be used. In this case, the overtube  30  and the endoscope  40  are fixed by applying a current to the electromagnet, and the overtube  30  and the endoscope  40  are unfixed by stopping the current. The current to the electromagnet may be controlled by the operation unit  12  or the processor  20 . 
     Alternatively, an engagement structure using a recess and a protrusion may be employed. In other words, a protrusion may be formed on one of the inner periphery of the overtube  30  and the outer periphery of the endoscope  40 , and a recess may be formed on the other, and these members may be engaged with each other to fix the overtube  30  and the endoscope  40 . In a case where the structure is designed such that the protrusion and the recess are disengaged when a force exceeding a predetermined threshold is applied in the longitudinal direction, it is possible to unfix the protrusion and the recess optionally. 
     In the first embodiment, the endoscope fixation  50  can be fixed again after disengagement. As a modification, a fixation may be designed not to be fixed again. 
     Note that the endoscope system  1  or the endoscope  40  is not limited to the configurations and functions described in this specification and may have the configurations and functions of known endoscopes. 
     The present disclosure includes the following specific elements. 
     [Specific Element 1] 
     An endoscope system including: an endoscope; and an overtube, 
     in which the overtube includes an endoscope channel that allows passage of the endoscope, the overtube being bendable according to an operation, and 
     the endoscope includes a light irradiation unit and an imaging unit. 
     [Specific Element 2] 
     The endoscope system of specific element 1, in which the overtube includes a forceps channel. 
     [Specific Element 3] 
     The endoscope system according to specific element 1 or 2, the endoscope system including an endoscope fixation configured to fix the overtube and the endoscope releasably. 
     [Specific Element 4] 
     The endoscope system according to any one of specific elements 1 to 3, in which the overtube includes a passage for carrying a fluid. 
     [Specific Element 5] 
     The endoscope system according to any one of specific elements 1 to 4, 
     the endoscope system including an endoscope operation unit for operating the endoscope, and 
     the endoscope system including an operation unit fixation for releasably fixing the overtube and the endoscope operation unit. 
     [Specific Element 6] 
     The endoscope system according to any one of specific elements 1 to 5, the endoscope system including an adjuster configured to adjust an insertion length of the endoscope with respect to the endoscope channel. 
     [Specific Element 7] 
     An overtube including an endoscope channel that allows passage of an endoscope, the overtube being bendable according to an operation. 
     REFERENCE SIGNS LIST 
     
         
           1  Endoscope system 
           10  Endoscope unit 
           11  Insertion portion 
           12  Operation unit 
           30  Overtube 
           31  Endoscope channel 
           32  Forceps channel 
           33  Air/water supply channel (passage) 
           34  Water jet channel (passage) 
           35  Light irradiation unit 
           40  Endoscope 
           41  Imaging unit 
           42  Light irradiation unit 
           50  Endoscope fixation 
           60  Overtube operation unit 
           70  Endoscope operation unit 
           81  Connection 
           81   a  Adjuster 
           90  Operation unit fixation 
       
    
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