Abstract:
One embodiment provides a balloon catheter which has an inner tube having a main lumen and an outer tube which forms an expansion lumen. A part of the inner tube is connected to the outer tube at a position closer to the proximal end than a balloon, a side hole is open at the connection section, and a weak section is provided to the inner tube a position closer to the distal end than the side hole. The weak section has lower rigidity than the remaining portion of the inner tube. When the balloon is expanded by fluid supplied to the expansion lumen, the weak section is pressed by the fluid pressure to thereby close the main lumen of the inner tube.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a balloon catheter through which, even in the case where a tubular organ branches into a main tube and a branch tube, a lesion part is in the branch tube, and the catheter cannot be introduced into the branch tube, for example, a medical solution or the like can be administered to the lesion part. 
       BACKGROUND ART 
       [0002]    Conventionally, a tube-like catheter is inserted into a tubular organ such as the blood vessel, the ureter, the bile duct, or the trachea, and a contrast agent or a medical solution such as an anticancer agent or a nutrient is injected through the catheter. In the case where a lesion part such as cancer cells is produced in the liver, for example, a tip end portion of a catheter is indwelled in the hepatic artery which is in front of the lesion part, and a medical solution such as an anticancer agent is administered. In a tubular organ such as the hepatic artery, however, it is usual that the organ has a thick main tube, and a thin branch tube which branches off the main tube, and a case sometimes occurs where a catheter cannot be introduced into the thin branch tube. 
         [0003]    In such a case, for example, a balloon catheter may be used which has: the tube-like body; an inflatable balloon which is placed on the outer circumference of a tip end portion of the body; and a side hole which is disposed on the side of the base end with respect to the place where the balloon is placed on the body. The balloon catheter is configured so that, by using a guide wire or the like, the tip end portion is placed in a portion of the main tube which is slightly beyond the portion where the branch tube branches off, the balloon is then inflated to close the main tube, a plug-like stopper is then inserted from the base end opening of the body to close the tip end opening of the body, a medical solution is injected from the base end side of the body in this state, to flow out from the side hole, and the medical solution is administered to the lesion part produced in the branch tube. In the case of such a balloon catheter, however, the plug-like stopper must be inserted into the body as described above, thereby closing the tip end opening of the body. Therefore, the work is cumbersome and troublesome, the surgical time is prolonged, and the burden on the patient is increased. Consequently, this countermeasure is not preferable. 
         [0004]    Therefore, a balloon catheter which does not require a plug-like stopper has been proposed. For example, Patent Literature 1 below discloses an intravascular indwelling catheter having: a catheter body having a main inner cavity for injecting a medical solution, and a balloon inner cavity for inflating a balloon; a side hole which is formed in the middle of the catheter body, and which communicates with the main inner cavity; and a balloon portion which is placed in a tip end portion of the catheter body so as to communicate with the tip end opening of the balloon inner cavity. A physiological saline solution or the like is caused to flow into the balloon inner cavity to inflate the balloon portion in the tip end of the catheter body, and therefore the tip end opening of the main inner cavity is closed. When a medical solution is injected into the main inner cavity in this state the medical solution is allowed to flow out from the side hole, while preventing the the medical solution from flowing out from the tip end opening of the main inner cavity. 
       CITATION LIST 
     Patent Literature 
       [0005]    Patent Literature 1: JP-A-2002-119597 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0006]    In the case of the intravascular indwelling catheter disclosed in Patent Literature 1, however, the balloon portion is placed in the tip end portion of the catheter body. Therefore, the outer diameter of the tip end side of the catheter is increased, and there is a possibility that the insertion characteristics of the catheter with respect to a tubular organ such as the blood vessel are lowered. 
         [0007]    It is an object of the invention to provide a balloon catheter in which the diameter can be reduced, and the insertion characteristics of the catheter with respect to a tubular organ or the like can be improved. 
       Solution to Problem 
       [0008]    To attain the object, the invention provides
       a balloon catheter which has an inflatable balloon in a tip end portion, the balloon catheter including:   an inner tube which has a main lumen thereinside; and   an outer tube which is placed on an outer circumference of the inner tube, and which forms an inflation lumen with the inner tube to flow a fluid for inflating the balloon therethrough,   wherein a base end side of the balloon is fixed to the outer tube, whereas a tip end side of the balloon is fixed to the inner tube or the outer tube,   wherein a part of the inner tube is coupled to the outer tube at a side of a base end with respect to the balloon, and a side hole is formed in the coupling portion to cause the main lumen to be opened to an exterior,   wherein a weakened portion which is lower in rigidity than another portion of the inner tube is disposed on the inner tube at a side of a tip end with respect to the side hole, and   wherein the weakened portion is configured such that, when the balloon is inflated by the fluid supplied to the inflation lumen, the weakened portion is pressed by a pressure of the fluid to thereby close the main lumen of the inner tube.       
 
         [0016]    There may be provided
       the balloon catheter,   wherein the weakened portion is configured by forming a part of the inner tube to be thinner than another part.       
 
         [0019]    There may be provided
       the balloon catheter,   wherein the weakened portion of the inner tube includes:
           an inner layer which is capable of closing the main lumen by being pressed by the fluid supplied to the inflation lumen; and   a reinforcing member which is placed on the outer circumference of the inner layer, and which is configured to allow the fluid to pass therethrough.   
               
 
         [0024]    There may be provided
       the balloon catheter,   wherein the inner tube includes:
           the inner layer;   the reinforcing member; and   an outer layer which is placed on the outer circumference of the reinforcing member, and which clamps the reinforcing member with the inner layer, and   
           wherein, in the weakened portion, a part of the outer layer is peeled off to thereby expose the reinforcing member.       
 
         [0031]    There may be provided
       the balloon catheter,   wherein a base end side of the weakened portion is placed on a side of the tip end of the inner tube with respect to a place where the base end side of the balloon is fixed to the outer tube.       
 
         [0034]    There may be provided
       the balloon catheter,   wherein the weakened portion is formed in a whole circumference of the inner tube.       
 
       Advantageous Effects of Invention 
       [0037]    According to the invention, when a fluid is supplied to the inflation lumen to inflate the balloon, the weakened portion disposed in the inner tube is pressed by the pressure of the fluid, and the main lumen of the inner tube is closed. When a fluid such as a medical solution is injected into the main lumen of the inner tube, therefore, the fluid is allowed to flow out through only the side hole to the exterior while not being allowed to flow out from the tip end opening of the main lumen. Accordingly, the diameter of the balloon catheter can be reduced, and the insertion characteristics of the catheter with respect to a tubular organ, a body cavity, and the like can be improved. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0038]      FIGS. 1A and 1B  show an embodiment of the balloon catheter of the invention.  FIG. 1A  is a perspective view of the balloon catheter.  FIG. 1B  is an enlarged perspective view of a state where a balloon is inflated. 
           [0039]      FIG. 2  is a side view of the balloon catheter. 
           [0040]      FIG. 3  is a sectional view of the balloon catheter. 
           [0041]      FIGS. 4A and 4B  show a state where, in the balloon catheter, the balloon is not inflated.  FIG. 4A  is an enlarged sectional view of main portions.  FIG. 4B  is a partially cutaway enlarged side view of main portions. 
           [0042]      FIG. 5A  is a sectional view taken along arrow lines A-A in  FIG. 4A .  FIG. 5B  is a sectional view taken along arrow lines B-B in  FIG. 3 . 
           [0043]      FIG. 6A  is a sectional view taken along arrow lines E-E in  FIG. 4A , and  FIG. 6B  is a sectional view taken along arrow lines F-F in  FIG. 4A . 
           [0044]      FIGS. 7A and 7B  show a state where, in the balloon catheter, the balloon is inflated.  FIG. 7A  is an enlarged sectional view of main portions.  FIG. 7B  is a partially cutaway enlarged side view of main portions. 
           [0045]      FIG. 8  is a view showing a state where the balloon catheter is used. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0046]    Hereinafter, an embodiment of the balloon catheter of the invention will be described with reference to the drawings. 
         [0047]    As shown in  FIGS. 1 to 4B , the balloon catheter  10  has an inflatable balloon  40  in a tip end portion, and has an inner tube  20 , and an outer tube  30  which is placed on the outer circumference of the inner tube. 
         [0048]    As shown in  FIGS. 3 and 5B , the inner tube  20  includes a main lumen  21  thereinside. A guide wire that is not shown, and a fluid such as an anticancer agent, a nutrient, or another medical solution are to be injected. 
         [0049]    As shown in  FIG. 3 , by contrast, the outer tube  30  is placed coaxially with the inner tube  20  to form a double tube structure. An inflation lumen  31  through which a fluid for inflating the balloon  40  is to flow is formed between the outer circumference of the inner tube  20  and the inner circumference of the outer tube  30  (see  FIG. 5B ). 
         [0050]    In  FIGS. 5A and 5B , for the sake of the drawings, the inner tube  20  is shown while omitting an inner layer  22  and outer layer  25  which will be described later. 
         [0051]    The outer tube  30  has a shape in which the diameter of a base end portion  33  is slightly increased. The base end portion  33  is press-fitted to the outer circumference of a tip end portion of a hub  50  which has a substantially tubular shape, whereby the hub  50  is coupled to the base end side of the outer tube  30 . 
         [0052]    The outer tube  30  is formed by, for example, polyethylene (PE), a fluorine resin, polyoxymethylene (POM), polypropylene (PP), a nylon resin, a polyester resin, an ABS resin, a polycarbonate resin, polyetheretherketone (PEEK), a polyimide resin, or polyurethane (PU). The outer tube  30  in the embodiment is formed by a resin with high transparency so that the inner side is visible (see  FIGS. 1A, 1B and 2 ). 
         [0053]    Alternatively, the outer tube  30  may be formed into one tube by coupling end portions of plural tubular members having different hardnesses. In this case, preferably, a tubular member having a higher hardness is placed in the base end side of the tube, and other tubular members in which the hardnesses are gradually lowered as further advancing toward the tip end of the tube are placed. The coupling structure between the outer tube  30  and the hub  50  is not limited to the above-described structure. 
         [0054]    The hub  50  has a tubular fluid injection port  51  which elongates in an oblique outer direction toward the base end side of the hub, in a predetermined place of the outer circumference. The fluid injection port  51  communicates with the inflation lumen  31  (see  FIG. 3 ). 
         [0055]    As shown in  FIG. 3 , a tube fixation wall portion  53  in which a fitting hole is disposed in the middle is disposed in the inner cavity on the side of the base end of the hub  50 . When the base end side of the inner tube  20  is fitted into the fitting hole of the tube fixation wall portion  53 , the hub  50  is coupled to the base end side of the inner tube  20 . The coupling structure between the inner tube  20  and the hub  50  is not limited to the above-described structure. 
         [0056]    As shown in  FIGS. 3, 4A and 4B , the balloon  40  covers the outer circumference of a tip end portion of the outer tube  30 , the base end side of the balloon is fixed to the outer tube  30 , the tip end side is fixed to the inner tube  20 , the peripheral edges are sealed, and the inner cavity communicates with the inflation lumen  31 . When a fluid such as a contrast agent or a physiological saline solution is injected from the fluid injection port  51  of the hub  50 , therefore, the fluid flows through the inflation lumen  31  and enters the inner cavity of the balloon  40 , and the balloon  40  is inflated by the pressure of the fluid (see  FIGS. 7A and 7B ). Alternatively, the the balloon  40  may be placed, for example, on the side of the inner circumference of the tip end portion of the outer tube  30 . The placement portion of the balloon is not particularly limited. 
         [0057]    The balloon  40  is formed by, for example, polyurethane, a nylon resin, or silicone. Although, in the balloon  40  in the embodiment, the tip end side is fixed to the inner tube  20 , the tip end side may be fixed to the outer tube  30 . 
         [0058]    Returning to the description of the inner tube  20 , as shown in  FIGS. 4A, 4B , and  6 A, the inner tube  20  in the embodiment is configured by: the inner layer  22  in which the main lumen  21  is disposed on the inner side; a reinforcing member  23  which is placed on the outer circumference of the inner layer  22 ; and the outer layer  25  which is placed outside the reinforcing member  23 , and which clamps the reinforcing member  23  between the outer layer and the inner layer  22 . 
         [0059]    The inner layer  22  is preferably formed by, for example, a fluorine resin such as polytetrafluoroethylene (PTFE), tetrafluoroethylene, or perfluoroalkylvinylether copolymer (PFA), polyethylene (PE), polyoxymethylene (POM), polypropylene (PP), a nylon resin, a polyester resin, or polyimide (PI). Particularly preferably, the inner layer is formed by a fluorine resin such as polytetrafluoroethylene (PTFE), tetrafluoroethylene, or perfluoroalkylvinylether copolymer (PFA). 
         [0060]    The outer layer  25  is preferably formed by, for example, polyurethane (PU), polyethylene (PE), polypropylene (PP), a nylon resin, or silicone. Particularly preferably, the outer layer is formed by polyurethane. 
         [0061]    Preferably, the thickness of the inner layer  22  is 5 to 30 μm, and more preferably 10 to 15 μm. By contrast, the thickness of the outer layer  25  is 20 to 300 μm, and more preferably 80 to 120 μm. 
         [0062]    As shown in  FIG. 4B , the reinforcing member  23  in the embodiment has a coil-like shape that is formed by spirally winding a wire member in the axial direction of the inner tube  20 , and has gaps which allow the fluid to pass therethrough. The reinforcing member  23  is placed on the outer circumference of the inner layer  22  without being fixed thereto, and can be separated from the outer circumference of the inner layer  22  when the diameter of the inner layer  22  is reduced (see  FIG. 7B ). 
         [0063]    The reinforcing member  23  is not limited to have the above-describe coil-like shape, and may be formed into, for example, a braided member which is formed by knitting and/or braiding a wire member, a tubular member in which a slit is disposed in the axial or circumferential direction, or a tubular member in which incisions are formed so as to form a reed-like shape. The reinforcing member may have any shape as far as the member can reinforce the inner layer  22  and the fluid can pass through the member. 
         [0064]    The reinforcing member  23  is formed by, for example, a metal wire member configured by a metal such as W, Au-plated W, stainless steel, or a Ni—Ti alloy, or a polyamide resin such as Nylon 6 or Nylon 66, a polyester resin such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), or a like synthetic resin. 
         [0065]    In the inner tube  20 , as shown in  FIGS. 2 to 4B , X-ray opaque annular markers  26 ,  27  are placed at a position which is separated by a predetermined distance from the tip end of the balloon, and that which is separated by a predetermined distance from the base end of the balloon, respectively. The markers  26 ,  27  are formed by, for example, Pt, Ti, Pd, Rh, Au, W, Ag, Bi, Ta, alloys of these metals, a synthetic resin containing powder of BaSO 4 , Bi, W, or the like, or stainless steel. 
         [0066]    In the inner tube  20 , moreover, a part on the side of the base end with respect to the balloon  40 , here, the portion where the marker  27  is placed is made close to a predetermined place of the inner circumference of the outer tube  30  as shown in  FIGS. 3 and 4A , and then fixed together with the marker  27  to the inner circumference of the outer tube  30  by thermal welding, an adhesive agent which is not shown, or the like, whereby the part of the inner tube  20  is coupled to the outer tube  30 . A side hole  45  which allows the main lumen  21  disposed in the inner tube  20  to be opened to the exterior is disposed in the coupling portion (see  FIGS. 4A and 5A ). The side hole  45  is configured so as to communicate with the main lumen  21  of the inner tube  20 , and not to communicate with the inflation lumen  31  (see  FIGS. 4A and 5A ). 
         [0067]    As shown in  FIG. 4A , the distance L from the position where the base end side of the balloon  40  and the inner tube  20  are fixed to each other, to the side hole  45  is preferably 10 mm or shorter, and more preferably 5 mm or shorter. 
         [0068]    In the embodiment, the portion of the inner tube  20  where the marker  27  is placed is coupled together with the marker  27  to the outer tube  30 , and the side hole  45  is disposed in the coupling portion. Alternatively, a portion of the inner tube  20  where the marker  27  is not placed may be coupled to the outer tube  30 , and the side hole  45  may be disposed. The side hole  45  is requested to be at least on the side of the base end with respect to the balloon  40 . 
         [0069]    Although, in the embodiment, the inner tube  20  is configured by one tube, the one tube may be configured by coupling end portions of plural tubular members having different hardnesses. In this case, preferably, a tubular member having a higher hardness is placed in the base end side of the tube, and other tubular members in which the hardnesses are gradually lowered as further advancing toward the tip end of the tube are placed. 
         [0070]    In the balloon catheter  10 , a weakened portion  28  which is in the inner tube  20 , and which is lower in rigidity than the other portion of the inner tube  20  is disposed on the side of the tip end with respect to the side hole  45 . 
         [0071]    The weakened portion  28  in the embodiment is structured in the following manner. As described above, the inner tube  20  is configured by the inner layer  22 , the reinforcing member  23 , and the outer layer  25 . By contrast, the weakened portion  28  in the embodiment has a structure which is configured by the inner layer  22  and the reinforcing member  23  that is placed on the outer circumference of the inner layer, and in which the outer circumference of the reinforcing member  23  is not covered by the outer layer  25 , and a part of the inner tube  20  is formed to be thinner than the other part (see  FIGS. 4A, 4B and 6B ). 
         [0072]    As shown in  FIG. 6B , the weakened portion  28  is formed in the whole circumference of the inner tube  20 . 
         [0073]    In the embodiment, as shown in  FIGS. 4A and 4B , a part of the outer layer  25 , here, the portion where the balloon  40  is placed is peeled off, and the reinforcing member  23  is exposed, whereby the weakened portion  28  is disposed. 
         [0074]    According to the embodiment, as described above, the weakened portion  28  can be formed simply by peeling off a part of the outer layer  25 , and therefore the productivity of the balloon catheter  10  can be enhanced. Moreover, the inner tube  20  is configured by the inner layer  22 , the reinforcing member  23 , and the outer layer  25 , and the reinforcing member  23  is clamped between the inner layer  22  and the outer layer  25 . Therefore, positional displacement of the reinforcing member  23  can be suppressed. 
         [0075]    As the means for exposing the reinforcing member  23 , for example, a predetermined range of the outer layer  25  may be melted by an agent or cut away by a cutter; the outer layer  25  may be formed by a resin with a melting point which is lower than that of the inner layer  22 , and a predetermined range of the outer layer  25  may be melted by heat; or the inner layer  22  and the reinforcing member  23  are covered by a pair of outer layers  25 ,  25  while forming a gap corresponding to the length of the weakened portion  28 . The means is not particularly limited. 
         [0076]    The weakened portion  28  in the embodiment is formed by the configuration in which a part of the inner tube  20  is formed to be thinner than the other portion by peeling a part of the outer layer  25 . The weakened portion is requested to be lower in rigidity than the other portion of the inner tube, and the structure of the weakened portion is not particularly limited. Although the weakened portion  28  is formed in the whole circumference of the inner tube  20 , the weakened portion may be disposed only in a predetermined range in the circumferential direction. 
         [0077]    As shown in  FIGS. 4A and 4B , moreover, the base end side of the weakened portion  28  is placed on the side of the tip end of the inner tube  20  with respect to the place where the base end side of the balloon  40  is fixed to the outer tube  30 . 
         [0078]    The weakened portion  28  is configured so that, when the balloon  40  is inflated by a fluid supplied to the inflation lumen  31 , the weakened portion is pressed by the pressure of the fluid to close the main lumen  21  of the inner tube  20  (see  FIGS. 7A and 7B ). 
         [0079]    In the embodiment, when a fluid is supplied into the inflation lumen  31 , and the balloon  40  is inflated, the fluid passes through the gaps of the reinforcing member  23 , and presses the inner layer  22  to reduce the diameter, thereby closing the main lumen  21  which is inside the inner layer  22  (see  FIG. 7A ). At this time, the reinforcing member  23  is placed on the outer circumference of the inner layer  22  without being fixed thereto, and, when the inner layer  22  is pressed and the diameter is reduced, the reinforcing member is therefore separated from the outer circumference of the inner layer  22  (see  FIG. 7B ). 
         [0080]    Next, an example of a method of using the balloon catheter  10  having the above-described structure will be described. 
         [0081]    The balloon catheter  10  can be used, for example, in the case where, in a bifurcation of a tubular organ, i.e., a portion having a thick main tube, and a thin branch tube which branches off the main tube, a catheter cannot be introduced into the branch tube. 
         [0082]    As shown in  FIG. 8 , the hepatic artery which is one of tubular organs has a a thick main tube  1 , and a thin branch tube  3  which branches off and extends from the middle of the main tube  1  through a bifurcation  3   a . A method of using the balloon catheter  10  in the case where a lesion part  5  such as liver cancer is produced on the tip end side of the branch tube  3 , and a fluid such as an anticancer agent is to be injected to the lesion part  5  will be described. The balloon catheter  10  may be used also in, for example, a tubular organ such as the bile duct, the pancreatic duct, the ureter, or the trachea, and other body cavities of the human body. The use of the balloon catheter is not limited to the above-described use mode. 
         [0083]    Firstly, a guide wire which is not shown is inserted into the main tube  1  by the well-known Seldinger technique or the like, and a tip end portion is caused to reach a position which is slightly beyond the bifurcation  3   a . In this state, the guide wire is inserted into the main lumen  21  of the balloon catheter  10 , and the balloon catheter  10  is moved by using the guide wire. Then, a tip end portion of the balloon catheter  10  is caused to reach a position which is slightly beyond the bifurcation  3   a , and indwelled so that the side hole  45  is at a position matching the bifurcation  3   a.    
         [0084]    Then, the guide wire is pulled out from the interior of the main lumen  21  while holding and fixing the position of the balloon catheter  10 , and thereafter a fluid such as a contrast agent is supplied from the fluid injection port  51  of the hub  50 . As shown in  FIGS. 7A and 7B , then, the fluid passes through the inflation lumen  31  to flow into the inner cavity of the balloon  40 , thereby inflating the balloon  40 . This causes the balloon  40  to butt against the wall surface of the main tube  1  to close the inner cavity of the main tube  1  (see  FIG. 8 ). In conjunction with the inflation of the balloon  40  due to the fluid, the fluid passes through the gaps of the reinforcing member  23  constituting the weakened portion  28 , and the pressure of the fluid presses the inner layer  22  constituting the weakened portion  28  to reduce the diameter, whereby the main lumen  21  which is inside the inner layer  22  is closed. 
         [0085]    Next, a fluid such as an anticancer agent is supplied into the main lumen  21  from the base end side of the hub  50 . Then, the fluid flows in the main lumen  21 . At this time, the tip end portion of the main lumen  21  has been closed as described above, and therefore the fluid can be caused to flow out to the exterior from only the side hole  45 , without allowing the fluid to flow out from the tip end opening of the main lumen  21 . 
         [0086]    As described above, the fluid flows out to the exterior from only the side hole  45 , and then flows into the branch tube  3  through the bifurcation  3   a . Therefore, the fluid such as an anticancer agent is blocked from flowing to the main tube  1  in which the lesion part  5  does not exist, and can be effectively administered to only the lesion part  5 . 
         [0087]    In the balloon catheter  10 , as described above, the weakened portion  28  is disposed in the inner tube  20 , and, when the balloon is inflated, the weakened portion is pressed by the pressure of a fluid to close the main lumen  21  of the inner tube  20 . Unlike the intravascular indwelling catheter disclosed in Patent Literature 1, therefore, it is not necessary to place a balloon portion for closing the main inner cavity, in the tip end of the catheter body, the diameter of the balloon catheter  10  can be reduced, and the insertion characteristics of the catheter with respect to a tubular organ, body cavity, and the like can be improved. 
         [0088]    In the balloon catheter  10 , unlike a conventional balloon catheter, moreover, it is not necessary to insert a plug-like stopper into the body to close the tip end opening. As described above, the inflation of the balloon  40  which is due to the supply of a fluid into the inflation lumen  31  causes the weakened portion  28  to be pressed by the fluid pressure, and the main lumen  21  can be closed. Therefore, the work of administering an anticancer agent or the like by using the balloon catheter  10  can be performed easily and smoothly, the surgical time can be shortened, and the burden on the patient can be reduced. 
         [0089]    In the embodiment, the weakened portion  28  is formed by thinning a part of the inner tube  20  as compared to the other part, and therefore the weakened portion  28  can be formed integrally with the inner tube  20 . As a result, the productivity of the balloon catheter  10  can be enhanced, and the responsiveness in the case where the weakened portion  28  is pressed by the balloon inflation can be enhanced, so that the main lumen  21  of the inner tube  20  can be smoothly closed. 
         [0090]    In the embodiment, furthermore, the weakened portion  28  of the inner tube  20  has the inner layer  22  which is pressed by a fluid supplied to the inflation lumen to be able to close the main lumen  21 , and the reinforcing member  23  which is placed on the outer circumference of the inner layer  22 , and which allows the fluid to pass therethrough. Therefore, the reduction of the rigidity in the weakened portion  28  can be suppressed by the reinforcing member  23 , and the operability of the balloon catheter  10  can be maintained while ensuring the pushability, the torque transmission characteristics, and the like. 
         [0091]    In the embodiment, as shown in  FIG. 4A , the base end side of the weakened portion  28  is placed on the side of the tip end of the inner tube  20  with respect to the place where the base end side of the balloon  40  is fixed to the outer tube  30 . Therefore, the side hole  45  can be disposed close to the base end side of the balloon  40  (when the base end side of the weakened portion  28  is on the side of the base end of the inner tube with respect to the fixation place of the base end side of the balloon  40 , the distance between the base end side of the balloon  40  and the side hole  45  is increased). As shown in  FIG. 8 , the side hole  45  can be placed in the vicinity of the bifurcation  3   a , and a fluid such as an anticancer agent can be caused to flow smoothly and effectively through the branch tube  3 . 
         [0092]    In the embodiment, as shown in  FIG. 6B , furthermore, the weakened portion  28  is formed in the whole circumference of the inner tube  20 . When the balloon  40  is inflated by the supply of a fluid into the inflation lumen  31 , and the weakened portion  28  is pressed, therefore, the pressing force acts on the the whole circumference of the weakened portion  28 , and the main lumen  21  of the inner tube  20  can be closed more smoothly. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           10  balloon catheter 
           20  inner tube 
           21  main lumen 
           22  inner layer 
           23  reinforcing member 
           25  outer layer 
           28  weakened portion 
           30  outer tube 
           31  inflation lumen 
           40  balloon 
           45  side hole 
           50  hub