Patent Publication Number: US-2022218353-A1

Title: Anastomosis assist tool and vascular anastomosis method

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Divisional of U.S. patent application Ser. No. 16/608,547 filed Oct. 25, 2019, which is the U.S. National Phase under 35 U.S.C. § 371 of International Application No. PCT/JP2018/015597 filed on Apr. 13, 2018, which claims the benefit of Japanese Application No. 2017-089957, filed on Apr. 28, 2017 and Japanese Application No. 2018-050364 filed on Mar. 19, 2018, the entire contents of each are hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to an anastomosis assist tool and a vascular anastomosis method using the anastomosis assist tool. 
     BACKGROUND ART 
     In various types of surgery such as organ transplant, vessels may be connected to each other through anastomosis. There is a method called triangular anastomosis known as a method of anastomosing vessels. According to the triangular anastomosis, each of the two vessels to be anastomosed is pulled at three points to form a cross section of each of the vessels to be sutured into a triangular shape, and corresponding sides are sutured together. 
     In some cases of surgery such as organ transplant surgery, while a catheter is inserted into either of two vessels and a liquid is fed, the two vessels are sutured together. A conventional catheter for liquid feed is disclosed in patent literature 1, for example. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Patent Application Laid-Open No. 7-70438 (1995) 
     SUMMARY OF INVENTION 
     Technical Problem 
     In many conventional catheters including a balloon catheter disclosed in patent literature 1, a catheter body to be inserted into a vessel has a cylindrical outer peripheral surface. Hence, if the inner wall of the vessel sticks to this outer peripheral surface, it becomes difficult to perform triangular anastomosis involving pulling at three points. 
     For implementation of triangular anastomosis, independently of the presence or absence of insertion of a catheter, suture threads put over respective three points of two vessels are required to be pulled under tension. To achieve this, a hand or a tool for holding each of the suture threads is located around an operative field, causing the risk of reduced workability of surgery. This extends a duration of the surgery, making it difficult to reduce damage on a vessel and an organ connected to the vessel. 
     The present invention has been made in consideration of the foregoing circumstances, and is intended to provide a technique for increasing workability of vascular anastomosis surgery. 
     Solution to Problem 
     To solve the foregoing problem, a first aspect of the present invention is intended for an anastomosis assist tool comprising: a body unit extending in a predetermined advancing direction and having a part to be inserted into a vessel; and an insertion unit arranged at the tip of the body unit. The insertion unit includes a tapered part of a diameter decreasing gradually toward a tip. The body unit includes an anastomosis assist part having an approximately constant cross-sectional shape in a plane perpendicular to the advancing direction. The anastomosis assist part includes a projection projecting outwardly as viewed in the cross section and extending in the advancing direction. 
     A second aspect of the present invention is intended for the anastomosis assist tool according to the first aspect wherein the projection of the anastomosis assist part includes two, three, or four projections. 
     A third aspect of the present invention is intended for the anastomosis assist tool according to the second aspect wherein the projections of the anastomosis assist part include three projections. 
     A fourth aspect of the present invention is intended for the anastomosis assist tool according to the third aspect wherein the cross section of the anastomosis assist part is a regular triangle. 
     A fifth aspect of the present invention is intended for the anastomosis assist tool according to any one of the first to fourth aspects wherein the projection is arranged uniformly in a peripheral direction. 
     A sixth aspect of the present invention is intended for the anastomosis assist tool according to any one of the first to fifth aspects wherein the insertion unit further includes a cylindrical part arranged closer to a rear end than the tapered part and having a cylindrical outer peripheral surface. 
     A seventh aspect of the present invention is intended for the anastomosis assist tool according to any one of the first to sixth aspects wherein the body unit includes a first linear part extending in a linear shape, a bent part bent in a curved shape, and a second linear part extending in a linear shape arranged in this order as viewed from the tip toward a rear end. 
     An eighth aspect of the present invention is intended for the anastomosis assist tool according to the seventh aspect wherein the angle of the advancing direction of the body unit changes in a range from 90 to 180° at the bent part. 
     A ninth aspect of the present invention is intended for the anastomosis assist tool according to any one of the first to eighth aspects wherein the anastomosis assist part has flexibility. 
     A tenth aspect of the present invention is intended for the anastomosis assist tool according to any one of the first to ninth aspects wherein the anastomosis assist part has a surface subjected to surface treatment. 
     An eleventh aspect of the present invention is intended for the anastomosis assist tool according to any one of the first to tenth aspects further comprising: a lumen extending in the advancing direction and connecting a first opening arranged at the tip and a second opening arranged at a rear end. 
     A twelfth aspect of the present invention is intended for the anastomosis assist tool according to the eleventh aspect wherein the lumen has a circular cross section in a plane perpendicular to the advancing direction. 
     A thirteenth aspect of the present invention is intended for a vascular anastomosis method using the anastomosis assist tool according to the third aspect or the fourth aspect wherein the three projections include a first corner, a second corner, and a third corner. The method comprises: a) a step of continuously suturing a site of a first vessel from a point facing the second corner to a point facing the third corner and a corresponding site of a second vessel together while the anastomosis assist tool is inserted in the first vessel; and b) a step of continuously suturing a site of the first vessel from a point facing the first corner to the point facing the second corner and a corresponding site of the second vessel together while the anastomosis assist tool is inserted in the first vessel. 
     A fourteenth aspect of the present invention is intended for the vascular anastomosis method according to the thirteenth aspect further comprising: c) a step of continuously suturing at least a part of a site of the first vessel from the point facing the first corner to the point facing the third corner and at least a part of a corresponding site of the second vessel together with a suture thread in a loosened state while the anastomosis assist tool is inserted in the first vessel, the step c) being performed after the step a) and the step b); d) a step of pulling the anastomosis assist tool out of the first vessel after the step c); and e) a step of tightening the suture thread after the step d). 
     A fifteenth aspect of the present invention is intended for the vascular anastomosis method according to the thirteenth aspect or the fourteenth aspect wherein, in the step a), the first corner is placed on a near side in an operative field, and the site of the first vessel from the point facing the second corner to the point facing the third corner is defined as a rear wall. 
     Advantageous Effects of Invention 
     According to the first to twelfth aspects of the present invention, the projection abuts on the inner wall of a vessel. This makes it unlikely that the inner wall of the vessel will stick to the body unit at a site other than a point abutting on the projection. This facilitates anastomosis at this site. Namely, workability of vascular anastomosis surgery can be increased. 
     In particular, according to the second aspect of the present invention, the inner wall of the vessel does not stick to the body unit at a site of the inner wall between points abutting on the projections. This facilitates anastomosis at this site. Namely, workability of vascular anastomosis surgery can be increased. 
     In particular, the third aspect of the present invention facilitates implementation of triangular anastomosis surgery. 
     In particular, according to the fourth aspect and the fifth aspect of the present invention, if the anastomosis assist tool is inserted into the vessel in a wrong direction, the uniform arrangement of the projection or the projections facilitates adjustment of the direction of the insertion. 
     In particular, according to the sixth aspect of the present invention, ligation of the vessel is facilitated at the cylindrical part. 
     In particular, according to the seventh aspect and the eighth aspect of the present invention, as the advancing direction is changed at the bent part, surgery is unlikely to be hindered by a part not inserted into the vessel. Thus, workability of vascular anastomosis surgery can be increased. 
     In particular, according to the ninth aspect of the present invention, the flexibility of the anastomosis assist part reduces the occurrence of damage on the vessel. Further, the anastomosis assist tool is easily movable to an intended position during surgery. 
     In particular, according to the tenth aspect of the present invention, as the anastomosis assist part is subjected to surface treatment, it becomes unlikely that a surgical needle will be hooked to or will stick into the body unit. This increases workability of surgery. 
     In particular, the eleventh aspect of the present invention allows supply or suction of a liquid such as a perfusate into or from the vessel through the anastomosis assist tool. 
     In particular, the twelfth aspect of the present invention suppresses increase in a resistance at a liquid flow path in the lumen. 
     According to the thirteenth to fifteenth aspects of the present invention, workability is increased during triangular anastomosis surgery. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a catheter connecting member according to a first embodiment; 
         FIG. 2  is a side view of the catheter connecting member according to the first embodiment; 
         FIG. 3  is a cross-sectional view of a body unit of the catheter connecting member according to the first embodiment; 
         FIG. 4  is a flowchart showing a flow of exemplary vascular anastomosis surgery; 
         FIG. 5  shows how the exemplary vascular anastomosis surgery is performed; 
         FIG. 6  shows how the exemplary vascular anastomosis surgery is performed; 
         FIG. 7  shows how the exemplary vascular anastomosis surgery is performed; 
         FIG. 8  shows how the exemplary vascular anastomosis surgery is performed; 
         FIG. 9  is a cross-sectional view of a body unit of a catheter connecting member according to a modification; 
         FIG. 10  is a cross-sectional view of a body unit of a catheter connecting member according to a modification; 
         FIG. 11  is a cross-sectional view of a body unit of a catheter connecting member according to a modification; and 
         FIG. 12  is a cross-sectional view of a body unit of a catheter connecting member according to a modification. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An embodiment of the present invention will be described below by referring to the drawings. “Donors” and “recipients” mentioned in the present invention may either be humans or non-human animals. More specifically, in the present invention, “organs” including livers may be human organs or organs of non-human animals. Further, in the present invention, “vessels” may be human vessels or vessels of non-human animals. Non-human animals may be rodents including mice and rats, ungulate animals including pigs, goats, and sheep, non-human primates including chimpanzees, other types of non-human mammals, and animals other than mammals. 
     1. First Embodiment 
     &lt;1-1. Configuration of Catheter Connecting Member&gt; 
       FIG. 1  is a perspective view of a catheter connecting member  1  according to a first embodiment of the present invention.  FIG. 2  is a side view of the catheter connecting member  1 .  FIG. 3  is a cross-sectional view of a body unit  2  of the catheter connecting member  1 . The catheter connecting member  1  of this embodiment is a member to be attached to the tip of a catheter and to be inserted into a vessel of a donor organ. The catheter connecting member  1  functions as an anastomosis assist tool for increasing workability of surgery in the field of vascular anastomosis. 
     As shown in  FIGS. 1 and 2 , the catheter connecting member  1  includes the body unit  2 , an insertion unit  3 , and a base end unit  4 . 
     The body unit  2  is a tubular unit extending in a predetermined advancing direction. An axis indicating the advancing direction of the body unit  2  is called an advancing axis  9 . The insertion unit  3  and the base end unit  4  are further arranged along the advancing axis  9 . The body unit  2  has an approximately constant cross-sectional shape in a plane perpendicular to the advancing axis  9 . As shown in  FIG. 3 , the cross section of the body unit  2  of this embodiment has an approximately regular triangular shape. 
     The cross section of the body unit  2  includes three projections  51  corresponding to the corners of a triangle, and three sides  52  of linear shapes connecting the projections  51 . In a cross section perpendicular to the advancing axis  9 , the projections  51  project outwardly. The projections  51  extend in the advancing direction of the body unit  2 . Namely, the projections  51  extend along the advancing axis  9 . More specifically, the three projections  51  include a first corner  511 , a second corner  512 , and a third corner  513 . The three sides  52  include a first side  521  facing the first corner  511 , a second side  522  facing the second corner  512 , and a third side  523  facing the third corner  513 . In this way, the body unit  2  in its entirety includes the projections  51 . Further, the body unit  2  forms an anastomosis assist part having an approximately constant cross-sectional shape in a plane perpendicular to the advancing direction. 
     As shown in  FIG. 2 , the advancing axis  9  of the body unit  2  includes a linearly extending part, a part bent into a curved shape, and a linearly extending part arranged in this order as viewed from the tip toward the rear end. Thus, the body unit  2  includes a first linear part  21  extending in a linear shape, a bent part  22  bent into a curved shape, and a second linear part  23  extending in a linear shape arranged in this order as viewed from the tip toward the rear end. 
     In this embodiment, the first corner  511  is arranged at the innermost position at the bent part  22 . Consequently, the first side  521  is arranged at the outermost position at the bent part  22 . In this embodiment, the angle of the advancing direction of the body unit  2  changes by about 120° at the bent part  22 . 
     The insertion unit  3  is arranged at the tip of the body unit  2 . The insertion unit  3  includes a first tapered part  31 , a first cylindrical part  32 , a second cylindrical part  33 , a third cylindrical part  34 , and a second tapered part  35  arranged in this order as viewed from the tip toward the base end. The insertion unit  3  is inserted into one of two vessels to be anastomosed for implementation of anastomosis surgery. 
     The first tapered part  31  has an outer peripheral surface formed into a circular conical surface with an outer diameter increasing gradually from the tip. As a result, when the insertion unit  3  is inserted into a vessel from the tip, the insertion without placing load on the vessel is facilitated. 
     The first cylindrical part  32 , the second cylindrical part  33 , and the third cylindrical part  34  are arranged closer to the rear end than the first tapered part  31 . Each of the first cylindrical part  32  and the third cylindrical part  34  has a cylindrical outer peripheral surface of an outer diameter same as the maximum outer diameter of the first tapered part  31 . This allows the inner wall of a vessel to tightly contact the outer peripheral surfaces of the first cylindrical part  32  and the third cylindrical part  34  when the insertion unit  3  is inserted into the vessel. 
     The second cylindrical part  33  has a cylindrical outer peripheral surface of a smaller outer diameter than the first cylindrical part  32  and the third cylindrical part  34 . Thus, when a vessel is ligated at the second cylindrical part  33 , the ligated site becomes unlikely to deviate in the direction of the advancing axis  9 . A position for ligation is not limited to the second cylindrical part  33 . For example, a vessel may be ligated at a position slightly closer to the rear end than the second tapered part  35  and around a tip side end portion of the body unit  2 . 
     In this embodiment, the second cylindrical part  33  of a small outer diameter is arranged between the first cylindrical part  32  and the third cylindrical part  34  having the same outer diameter. Alternatively, these parts may be configured as a single cylindrical part having an approximately constant outer diameter. By the provision of the cylindrical part having a cylindrical outer peripheral surface to the insertion unit  3 , it becomes possible to ligate a vessel easily at this part of the insertion unit  3 . 
     The second tapered part  35  has an outer peripheral surface of a diameter decreasing gradually from the rear end of the third cylindrical part  34  toward the body unit  2 . By the presence of the tapered part at the rear end of the insertion unit  3 , when the insertion unit  3  is pulled out of a vessel, the pulling-out without placing load on the vessel is facilitated. 
     The base end unit  4  is arranged at the rear end of the body unit  2 . The base end unit  4  has a cylindrical outer peripheral surface. For connecting the catheter connecting member  1  to a catheter, the base end unit  4  functions as a connection to the catheter. A destination of connection of the catheter connecting member  1  is not limited to a catheter. The catheter connecting member  1  may also be connected to a fitting, a connector, or a tube other than a catheter, for example. 
     The catheter connecting member  1  includes a lumen  10  extending from the tip toward the rear end along the advancing axis  9 . The tip of the catheter connecting member  1 , namely, the tip of the insertion unit  3  is provided with a first opening  11 . The rear end of the catheter connecting member  1 , namely, the rear end of the base end unit  4  is provided with a second opening  12 . The lumen  10  passes through the interior of the catheter connecting member  1  between the first opening  11  and the second opening  12 . Namely, the lumen  10  connects the first opening  11  and the second opening  12 . 
     Thus, when the base end unit  4  is connected to a catheter, a lumen in the catheter communicates with the first opening  11  through the second opening  12  and the lumen  10 . This allows supply of a liquid such as a perfusate into a vessel or sucking of the liquid from the interior of the vessel. 
     The catheter connecting member  1  itself may be used as a catheter. More specifically, the rear end of the catheter connecting member  1  may directly be connected to a source of a liquid such as a perfusate or a liquid sucking mechanism. In this case, a liquid such as a perfusate can also be supplied into a vessel or the liquid can also be sucked from the interior of the vessel. 
     As shown in  FIG. 3 , the lumen  10  of this embodiment has a circular cross-sectional shape in a plane perpendicular to the advancing axis  9 . The cross-sectional shape of the lumen  10  is approximately constant from the first opening  11  to the second opening  12 . This suppresses increase in a resistance at a liquid flow path in the lumen  10 . 
     The catheter connecting member  1  of this embodiment is integrally formed. Namely, the body unit  2 , the insertion unit  3 , and the base end unit  4  are formed as one member. The body unit  2 , the insertion unit  3 , and the base end unit  4  may be configured using different members. 
     In this embodiment, the body unit  2  has flexibility. The body unit  2  having flexibility is made of flexible resin, rubber, or elastomer, for example. More specifically, the flexible resin to be used is silicon resin such as silicon resin for medical purposes or epoxy resin, for example. This reduces the occurrence of damage on a vessel even when the catheter connecting member  1  is moved while the catheter connecting member  1  is inserted in the vessel. This also facilitates move of the catheter connecting member  1  to an intended position during surgery. 
     The body unit  2  may be configured not to be flexible. In this case, the body unit  2  may be made of polypropylene, polycarbonate, stainless steel, or titanium, for example. 
     During use of the catheter connecting member  1 , the insertion unit  3  in its entirety and at least a part of the body unit  2  are inserted into a vessel. With the body unit  2  located at a position of anastomosis of vessels, the vessel in which the catheter connecting member  1  is inserted and the other vessel are anastomosed. The catheter connecting member  1  is mainly used for continuous suture in end-to-end anastomosis, end-to-side anastomosis, side-to-end anastomosis, or side-to-side anastomosis of vessels. 
     When the body unit  2  is inserted into a vessel, the vessel is widened with the projections  51  of the body unit  2  from the interior toward the exterior of the vessel. This can make it unlikely that the vessel will be flattened and the inner walls of the vessel will unintentionally stick to each other. If the body unit  2  is too thin for the vessel, it becomes difficult to widen the vessel in this way. By contrast, if the body unit  2  is too thick for the vessel, heavy load is applied to the vessel at points contacting the projections  51  and the body unit  2  and the vessel adhere each other even at a point not contacting the projection  51 , causing the risk of failing to perform anastomosis successfully. In this regard, the diameter of the circumscribed circle of the body unit  2  in a cross section in a plane perpendicular to the advancing axis  9  is preferably in a range from 60 to 80% of the vascular size (diameter) of a vessel to receive insertion of the catheter connecting member  1  determined when the vessel is in a natural flowing state in a biological body. In this range, the vessel can be widened appropriately with the projections  51 , while the probability of adherence between the body unit  2  and the catheter connecting member  1  can be reduced at a point not contacting the projection  51 . 
     If at least a part of the catheter connecting member  1  has flexibility, this part preferably has hardness greater than the hardness of a vessel into which the catheter connecting member  1  is to be inserted. More specifically, the body unit  2  is preferably A 50 or more and less than D  80  according to the definition of JIS K 6253. When the body unit  2  is inserted into a vessel, the hardness of the body unit  2  falling within this range allows widening of the vessel from the interior toward the exterior of the vessel with the projections  51  and allows the catheter connecting member  1  to move easily during vascular anastomosis. 
     &lt;1-2. Flow of Vascular Anastomosis Surgery&gt; 
     A flow of vascular anastomosis surgery using the catheter connecting member  1  will be described next by referring to  FIGS. 4 to 8 .  FIG. 4  is a flowchart showing a flow of exemplary vascular anastomosis surgery using the catheter connecting member  1 .  FIGS. 5 to 8  show how the exemplary vascular anastomosis surgery is performed. In each of  FIGS. 5 to 8 , a photograph in the upper region shows how the vascular anastomosis surgery is performed, and a view in the lower region shows principal parts of the photograph. 
     The vascular anastomosis surgery shown in  FIG. 4  is surgery for anastomosis of a first vessel  81  of a donor organ to a second vessel  82  of a recipient. 
     As shown in  FIG. 4 , the second vessel  82  of the recipient is occluded in advance with a clamp, for example (step S 101 ). Meanwhile, a perfusate is supplied to the donor organ through the catheter connecting member  1  inserted in the first vessel  81  and a catheter connected to the catheter connecting member  1 . While the catheter connecting member  1  is inserted in the first vessel  81  and the perfusate flows, the donor organ is located at a position for transplant (step S 102 ). At this time, the insertion unit  3 , the first linear part  21  of the body unit  2 , and a part of the bent part  22  of the body unit  2  of the catheter connecting member  1  are inserted in the first vessel  81 . The first vessel  81  is ligated to the insertion unit  3  of the catheter connecting member  1 . 
     In this state, the first vessel  81  has an approximately regular triangular cross-sectional shape conforming to the outer peripheral surface of the body unit  2  of the catheter connecting member  1 . At this time, the inner wall of the first vessel  81  receives strong force of widening the first vessel  81  outwardly applied at a point P 1  contacting the first corner  511 , a point P 2  contacting the second corner  512 , and a point P 3  contacting the third corner  513 . This avoids application of large tension to a site facing the first side  521 , a site facing the second side  522 , and a site facing the third side  523  of the inner wall of the first vessel  81 , while controlling force of sticking to the outer peripheral surface of the body unit  2  at relatively low. Thus, when the catheter connecting member  1  is inserted in the first vessel  81 , a surgical needle is hooked easily to a part of the first vessel  81  between the projections  51 . 
     As shown in  FIG. 5 , in this embodiment, while an end portion as an anastomosis point of the first vessel  81  and an end portion as an anastomosis point of the second vessel  82  are located at predetermined positions, the first corner  511  of the first linear part  21  is located at a higher position. By doing so, the body unit  2  extending externally from the first vessel  81  is bent upwardly at the bent part  22 . Further, the second linear part  23  is located above the first vessel  81 . 
     As described above, the presence of the bent part  22  of the body unit  2  prevents a part of the catheter connecting member  1  located outside the first vessel  81  from extending above a site from the point P 2  to the point P 3  where the first vessel  81  and the second vessel  82  are to be anastomosed. This reduces the probability of hindrance to the vascular anastomosis surgery. As a result, working efficiency of the vascular anastomosis surgery is increased. 
     As described above, in the catheter connecting member  1  of this embodiment, the angle of the advancing direction of the body unit  2  changes by 120° at the bent part  22 . In this way, the angle of the advancing direction of the body unit  2  preferably changes in a range from 90 to 180° at the bent part  22 . This reduces the probability that the second linear part  23  or the base end unit  4  will overlap a position of anastomosis of the first vessel  81  and the second vessel  82 . Even in the absence of the bent part  22 , the body unit  2  can still be bent upwardly if the body unit  2  has flexibility. 
     After the anastomosis point of the first vessel  81  and the anastomosis point of the second vessel  82  are located at the predetermined positions, the first vessel  81  and the second vessel  82  are connected at two points with threads (step S 103 ). More specifically, a surgical needle is hooked to the point P 2  of the first vessel  81  facing the second corner  512  and a corresponding point of the second vessel  82 , and these points are connected with a suture thread. Likewise, a surgical needle is hooked to the point P 3  of the first vessel  81  facing the third corner  513  and a corresponding point of the second vessel  82 , and these points are connected with a suture thread. 
     Next, sites between the point P 2  and the point P 3  are sutured together (step S 104 ). More specifically, a site of the first vessel  81  facing the first side  521  of the body unit  2  and a corresponding site of the second vessel  82  are sutured together. At this time, as shown in  FIG. 5 , while the body unit  2  is pulled toward the direction of the first corner  511  (namely, upward direction), the sites between the point P 2  and the point P 3  are sutured continuously. 
     In step S 104 , the body unit  2  is arranged so as to place the first corner  511  on a near side in an operative field. By doing so, the site of the first vessel  81  from the point P 2  facing the second corner  512  to the point P 3  facing the third corner  513  is defined as a rear wall. Pulling the body unit  2  toward the direction of the first corner  511  expands a viewing field around the rear walls of the first vessel  81  and the second vessel  82  (between the point P 2  and the point P 3 ). This allows the rear walls of the first vessel  81  and the second vessel  82  to be sutured together from inside (from the intima). 
     During vascular anastomosis for organ transplant, vessels are generally anastomosed from outside the vessels (from the adventitia). If a margin of suture for anastomosis is short like in the case of vascular anastomosis of suprahepatic inferior vena cava for liver transplant, for example, it is difficult to reverse vessels for suture of their rear wall sides. This necessitates suture of the rear walls of the vessels from inside. Compared to suture of the vessels from outside, suture of the vessels from inside should proceed with great care so as not to damage the intimae of the vessels. During suture of the rear walls, care should also be taken so as to prevent a surgical needle from being hooked to the front walls of the vessels. For these reasons, it becomes necessary to ensure a sufficient viewing field around a suture site. In this case, pulling the front wall of the vessel with tweezers, for example, for ensuring a viewing field causes the risk of damage on the vessel near the front wall. 
     In this regard, as shown in  FIG. 5 , in the use of the catheter connecting member  1 , pulling the front wall of the first vessel  81  upwardly by pulling the body unit  2  toward the direction of the first corner  511  makes it possible to expand a viewing field around the rear walls of the first vessel  81  and the second vessel  82 . In this case, the body unit  2  contacts a wide range inside the vessel during the upward pulling, allowing significant reduction in damage on the vessel compared to pulling of the vessel with tweezers, for example. As described above, in step S 104 , suture preferably proceeds while the body unit  2  is pulled toward the direction of the first corner  511 . 
     Next, as shown in  FIG. 6 , sites between the point P 1  and the point P 2  are sutured together (step S 105 ). More specifically, a site of the first vessel  81  facing the third side  523  of the body unit  2  and a corresponding site of the second vessel  82  are sutured together. At this time, while the body unit  2  is pulled toward the direction of the third corner  513 , the sites between the point P 1  and the point P 2  are sutured continuously. This facilitates suture of sites around the third side  523 . 
     In step S 105 , the sites from the point P 2  to the point P 1  (left walls of the first vessel  81  and the second vessel  82 ) are continuously sutured together from outside. In doing so, the first vessel  81  is widened outwardly at the point P 1  contacting the first corner  511  and the point P 2  contacting the second corner  512 . This makes it unlikely that the first vessel  81  will stick to the body unit  2  between the point P 1  and the point P 2 . In this state, a surgical needle is hooked easily to the sites from the point P 2  to the point P 1  from outside the first vessel  81  and the second vessel  82 . 
     Then, a surgical needle is hooked to remaining sites between the point P 1  and the point P 3  and a suture thread is put over these sites (step S 106 ). More specifically, the suture thread is put between a site of the first vessel  81  facing the second side  522  of the body unit  2  and a corresponding site of the second vessel  82 . 
     In step S 106 , the sites from the point P 1  to the point P 3  (right walls of the first vessel  81  and the second vessel  82 ) are continuously sutured together partially from outside in a direction from the point P 1  toward the point P 3 . At this time, the suture thread is not tightened but is kept in a loosened state. At this time, the body unit  2  may be pulled toward the direction of the second corner  512  during the suture. In this case, the right wall of the first vessel  81  is separated from the body unit  2 . By doing so, the surgical needle is hooked more easily to the first vessel  81  at the site between the point P 1  and the point P 3 . 
     Next, while a perfusate is supplied through the first opening  11 , the catheter connecting member  1  is pulled out of the first vessel  81  (step S 107 ).  FIG. 7  shows a state immediately after the catheter connecting member  1  is pulled out in step S 107 . Shortly thereafter, the suture thread put between the point P 1  and the point P 3  is tightened (step S 108 ).  FIG. 8  shows a state where the suture thread is being tightened in step S 108 . If there are sites between the point P 1  and the point P 3  left without being sutured, these sites are successively subjected to the continuous suture. By doing so, the sites between the point P 1  and the point P 3  are sutured together. In this way, the first vessel  81  and the second vessel  82  are sutured together along their entire peripheries to finish anastomosis of the first vessel  81  and the second vessel  82 . 
     Finally, the clamp and others are removed to restore a flow of blood in the second vessel  82  of the recipient (step S 109 ). By doing so, a blood flow is generated between the first vessel  81  and the second vessel  82 . 
     As described above, for suture of the site of the first vessel  81  facing the first side  521  in step S 104 , the body unit  2  is pulled toward the direction of the first corner  511  to separate the rear wall to be sutured from the catheter connecting member  1  and the front wall. Likewise, for suture of the site of the first vessel  81  facing the third side  523  in step S 105 , the body unit  2  is pulled toward the direction of the third corner  513  to separate the left wall to be sutured from the catheter connecting member  1 . Further, for putting of the suture thread over the site of the second vessel  81  facing the second side  522  in step S 106 , the body unit  2  is pulled toward the direction of the second corner  512  to separate the right wall to be sutured from the catheter connecting member  1 . In this way, suture of the first vessel  81  and the second vessel is facilitated. Namely, compared to the conventional triangular anastomosis surgery, workability of surgery is increased. 
     According to this embodiment, like in the conventional triangular anastomosis surgery, each of the first vessel  81  and the second vessel  82  are divided into three suture regions for suture. In this case, as each suture region of the first vessel  81  is located between the projections  51 , a surgical needle is hooked easily to a corresponding site. Thus, even when a catheter for supply or suction of a perfusate is connected to the first vessel  81  to be anastomosed, workability of surgery is still unlikely to be reduced. 
     The three suture regions formed between the three projections  51  each have a length of about one-third of the entire periphery of a vessel. This achieves continuous suture over a region of a comparatively great length of about one-third of the entire periphery of the vessel. If there are a large number of finely divided regions each defined as a region allowing continuous suture, the number of points to be ligated with a suture thread is increased to cause a problem of an extended duration of vascular anastomosis. In this regard, the number of the projections  51  is preferably two, three, or four. This achieves continuous suture over a region of a comparatively great length of about one-fourth or more of the entire periphery of a vessel in each suture region. As a result, it becomes possible to shorten a duration of vascular anastomosis. According to vascular anastomosis surgery by means of the conventional triangular anastomosis, a duration of the vascular anastomosis is about 15 minutes. By contrast, according to vascular anastomosis surgery using the catheter connecting member  1  as an anastomosis assist tool, a duration of the vascular anastomosis can be shortened to about five minutes. 
     The foregoing vascular anastomosis surgery performed while a perfusate is supplied to the first vessel  81  allows shortening of a duration of ischemia in a donor organ. According to the vascular anastomosis surgery by means of the conventional triangular anastomosis performed in the absence of a connected catheter, a duration of ischemia in a donor organ is about 15 minutes, which is equal to a duration of the vascular anastomosis. By contrast, the vascular anastomosis surgery using the catheter connecting member  1  as an anastomosis assist tool allows supply of a perfusate during implementation of the vascular anastomosis surgery, making it possible to shorten a duration of ischemia in a donor organ further to a duration less than a duration of the vascular anastomosis, which is about five minutes. 
     According to the conventional vascular anastomosis surgery, to reduce the occurrence of mixing of air bubbles into a vessel, a liquid such as physiological saline solution is required to be supplied into the vessel using a syringe, for example, immediately before suture of a last site. By contrast, according to this embodiment, immediately after the catheter connecting member  1  is pulled out in step S 107  while a perfusate is supplied to the first vessel  81 , the last sites can be sutured together in step S 108 . This allows omission of a step of supplying a liquid into a vessel using a syringe, for example. As a result, workability of surgery is increased. 
     According to this embodiment, the body unit  2  is a regular triangle in a cross section. The “regular triangle” mentioned in the present invention includes an “approximately regular triangle.” To be more specific, the catheter connecting member  1  of this embodiment is an approximately regular triangle with the rounded first corner  511 , the rounded second corner  512 , and the rounded third corner  513  corresponding to the three projections  51 . These three projections  51  are arranged uniformly in a peripheral direction. The “peripheral direction” mentioned herein means a direction along the circumference of a circle centered on the advancing axis  9 . If the catheter connecting member  1  is inserted into a vessel in a wrong direction, uniformly arranging the projections  51  facilitates adjustment of the direction of the insertion. 
     According to this embodiment, the body unit  2  in its entirety forms an anastomosis assist part including the projections  51  and having an approximately constant cross-sectional shape in a plane perpendicular to the advancing axis  9 . However, this is not intended to limit the present invention. The anastomosis assist part with a projection may be configured using only a part of the body unit  2 . For example, only the first linear part  21  of the body unit  2  may function as an anastomosis assist part with the projections  51 , and the other part of the body unit  2  may have a cylindrical outer peripheral surface. Alternatively, only the first linear part  21  and the bent part  22  of the body unit  2  may function as an anastomosis assist part with the projections  51 . 
     2. Modifications 
     While the one embodiment of the present invention has been described hereinabove, the present invention is not limited to the foregoing embodiment. 
       FIG. 9  is a cross-sectional view of a body unit  2 A of a catheter connecting member  1 A according to a modification. The body unit  2 A of the catheter connecting member  1 A in the illustration of  FIG. 9  includes three projections  51  arranged at uniform intervals in a peripheral direction. In the catheter connecting member  1 A, a side  52 A between two of projections  51 A adjacent to each other in the peripheral direction extends not in a linear shape but in a curved shape recessed inwardly. Thus, when a vessel is located along the outer periphery of the body unit  2 A, the probability of sticking of the vessel to the side  52 A is reduced further, compared to the case of a linear side. This increases workability further during implementation of vascular anastomosis surgery. 
       FIG. 10  is a cross-sectional view of a body unit  2 B of a catheter connecting member  1 B according to a different modification. In the catheter connecting member  1 B in the illustration of  FIG. 10 , a first corner  511 B corresponding to one of three projections  51 B has a different shape from a second corner  512 B and a third corner  513 B corresponding to the other two projections  51 B. Like in this case, the projections are not always required to have the same shape. 
       FIG. 11  is a cross-sectional view of a body unit  2 C of a catheter connecting member  1 C according to a different modification. In the catheter connecting member  1 C in the illustration of  FIG. 11 , the body unit  2 C has a rectangular cross-sectional shape. The body unit  2 C includes four projections  51 C and four linear sides  52 C. The four sides  52 C include two long sides  531 C and two short sides  532 C. 
     When this catheter connecting member  1 C is inserted into a vessel, the inner wall of the vessel receives strong force of widening the vessel outwardly applied to a point contacting each of the projections  51 C. This avoids application of large tension to a site of the vessel facing the side  52 C and controls force of sticking to the outer peripheral surface of the body unit  2 C at relatively low. Force of sticking to the outer peripheral surface of the body unit  2  is particularly small at a site of the vessel facing the long side  531 C. This facilitates suture of parts facing the long side  531 C during implementation of vascular anastomosis surgery using the catheter connecting member  1 C. Namely, workability is increased during implementation of the vascular anastomosis surgery. Like in the illustration of  FIG. 11 , the number of the projections  51 C provided to the body unit  2 C may be four. 
     The cross-sectional shape of a body unit with four projections is not always required to be a rectangle. The cross-sectional shape of the body unit may be a square or a rhombus, for example. Even in such cases, the inner wall of a vessel is still unlikely to stick to a side between the projections. This facilitates suture of parts facing the side to increase workability of vascular anastomosis surgery. 
       FIG. 12  is a cross-sectional view of a body unit  2 D of a catheter connecting member  1 D according to a different modification. In the catheter connecting member  1 D in the illustration of  FIG. 12 , the body unit  2 D has an oval cross-sectional shape. The body unit  2 D includes two projections  51 D projecting in the direction of the major axis of the oval shape, and two curved sides  52 D. 
     When this catheter connecting member  1 D is inserted into a vessel, the inner wall of the vessel receives strong force of widening the vessel outwardly applied to a point contacting each of the projections  51 D. This avoids application of large tension to a site of the vessel facing the side  52 D and controls force of sticking to the outer peripheral surface of the body unit  2 D at relatively low. This facilitates suture of parts facing the side  52 D during implementation of vascular anastomosis surgery using the catheter connecting member  1 D. Namely, workability is increased during implementation of the vascular anastomosis surgery. Like in the illustration of  FIG. 12 , the number of the projections  51 D provided to the body unit  2 D may be two. 
     In the foregoing embodiment, the shape of the body unit of the catheter connecting member is such that the bent part is arranged between the two linear parts. However, this is not the only shape of the body unit of the anastomosis assist tool according to the present invention. For example, the body unit may be formed only of a linear part, or may be formed of one linear part and one bent part. Alternatively, the body unit may be formed only of a curved part gently bent in its entirety. If appropriate, the shape of the body unit may be changed in response to location of a vessel during surgery into which the body unit is to be inserted, for example. 
     In the foregoing embodiment, the catheter connecting member is made only of elastomer. In the anastomosis assist tool of the present invention, however, a surface of the body unit  2  functioning as the anastomosis assist part may be subjected to surface treatment. Examples of the available surface treatment to be performed include surface lubricating treatment of reducing surface friction such as film coating, silicon-based thin film coating, Teflon (registered trademark) thin film coating, and surface chemical treatment for lower friction, and surface hardening treatment of increasing surface hardness. Implementation of the surface lubricating treatment makes it possible to reduce a coefficient of friction between the surface of the body unit  2  and a surgical needle. As a result, the occurrence of hooking of the surgical needle to the surface of the body unit  2  is reduced. Implementation of the surface hardening treatment makes it possible to reduce the occurrence of sticking of a surgical needle into the surface of the body unit  2 . As a result, workability of vascular anastomosis surgery is increased. 
     The anastomosis assist tool used in the foregoing embodiment and modifications is the catheter connecting member having a lumen to be connected to a lumen in a catheter. Meanwhile, an anastomosis assist tool without a lumen is applicable to vascular anastomosis surgery. Even in this case, workability can still be increased and a duration of surgery can still be shortened, compared to triangular anastomosis surgery generally performed. As a result, it becomes possible to shorten a duration of an ischemia state during organ transplant. 
     The components described in the foregoing embodiment and modifications may be consistently combined together, as appropriate. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1 ,  1 A,  1 B,  1 C,  1 D Catheter connecting member 
               2 ,  2 A,  2 B,  2 C,  2 D Body unit 
               3  Insertion unit 
               9  Advancing axis 
               10  Lumen 
               11  First opening 
               12  Second opening 
               21  First linear part 
               22  Bent part 
               23  Second linear part 
               31  First tapered part 
               32  First cylindrical part 
               33  Second cylindrical part 
               34  Third cylindrical part 
               35  Second tapered part 
               51 ,  51 A,  51 B,  51 C,  51 D Projection 
               52 ,  52 A,  52 C,  52 D Side