Surgical treatment device

A biotissue excising instrument includes a tubular sheath inserted into a body, manipulator inserted into the sheath through leading end of the manipulator and having a loop portion that can be unfolded and contracted to accommodate biotissue to be excised. A slit is formed leading end the sheath to project and sink loop portion of the treatment portion so that manipulator is advanced or retreated to laterally project or sink the loop portion out of or into the or contract the loop portion, the sheath, and a treatment portion provided at thus excising the biotissue loop portion.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from the prior Japan Patent Applications No. 2002-239615 filed on Aug. 20, 2002, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a biotissue excising instrument used to excise biotissue using, for example, a high-frequency current.

A high-frequency snare has hitherto been known as biotissue excising instrument used to excise biotissue using a high-frequency current. The high-frequency snare is, for example, composed of a sheath100inserted endoscopically into a coelom through, for example, a treatment instrument insertion channel in an endoscope, a manipulation portion102provided at a proximal end of the sheath100, a manipulation wire104inserted into the sheath100from the manipulation portion102, and a slider106provided in the manipulation portion102to manipulate the manipulation wire104so as to advance and retreat freely, as shown inFIG. 26.

The manipulation wire104has a snare wire110at its leading end portion as a treatment portion that freely projects out of and sinks into an opening100ain the leading end of the sheath100. The snare wire110is shaped like a loop. It unfolds owing to its own recovery force when projected out of the opening100ain the leading end of the sheath100when the slider106slides forward as shown inFIG. 26. Further, the snare wire110is compressed to reduce its own diameter when the slider106is slid toward an operator to pull part of the snare wire110into the sheath100via the manipulation wire104as shown inFIG. 27.

Accordingly, to excise biotissue, for example, a polyp using a high-frequency snare configured as described above, the snare wire110projected out of the opening100ain the leading end of the sheath100and then unfolded is first caught on the polyp A as shown inFIG. 28A. Subsequently, in this caught state, the manipulation wire104is pulled toward the operator (the slider106is slid toward the operator) to reduce the diameter of the snare wire110as shown inFIG. 28B. Thus, the polyp A is bound tightly. In this tightly bound state, a high-frequency current is passed through the snare wire110to excise the polyp A.

All conventional high-frequency snares are of a frontward projecting type in which the snare wire110projects out of the opening100ain the leading end of the sheath100. Thus, when biotissue is excised using only this forward-projecting type of high-frequency snare, several problems may occur as described below.

That is, with the forward projecting type high-frequency snare, the snare wire110is continuously contracted by the inner surface of the sheath100until the snare wire110projects out of the opening100ain the leading end of the sheath100. Thus, the snare wire100is not opened until it is projected out of the opening100ain the leading end of the sheath100by a certain distance by sliding the slider106of the manipulation portion102forward by a predetermined stroke. That is, with the forward projecting type high-frequency snare, the stroke of the slider106of the manipulation portion102cannot be used efficiently for the operation of increasing the diameter of the snare wire110. Thus, the snare wire110cannot be linearly unfolded according to the stroke of the slider106.

Further, with the forward projecting type high-frequency snare, the snare wire100must be unfolded with the leading end of the sheath100located in front of the polyp A and then allowed to approach the polyp A from above it so that the loop portion of the snare wire100is caught on the polyp A as shown inFIGS. 29A and 29B. However, the polyp A formed in the body does not always accommodate such an approach. It may be difficult to excise the polyp using the forward projecting type high-frequency snare depending on the manner of formation of the polyp.

Furthermore, with the forward projecting type high-frequency snare, rotation of the sheath100only causes the snare wire100to rotate around the axis of the sheath100. Thus, in spite a change in the direction in which the loop is opened, the position of the snare wire110is not changed. Consequently, if the polyp A is located, for example, at the side of the snare wire110and it is difficult to allow the snare wire to approach the polyp A (direct the opening100ain the leading end of the sheath100toward the polyp A), then the snare wire110cannot be caught on the polyp A. Therefore, it may be virtually impossible to carry out excision using the snare wire110.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide a biotissue excising instrument which allows the efficient unfolding of a loop used to tightly bind biotissue and which allows the loop to easily approach biotissue that may be located in various directions.

The object of the present invention is accomplished by the biotissue excising instrument described below. That is, according to an aspect of the present invention, there is provided a biotissue excising instrument comprising a tubular sheath inserted into a body, a manipulator inserted into the sheath so as to advance and retreat freely through the sheath, and a treatment portion provided at a leading end of the manipulator and having a loop portion that can be unfolded and contracted to accommodate biotissue to be excised, wherein a slit is formed in a side of a leading end of the sheath to project and sink the loop portion of the treatment portion so that the manipulator is advanced or retreated to laterally project or sink the loop portion out of or into the sheath through the slit to unfold or contract the loop portion, thus excising biotissue in the loop portion.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1A to 6show an embodiment of the present invention.FIGS. 1A and 1Bshow a high-frequency snare1as a biotissue excising instrument according to the present embodiment. As shown in the figures, the high-frequency snare1comprises a sheath2inserted endoscopically into a coelom through, for example, a treatment instrument insertion channel in an endoscope, and a manipulation portion3connected to a proximal end of the sheath2. In this case, the sheath is formed of a flexible tube. A conductive manipulation wire (a manipulator)4is inserted into the sheath2from the manipulation portion3so as to advance and retreat freely through the sheath2. The manipulation wire4also has a snare wire (treatment portion)10at its leading end portion, which freely projects out of and sinks into a side slit (an opening)2aformed in a side of leading end of the sheath2.

The manipulation portion3is comprised of a manipulation portion main body7and a slider8movably attached to the manipulation portion main body7to advance and retreat the manipulation wire4. Further, a finger placement portion9is provided on the proximal end portion of the manipulation portion main body7and on the slider8. Furthermore, the slider8is provided with an electrode cord connector11. The electrode cord connector11is adapted to electrically connect to the manipulation wire4and to a high-frequency power supply13via an electrode code16, the power supply providing a high-frequency current.

As shown inFIGS. 2A and 2Bin detail, the snare wire10is shaped like a loop by folding a conductive wire20. Specifically, the conductive wire20is folded so as to form a loop portion22. Then, one end portion20aof the conductive wire is waxed and fixed to the leading end of the manipulation wire4. On the other hand, the other end portion20bis waxed and fixed to a tubular slide member32located between the manipulation wire4and the loop portion22.

The slide member32can slide through the sheath2together with the snare wire10as the manipulation wire4advances and retreats. As shown in the enlarged views inFIGS. 3A to 3C, the slide member32has an insertion tube41through which the one end portion20aof the conductive wire20is inserted so as to advance and retreat freely through the tube. In the present embodiment, with the other end portion20bof the conductive wire20and the insertion tube41positioned in an inner hole in the slide member32, wax45is filled into the gaps between the members20band32and41to integrate the other end portion20bof the conductive wire20, the insertion tube41, and the slide member32together (seeFIG. 3B). Further, the one end portion20aof the conductive wire20is inserted into the insertion tube41so as to advance and retreat freely through the tube.

Furthermore, a pipe43is fitted, waxed, and fixed around the outer periphery of the one end portion20aof the conductive wire20located in front of the slide member32. In this case, the outer diameter of the pipe43is set at such a value that it cannot pass through the inner diameter of the insertion tube41.

Moreover, a bent convex portion25is formed at a leading end portion of the loop portion22corresponding to a turning point of the loop so as to project along the axial direction of the manipulation wire4within an opening surface24of the loop portion22.

Further, as shown inFIG. 2B, a conductive rod29is waxed and fixed to the proximal end of the manipulation wire4. A conductive connection portion27provided at the proximal end of the rod29is connected to the electrode cord connector11, provided in the slider8of the manipulation portion3.

As shown inFIGS. 4A to 4Din detail, the sheath2is formed as an elongated member consisting of resin material. It has a slit2ain a side of its leading end, out of which the loop portion22of the snare wire10is projected. In this case, the shape and dimensions (width W and length L2[seeFIG. 4C] or their dimensional ratio) of the side slit2aare set so that the loop portion22can be projected and unfolded stably without being twisted. In particular, the side slit2ais an area that does not only support the unfolding loop portion22at its root but also has biotissue such as a polyp pressed against itself when the loop portion22is used to tightly bind the biotissue as described later. Furthermore, the side slit2ais an area of the sheath2having a smaller strength because the sheath2is cut out in this area. Accordingly, if its shape and dimensions are set, considerations must be given to enable the side slit to stably support the loop portion22, allow the side slit to resist being pressed against the biotissue, and avoid reducing the strength of the sheath2. The length L2of the side slit2ais set depending on the previously described conditions and the size of the polyp to be excised.

Further, in the present embodiment, to compensate for the loss of strength of the sheath resulting from the formation of the side slit2a, a collar member30is arranged so as to be fitted in the sheath2and extends from the proximal edge of the side slit2atoward the proximal end of the sheath2by a predetermined length. The collar member30consists of, for example, a stainless steel pipe. When biotissue bound tightly by the loop portion22is pressed against the proximal edge of the side slit2a, the collar member30resists the pushing force from the biotissue to prevent the slit2afrom being torn and the sheath2from being deformed. It also prevents the tightly bound biotissue from entering the sheath2(to prevent sheath2from being clogged with the biotissue).

Furthermore, a wire holding portion2bis formed at the leading end of the sheath2to hold the leading end of the loop portion22while it is unfolding. A reduced diameter portion2cis also formed at the leading end of the sheath2as a stopper against which the leading end of the loop portion22is abutted to prevent the loop portion22from projecting out of the leading end of the sheath2. In this case, the wire holding potion2bis formed of an area of the sheath2which is located in front of the side slit2a. The inner diameter r and length L1of the wire holding portion2bare set so that a leading end portion of the snare wire10(loop portion22) can be inserted easily into the wire holding portion2band held reliably by it (seeFIG. 4A).

Moreover, the outer and inner diameters of the reduced diameter portion2care set to be smaller than those of other areas of the sheath2so as to form an opening39in the leading end surface of the sheath2. In the present embodiment, the leading end of the reduced diameter portion2cmay be fully closed instead of forming the opening39. However, the leading end of the reduced diameter portion2cdesirably has an opening in order to allow the sheath2to be washed properly.

Further, the proximal end portion of the sheath2is fixedly attached to a tubular member54. A fold preventing tube50are fitted around the outer periphery of the connection area between the tubular member54and the sheath2. Furthermore, the tubular member54is provided with a pipe sleeve52used to feed a liquid into the sheath2and a connection tube55connected to the manipulation portion3.

In the present embodiment, the lengths of the wire4and sheath2and the stroke S of the slider8are set so that the loop portion22is opened (unfolded) maximally when the slider8is placed at the front end of its movement path, whereas the loop portion22sinks in an area closer to the operator (a proximal end of the sheath2) than the collar member30(slit2a) when the slider8is placed at the rear end of its movement path (the position shown by the alternate long and short dash line inFIG. 1B). Further, in the present embodiment, the sheath2is preferably reinforced with a metal mesh (blade) over its total length so that rotation of the sheath2enables the loop portion22to rotate (the direction in which the opening surface24of the loop portion22is opened changes), i.e., so that the rotating force of the manipulation portion3can be transmitted properly to the loop portion22via the sheath2. In this case, as with generally known pressure-resistant hoses, the mesh is preferably embedded in the resin forming the sheath2. Furthermore, the manipulation wire4is desirably formed of a solid wire consisting of material with a high torque transferability so that rotation of the wire4enables the loop portion22to rotate (the direction in which the opening surface24of the loop portion22is opened changes), i.e., so that the rotating force of the manipulation portion3can be transmitted properly to the loop portion22via the wire4.

Now, description will be given of a case in which a polyp as biotissue is excised using the high-frequency snare1configured as described above.

First, with the leading end portion of the snare wire10(loop portion22) held by the wire holding portion2bso as to sink the loop portion22fully into the sheath (the loop portion22is not projected out of the side slit2a), the sheath2is inserted into a treatment instrument insertion channel in an endoscope (not shown). Then, while using the endoscope for observation, the manipulation portion of the endoscope is manipulated to guide the leading end portion of the sheath2to the lateral neighborhood of the polyp (affected area).

Next, the slider8is slid forward to advance the manipulation wire4. Then, since the snare wire10, connected to the manipulation wire4, has its leading end portion abutted against the reduced small portion2cand held by the wire holding portion2b, the loop portion22starts to project out of the side slit2ain the sheath2. That is, only the one end portion20aof the conductive wire20, connected to the manipulation wire4, slides and unfolds like a loop out of the side slit2aowing to its own recovery force. At this time, the loop portion22unfolds from the state shown by the solid line to the state shown by the broken line inFIG. 1with the width of its root kept equal to the length L2of the side slit2a(with a predetermined loop diameter initially maintained). Further, because of the effects of shape and dimensions of the side slit2aand the like, the loop portion22unfolds while being stably supported and without being twisted.

Furthermore, at this time, the opening direction of the opening surface24of the loop portion22is changed by, for example, rotating the sheath2or the manipulation wire4, so that the opening surface24of the loop portion22lies opposite the polyp A. In this case, if the manipulation wire is formed of a solid wire or the sheath2is reinforced with a metal mesh, then the rotating force of the manipulation portion3can be transmitted easily to the loop portion22. Accordingly, the opening surface24of the loop portion22can be placed opposite the polyp A easily. Then, the loop portion22unfolds until it becomes large enough to accommodate the polyp A. Then, the loop portion22is caught on the polyp A. This state is shown inFIG. 5A.

Once the loop portion22of the snare wire10is caught on the polyp A, the slider8is pulled toward the operator. Thus, the leading end portion of the loop portion22is released from the wire holding portion2bto pull part of the loop portion22into the sheath2. As shown inFIG. 5B, the loop portion22has its diameter reduced and tightly binds the polyp A. Then, the slider8is further slid toward the operator to press the polyp A, bound tightly by the loop portion22, against the proximal edge of the side slit2aas shown inFIG. 6. Subsequently, the high-frequency power supply13provides a high-frequency current to the snare wire10via the connector11to cut off the polyp A at the tightly bound part. At this time, even if the polyp A is pressed against the proximal edge of the side slit2a, it is possible to prevent the slit2afrom being torn, the sheath2from being deformed, and the pressed polyp A from entering the sheath2. This is because the collar member30as a reinforcing member is arranged at the proximal edge of the side slit2aagainst which the polyp A is pressed. When the polyp A is cut off and the slider7moves to the rear end of its movement path (the position shown by the alternate long and short dash line inFIG. 1B), the loop portion22fully sinks in an area closer to the operator than the color member30.

As described above, the high-frequency snare1as a biotissue excising instrument according to the present embodiment comprises the tubular sheath2inserted into a body, the manipulation wire4as a manipulator inserted into the sheath so as to advance and retreat through the sheath, and the snare wire10as a treatment portion provided at the leading end of the manipulation wire4and having the loop portion22that can be unfolded and contracted to accommodate biotissue to be excised. The high-frequency snare1is characterized in that the side slit2ais formed in the side of the leading end of the sheath2to project and sink the loop portion22of the treatment portion so that the manipulation wire4is advanced or retreated to laterally project or sink the loop portion22out of or into the sheath2through the side slit2ato unfold or contract the loop portion22, thus excising biotissue in the loop portion22.

Thus, by enabling the loop portion22, which tightly binds biotissue (tissue to be excised), to project and sink at the side of the sheath2, the loop portion22of the snare wire10can be caught easily on the tissue to be excised even if it is difficult to direct the leading end of the sheath2toward the tissue to be excised. In this case, when the sheath2is rotated, for example, around its axis0as shown inFIG. 7A, the loop portion22rotates over a wide range R from one end to the other end of the sheath2relative to the shaft0. Not only the opening direction of the opening surface23but also its position (the position of the loop portion22in which the biotissue is accommodated) change. Consequently, the loop portion22is allowed easily to approach biotissue that may be located in various directions. In contrast, with the frontward-projecting type in which the snare wire (loop portion)110is projected out of the front of the sheath100(the type shown inFIG. 26), rotation of the sheath100only causes the snare wire110to rotate around the axis0of the sheath100(rotation range R′) as shownFIG. 7B. Accordingly, in spite of a change in the opening direction of the loop, the position of the snare wire110remains unchanged. Consequently, substantially only the tissue located in front of the snare wire110(the projecting direction of the snare wire110) can be excised.

Further, in the present embodiment, the loop portion22is unfolded or contracted by projecting only one side of the loop portion22out of the slit2a, formed in the side of the sheath2. Thus, compared to the forward-projecting-type high-frequency snare in which the loop diameter of the snare wire does not become large enough until the snare wire unfolds to some degree after projecting out of the opening in the leading end of the sheath, the loop portion22starts to unfold simultaneously with its own projection out of the slit2awith the width of its root kept equal to the length L2of the side slit2a(with a predetermined loop diameter initially maintained). Further, in the present embodiment, the lengths of the wire4and sheath2and the stroke S of the slider8are set so that the loop portion22is opened maximally when the slider8is located at the front end of its movement path, whereas the loop portion22sinks in an area closer to the operator than the collar member30when the slider8is located at the rear end of its movement path (the position shown by the alternate long and short dash line inFIG. 1B). Accordingly, the stroke of the slider8can be used efficiently for the diameter increasing operation of the snare wire10(substantially all stroke of slider8of the manipulation portion3can be used for the diameter increasing operation of the snare wire10). Consequently, the loop portion22of the snare wire10can be unfolded efficiently.

In the present embodiment, the snare wire10(loop portion22) is projected out of the side slit2aand then unfolded by abutting its leading end portion against the reduced diameter portion2cso as to be held by the wire holding portion2b. However, as shown inFIGS. 8 and 9, the bent convex portion25at the leading end of the loop portion22may be fitted into the reduced diameter portion2cso as to allow the leading end portion of the loop portion22to be held mainly by the reduced diameter portion2c(seeFIG. 8). In this state, the loop portion22may be projected out of the side slit2aand then unfolded (seeFIG. 9).

If the bent convex portion25is thus held by the reduced diameter portion2c, the reduced diameter portion2cmust hold the bent convex portion25with such predetermined locking force that the loop portion22will not slip out of the side slit2awhile the loop portion22is unfolding. Specifically, the inner diameter of the reduced diameter portion2cis set so that when the bent convex portion25at the leading end of the loop portion22is fitted into the reduced diameter portion2c, the bent convex portion25has its diameter resiliently reduced (in this case, the bent convex portion25is contracted and deformed, for example, until the opposite portions of the conductive wire20which form the bent convex portion25are substantially parallel to each other), so that the resilient recovery force (reaction force) resulting from the decrease in diameter causes the bent convex portion25to be locked in the reduced diameter portion2c. The inner diameter of the reduced diameter portion2cis also set so that when the manipulation wire4is pulled to reduce the diameter of the loop portion22to tightly bind the polyp A, the bent convex portion25slips smoothly out of the reduced diameter portion2c.

The inner diameter of the reduced diameter portion2cis smaller than that of the wire holding portion2b. Accordingly, the leading end portion of the loop portion22can be held with strong locking force compared to the use of the wire holding portion2b. Then, by thus locking the bent convex portion25in the reduced diameter portion2cto hold it, the leading end portion of the loop portion22is held mainly by the reduced diameter portion2c. Thus, the wire holding portion2bhas only to lightly hold the leading end portion of the loop portion22. (to illustrate this sensuously, inFIG. 8, the force of the loop portion22reacting to the holding force of the reduced diameter portion2ais shown by a larger arrow f1, while the force of the loop portion22reacting to the holding force of the wire holding portion2bis shown by a smaller arrow f2). Thus, the length L1of the wire holding portion2bcan be minimized without reducing the total holding force. That is, the length L1of the wire holding portion2bcan be reduced compared to the case in which the leading end portion of the loop portion22is held mainly by the wire holding portion2b. Further, a decrease in the length L1of the wire holding portion2bserves to reduce the length m from the leading edge of the side slit2ato the leading end of the sheath2(because it is possible to reduce the size of part of the sheath2which projects forward from the unfolding area [treatment area] of the loop portion). This allows the device to be manipulated easily in a narrow lumen.

Further, when the loop portion22is unfolded or contracted by projecting only one side of the loop portion22out of the slit2a, formed in the side of the sheath2as in the present embodiment, if the length L2of the side slit2ais small, then an attempt to project more of the loop portion22out of the side slit2aincreases the curvature of the loop. Then, the force that increases the curvature of the loop acts on the wire10(20), thus twisting the loop22. Thus, as previously described, in the present embodiment, the shape and dimensions (the width W and length L2[seeFIG. 4C] or their dimensional ratio) of the side slit2aare set so that the loop portion22can be projected and unfolded stably without being twisted. Specifically, the width W of the slit2ais reduced (the width must be slightly larger than the outer diameter of the wire20) or the length L2of the slit2ais increased so as not to increase the loop curvature to the extent that the loop portion is twisted. However, if the length L2or width W of the slit2ais increased excessively, the strength of the sheath2decreases. In this case, part of the collar member30may be axially extended toward the slit2aby a predetermined amount to increase the reinforced area as shown inFIG. 11. In this case, the collar member30can be used to change the hardness of the sheath2step by step. This prevents the hardness of the sheath2from changing rapidly because of the slit2a, thus preventing the sheath2from being deformed when biotissue is bound tightly. Alternatively, to prevent the loop portion22from being twisted, it is contemplated that the wire20is formed of a solid wire. In this case, the wire20may have, for example, a rectangular cross section. It is also contemplated that the wire20may be formed of ultra-resilient alloy or may be provided with a tendency to bend so as to prevent twists on unfolding the loop.

Further, in the previously described embodiment, the opening direction of the opening surface24of the loop portion22is changed (the loop portion22is rotated) by rotating the sheath2or the manipulation wire4. However, many other methods can be used to change the opening direction of the opening surface24of the loop portion22. For example, as shown inFIGS. 12A and 12B, another tube60may be fitted around the outer periphery of the sheath2so as to advance and retreat freely. Then, the opening direction of the opening surface24of the loop portion22may be changed by pushing the tube60forward to change the direction in which the loop portion22projects out of the slit2a. Specifically, the leading end surface of the tube60is formed as a slope62by cutting the tube60obliquely relative to the axial direction. Thus, when the tube60is moved forward, the loop portion22projecting out of the slit2ais pushed against the slope62. Then, the loop portion22is displaced (brought down) along the slope62to change the direction in which the loop portion22projects out of the slit2a(seeFIG. 12B). That is, as the tube60is further moved forward, the amount of change in the projecting direction of the loop portion22increases. Consequently, the opening direction of the opening surface24of the loop portion22changes more significantly.

Furthermore,FIGS. 13A and 13Bshows another means for changing the opening direction of the opening surface24of the loop portion22. That is, in this example, another tube65is fitted around the outer periphery of the sheath2so as to advance and retreat freely, the tube having a plurality of openings65a,65b,65c, . . . that can be placed opposite the slit2ain the sheath2from different directions. Specifically, the plurality of openings65a,65b,65c, . . . , separated from one another along the axial direction, are formed in the tube65at different circumferential positions (they are separated from one another along the circumferential direction of the tube65). Further, the slit2ain the sheath2is formed to have such a width that the loop portion22can be projected in any directions in which the openings65a,65b,65c, . . . are formed in the tube65.

With such a configuration, the opening65a,65b,65c, . . . that is opposite to the slit2ain the sheath2can be changed (selected) simply by advancing or retreating the tube65. The loop portion22, projecting out of the slit2a, projects laterally out of the tube65through one of the openings65a,65b,65c, . . . which is opposite to the slit2a. That is, with the present configuration, the projecting direction of the loop portion22, projecting out of the slit2a, can be changed by advancing or retreating the tube65to selectively place an arbitrary one of the openings65a,65b,65c, . . . opposite the slit2a.

In this example, the openings65a,65b,65c, are separated from one another along the axial direction. However, the tube65may have only one opening, thereby, the projecting direction of the loop portion22may be changed by advancing the tube65to place the opening opposite the slit2aand, in this state, rotating the tube65to change the direction in which the opening lies opposite the slit2a.

FIG. 14shows a variation of the loop portion22. The loop portion22according to this variation has a guide portion70that can be inserted into an inner hole in the reduced diameter portion2cof the sheath2. In this case, the guide portion70extends axially forward from the bent convex portion25of the loop portion22. With such a guide portion70, after the polyp A has been bound tightly and then excised as shown inFIG. 6, the manipulation wire4can then be simply pushed in to allow the leading end of the loop portion22to be held by the wire holding portion2bagain, thus providing for the subsequent treatment. That is, simply by sliding the manipulation wire4forward without taking the sheath out of the body, the guide member70can be inserted into the inner hole in the reduced diameter portion2c. Further, the guide member70can then be used to easily guide and set the leading end portion of the loop portion22so as to be held by the wire holding portion2b.

In the present variation, the leading end portion of the loop portion22need not be held by the wire holding portion2bprovided that the guide member70is inserted into the reduced diameter portion2c. That is, the wire holding portion2bmay be omitted. Further, even when the polyp A is bound tightly and excised as shown inFIG. 6, the guide member70may remain inserted into the inner hole in the reduced diameter portion2c.

FIG. 15shows another means for more easily allowing the leading end portion of the loop portion22to be held by the wire holding portion2bagain. In general, after the leading end portion of the loop portion22has been released from the wire holding portion2b, when the manipulation wire4is pushed in forward again to allow the leading end portion of the loop portion22to be held by the wire holding portion2b, the loop portion22projects out of the side slit2aand unfolds. Accordingly, it becomes difficult to allow the leading end portion of the loop portion22to be held by the wire holding portion2b. Thus, in the example inFIG. 15, the tube75that can close the side slit2ais slidably fitted around the outer periphery of the sheath2. That is, if the leading end portion of the loop portion22is allowed to be held by the wire holding portion2bagain, the tube75may be slid forward to close the side slit2aas shown by the alternate long and short dash line inFIG. 15. Then, even if the manipulation wire4is pushed in forward, the loop portion22does not project out of the side slit2aor unfold. Consequently, it is possible to smoothly allow the leading end portion of the loop portion22to be held by the wire holding portion2b. In this regard, any of these functions of the tube75may be provided using the previously described tube60or65(seeFIGS. 12A,12B,13A, and13B).

As another means for smoothly allowing the leading end portion of the loop portion22to be held by the wire holding portion2b, a guide that directs the leading end of the loop portion22pushed out forward by the manipulation wire4, toward the wire holding portion2bmay be provided, for example, close to the leading edge of the side slit2a.

FIGS. 16A to 16Cshow another means for preventing the loop portion22projecting out of the side slit2afrom being twisted. As shown in these figures, a slot80is formed in the wire holding portion2bof the sheath2to hold the leading end portion of the loop portion22. The slot80has a width W′ substantially equal to the outer diameter of the conductive wire20and a major axis O′ extending in the direction in which the opening surface24of the loop portion22extends. Further, the collar member30is provided with a pair of holes30aand30bthrough which the one end portion20aand the other end portion20bof the conductive wire20, respectively, are inserted. These holes30aand30bhave an inner diameter substantially equal to the outer diameter of the conductive wire20.

With such a configuration, the loop portion22(opening surface24) is held substantially within one surface owing to the pair of holes30aand30bin the collar member and the slot80in the wire holding portion2b. This prevents the loop portion22projecting out of the side slit2afrom being twisted while unfolding.

Thus, the twist of the loop portion22projecting out of the side slit2acan be prevented by regulating the movement of the conductive wire20(holding the loop portion22substantially within one surface). In contrast, however, such twist can be prevented by allowing a large amount of the movement of the conductive wire20in a specified area. That is, in general, the loop portion22projecting out of the side slit2ais twisted when the curvature radius of the loop decreases to cause the force that increases the curvature radius (the force that avoids bending) to act on the wire10(20). Specifically, as shown inFIG. 17A, when the loop portion22unfolds, it is pushed at two locations, i.e., the leading edge P1and proximal edge P2of the side slit2a. The loop portion22is bent particularly significantly at the leading edge P1to increase the bending reaction force on the leading end side. Thus, the curvature increases. Accordingly, the twist of the loop portion22can be effectively prevented by hindering the loop portion22from undergoing strong bending reaction force at the leading edge P1of the side slit2awhile unfolding.

As means for hindering the loop portion22from undergoing strong bending reaction force at the leading edge P1of the side slit2a, the loop portion22may be allowed to move freely at the leading edge P1of the side slit2aso as not to bend under strong pushing force from the leading edge P1while unfolding (the proximal edge P2is the only pushing portion contributing to bending the loop portion), as shown inFIG. 17B. Specifically, for example, as shown inFIG. 19, when the length of bent convex portion25of the loop portion22(the distance from the leading end of the loop portion22to a shoulder portion T of the bent convex portion25) is defined as q, the inner diameter r′ of the wire holding portion2bis set to be equal to or larger than q (r′≧q) as shown inFIG. 18. Thus, while the loop is unfolding, the leading end portion (bent convex portion25) of the loop portion22can rotate freely within an internal space S of the wire holding portion2baround the shoulder portion T, which rests against the leading edge P1.

In this case, to reliably rest the shoulder portion T of the loop portion22against the leading edge P1of the side slit2abefore the loop unfolds, the length L1of the wire holding portion2bis preferably set to be substantially equal to the length q of the bent convex portion25. However, actually, even if the length q of the bent convex portion25is smaller than the length L1of the wire holding portion2b, the shoulder portion T of the loop portion22engages with the leading edge P1of the side slit2awhile the loop portion22is unfolding. This enables the loop portion22to unfold as shown inFIG. 17B. To clarify this point, separate and step-by-step description will be given of an unfolding operation performed by the loop if the length L1of the wire holding portion2bis substantially equal to the length q of the bent convex portion25, and of an unfolding operation performed by the loop if the length q of the bent convex portion25is smaller than the length L1of the wire holding portion2b.

FIGS. 20A to 20Dshow, step by step, the unfolding operation performed by the loop if the length L1of the wire holding portion2bis substantially equal to the length q of the bent convex portion25. First, as shown inFIG. 20A, when the leading end portion of the loop portion22is allowed to be held by the wire holding portion2b, the shoulder portion T of the loop portion22substantially automatically rests against the leading edge P1of the side slit2a. In this state, when the manipulation wire4is advanced, the loop portion22, connected to the manipulation wire4, starts to project out of the side slit2ain the sheath2because its leading end portion has been abutted against the reduced diameter portion2C and held by the wire holding portion2b. At this time, the leading end portion of the loop portion22rotates around the shoulder portion T resting against the leading edge P1, as shown inFIG. 20B(the bent convex portion25rotates within the internal space S of the wire holding portion2baround the shoulder portion T). In this initial stage of rotation, as shown by arrows inFIG. 20B, the loop portion22unfolds upward and backward. However, as the loop portion22further unfolds to further rotate its leading end portion around the shoulder portion T, the bent convex portion25is directed downward as shown inFIGS. 20C and 20D. Then, the-loop portion22starts to unfold upward and forward rather than upward and backward. Even in this case, the shoulder portion T engages with the leading edge P1, thus preventing the loop portion22from entirely slipping out of the sheath2through the side slit2a.

Provided that the leading end portion of the loop portion22can thus rotate freely around the shoulder portion T, which rests against the leading edge P1of the side slit2a(provided that the leading end portion of the loop portion22can be provided with a larger degree of freedom) on unfolding, it is impossible that the unfolding loop portion22bends under strong pushing force from the leading edge P1. This serves to reduce the bending reaction force to effectively prevent the loop portion22from being twisted.

FIGS. 21A to 21Eshow, step-by-step, the unfolding operation performed by the loop if the length q of the bent convex portion25is smaller than the length L1of the wire holding portion2b. First, as shown inFIG. 21A, when the leading end portion of the loop portion22is allowed to be held by the wire holding portion2b, the shoulder portion T of the loop portion22sinks completely into the wire holding portion2b. Then, in this state, when the manipulation wire4is advanced, the loop portion22projects out of the side slit2ain the sheath2and starts to unfold as shown inFIG. 21B. At this time, the loop portion22unfolds upward and backward. Accordingly, the shoulder portion T of the loop portion22slips out of the wire holding portion2band rests against and engages with the leading edge P1of the side slit2aas shown inFIG. 21C. Then, the leading end portion of the loop portion22starts to rotate around the shoulder portion T. Subsequently, as described inFIGS. 20B to 20D, the leading end portion continues to rotate so as to direct the bent convex portion25downward. Thus, the loop portion22starts to unfold upward and forward rather than upward and backward (seeFIGS. 21D and 21D).

FIGS. 22A and 22Bshow a variation of the high-frequency snare1. As shown in these figures, in this variation, the conductive wire20of the snare wire10is composed of a hard first wire portion20b′ and a second wire portion20a′ which is softer than the first wire portion20b′ and which has a smaller diameter than the first wire portion20b′. The first wire portion20b′ has one end secured to the slide member32and the other end turned up so as to form the bent convex portion25. On the other hand, the second wire portion20a′ has one end secured to the manipulation wire (multiple wires or torque wire)4and the other end secured to the first wire portion20b′. The manipulation wire4is electrically connected to the electrode cord connector11, provided in the slider8. It is also fixed to a rotator74provided in the manipulation portion3so that it can rotate with the rotator74.

Further, in the second wire portion20a′, at least one needle or projection-like non-slip chip73is formed inside the opening surface24of the loop portion22. Furthermore, the second wire portion20a′ is provided with a tendency to bend in its predetermined areas. Specifically, the second wire portion20a′ is provided with a tendency to bend in such a direction as resists the twist of the loop portion, in its areas70and71that cross the leading and proximal edges, respectively, of the side slit2aimmediately before the loop portion22starts to be twisted after projecting out of the side slit2a(the state shown in FIG.22A)(the areas provided with the tendency to bend are shown by the wavy lines in the figure).

Thus, in the present variation, the first wire portion20b′ is formed to be hard (have a large diameter), while the second wire portion20a′ is formed to be soft and to have a smaller diameter. Further, the second wire portion20a′ is provided with the tendency to bend in its areas70and71. This effectively suppresses the twist of the loop portion22projecting out of the side slit2a. Furthermore, even if the loop portion22is twisted, its twist can be easily cleared by rotating the rotator74and thus the manipulation wire4.

Moreover, in the present variation, the at least one needle or projection-like non-slip chip73is formed inside the opening surface24of the loop portion22. Accordingly, when the loop portion22is caught on the polyp A, the chip73cuts into the polyp A to prevent the loop portion22from slipping. Consequently, the loop portion22can be reliably caught on the polyp A to tightly bind it. In the present variation, to prevent the sheath2from slipping on the polyp A, the sheath2may be provided with non-slip means around the outer periphery of its leading end portion, located opposite the polyp A. Such non-slip means may be formed by, for example, making cuts like meshes or knurls in the outer peripheral surface of the sheath2.

FIGS. 23A to 23Cshow a variation of the manner in which the loop portion22is projected out of the side slit2ausing the slider8. As shown in these figures, in the present variation, the manipulation portion3is provided with two sliders8A and8B. The loop portion22can be projected out of the side slit2aby moving the sliders8A and8B relative to each other. Specifically, the one end portion20aof the conductive wire20, forming the snare wire10, is connected to the first slider8A, located in the front. On the other hand, the other end portion20bof the conductive wire20is electrically connected to the electrode cord connector11of the second slider8B, located in the rear.

With such a configuration, if the loop portion22is to be projected out of the side slit2a, then first, in the state shown inFIG. 23A, i.e., with the leading end of the snare wire10abutting against the reduced diameter portion2c, only the second slider8B is slid toward the operator. This state is shown inFIG. 23B. At this time, due to the bent convex portion25, the other end portion20bof the conductive wire20is pulled back toward the operator, while the one end portion20aof the conductive wire20is not pulled back toward the operator. Accordingly, the one end portion20aof the conductive wire20aprojects out of the side slit2aby an amount corresponding to the above difference (the amount by which the other end portion20bof the conductive wire20is pulled back). Further, in the state shown inFIG. 23B, when the first slider8A is slid toward the operator, the loop portion22can be pulled into the sheath2. This state is shown inFIG. 23C.

Consequently, this loop portion projecting manner also makes it possible to carry out a polyp excision procedure similar to that in the previously described embodiment.

FIGS. 24A to 25Eshow a method of utilizing the twist of the loop portion22to catch the loop portion22on the polyp A from its front or rear to tightly bind it.

FIGS. 24A to 24Eshow a method of catching the loop portion22on the polyp A from its front to tightly bind it. Specifically, first, as shown inFIG. 24A, the leading end of the sheath2is placed in front of and at the side of the polyp A. In this state, the loop portion22is projected out of the side slit2a. The loop portion22is also twisted to the degree that its opening surface24is not completely closed, so as to place the opening surface24in front of and opposite the polyp A. This state is shown inFIGS. 24B and 24C. Then, in this state, the sheath2is advanced at the side of the polyp A. Then, the loop portion22can be caught on the polyp A as shown inFIGS. 24D and 24E.

On the other hand,FIGS. 25A to 25Eshow a method of catching the loop portion22on the polyp A from its rear to tightly bind it. Specifically, first, as shown inFIG. 25A, the leading end of the sheath2is placed at the side of and behind the polyp A. In this state, the loop portion22is projected out of the side slit2a. The loop portion22is also twisted to the degree that its opening surface24is not completely closed, so as to place the opening surface24behind and opposite the polyp A. This state is shown inFIGS. 25B and 25C. Then, in this state, the sheath2is retreated at the side of the polyp A. Then, the loop portion22can be caught on the polyp A as shown inFIGS. 25D and 25E.

It should be appreciated that the present invention is not limited to the previously described embodiments and many variations of them may be made without deviating from the spirit of the present invention. For example, in the previously described embodiments, a high-frequency current is used to excise biotissue. However, the biotissue excising instrument according to the present invention is not limited to electric excision. It is also applicable to various excision forms such as thermal and mechanical excisions.