Medical instrument for use in combination with an endoscope

A flat section is provided at a distal end of a snare pipe located in a sheath. When a snare is pushed, the snare is moved in the snare pipe with a looped expansible section of the snare kept in contact with both opposite sides of the flat section. As a result, the expansion direction of the looped section is regulated.

BACKGROUND OF THE INVENTION 
This invention relates to a medical instrument which is designed to be 
inserted into a patient's body through the instrument guiding channel of 
an endoscope, already inserted into the patient's body, for continuously 
cutting living tissue and collecting a plurality of living tissue samples. 
International Publication PCT WO95/08291, for example, discloses a medical 
instrument for sampling living tissue. FIG. 13A shows an essential part of 
a medical instrument (a) described in the publication. The medical 
instrument (a) has a flexible sheath (b) which can be inserted into an 
endoscope. The sheath (b) has an opening (d) at its distal end. A 
small-diameter inner tube (c) is inserted in the sheath (b). The inner 
tube (c) is fixed on the inner peripheral surface of the sheath (b). 
An operational wire (e) is inserted in the inner tube (c). A looped cutting 
wire (h) is connected to an end of the operational wire (e). The cutting 
wire (h) can be protruded to the outside of the opening (d) of the 
flexible sheath (b) by operating the operational wire (e). 
When the operational wire (e) has been pulled to the hand side, the cutting 
wire (h) is retreated into the flexible sheath (b) and the loop of the 
wire (h) is contracted. 
When the operational wire (e) has been pushed, the cutting wire (h) is 
protruded to the outside of the sheath (b) through the opening (d). At 
this time, the loop of the cutting wire (h) expands due to its elastic 
force such that it crosses the opening (d). A retractor (f) is provided in 
the flexible sheath (b) for pushing and moving an excised tissue piece 
(p). 
When using the medical instrument (a), it is inserted into the forceps 
channel of the endoscope. Then, the operational wire (e) is pushed to 
protrude the cutting wire (h) to the outside of the sheath (b) and expand 
it. In this state, living tissue is inserted into the sheath (b) through 
the opening (d) using the cutting wire (h). 
After that, the operational wire (e) is pulled to the hand side, thereby 
pulling the cutting wire (h) into the flexible sheath (b). At this time, 
the loop diameter of the cutting wire (h) is gradually reduced while it is 
pulled into the flexible sheath (b). The living tissue already inserted in 
the sheath (b) is cut by the tightening force of the gradually 
diameter-reduced wire (h). The excised tissue piece (p) is contained in a 
tissue storing space (g) defined in the sheath (b). 
This cutting operation is repeated a necessary number of times, and a 
plurality of excised tissue pieces p1, p2, p3 and p4 are sequentially 
stored in the tissue storing space (g). Thereafter, the medical instrument 
(a) is removed from the endoscope, and the retractor (f) is protruded to 
the outside of the sheath through the opening (d), thereby pushing the 
excised tissue pieces p1, p2, p3 and p4 out of the tissue storing space 
(g). Thus, the tissue pieces are collected. 
European Patent EP 0761170 discloses a medical instrument of another 
structure. As is shown in FIG. 13B, it discloses a medical instrument (k) 
which has an outer cylinder (i), and a looped cutting wire (j) which can 
expand at an end of the outer cylinder (i). In this case, a living tissue 
piece is excised by pulling the cutting wire (j) from the end of the outer 
cylinder (j) into it. 
Moreover, Japanese Patent Application No. 8-310664 (this document was 
published on Jun. 12, 1998 (KOKAI publication No. 10-146345) and had not 
yet been published when the present application was filed) discloses a 
medical instrument for endoscopes, which excises living tissue through an 
endoscope when a high frequency current is flown. In this case, as shown 
in FIG. 13C, an operational wire (q) is axially movably provided in a 
flexible sheath (m). A substantially looped cutting wire (n) is mounted at 
an end of the operational wire (q) such that it can protrude out of and 
retreat into the sheath (m). When a high frequency current is flown into 
the cutting wire (n) via the operational wire (q), it can excise living 
tissue. 
Further, in this instrument, the sheath (m) has a slotted end portion (o). 
The loop of the cutting wire (n) is engaged with the slotted portion (o) 
when the wire (n) is pulled into the sheath (m). Where the loop of the 
cutting wire (n) is engaged with the slotted portion (o) of the sheath 
(m), the direction of the high frequency cutting wire (n) can be changed 
by rotating the wire (n) together with the sheath (m) when axially 
rotating the sheath (m). 
When, in the case of the medical instrument disclosed in PCT WO95/08291, 
the cutting wire (h) has been pulled out of the flexible sheath (b) and 
has expanded due to its own elastic force, the expanded section of the 
wire (h) must be situated at the opening (d) of the sheath in order to 
excise tissue in good condition by the wire (h). 
Since, however, the cutting wire (h) inserted in the sheath (b) is a 
relatively slender flexible wire, it may not sufficiently follow the 
rotation of the sheath (b). Accordingly, where the sheath (b) can easily 
rotate about its axis as in the operation of inserting the medical 
instrument (a) into the endoscope, it is highly possible that the cutting 
wire (h) inserted in the sheath (b) will not follow the axial rotation of 
the sheath (b). In this case, it is possible that the expanded section (h) 
of the cutting wire (h) will be displaced from the opening (d) of the 
flexible sheath (b) when the medical instrument (a) protrudes from the tip 
of the endoscope, thereby disabling collection of tissue. 
Moreover, to correct the displacement of the expanded section of the 
cutting wire (h) from the opening (d) of the sheath (b), it is necessary 
to rotate the expanded section relative to the opening (d). Thus, handling 
of the medical instrument (a) is too much trouble. 
Furthermore, European Patent EP 0761170 discloses means for limiting the 
direction of expansion of the cutting wire (j) by providing strap (s) at 
an end of the wire (j) and fixing one end of strap (s) to the outer 
peripheral surface of the outer cylinder (i). 
In this case, however, fixing the strap (s) on the outer peripheral surface 
of the outer cylinder (i) inevitably complicates the structure of the 
medical instrument (k) and increases the outer diameter of the entire 
insertion section of the instrument (k). Accordingly, it is difficult to 
reduce the outer diameter of the entire insertion section to an extent 
which enables insertion of the insertion section of the instrument (k) 
into the forceps channel of the endoscope. 
In addition, the strap (s) of the cutting wire (j) limit the movement of 
the wire (j) toward the axis of the outer cylinder (i). Thus, the strap 
(s) not only reduce the degree of freedom of the movement of the wire (j), 
but also become obstacles when grasping tissue by the wire (j). 
In the case of the structure described in Japanese Patent Application No. 
8-310664, a rather sharp edge portion may be formed at the slotted portion 
(o) of the sheath (m) with which the cutting wire (n) is engaged. This 
sharp edge portion may damage the wall surface of the forceps channel of 
the endoscope while the medical instrument is inserted into it, or may 
injure a mucous membrane in a cavity of the body. 
BRIEF SUMMARY OF THE INVENTION 
The invention has been developed in light of the above-described matters, 
and is aimed at providing a medical instrument for use in combination with 
an endoscope, which has a simple structure and can reliably excise tissue, 
with a predetermined relationship maintained between the expansion 
direction of a cutting wire and the direction of an open end of an outer 
sheath, and without damaging the wall of a forceps channel or injuring a 
mucous membrane in a cavity of the body. 
To attain the aim, there is provided a medical instrument for use in 
combination with an endoscope, comprising: 
a long, slender flexible sheath to be inserted into a patient's body 
through a channel of the endoscope; 
operation means inserted in the sheath such that it is axially movable; 
a looped cutting wire connected to a distal end of the operation means; and 
an operation section provided at a proximal end side of the flexible sheath 
for pushing and pulling the operation means to thereby protrude the 
cutting wire to the outside of the sheath and retreat the cutting wire 
into the sheath through a distal end of the sheath, 
wherein: 
the cutting wire is elastically deformed in a direction in which its loop 
contracts, when it is retreated into the sheath, and deformed in a 
direction in which its loop expands, when it is protruded to the outside 
of the sheath; 
the cutting wire cuts part of living tissue of the patient's body while it 
is pulled into the sheath after it is protruded to the outside of the 
sheath, thereby storing a cut and sampled piece in the sheath; and 
the sheath has, at its distal end, flat loop expansion direction regulating 
means for regulating the loop expansion direction of the cutting wire. 
As described above, the cutting wire is guided by the flexible sheath, and 
engaged, at the distal end of the sheath, with those inner surfaces of the 
flat section of the flat loop-expansion-direction regulating means, which 
are situated in a direction of the major diameter of the flat section. By 
virtue of this structure, rotation of the cutting wire relative to the 
flexible sheath, which will occur when the loop of the cutting wire is 
protruded to the outside of the sheath, is prevented to thereby regulate 
the expansion direction of the loop of the cutting wire so that the wire 
can be always protruded in a predetermined direction. Therefore, the 
cutting wire is developed at the flat opening, which enables rotation of 
the cutting wire in accordance with the rotation of the sheath, i.e. 
enables positioning of the wire in a direction in which the wire can 
easily grasp tissue. Further, when sampling living tissue, the instrument 
is inserted into the patient's body through the forceps channel of the 
endoscope, thereby sucking target tissue into the expanded section of the 
cutting wire. The cutting wire is then axially moved to tightly hold and 
cut the target tissue. After that, the instrument is removed from the 
forceps channel of the endoscope. 
The invention employs, at the distal end of the flexible sheath, the flat 
loop-expansion-direction regulating means for regulating the loop 
expansion direction of the cutting wire. This means that the positional 
relationship between the expansion direction of the cutting wire and the 
outside sheath can be kept constant with a simple structure, whereby 
living tissue can be sampled in a reliable manner without greatly damaging 
the wall of the forceps channel or a mucous membrane of the patient's 
body. 
Additional objects and advantages of the invention will be set forth in the 
description which follows, and in part will be obvious from the 
description, or may be learned by practice of the invention. The objects 
and advantages of the invention may be realized and obtained by means of 
the instrumentalities and combinations particularly pointed out 
hereinafter.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to FIGS. 1A-4D, a first embodiment of the invention will be 
described. FIG. 1A shows the entire structure of a medical instrument 1 
according to the first embodiment, which is designed for use in 
combination with an endoscope. The medical instrument 1 comprises an 
insertion section 2 and an operation section 3. The insertion section 2 is 
long and slender and can be inserted into the forceps channel (instrument 
guiding channel) of an endoscope (not shown). The operation section 3 is 
secured to the proximal end of the insertion section 2. 
The operation section 3 comprises a casing 4, which is formed of a 
substantially cylindrical member. The casing 4 has a suction port 5 
outwardly projecting from an end thereof connected to the insertion 
section 2. An external suction means 6 having a connection tube 6a can be 
connected to the suction port 5 via the connection tube 6a. The suction 
means 6 may be an electrically driven pump, a manual pump, a rubber ball, 
a large syringe, etc. 
A finger ring 7 is provided on the proximal end of the casing 4. An axially 
slidable slider 8 is mounted on the casing 4 between the suction port 5 
and the finger ring 7. 
The insertion section 2 comprises a thin, long flexible sheath 9 and a hard 
distal section 10 connected to the distal end of the sheath 9. The sheath 
9 includes an outer tube 11 as shown in FIG. 1B. The outer tube 11 is made 
of a material which is flexible and has a sufficient strength against 
compression or tension. It is preferable that the outer tube 11 is a 
tightly wound coil, or a reinforced tube which is obtained by, for 
example, coating the inner and outer surfaces of a tube formed by weaving 
stainless steel wires, with a resin such as polyamide, 
tetrafluoroethylene, copolymer of tetrafluoroethylene and 
hexafluoropropylene, or polyethelene. Alternatively, the outer tube may be 
a reinforced tube which is obtained by attaching plural wires, over the 
entire length, to a tube formed of a resin material as above. 
Further, as shown in FIG. 1D, a suction lumen 12 and a snare lumen 13 are 
provided in a cavity within the outer tube 11. The suction lumen 12 is 
airtightly provided in the cavity of the outer tube 11. The proximal end 
of the suction lumen 12 is airtightly connected to the suction port 5 of 
the operation section 3. The suction lumen 12 is formed of a material 
which can secure the airtightness of the lumen over the length thereof up 
to the hard distal section 10. The material is, for example, a resin such 
as tetrafluoroethylene, polyethylene, etc. or a metal having a high 
elasticity. 
A snare wire (operating means) 14 is inserted in the snare lumen 13 such 
that it can axially move relative to the sheath 9. The distal end of the 
snare wire 14 is connected to the proximal end of a looped snare (cutting 
wire) 16 via a connection pipe 15. 
As shown in FIG. 1B, the distal hard section 10 comprises a distal cover 17 
fixed to the distal end of the outer tube 11, a snare pipe 18 fixed to the 
distal end of the snare lumen 13, and a suction pipe 19 fixed to the 
distal end of the suction lumen 12. 
It is desirable that the distal cover 17 should be made of a flexible and 
transparent material, for example, a resin such as polyamide, 
tetrafluoroethylene, copolymer of tetrafluoroethylene and 
hexafluoropropylene, or polyethelene. However, the cover may be formed of 
a relatively hard resin such as polycarbonate. 
An inclined portion 17a with an appropriate inclination angle .theta.a to 
the axis of the medical instrument 1 is formed at the distal end of the 
cover 17. An elliptic opening 17b is formed in the inclined portion 17a. 
An index 20 is secured to the outer peripheral surface of the cover 17 
close to the distal end of the inclined portion 17a. The edge which 
defines the opening 17b is rounded so that it will not damage the forceps 
channel of the endoscope and the cavity of the patient's body. The distal 
end of the snare pipe 18 is secured to the rear end side of the inclined 
portion 17a of the cover 17. 
The snare pipe 18 is a cylindrical guide means for guiding the snare 16. 
While being guided by the snare pipe 18, the snare 16 is movable along the 
axis of the flexible sheath 9 between a position shown in FIG. 2A in which 
the snare 16 projects to the outside of the distal cover 17 through the 
opening 17b, and a position shown in FIG. 2B in which the snare 16 is 
stored within the distal cover 17 through the opening 17b. 
The snare pipe 18 may be formed of a relatively hard resin such as 
polysulfon, polyfenylsulfon, polycarbonate, etc. However, it is desirable 
that the pipe should be formed of a relatively flexible metal such as 
stainless steel or an Ni--Ti alloy with superelasticity. 
The distal end of the snare pipe 18 is flattened and forms a flat section 
(loop expansion direction regulating means) 21. The flat section 21 
regulates the direction of loop expansion of the snare 16. The flat 
section 21 has an edge 22 formed at the distal opening of the pipe is 
level with the opening 17b. 
The outer diameter of the connection pipe 15 is slightly smaller than the 
inner diameter of the snare pipe 18. The forward movement of the 
connection pipe 15 is interrupted when the distal end of the pipe 15 
contacts the proximal end of the flat section 21 within the snare pipe 18. 
A stop ring 23 is secured to the proximal end of the snare pipe 18. The 
stop ring 23 has a hole 24 whose inner diameter is smaller than the outer 
diameter of the connection pipe 15. The rearward movement of the 
connection pipe 15 is interrupted when the proximal end of the pipe 15 
contacts the front end of the stop ring 23. 
The snare 16 has an expansible section 16a formed at its distal end, and a 
support section 16b formed in the rear of the expansible section 16a and 
consisting of a pair of linear wires. The expansible section 16a will show 
a substantially circular shape when it is expanded. Moreover, as shown in 
FIG. 1B, the expansible section 16a of the snare 16 is bent at a 
predetermined angle .theta.b with respect to the rear support section 16b. 
The inclination angle .theta.b is set smaller than the inclination angle 
.theta.a of the distal cover 17 (.theta.b&lt;.theta.a). 
The area occupied by the loop section 16a when it is expanded is set 
sufficiently greater than the area of the opening 17b of the inclined 
portion 17a of the distal cover 17. 
The snare 16 may be formed of stainless spring steel, a superelasticity 
alloy wire material such as an Ni--Ti alloy, or a resin such as polyamide, 
which are elastic sufficient to expand and contract and have a sufficient 
sharpness as knives. The outer diameter .phi. of the snare wire is set at, 
for example, about 0.1-0.2 mm to secure both sufficient tensile strength 
and sharpness necessary to cut living tissue. The minor diameter (opening 
width) of the edge 22 of the flat section 21 of the snare pipe 18 is set 
at a value at which almost no clearance is defined when the snare 16 
passes through the opening. 
A cutout 25 is formed in the outer peripheral surface of the distal end of 
the suction pipe 19. Further, a retractor 26 in the form of a wire is 
inserted in the suction pipe 19 such that it can protrude and retreat. A 
tissue stopper 27 is secured to the distal end of the retractor 26. 
The size of the tissue stopper 27 is set at a value which enables its 
insertion into the distal cover 17 and also prevents movement of living 
tissue over the stopper 27 to the proximal end of the cover 17. 
Specifically, as shown in FIG. 1C, the area of the stopper 27 is set at 
about 60-80% of the area which is obtained by subtracting the cross 
section of the interior and wall of the snare pipe 18 from the cross 
section of the interior of the distal cover 17. Further, the shape of the 
stopper 27 is set at one which can be formed in the area obtained by 
subtracting the cross section of the snare pipe 18 from that of the cover 
17. 
A drawing section 28 for drawing the retractor 26 is protruded on the outer 
peripheral surface of the casing 4 of the operation section 3. The 
proximal end of the retractor 26 is extended to the outside of the 
instrument through the drawing section 28. An operation knob 29 for 
operating the retractor 26 is secured to the proximal end of the retractor 
26. 
The proximal end of the outer tube 11 is secured to the distal end of the 
operation section 3. The proximal end of the snare wire 14 is fixed to the 
slider 8 within the operation section 3. A movable pipe 30 is provided in 
the operation section 3 as shown in FIGS. 3A and 3B such that it can move 
along the axis of the medical instrument 1. The slider 8 is also secured 
to the movable pipe 30 in the operation section 3. 
The distal end of the movable pipe 30 is airtightly and slidably connected 
to the proximal end of the suction lumen 12 by a sealing member 31. A 
suction hole 32 is formed in a proximal end portion of the movable pipe 
30. 
As illustrated in FIGS. 3A and 3B, three O-rings 33a, 33b and 33c are 
fitted in the casing 4 at appropriate intervals along the axis of the 
medical instrument 1. 
The three O-rings 33a, 33b and 33c are fitted on the movable pipe 30. A 
first airtight chamber 34 is defined between the O-rings 33a and 33b, and 
a second airtight chamber 35 between the O-rings 33b and 33c. The first 
airtight chamber 34 communicates with the suction port 5 of the operation 
section 3. 
The suction hole 32 of the movable pipe 30 is shifted between a first 
position shown in FIG. 3A and a second position shown in FIG. 3B as the 
slider 8 is moved back and forth in the axial direction of the operation 
section 3. 
More specifically, when the slider 8 is in its fore position, the suction 
hole 32 is kept at the first position shown in FIG. 3A, where the hole 32 
communicates with the first airtight chamber 34. At this time, the snare 
16 is protruded to the outside of the snare pipe 18 as shown in FIG. 2A. 
When the slider 8 is shifted to its rear position, the suction hole 32 is 
shifted to the second position shown in FIG. 3B, where the hole 32 
communicates with the second airtight chamber 35. At this time, the snare 
16 is stored within the distal cover 17 through the opening 17b as shown 
in FIG. 2B. 
The operation of the above-described structure will now be described. When 
the medical instrument 1 according to the embodiment is used, the 
connection tube 6a of the external suction means 6 is previously connected 
to the suction port 5 of the operation section 3 and operated. In this 
state, the slider 8 is pulled to store the snare 16 into the snare pipe 18 
as shown in FIG. 2B. At this time, the expansible section 16a of the snare 
16 is kept elastically deformed between both the sides of the flat section 
21 of the snare pipe 18. 
Where the snare 16 is stored in the snare pipe 18, the suction hole 32 of 
the movable pipe 30 is shifted to the second position shown in FIG. 3B, 
where the hole 32 communicates with the second airtight chamber 35. 
Accordingly, in this state, negative pressure (i.e. a suction force 
created by the suction means 6) is prevented from being applied in the 
suction lumen 12. 
Also, at that time, the proximal end of the connection pipe 15 in the 
distal hard section 10 is kept in contact with the front end of the stop 
ring 23. In this state, the insertion section 2 is inserted into the 
patient's body through the forceps channel of the endoscope. 
To insert the insertion section 2, the endoscope or the medical instrument 
1 is moved while observing the interior of the body through the endoscope, 
thereby guiding the distal hard section 10 of the insertion section 2 to a 
target mucous membrane H. 
When the target mucous membrane H has been reached, the slider 8 is shifted 
to the distal end, thereby pushing the snare 16 out of the snare pipe 18 
as shown in FIG. 2A. While the snare 16 is pushed, the expansible section 
16a of the snare 16 moves in contact with longitudinal side surfaces of 
the edge 22 of the flat section 21 of the pipe 18. After the expansible 
section 16a passes through the flat section 21 of the pipe 18, it expands 
into a circular shape due to its own expanding force. More specifically, 
outside the snare pipe 18, the section 16a shows a circular shape just 
ahead of the opening 17b of the inclined portion 17a of the distal cover 
17. The circular shape of the section 16a is similar in shape to and 
parallel in plane to the opening 17a as shown in FIG. 2A. 
Further, when the section 16a of the snare 16 has expanded into a circular 
shape outside the snare pipe 18, the distal end of the connection pipe 15 
in the distal hard section 10 contacts the proximal end of the flat 
section 21 of the snare pipe 18. At this time, the suction hole 32 of the 
movable pipe 30 is situated in the first position shown in FIG. 3A, where 
the hole 32 communicates with the first airtight chamber 34. Accordingly, 
negative pressure (a suction force created by the suction means 6) is 
applied in the suction lumen 12. 
In this state, the opening 17b of the distal cover 17 is brought into 
contact with the target mucous membrane H, thereby sucking it into the 
opening 17b as shown in FIG. 4A. 
Then, the slider 8 is pulled, thereby storing the section 16a of the snare 
16 into the snare pipe 18 and tightly holding the membrane H, as is shown 
in FIG. 4B. 
Subsequently, the slider 8 is further pulled, thereby cutting the membrane 
H sucked in the opening 17b of the distal cover 17, using the snare 16 and 
the edge 22 of the snare pipe 18, as is shown in FIG. 4C. The sampled 
piece Ha is located close to the opening 17b of the cover 17. Since at 
this time, as is shown in FIG. 3B the suction hole 32 of the movable pipe 
30 is shifted into the second airtight chamber 35, the negative pressure 
applied in the suction lumen 12 is cut off. 
Subsequently, the endoscope or the medical instrument 1 is operated to 
guide the distal hard section 10 to the next target mucous membrane H. 
After the next target membrane is reached, the distal end of the slider 8 
is moved to protrude the snare 16 from the snare pipe 18. Since at this 
time, the suction hole 32 of the movable pipe 30 is shifted to the first 
airtight chamber 34, negative pressure is applied in the suction lumen 12. 
The negative pressure applied moves the first sampled piece Ha located in 
the cover 17 close to the opening 17b, to an inner portion of the cover 17 
as indicated by the broken line in FIG. 4C. More precisely, the piece Ha 
is moved until it contacts the tissue stopper 27 of the retractor 26. 
The above-described operation is repeated, thereby storing the first, the 
second, . . . and the n-th sampled pieces Ha, Hb, . . . in the distal 
cover 17 in this order. The second sampled piece Hb, for example, is 
stored in a portion of the cover 17 closer to the opening 17b than the 
first sampled piece Ha. 
The maximum number of the pieces Ha, Hb, . . . which can be stored in the 
cover 17 is determined when the interior of the distal cover 17 is filled 
with such pieces and no negative pressure can be applied thereto. 
After a desired number of pieces are sampled, the medical instrument 1 is 
removed from the forceps channel. Then, the suction means 6 is detached 
from the suction port 5, and the knob 29 is moved to the distal end side 
to protrude the tissue stopper 27 from the distal cover 17, thereby 
collecting the sampled pieces Ha, Hb, . . . in the order opposite to the 
storing order. 
The above-described structure provides the following advantages: Since the 
embodiment employs the flat section 21 at that distal end of the snare 
pipe 18 through which the snare 16 is protruded and retreated, the 
direction of expansion of the section 16a of the snare 16 is kept constant 
and kept parallel to the opening 17b of the inclined portion 17a of the 
cover 17 when the section 16a is protruded to the outside of the snare 
pipe 18. Accordingly, it is not necessary to perform positioning for 
aligning the snare 16 with the opening 17b, which means that reliable 
sampling of tissue can be performed by a simple operation. 
Moreover, the distal hard section 10 at the distal end of the sheath 9 is 
provided with both the opening of the flat section 21 of the snare pipe 18 
for protruding the snare 16, and the opening 17b of the inclined portion 
17a of the cover 17. By virtue of this structure, the medical instrument 1 
can instantly cut living tissue having entered the distal cover 17, using 
the snare 16. 
The snare pipe 18 provided at the distal end of the sheath 9 cooperates 
with the snare 16 to cut living tissue. Thus, sharply cut living tissue 
can be sampled. 
Furthermore, the distal end of the cover 17 has the inclined portion 17a 
which inclines at the appropriate angle .theta.a with respect to the axis 
of the medical instrument 1. This enables the formation of an opening 17b 
of a large area in the distal cover 17, and hence sampling of large 
tissue. Also, the inclined structure enables easier, smoother 
expansion/storage operation of the snare 16 than the case where the 
opening 17b is perpendicular to the axis of the medical instrument 1. 
Since the expansible section 16a of the snare 16 is formed oblique, the 
distance between itself and the inclined portion 17a, i.e. the opening 
17b, of the cover 17 can be minimized, which facilitates reception of the 
living tissue into the opening 17b. This also enables easy and smooth 
expansion/storage of the expansible section 16a of the snare 16. 
Further, since the distal edge 22 of the flat section 21 of the snare pipe 
18 is level with the distal opening 17b of the distal cover 17, living 
tissue received in the opening 17b can be reliably caught and cut. 
Since living tissue can be kept sucked in the distal opening 17b of the 
cover 17 by negative pressure which is created by the suction means 6, it 
is not necessary to puncture the tissue with the opening 17b, and hence 
not necessary to form a very sharp opening 17b. This being so, tissue 
sampling can be performed without hurting the patient's body. 
Since the distal cover 17 has a storage space for storing excised tissue 
pieces Ha, . . . , a plurality of living tissue pieces can be sampled 
without removing the medical instrument 1 from the endoscope. 
In addition, since the distal cover 17 is made of a transparent material, 
storage of pieces Ha, Hb, . . . can be confirmed with the eyes through the 
endoscope, and hence sampling be performed without failure. Further, the 
tissue stopper 27 and the retractor 26 much facilitate the collection of 
plural sampled pieces. 
The edge 22 of the flat section 21 of the snare pipe 18 cooperates with the 
snare 16 to cut tissue. Thus, a mucous membrane H can be cut sharply. 
The outer diameter of the wire material of the snare 16 is set at about 
0.1-0.2 mm, which enables mechanical cutting of the membrane H even when 
no high frequency current is flown into the snare 16. 
Yet further, since the snare 16 is made of a superelastic material, the 
shape of the expanded snare 16 is not easily deformed even after storage 
of the snare 16 is repeated or holding/cutting of living tissue by the 
snare 16 is repeated. Thus, the medical instrument 1 is highly durable 
under repeated use. 
FIGS. 5A and 5B show a second embodiment of the invention. This embodiment 
is obtained by altering the medical instrument 1 of the first embodiment 
(shown in FIGS. 1A-4D) as described below. In FIGS. 5A and 5B, similar 
structural elements to those in the first embodiment are denoted by 
corresponding reference numerals, and no explanations will be given 
thereof. 
In the second embodiment, a grasping means 41 which can be protruded from 
and retreated into the distal cover 17 is provided in the suction lumen 12 
of the outer tube 11, in place of the suction means 6. 
The grasping means 41 includes an operation wire 42 which is slidable 
inserted in the suction lumen 12, a distal unit 43 connected to the distal 
end of the wire 42, a pair of openable grasping members 44 incorporated in 
the distal unit 43, and an opening/closing mechanism incorporated in the 
distal unit 43 for opening/closing the grasping members 44. 
To protrude the grasping means 41 to the outside of the distal opening 17b 
of the distal cover 17 during use of the medical instrument 1 of the 
embodiment, the grasping means 41 is protruded through the expansible 
section 16a of the snare 16 to grasp a mucous membrane H. Then, the 
grasping means 41 is pulled to the proximal end of the instrument to 
thereby pull the membrane H into the distal cover 17 as shown in FIG. 5A. 
After that, the slider 8 is pulled, thereby storing the expansible section 
16a of the snare 16 into the snare pipe 18 to tightly hold the membrane H, 
as is shown in FIG. 5B. 
The above-described structure provides the following advantages: 
The second embodiment employs, in the suction lumen of the outer tube 11, 
the grasping means 41 which can be protruded from and retreated into the 
distal cover 17, in place of the suction means 6 provided at the proximal 
end side of the sheath 9 in the first embodiment. Accordingly, living 
tissue can be pulled into the distal cover 17 without using the suction 
means 6. 
Further, since the grasping means 41 for grasping the target mucous 
membrane H makes it unnecessary to bring the distal opening 17b of the 
inclined portion 17a of the cover 17 into precise contact with the 
membrane H. This means that the degree of target shooting is enhanced. 
FIG. 6A shows a third embodiment of the invention. This embodiment is 
obtained by altering the medical instrument 1 of the first embodiment 
(shown in FIGS. 1A-4D) as described below. 
In this embodiment, an external snare pipe 51 for storing the snare 16 is 
provided on the outer peripheral surface of the sheath 9 of the insertion 
section 2. The distal end of the snare pipe 51 extends to the distal 
opening 17b of the distal cover 17. The other structural elements of the 
third embodiment are similar to those employed in the first embodiment, 
and hence no explanations will be given thereof. 
Since in this structure, the snare pipe 51 is externally provided on the 
sheath 9 of the insertion section 2, the entire inner space of the distal 
cover 17 can be used as a sample storing space. Further, the instrument is 
free from, for example, the disadvantage that sampled pieces Ha, . . . 
stored in the cover 17 are caught and damaged by the snare pipe 51. 
FIG. 6B shows a fourth embodiment of the invention. This embodiment is 
obtained by altering the medical instrument 1 of the third embodiment 
(shown in FIG. 6A) as described below. 
This embodiment employs a multi-lumen tube 61 which is obtained by 
integrally forming, as one body, the external snare pipe 51 and the sheath 
9 of the insertion section 2. The multi-lumen tube 61 includes a large 
first lumen 62 corresponding to the sheath 9 of the insertion section 2 of 
the third embodiment, and a small second lumen 63 corresponding to the 
external snare pipe 51. The first lumen 62 is used to store sampled 
pieces, while the second lumen 63 is used to store the snare 16. The other 
structural elements are similar to those employed in the first embodiment, 
and hence no description will be given thereof. 
As in the third embodiment, the instrument of the fourth embodiment is free 
from, for example, the disadvantage that sampled pieces Ha, . . . stored 
in the first lumen 61 are caught and damaged by the snare pipe 51. The 
instrument of the fourth embodiment is also advantageous in that the 
multi-lumen tube 61 obtained by integrally forming the external snare pipe 
51 and the sheath 9 of the insertion section 2 in the third embodiment 
reduces the number of the entire component parts and hence facilitates the 
assemblage of the medical instrument. 
FIG. 7 shows a fifth embodiment of the invention. This embodiment is 
obtained by altering the medical instrument 1 of the first embodiment 
(shown in FIGS. 1A-4D) as described below. 
In this embodiment, the snare pipe 18 can be protruded to the outside of 
the distal cover 17 and retreated into the cover 17 through the opening 
17b. The snare pipe 18 is supported by the inner peripheral surface of the 
cover 17 using an appropriate support member, such that it is slidable 
along the axis of the sheath 9, together with, for example, a snare lumen 
13. The other structural elements in this embodiment are similar to those 
employed in the first embodiment, and hence will not be described. 
When using the medical instrument 1 of the fifth embodiment, first, the 
snare 16 is protruded from the opening 17b of the distal cover 17 to suck 
a mucous membrane H into the expanded section 16a of the snare 16. 
Subsequently, the snare pipe 18 is protruded out of the opening 17b of the 
cover 17 with the snare fixed, as is shown in FIG. 7. After that, the 
snare 16 is retreated into the snare pipe 18 to thereby tightly hold the 
membrane H. 
Since in the above structure, the snare 16 does not move axially with 
respect to the opening 17b of the cover 17 when the membrane H is held 
after it is sucked into the expanded section 16a of the snare 16, there is 
no possibility of the membrane's slipping and escaping therefrom. 
FIG. 8 shows a sixth embodiment of the invention. This embodiment is 
obtained by altering the medical instrument 1 of the first embodiment 
(shown in FIGS. 1A-4D) as described below. 
In this embodiment, the expansible section 16a of the snare 16 is not 
inclined with respect to a rear-side support section 16b of the snare 16 
(the inclination angle .theta.b=0), while a distal end section 71 of the 
snare pipe 18 has a bent section 73 which is inclined at a predetermined 
angle .theta.c with respect to a rear-side section 72 of the pipe 18. 
When the snare 16 has been protruded from the snare pipe 18 during the use 
of the medical instrument 1, it is developed in accordance with the shape 
of the bent section 73, thereby forming a loop section 16a just ahead of 
the opening 17b of the distal cover 17. 
Although in the above structure, the expansible section 16a of the snare 16 
is not inclined with respect to the rear-side support section 16b, it can 
be arranged parallel in plane to the opening 17b of the distal cover 17. 
Therefore, the snare 16 is free from reaction of bending which will occur 
in the case where the section 16a is bent from the rear-side support 
section 16b. Accordingly, the snare 16 is free from non-plastic 
deformation. 
FIGS. 9A and 9B show a seventh embodiment of the invention. This embodiment 
is obtained by altering the medical instrument 1 of the first embodiment 
(shown in FIGS. 1A-4D) as described below. 
In this embodiment, a male screw section 81 is provided at the distal end 
of the outer tube 11 of the sheath 9 as shown in FIG. 9B. Further, a 
sleeve 82, which is screwed onto the male screw section 81, is provided at 
the proximal end of the distal cover 17. Thus, the medical instrument 1 is 
constructed such that the cover 17 can be connected to the outer tube 11 
of the sheath 9 by screwing the sleeve 82 onto the male screw section 81. 
After the medical instrument 1 is removed from the forceps channel of the 
endoscope, the distal cover 17 can be pulled out of the distal end of the 
outer tube 11 by rotating the sleeve 82 and disengaging it from the male 
screw section 81. As a result, plural sampled pieces Ha, Hb, . . . stored 
in the distal cover 17 can be easily exposed to the outside of the 
instrument and collected. 
Since in the above structure, plural sampled pieces Ha, Hb, . . . stored in 
the distal cover 17 can be collected without using the axially movable 
retractor 26 and the tissue stopper 27, the piece collecting mechanism can 
be made simple in structure, and the collecting operation can be performed 
more easily. 
FIGS. 10-11C show an eighth embodiment. This embodiment is obtained by 
altering the medical instrument 1 of the first embodiment (shown in FIGS. 
1A-4D) as described below. FIG. 10 roughly shows the entire structure of 
the medical instrument 1 of the eighth embodiment. In this embodiment, 
similar elements to those in the first embodiment are denoted by 
corresponding reference numerals, and no description will be given 
thereof. 
This embodiment employs a collecting system 101 for collecting sampled 
pieces Ha, Hb, . . . without removing the medical instrument 1 from the 
forceps channel of the endoscope. The collecting system 101 includes a 
water supply unit 102 and a sample collecting unit 103, which are to be 
coupled to the operation section 3 of the instrument 1. 
A projecting water supply port 104 is provided on that distal end portion 
of the casing 4 of the operation section 3 which is close to the insertion 
section 2 of the instrument 1. Further, a rear end opening 105 is formed 
in the proximal end of the casing 4. A distal end portion of a substantial 
cylindrical slider 106 is axially movably inserted in the rear end opening 
105. A collecting port 107 is provided in the rear end of the slider 106. 
As is shown in FIGS. 11A-11C, the suction lumen 12 in the sheath 9 of the 
instrument 1 is airtightly connected to the distal end of the slider 106 
with a seal member 12s interposed therebetween, and communicates with the 
collecting port 107 via the slider 106. The proximal end of the snare wire 
14 is secured, in the operation section 3, to a connecting tube 108 at the 
collecting port 107 side, as is shown in FIG. 11C. 
The snare lumen 13 is formed of an air-impermeable material and airtightly 
connected to the water supply port 104 of the operation section 3. Two 
water lumens 91 made of an air-impermeable material is provided in the 
sheath 9 as shown in FIG. 11B. The water supply lumens 91 has a distal end 
opening into the distal cover 17 and a proximal end airtightly connected 
to the water supply port 104 of the operation section 3. 
The cross section of the inner space of the suction lumen 12 is set at 1.0 
mm.sup.2 or more. The sum of the cross section of the snare lumen 13 
except for that of the snare wire 14, and the cross section of the water 
supply lumens 91 is set at 0.5 mm.sup.2 or more. 
The sheath 9 is formed of a flexible material which has a sufficient 
strength against compression and tension. For example, a reinforced tube 
is suitable for the sheath 9, which is obtained by coating the inner and 
outer surfaces of a tube formed by weaving stainless steel wires, with a 
resin such as polyamide, tetrafluoroethylene, copolymer of 
tetrafluoroethylene and hexafluoropropylene, or polyethelene. Moreover, 
the outer diameter of the sheath 9 is set at a value which permits its 
insertion into the forceps channel of the endoscope, i.e. about 2-4 mm. A 
communication hole 92 is formed in a distal end portion of the snare pipe 
18, thereby causing the snare lumen 13 and the suction lumen 12 to 
communicate with each other. A sample trap 117 is provided in the sample 
collecting unit 103. A sample filter 118 is detachably provided in the 
sample trap 117, and a water reservoir tank 119 is provided below the trap 
117. The collecting port 107 of the casing 4 of the operation section is 
connected to a suction means 120 via the sample trap 117. 
The water supply unit 102 includes a water supply tank 121 and a water 
supply pump 122. The water supply tank 121 is connected to the water 
supply port 104 of the casing 4. The water supply pump 122 is interposed 
between the water supply port 104 and the water supply tank 121, and is 
operable when necessary. A stop valve 123 is provided between the water 
supply pump 122 and the water supply port 104. A finger position section 
124 is secured to a portion of the operation section 3 close to the 
collecting port 107. 
The operation of the above-described structure will be described. When 
using the medical instrument 1 of this embodiment, the water supply unit 
102 is beforehand connected to the water supply port 104 of the operation 
section 3, and the sample collecting unit 103 is connected to the 
collecting port 107. The suction means 120 is started to be driven before 
using the instrument. 
After that, the slider 106 is pulled to store the snare 16 into the snare 
pipe 18. Keeping this state, the insertion section 2 is inserted into the 
patient's body through the forceps channel of the endoscope. 
While observing the inserted state of the insertion section 2 through the 
endoscope, the endoscope or the medical instrument 1 is moved to guide the 
distal hard section 10 of the insertion section 2 to a target mucous 
membrane H. When the section 10 has reached the target mucous membrane H, 
the slider 106 is shifted to the distal end side, thereby pushing the 
snare 16 out of the snare pipe 18 and permitting it to expand. In this 
state, the opening 17b of the distal cover 17 is brought into contact with 
the target mucous membrane H, thereby sucking it into the opening 17b. 
Thereafter, the slider 106 is pulled, thereby storing the section 16a of 
the snare 16 into the snare pipe 18 and tightly holding the membrane H 
(shown in FIG. 4B). Subsequently, the slider 106 is further pulled, 
thereby cutting the membrane H sucked in the opening 17b of the distal 
cover 17, using the snare 16 and the edge 22 of the snare pipe 18. The 
sampled piece Ha is located close to the opening 17b of the cover 17. 
When in this state, the stop valve 123 has been opened, negative pressure 
is applied to the snare lumen 13 and the water supply port 104 via the 
water supply lumens 91 and the communication hole 92, with the result that 
water in the water supply tank 121 is sucked into the distal cover 17. 
At this time, the sampled piece Ha is mixed with the sucked water and air 
flown through the opening 17b of the distal cover 17, and is flown into 
the suction lumen 12 and then into the collecting port 107. 
If the sampled piece Ha blocks the suction lumen 12, the water supply pump 
122 is driven to increase the amount of water supplied to the suction 
lumen 12 via the water supply lumens 91 and the snare lumen 13, thereby 
releasing the blocking. 
Moreover, the sampled piece Ha having passed the collecting port 107 is 
caught by the sample filter 118, and at the same time, the sucked water is 
stored in the reservoir tank 119. After that, the sample filter 118 is 
detached from the sample trap 117, thereby permitting collection of the 
piece Ha. 
After collecting the sampled piece Ha, the same operation as above is 
repeated to thereby collect a desired number of sample pieces, and then 
the medical instrument 1 is removed from the forceps channel. 
The above-described structure has the following advantages: 
A plurality of sampled pieces Ha, Hb, . . . can be collected immediately 
after they are sampled, before the instrument 1 is removed from the 
forceps channel. Further, since the pieces Ha, Hb, . . . are collected one 
by one, this instrument is free from the disadvantage that the sampled 
pieces are mixed and the sampling order of the pieces becomes ambiguous, 
or that the pieces become indiscriminable from each other. 
FIGS. 12A-12D show a ninth embodiment. A high frequency snare 131 employed 
in this embodiment comprises a flexible sheath 132 and an operation 
section 133 connected to the proximal end of the sheath 132. 
An operational wire 134 is provided in the sheath 132 such that it is 
movable back and forth. A snare 135 is secured to the distal end of the 
operational wire 134. 
The operation section 133 includes a slider 136 connected to the distal end 
of the operational wire 134, and an operation main section 137 secured to 
the proximal end of the sheath 132. The slider 136 has a connection 
terminal 138 electrically connected to the operational wire 134. The 
connection terminal 138 can be connected to the connector of a high 
frequency power supply cord (not shown). 
As shown in FIG. 12B, the sheath 132 is formed by adhering inner and outer 
resin tubes 139 and 140 to other, with a metallic reinforcing member 141 
of a multi-start coil shape interposed therebetween. The reinforcing 
member 141 increases the torque transmission force of the flexible sheath 
132. 
The flexible sheath 132 has a flat section 142 at its distal end. The flat 
section 142 has opposite end surfaces 143a and 143b which can be engaged 
with proximal-end-side inclined sections 144a and 144b of a snare 135. 
The operation of the above structure will be described. When a surface 
lesion 151 as shown in FIG. 12C has been found as a result of observation 
through the endoscope (not shown), a physiological salt solution is 
injected into the tissue with the surface lesion to thereby form a raised 
portion 153. 
Subsequently, the high frequency snare 131 is inserted into the cavity 
through the forceps channel of the endoscope, thereby pushing the slider 
136, and protruding the snare 135 from the distal end of the flexible 
sheath 132 to permit the snare to develop into a circular shape. If at 
this time, the resultant circular snare 135 is parallel in plane to a 
mucous membrane surface 152 with the surface lesion 151, it can easily 
catch the raised portion 153 therein. 
If, on the other hand, the circular snare 135 is perpendicular to the 
mucous membrane surface 152 as shown in FIG. 12C, it cannot easily catch 
the raised portion 153 therein. In this case, the entire high frequency 
snare 131 is rotated by operating the proximal end of the instrument, 
thereby engaging the snare 135 with the distal flat section 142 of the 
sheath 132. As a result, the snare 135 rotates in accordance with the 
rotation of the sheath 132. The sheath 132 is rotated until the circular 
snare 135 becomes parallel in plane to the membrane surface 152 as shown 
in FIG. 12D. Then, the raised portion 153 is taken into the circular snare 
135. 
In this state, the slider 136 is pulled to pull the snare 135 into the 
flexible sheath 132, thereby contracting the snare 135 and tightly holding 
the root of the raised portion 153. Then, a high frequency current is 
flown into the snare 135 to thereby cut the raised portion 153. 
Since in the above structure, the snare 135 can be reliably rotated by 
rotating the proximal-end of the flexible sheath 132, the loop of the 
snare 135 can be easily and reliably made parallel in plane to the 
membrane surface 152. 
Naturally, the invention can be modified in various manners without 
departing from the scope thereof. 
Additional advantages and modifications will readily occur to those skilled 
in the art. Therefore, the invention in its broader aspects is not limited 
to the specific details and representative embodiments shown and described 
herein. Accordingly, various modifications may be made without departing 
from the spirit or scope of the general inventive concept as defined by 
the appended claims and their equivalents.