Stent

Provided is a stent which is not easily displaced from a dwell site in a biological lumen and which has an excellent ability to follow a biological lumen. This stent (bile duct stent 100) is to dwell inside a biological lumen (bile duct B) and is provided with a stent main body section (110) having a cylindrical shape. The stent main body section is configured to be capable of expanding and contracting in the radial direction that is approximately orthogonal to an axial direction, has a relatively large expanding force in one portion (center portion) corresponding to the predetermined position at the indwelling site in the biological lumen, and a relatively small expanding force at other portions (both end portions) which have different positions in the axial direction from that of the one portion.

TECHNICAL FIELD

The present invention relates to a stent to be placed in a living body lumen.

BACKGROUND ART

Conventionally, there has been a known stent that is placed in a stenosis site or an occluded site generated in a living body lumen such as blood vessel, esophagus, bile duct, trachea, and urinary duct, and increases a diameter of a lesion site to maintain an opening state of the living body lumen (for example, see Patent Document 1).

PRIOR ART DOCUMENT

Patent Document

Patent Document 1: Japanese Patent Publication No. 4651943

SUMMARY OF THE INVENTION

Technical Problem

However, in the cases of Patent Document 1 and the like, a stent can easily follow a living body lumen by improving flexibility of the stent, but if an expanding force of the stent is small, there is a problem that the stent tends to be displaced from an indwelling site in the living body lumen.

On the other hand, if the expanding force of the stent is increased, adhesiveness of the stent to the living body lumen is improved, so that the stent is hardly displaced, but accordingly an axial force also increases, and the stent hardly follows the living body lumen. In addition, when the stent is placed again, the stent may be difficult to remove from the living body lumen. To improve adhesiveness to the living body lumen, it is not sufficient to simply increase the expanding force of the stent.

An object of the present invention is to provide a stent that is hardly displaced from an indwelling site in a living body lumen and has good followability to the living body lumen.

Solution to Problem

The stent according to the present invention is

a stent that is placed in a living body lumen, the stent including a stent main body section in a cylindrical shape, wherein

the stent main body section is formed expandably and contractibly in a radial direction substantially orthogonal to an axial direction, and has a portion that corresponds to a predetermined position on an indwelling site in the living body lumen and exerts a relatively large expanding force, and a different portion that is different in axial position from the portion and exerts a relatively small expanding force.

Advantageous Effect of the Invention

According to the present invention, the stent is hardly displaced from the indwelling site in the living body lumen, and followability of the stent to the living body lumen can be improved.

DESCRIPTION OF THE EMBODIMENT

Hereinafter, the embodiment of the present invention will be explained in detail with reference to the figures. In this embodiment, as an example of the present invention, a bile duct stent100will be explained, which is placed in a bile duct B and used in order to treat occlusion (stenosis) by widening a lesion site of the bile duct B (e.g. occluded site or stenosis site of the bile duct B) (seeFIG. 4A) outward in a radial direction.

FIG. 1is a perspective view illustrating the bile duct stent100,FIG. 2Ais a plan view illustrating the bile duct stent100viewed from an X direction inFIG. 1, andFIG. 2Bis a side view illustrating the bile duct stent100viewed from a Y direction inFIG. 1. In addition,FIG. 3is a sectional view illustrating a stent main body section110taken along line A-A inFIG. 2A. As illustrated inFIG. 1toFIG. 3, the bile duct stent100includes the stent main body section110, a valve section120, and a removal assistant130.

The stent main body section110has a cylindrical shape that demarcates a flow path for bile. In the stent main body section110, one end portion110apositioned on a left front side inFIG. 1is referred to as “first end portion110a”, and a different end portion110bpositioned on a right back side inFIG. 1is referred to as “second end portion110b”. The bile duct stent100is placed in the bile duct B such that the first end portion110ais positioned on a downstream side and the second end portion110bis positioned on an upstream side in a bile flow direction (seeFIG. 4, and the like).

The stent main body section110has a skeleton portion111, a membrane portion112, and a stretch restriction portion113.

The skeleton portion111is a stiffening member that holds the membrane portion112in a predetermined expansion state. For example, the skeleton portion111is a self-expandable stent skeleton formed into a cylindrical shape by spirally winding a metal wire rod while the metal wire rod is bended such that crest portions and trough portions are alternately formed in the axial direction.

The skeleton portion111is configured to be self-expandable in the radial direction substantially orthogonal to the axial direction, from a contraction state where the skeleton portion111contracts inward to an expansion state where the skeleton portion111expands outward to demarcate a cylindrical flow path. For example, when the skeleton portion111is pulled in the axial direction, the skeleton portion111contracts inward in the radial direction and stretches in the axial direction. On the other hand, when the skeleton portion111is released from the contraction state, the skeleton portion111shortens in the axial direction while expanding outward in the radial direction by a self-expanding force.

In the bile duct stent100, an outer face of the stent presses an inner face of the bile duct B by the self-expanding force of the skeleton portion111, and in this state, the skeleton portion111can be deformed according to an external force applied from the outer face side of the stent. That means, the skeleton portion111is stretchable in the axial direction and has a cylindrical shape capable of expanding and contracting in the radial direction substantially orthogonal to the axial direction.

Examples of a material of the metal wire rod for forming the skeleton portion111include known metals or metal alloys typified by a stainless steel, an Ni—Ti alloy (Nitinol), a titanium alloy, and the like. Also, an X-ray detectable alloy material may be used. In this case, a position of the bile duct stent100can be confirmed from outside of the body. Incidentally, the skeleton portion111may be made of a material other than metal materials (e.g. ceramic, resin, or the like).

Additionally, in the skeleton portion111, there is a difference in a winding frequency per a unit length of the metal wire rod in the axial direction between the first and second end portion110aand110bsides and a middle side. The middle side portion of the stent main body section110in the axial direction exerts a relatively large expanding force, and the first and second end portion110aand110bsides of the stent main body section110in the axial direction exert a relatively small expanding force.

That means, the bile duct stent100is placed such that the middle side portion in the axial direction of the stent main body section110corresponds to a predetermined position of the bile duct B (e.g. a central or similar position of an occluded site or stenosis site). A region R1(hereinafter referred to as a proximal side region R1) on the first end portion110aside where the removal assistant130is provided, and a region R2(hereafter referred to as a distal side region R2) on the second end portion110bside exert expanding forces that are smaller than an expanding force exerted by a region R3(hereinafter referred to as a middle side region R3) on the middle side. Herein, the compared expanding forces are values when inner diameters of the proximal side region R1, the distal side region R2, and the middle side region R3are equal, typically when the bile duct stent100is placed in the bile duct B. Since the expanding force depends on a ratio of the skeleton portion111(amount of the skeleton), a magnitude of the expanding force can be determined depending on a density of the skeleton portion111. That means, in the proximal side region R1and the distal side region R2of the stent main body section110, the skeleton portion111is “sparser” than the middle side region R3.

Specifically, when the skeleton portion111is formed by weaving one wire rod with a substantially constant wire diameter (sectional area) while spirally winding the wire rod, the portion having a smaller winding frequency per the unit length in the axial direction (portion having a long spiral pitch) is “sparser” than the portion having a larger winding frequency (portion having a short spiral pitch) in the skeleton portion111. That means, the proximal side region R1and the distal side region R2of the stent main body section110has a relatively smaller winding frequency per the unit length in the axial direction than of the middle side region R3.

For example, when the bile duct stent100in the most expanded state has a straight cylindrical shape, since the inner diameter of the bile duct stent100is constant over the whole length in the axial direction, the magnitude of the expanding force can be determined depending on the density of the skeleton portion111regardless of the expansion state. Thus, in the stent main body section110, the expanding force exerted by the middle side region R3corresponding to the predetermined position of the occluded site or the stenosis site of the bile duct B is relatively large, so that adhesiveness to the occluded site or the stenosis site of the bile duct B can be improved, and the stent is hardly displaced.

In addition, since the proximal side region R1and the distal side region R2exert relatively small expanding forces, an axial force of the stent main body section110can be prevented from increasing excessively. That means, since the stent main body section110can follow a shape of the bile duct B even if the middle side region R3exerts a large expanding force, it is possible to prevent development of so-called kink in which the end portion of the stent main body section110is embedded in the bile duct wall with time and occluded by the axial force.

Herein, when the bile duct stent100is removed, the proximal side region R1of the stent main body section110is a portion closest to a recovery catheter22. In the indwelling state, the proximal side region R1of the stent main body section110exerts an expanding force smaller than the expanding force exerted by the middle side region R3, and adhesiveness of the proximal side region R1to the bile duct wall is lower than of the middle side region R3. Thereby, the proximal side region R1of the stent main body section110is easily peeled from the bile duct wall, so that workability for removing and recovering the bile duct stent100is improved.

In addition, when the bile duct stent100is placed, the distal side region R2of the stent main body section110is a portion that is first released from a sheath. That means, when the stent is accommodated in the sheath, the distal side region R2of the stent main body section110exerts an expanding force smaller than the expanding force exerted by the middle side region R3, and adhesiveness of the distal side region R2to the sheath is lower than of the middle side region R3. Thereby, when the bile duct stent100is released by relatively moving the sheath and the bile duct stent100, a friction resistance between the distal side region R2of the stent main body section110and the sheath is reduced, so that the bile duct stent100can be easily released.

Incidentally, a material, a wire type (e.g. a round wire rod such as a wire, or a rectangular wire rod obtained by laser cutting), a wire diameter (sectional area), a folding frequency and a folded shape in the circumferential direction (a number and a shape of the crest portions), an interval in the axial direction between the wire rods (spiral pitch (amount of skeleton per a unit length)), and the like, of the wire rod for forming the skeleton portion111are appropriately selected on the basis of flexibility of the stent main body section110required depending on the living body lumen where the stent is placed. Herein, the flexibility refers to bendability of the stent main body section110, and is defined particularly depending on a bending rigidity in the axial direction. That means, the high flexibility of the stent main body section110means a property that the stent has a moderately low bending rigidity in the axial direction and can follow the shape of the living body lumen or the sheath without causing kink in the living body lumen or the sheath.

The membrane portion112is a membrane body for forming the flow path for bile, and is disposed so as to cover the peripheral face of the skeleton portion111. The membrane portion112may be disposed on the outer peripheral face and the inner peripheral face of the skeleton portion111so as to sandwich the skeleton portion111, or disposed only on the outer peripheral face or only on the inner peripheral face of the skeleton portion111.

Examples of the material for forming the membrane portion112include a silicon resin, a fluorine resin such as PTFE (polytetrafluoroethylene), a polyester resin such as polyethylene terephthalate, and the like.

The stretch restriction portion113is disposed, for example, along the axial direction of the skeleton portion111and is formed from a rectangular long member. Specifically, the stretch restriction portion113is fixed to the outer peripheral face (inside of the membrane portion112) of the skeleton portion111(by adhesion, for example) so as to extend to both end portions in the axial direction of the skeleton portion111.

In addition, for example, the stretch restriction portion113is made of a biocompatible thread (e.g. polyester thread, or the like) or cloth (woven fabric (textile) or knit) and has a strength capable of restricting stretch of the skeleton portion111in the axial direction at least without impairing expandability of the bile duct stent100in the radial direction. In addition, a plurality of the stretch restriction portions113may be disposed at a predetermined interval in the circumferential direction. For example, two stretch restriction portions113are arranged at different positions 180 degrees away from each other.

When the bile duct stent100is contracted in the radial direction and accommodated in the sheath, the stretch restriction portion113suppresses the stretch in the axial direction. Thus, when the bile duct stent100is accommodated in the sheath, compared to a stent having no stretch restriction portion113, a length in the axial direction of the bile duct stent100is shorter, a contact area between the bile duct stent100and the sheath is smaller, and the friction resistance when releasing the bile duct stent100from the sheath is lower. In addition, when the bile duct stent100is released from the sheath and the stent main body section110expands, a reduction rate in the axial direction decreases, so that the bile duct stent100can be placed on a target indwelling site in the bile duct B.

The valve section120is disposed on the first end portion110aof the stent main body section110. That means, the valve section120is disposed on a downstream side end portion110aof the stent main body section110, positioned on a downstream side in the flow direction of a fluid (bile) flowing in the bile duct B. The valve section120is formed from a membrane body similarly to the membrane portion112of the stent main body section110, and is formed integrally with the membrane portion112.

The valve section120has a streamer shape whose outer shape deforms by a fluid pressure. The valve section120has a bile (fluid) inlet120aon the stent main body section110side, and a bile outlet120bon the opposite side to the stent main body section110. The outlet120bhas a flat shape in which a width in a first direction D1orthogonal to the axial direction is smaller than a width in a second direction D2substantially orthogonal to the axial direction and the first direction D1.

The outlet120bthrough which bile does not passes is occluded in a straight line. On the other hand, the outlet120bthrough which bile passes is widened by an internal pressure due to bile. Thereby, bile can be prevented from reversely flowing into the bile duct stent100without inhibiting the flow of bile. Incidentally, a shape of the outlet120bthrough which bile passes is not particularly limited as long as bile can pass, and examples of the shape include an elliptical shape, a long rectangular shape, and the like.

In addition, the valve section120has a tapered portion121and a flat portion122. The tapered portion121is consecutively connected to the membrane portion112of the stent main body section110. One end of the tapered portion121is the inlet120a. The tapered portion121is formed such that a width in the second direction D2scarcely changes but a width in the first direction D1decreases from the inlet120atoward the flat portion122. The flat portion122is consecutively connected to the tapered portion121. One end of the flat portion122is the outlet120b. The flat portion122is formed such that the widths in the first direction D1and the second direction D2are maintained. That means, the valve section120is composed of a film-like check valve. This check valve makes it possible to more effectively prevent bile from flowing reversely.

Furthermore, the membrane body of the valve section120is formed along two support portions123and124. Specifically, the support portions123and124are formed integrally with the skeleton portion111. For example, on a frontmost portion positioned on the valve section120side of the skeleton portion111, two crest portions opposite to each other in the radial direction are higher than the other crest portions, and the two crest portions protruding toward the distal side functionally serves as the support portions123and124. That means, the support portions123and124have a V-shape that is closed on the distal side and opened on the rear end.

In addition, in the support portions123and124, for example, V-shaped apex portions123aand124aare positioned on the distal side of the tapered portion121, and two foot portions123band124bare positioned on the inlet120aside of the tapered portion121(side consecutively connected to the stent main body section110).

Also, the two support portions123and124are arranged opposite to each other in the second direction D2e.g. at an 180° interval in the circumferential direction.

Incidentally, the support portions123and124may be biased such that, for example, the apex portions123aand124aare separated from each other along the second direction D2. As a result, when bile does not pass through the outlet120b, the distal end side of the tapered portion121(rear end side of the flat portion122) is pulled toward both outsides in the second direction D2by the two support portions123and124, and therefore the outlet120bof the valve section120can be easily closed. Thus, when bile does not flow, the valve section120can quickly transition from the open state to the closed state, so that bile can be more effectively prevented from flowing reversely.

The removal assistant130is an auxiliary implement used for removing the bile duct stent100placed in the bile duct B. The removal assistant130has an engaging portion130awith which a hooking implement (snare: (recovery member)22a(seeFIG. 4A) is engaged disposed on the distal end of the recovery catheter. This engaging portion130amay be formed, for example by bending a wire rod and may have a shape such as a hook shape, or a loop shape.

In addition, the removal assistant130extends in the axial direction from the stent main body section110(e.g. end portion of the skeleton portion111), and the engaging portion130ais disposed on the distal end of the removal assistant130. That means, the removal assistant130is disposed so as to protrude in the axial direction from the first end portion110a(downstream side end portion) among both end portions in the axial direction of the stent main body section110.
Incidentally, for the wire rod for forming the removal assistant130, for example, the same wire rod as for the skeleton portion111can be applied, and the removal assistant130may be formed integrally with the skeleton portion111.

FIG. 4AtoFIG. 4Dare diagrams illustrating state transition when recovering the bile duct stent100placed in the bile duct B. Incidentally,FIG. 4A to 4Dschematically illustrate the bile duct stent100.

As illustrated inFIG. 4A, the bile duct stent100is placed such that the first end portion110ais positioned on the downstream side of the bile flow direction. In this state, the recovery catheter22is introduced from the downstream side of the flow direction.

The hooking implement22aof the recovery catheter22is hooked on the engaging portion130aof the removal assistant130and the recovery catheter22is pulled, the proximal side region R1of the stent main body section110stretches in the axial direction and contracts inward in the radial direction (seeFIG. 4BandFIG. 4C). Thereby, the proximal side region R1of the stent main body section110is peeled off from the bile duct wall to which the proximal side region R1has adhered.

Then, the recovery catheter22is pulled and the bile duct stent100is drawn into a recovery sheath21, so that the bile duct stent100is removed and recovered (seeFIG. 4D). In an initial stage of the removal operation, the proximal side region R1of the stent main body section110is first peeled off from the bile duct wall, and therefore the middle side region R3and the distal side region R2positioned on the upstream side can also be easily peeled off from the bile duct wall.

In this way, the bile duct stent100according to this embodiment is placed in the bile duct B (living body lumen) and has the stent main body section110in a cylindrical shape. The stent main body section110is formed expandably and contractibly in the radial direction substantially orthogonal to the axial direction, in which one portion (middle side region R3) corresponding to a predetermined position (e.g. the central position of the occluded site or stenosis site) on the indwelling site in the bile duct B exerts relatively large expanding forces, and the different portions (proximal side region R1, distal side region R2) that are different in axial position from that of the aforementioned one portion, exert relatively small expanding forces.

According to the bile duct stent100, since the one portion (middle side region R3) corresponding to a predetermined position on the indwelling site in the bile duct B exerts a relatively large expanding force in the stent main body section110, adhesiveness to, for example, the occluded site or stenosis site in the bile duct tube B can be improved, and the stent can be made difficult to displace from the indwelling site. Furthermore, in the stent main body section110, the different portions (proximal side region R1, distal side region R2) positioned on the end portion sides in the axial direction of the aforementioned one portion exert relatively small expanding forces, so that flexibility can be increased and followability to the bile duct B can be improved.

In this way, the bile duct stent100can be made difficult to displace from the indwelling site in the bile duct B, and followability of the bile duct stent100to the bile duct B can be improved. In addition, development of kink by the axial force of the stent main body section110with time can be prevented.

In addition, the bile duct stent100further includes the removal assistant130provided on one (first end portion110a) of the both end portions in the axial direction of the stent main body section110and for assisting removal of the stent main body section110from the bile duct B (living body lumen). The bile duct stent100is configured such that when the removal assistant130is pulled in the axial direction, the stent main body section110contracts inward in the radial direction while stretching in the axial direction on the first end portion110aside.

Thereby, when the bile duct stent100is pulled in the axial direction via the removal assistant130provided on the first end portion110ahaving the expanding force relatively smaller than of the middle portion side, the stent main body section110stretches in the axial direction and contracts inward in the radial direction, so that the stent can be easily peeled off from the bile duct wall. Thus, workability for removing the placed bile duct stent100can be improved.

Additionally, in the bile duct stent100, the first end portion110arefers to the downstream side end portion positioned on the downstream side of the flow direction of bile (fluid) flowing in the bile duct B (living body lumen). The bile duct stent100is removed by introducing the recovery catheter from the downstream side end portion.

Thereby, the removal direction of the bile duct stent100coincides with the flow direction of bile, so that the bile duct stent100can be easily removed without receiving a fluid resistance.

In addition, the bile duct stent100is formed from a membrane body and includes the valve section120disposed on the downstream side end portion of the stent main body section110, positioned on the downstream side in the flow direction of bile (fluid) flowing in the bile duct B (living body lumen). The valve section120has the outlet120bfrom which bile flows out. The outlet120bhas a width in the first direction D1orthogonal to the axial direction, that is smaller than a width in the second direction D2substantially orthogonal to the axial direction and the first direction. This makes it possible to prevent bile from reversely flowing into the bile duct stent100.

As described above, the invention made by the present inventors has been specifically explained on the basis of the embodiments, but the present invention is not limited to the above embodiments, and can be modified without departing from the gist of the present invention.

For example, in the above embodiment, one portion of the stent main body section110corresponding to the predetermined position (e.g. the central position of the occluded site or stenosis site, or the like) on the indwelling site in the bile duct B is set as an middle side portion (middle side region R3) in the axial direction of the stent main body section110, and different portions on the axial-direction end portion sides of the aforementioned one portion are set as the both end side portions in the axial direction (proximal side region R1and distal side region R2) of the stent main body section110, but this configuration is merely an example and the present invention is not limited to this configuration. That means, any configuration is allowed as long as the portion corresponding to the predetermined position on the indwelling site in the bile duct B exerts a relatively large expanding force. For example, the expanding force of the distal side region R2of the stent main body section110may be increased, the distal side region R2may be disposed corresponding to the predetermined position on the indwelling site in the bile duct B, and the expanding force of the proximal side portion of the distal side region R2may be decreased. Alternatively, the expanding force of the distal side region R2of the stent main body section110may be decreased, and the expanding forces of the middle side region R3and the proximal side region R1of the stent main body section110may be increased. Alternatively, portions with a large expanding force and portions with a small expanding force may be arranged alternately in the axial direction.
Incidentally, no matter what the aforementioned configuration is, whether or not at least one removal assistant130is provided can be appropriately and arbitrarily changed.

In addition, in this embodiment, the expanding force is controlled by adjusting a winding frequency per a unit length of the metal wire rod for forming the skeleton portion111, but the expanding force may be controlled by other methods. For example, the expanding force can be controlled by appropriately selecting a wire diameter, a circumferential folding frequency, a folding shape, and the like, of the metal wire rod for forming the skeleton portion111.

In addition, the skeleton portion111may be a laser-cut type formed by laser-cutting a metal cylindrical member. Also in this case, the expanding force can be controlled by appropriately selecting a material, a wall thickness, a shape after laser cutting, an interval between skeletons, and the like, of the cylindrical member on the basis of flexibility of the stent main body section110required depending on the living body lumen where the stent is placed. Furthermore, in this embodiment, the expanding force on the second end portion110bside as the upstream side in the fluid flow direction is also smaller than the expanding force on the middle portion side, but the expanding force on the second end portion110bside may be equivalent to the expanding force on the middle portion side.

Additionally, in this embodiment, although the bile duct stent100including the valve section120has been explained, the present invention can also be applied to a stent having no valve section, i.e. composed only of a stent main body section. In addition, the stent main body section may be composed of a bare stent consisting only of skeleton portions.

In addition, for example, in this embodiment, although the case where the valve section120has the flat portion122has been explained, the valve section120does not necessarily have the flat portion122. However, as in this embodiment, the valve function is improved rather by installing the flat portion122on the valve section120. Also, the valve section120does not necessarily have the support portions123and124. For example, the membrane body is formed along the substrate having the same shape as of the valve section120, so that the shape of the valve section120can be maintained without the support portions123and124.

Furthermore, in this embodiment, although the case where the stent main body section110has two stretch restriction portions113has been explained, the stretch restriction portions113may be omitted, alternatively three or more stretch restriction portions113may be disposed at a predetermined interval in the circumferential direction, alternatively the stretch restriction portions113may be disposed over the whole peripheral face of the stent main body section110(inner peripheral face or outer peripheral face of the skeleton portion111).

In addition, the stretch restriction portions113may be disposed outside the membrane portion112. In this case, when the bile duct stent100is placed in the bile duct B, the bile duct wall and the stretch restriction portions113come into contact with each other, and therefore the bile duct wall make inroads into the stretch restriction portions113. Thus, the bile duct stent100can be prevented from being displaced from the indwelling position. That means, the stretch restriction portions113can functionally serves as a displacement-preventing means for the bile duct stent100.

In addition, the stent main body section110may or may not have a straight cylindrical shape as described in this embodiment, and may have, for example, a spindle shape in the most expanded state. In this case, even if density of the skeleton portion111is constant over the whole length in the expanded state, the middle side region R3is “denser” when the stent is placed in the bile duct B (the inner diameter is constant), and therefore the proximal side region R1and the distal side region R2exert expanding forces smaller than the expanding force exerted by the middle side area R3.

Furthermore, the present invention can be applied not only to the bile duct stent100explained in this embodiment but also to a stent that is placed in a living body lumen such as digestive system lumen and blood vessel. In this case, the fluid that flows through the living body lumen includes e.g. food immediately after intake, that has not been digested at all, decomposed food that has passed through the digestive tract, a matter that has not been digested even through the digestive tract (e.g. stool, or the like), and the like, regardless of a state of the matter.

In addition, although the case where the stent main body section110has a straight cylindrical shape has been described, this case is merely an example and the present invention is not limited to this case. The stent main body section110may have a curved shape depending on the indwelling site, or the stent main body section110will have a curved shape following a bile duct shape after placement.

Furthermore, in this embodiment, although the configuration in which the removal assistant130is provided on the first end portion110a(downstream side end portion) positioned on the downstream side in the flow direction of bile (fluid) in the stent main body section110has been described as an example, this configuration is merely an example, and the present invention is not limited to this configuration. For example, the removal assistant130may be provided on the second end portion110b(upstream side end portion) positioned on the upstream side in the flow direction of bile (fluid) in the stent main body section110. In addition, a plurality of the removal assistants130may be provided on at least one end side in the axial direction of the stent main body section110. That means, the number of the removal assistants130is not limited to one, and a plurality of the removal assistants130may be provided.

In addition, the following inventions are also disclosed in this embodiment.

This means, a stent that is placed in the bile duct B (living body lumen), includes the tent main body section110in a cylindrical shape, the removal assistant130that is provided on the first end portion110a(downstream side end portion) positioned on the downstream side in the flow direction of bile (fluid) flowing in the bile duct B among both end portions in the axial direction of the stent main body section110and assists removal of the stent main body section110from the bile duct B, and the valve section120that is formed from a membrane body and consecutively connected to the first end portion110aof the stent main body section110. The stent main body section110is formed expandably and contractibly in the radial direction substantially orthogonal to the axial direction. The valve section120has the outlet120bfrom which bile flows out. The outlet120bhas a width in the first direction D1orthogonal to the axial direction that is smaller than the width in the second direction D2substantially orthogonal to the axial direction and the first direction D1. Constitutionally, when the removal assistant130is pulled in the axial direction, the stent main body section110contracts inward in the radial direction while stretching in the axial direction on the first end portion110aside.

In addition, a stent that is placed in the bile duct B (living body lumen), includes the stent main body section110in a cylindrical shape, and the valve section120that is formed from a membrane body and disposed on the first end portion110a(downstream side end portion) positioned on the downstream side in the flow direction of the fluid flowing in the bile duct B among both end portions in the axial direction of the stent main body section110. The stent main body section110is formed expandably and contractibly in the radial direction substantially orthogonal to the axial direction, in which the first end portion110aside exerts a relatively smaller expanding force than an expanding force exerted by the middle portion side. The valve section120has the outlet120bfrom which bile flows out. The outlet120bhas a width in the first direction D1orthogonal to the axial direction that is smaller than the width in the second direction D2substantially orthogonal to the axial direction and the first direction D1. Constitutionally, when the first end portion110aof the stent main body section110is pulled in the axial direction, the first end portion110aside of the stent main body section110stretches in the axial direction and contracts inward in the radial direction.

The embodiments disclosed in this specification should be regarded as examples in all regards and considered to be unrestrictive. The scope of the present invention is stipulated not by the aforementioned explanation but by claims, and intended to include meanings equivalent to claims and all changes within the scope of claims.

Disclosure contents of specifications, figures, and abstracts included in Japanese Patent Application No. 2018-086854 filed on Apr. 27, 2018 are all incorporated in this application.

DESCRIPTION OF REFERENCE NUMERALS