Tube stent

Abstract

To provide a tube stent capable of discharging a body fluid through a gap with the lumen of a body even when the lumen of a stent body is closed.SOLUTION: The tube stent 1 is a tubular stent to be indwelled in a lumen of a body and includes a main stent body 2 made of a resin and having a lumen 20 defined by an inner peripheral surface 21 along the longitudinal direction, and the main stent body 2 has a groove 23 (external flow path) formed over the entire length so that a body fluid from the body can flow outside an outer peripheral surface 22 of the main stent body 2 along the longitudinal direction when the tube stent 1 is indwelled in the lumen.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a tube stent. [Background technology]

[0002] 2. Description of the Related Art Conventionally, stents have been placed to dilate strictures formed in the lumens of the body, such as the bile duct and pancreatic duct, and to maintain an open state.

[0003] Stents are used in procedures such as endoscopic retrograde biliary drainage (ERBD). ERBD is a treatment that maintains bile flow by inserting a drainage tube from the duodenal papilla into the bile duct using an endoscope. Resin or metal stents are inserted into areas of the bile duct that are blocked by gallstones or cancer to improve the flow of bile, a digestive fluid. Resin stents have a smaller lumen diameter than metal stents, making them more prone to blockage. However, they are easily removed, making them widely used in recent years.

[0004] A known example of a resin stent is that described in Patent Document 1. The stent described in Patent Document 1 is a bile duct tube stent made of a resin material, and the tube stent has spiral or annular grooves along the circumferential direction on at least a portion of its outer surface, with the groove depth being 1.3 to 5.5% (e.g., 0.015 mm) of the wall thickness of the tube stent and the groove pitch being 0.04 mm or more and 1.0 mm or less, which is said to be able to suppress the occurrence of kinking even when used in a bent state. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-121577 Summary of the Invention [Problem to be solved by the invention]

[0006] According to the above-mentioned conventional example, when the lumen of the tube stent is blocked, it is difficult to drain bodily fluids from the body through the grooves because the depth of the grooves on the outer surface is small.

[0007] An object of the present invention is to provide a tube stent that can discharge bodily fluids through a gap between the stent body and the lumen of the body even if the lumen of the stent body is closed. [Means for solving the problem]

[0008] [1] A tubular stent to be placed in a lumen of the body, a stent body made of resin having a lumen defined by an inner circumferential surface along a longitudinal direction; The stent body has an external flow path formed along its entire length so that when the tube stent is placed in the lumen, bodily fluids from the body can flow along the longitudinal direction outside the outer surface of the stent body. [2] The tube stent described in [1], wherein the external flow path is a groove formed by partially thinning the wall thickness of the stent body. [3] The tube stent described in [2] above, wherein the groove is a plurality of grooves. [4] The tube stent described in [3], wherein the plurality of grooves are two or more and five or less grooves formed at equal intervals in the circumferential direction. [5] A tube stent as described in [4], wherein the plurality of grooves are formed parallel to the axial direction of the lumen. [6] A tube stent as described in [4], wherein the plurality of grooves are formed in a spiral shape. [7] A tube stent as described in [5] or [6], wherein the stent body has a reinforcing layer over its entire length. [8] The stent body comprises an inner layer having the lumen therein, and an outer layer provided outside the inner layer and having the plurality of grooves formed on the outer peripheral surface side, The tube stent described in [7] above, wherein the reinforcing layer is formed between the inner layer and the outer layer. [9] The tube stent described in [8], wherein the reinforcing layer is composed of a coil body formed by spirally winding a linear member, or a braided body formed by weaving the linear member.

[10] A tube stent as described in [5] or [6], wherein when Vs is the volume over the entire length between a circle circumscribing the protrusion of the thick-walled portion formed by partially thinning the wall thickness of the stent body and one groove, and Vm is the volume over the entire length of the inner lumen, the following relationship is satisfied: NVs = kVm (where N is the number of grooves and k is 0.8 to 1.2)

[11] A tube stent as described in [5] or [6], wherein the ratio of the depth of the groove to the inner diameter of the lumen is 0.025 or more and 0.55 or less. [Effects of the Invention]

[0009] According to the present invention, even if the lumen of the stent body is closed, bodily fluids can be discharged through the gap between the stent body and the lumen of the body. [Brief explanation of the drawings]

[0010] [Figure 1] 1(a) to 1(d) are front views of a tube stent according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 3] Figure 3(a) is a left side view of the tube stent of Figure 1(a) viewed from the tip side, Figure 3(b) is a longitudinal cross-sectional view of Figure 3(a), and Figure 3(c) is a longitudinal cross-sectional view of the main part showing a modified shape of the end portion. [Figure 4] FIG. 4 is a diagram showing an example of a method of using the tube stent according to the first embodiment. [Figure 5] FIG. 5 is a diagram showing an example of a method of using the tube stent according to the first embodiment. [Figure 6]FIG. 6 is a cross-sectional view corresponding to FIG. 2 of a tube stent according to a second embodiment of the present invention. [Figure 7A] FIG. 7A shows an Amsterdam-type tube stent according to a third embodiment of the present invention, where (a) is a left side view seen from the distal end side, and (b) is a longitudinal cross-sectional view of a main part. [Figure 7B] FIG. 7B shows a Tanenbaum-type tube stent according to a third embodiment of the present invention, where (a) is a left side view seen from the distal end side, and (b) is a front view of the main part. [Figure 8] FIG. 8 is a diagram showing a schematic diagram of an experimental model for evaluating the drainage capacity. [Figure 9] FIG. 9 is a photograph showing the results of an experiment conducted using the experimental model shown in FIG. [Figure 10] FIG. 10 is a photograph showing the results of an experiment conducted using the experimental model shown in FIG. [Figure 11] FIG. 11 is a photograph showing a cross section of a tube stent placed in a constricted simulated lumen. [Figure 12] FIG. 12 is a photograph showing an example of an experiment for evaluating kink resistance with and without a reinforcing layer. [Figure 13] 13(a) and 13(b) are perspective views of the essential parts showing groove modifications 3 and 4, respectively. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, components having substantially the same functions are designated by the same reference numerals, and redundant explanations will be omitted. In this specification, the side inserted into the body is referred to as the distal end, and the side operated by the surgeon is referred to as the proximal end.

[0012] [First embodiment] Figures 1(a) to 1(d) are front views of a tube stent according to a first embodiment of the present invention. Figure 2 is a cross-sectional view taken along line AA in Figure 1(a). Figure 3(a) is a left side view of the tube stent in Figure 1(a) as seen from the distal end side, Figure 3(b) is a longitudinal cross-sectional view of Figure 3(a), and Figure 3(c) is a longitudinal cross-sectional view of a main part showing a modified shape of the end portion.

[0013] The tube stent 1 is placed in a body lumen (bile duct, pancreatic duct, ureter, etc.) and has an overall tubular shape. The tube stent 1 includes a resin stent body 2 having a longitudinal lumen 20 defined by an inner circumferential surface 21. The cross-sectional shape of the inner circumferential surface 21 is, for example, circular, but may be other shapes such as elliptical.

[0014] The tube stent 1 has a length (e.g., 30 mm, 80 mm, 150 mm, etc.) that corresponds to the site in the body lumen where it is to be placed. A plurality of tube stents 1 of different lengths can be prepared in advance, and when placing the tube stent 1 in the lumen, a tube stent 1 of an appropriate length can be selected depending on the site where it is to be placed.

[0015] Stents include resin stents with relatively small lumens and metal stents with relatively large lumens. Even if the lumen in which they are placed is the same, they are used differently depending on the medical condition. Commercially available resin stents have outer diameters ranging from 7 Fr (2.33 mm) to 12 Fr (4.00 mm), for example. When a stent is placed in a lumen (e.g., the bile duct), the lumen of the stent becomes blocked after a certain period of time (approximately 5 months for a resin stent). This is thought to occur because dietary fiber and intestinal bacteria flowing through the duodenum flow back into the stent, causing bacterial solids to form and accumulate in the lumen of the stent, resulting in blockage of the lumen. Even if the lumen of the stent (the main excretion route) becomes blocked, the presence of a secondary excretion route can be expected to extend the stent's placement period. Therefore, in this embodiment, a secondary excretion route is formed between the outer surface 22 of the tube stent 1 and the inner wall of the lumen of the body.

[0016] In the stent body 2 of this embodiment, grooves 23 are formed along the entire length on the outside of the outer circumferential surface 22 so that when the tube stent 1 is placed in a body lumen, bodily fluids can flow longitudinally outside the outer circumferential surface 22 of the stent body 2. The grooves 23 are formed, for example, by partially thinning the wall thickness of the stent body 2. When the tube stent 1 is placed in a body lumen, the space between the grooves 23 and the inner wall of the body lumen becomes a secondary discharge route. The grooves 23 are an example of an external flow path.

[0017] Specifically, as shown in FIG. 2 , the stent body 2 has a plurality of (e.g., four) grooves 23 formed on its outer peripheral surface 22 at equal intervals in the circumferential direction, thereby forming a plurality of (e.g., four) protrusions 24 between the grooves 23. The plurality of protrusions 24 are circumscribed by, for example, a circle (circumscribed circle) 22a having a diameter D1. The four grooves 23 are inscribed by, for example, a circle (inscribed circle) 22b having a diameter D2. The depth h of the grooves 23 can be defined as h = (D1 - D2) / 2. The protrusions 24 are thick portions formed by partially thinning the wall of the stent body 2. Forming a plurality of protrusions 24 on the outer peripheral surface 22 can increase bending rigidity (kink resistance) so that kinking is less likely to occur when the tube stent 1 is placed in a curved lumen. The number of grooves 23 and protrusions 24 is not limited to four and may be one, two, three, five, or more. In particular, by forming two to five grooves 23 and protrusions 24 at equal intervals in the circumferential direction, even if some sub-exhaust routes cannot be secured due to compression caused by infiltration of a tumor or the like from one of the four sides, it is possible to secure at least one sub-exhaust route.

[0018] The diameter d of the lumen 20 may be, for example, 0.80 mm or more and 2.00 mm or less. The thickness t of the groove 23 may be, for example, 0.05 mm or more and 0.50 mm or less. The depth h of the groove 23 may be, for example, 0.30 mm or more and 0.60 mm or less. The maximum outer diameter (diameter D1) of the outer peripheral surface 22 may be, for example, 1.50 mm or more and 3.20 mm or less.

[0019] The outer shape of the stent body 2 is such that a circumscribing circle 22a circumscribes the entire outer circumferential surface 22 of each of the four protrusions 24, i.e., a shape in which grooves 23 are formed on the outside of a concentric tubular member, as shown in FIG. 2, so that the tube stent 1 can be placed gently in a body lumen. Furthermore, corners 24a where the outer circumferential surface 22 of each protrusion 24 intersect with the outer circumferential surface 22 of each groove 23 are rounded as shown in FIG. 2. Furthermore, corners 24b where each protrusion 24 intersects with the distal end surface 2a and the proximal end surface 2b are rounded as shown in FIG. 3(b). Incidentally, corners 24c where each outer circumferential surface 22 of each protrusion 24 intersects with the distal end surface 2a and the proximal end surface 2b may be tapered as shown in FIG. 3(c). Furthermore, the corners where each outer circumferential surface 22 of each protrusion 24 intersect with the proximal end surface 2b may be tapered like the distal end surface 2a, or may be rounded like the corners 24b shown in FIG. 2.

[0020] (Configuration of grooves and protrusions) The grooves 23 and protrusions 24 may be formed parallel to the axial direction of the lumen 20 as shown in FIG. 1(a), or may be formed helically as shown in FIGS. 1(b) to 1(d). In FIG. 1(b), the helical pitch p of the grooves 23 is 45 mm, in FIG. 1(c), the helical pitch p is 11.5 mm, and in FIG. 1(d), the helical pitch p is 4.5 mm. The grooves 23 and protrusions 24 formed helically with a smaller helical pitch tend to be less likely to be blocked by a narrowed portion in the external flow path 25 formed by the grooves 23 than those formed parallel to the axial direction of the lumen 20. Furthermore, forming the grooves 23 helically increases the volume of the sub-drainage route, which facilitates drainage. That is, the helical pitch p of the grooves 23 is preferably 50 mm or less, more preferably 10 mm or less or 5 mm or less. From the viewpoint of ease of manufacture, the spiral pitch p of the groove 23 is preferably 2 mm or more, and more preferably 4.5 mm or more.

[0021] 2, the cross-sectional shape of groove 23 is semicircular with a radius of about 0.2 to 0.4 mm, but may be other shapes such as elliptical or U-shaped. From the viewpoint that the sub-discharge route takes the place of the main discharge route when the main discharge route is blocked, when the volume of one sub-discharge route, i.e., the volume over the entire length between circumscribed circle 22a circumscribing protrusion 24 and one groove 23, is Vs, and the volume of the main discharge route, i.e., the volume over the entire length of lumen 20, is Vm, the following relational expression (1) may be satisfied. NVs = kVm (where N is the number of grooves 23, k = 0.8 to 1.2) (1) The volume Vs of the sub-discharge route is calculated by multiplying the cross-sectional area As between the circumscribing circle 22a and the groove 23 by the total length Lout of the groove 23.

[0022] In order to ensure at least one sub-exhaust route when the tube stent 1 is placed in a curved lumen or when some sub-exhaust routes cannot be secured due to infiltration by a tumor or the like, it is preferable that the depth h of the groove 23 has a certain size relative to the diameter d of the lumen 20. The relative size of the groove 23 to the diameter d of the lumen 20 can be determined by the ratio (h / d) of the depth h (= D1 - D2) / 2 of the groove 23 to the diameter d of the lumen 20. The ratio (h / d) is preferably, for example, 0.025 or more and 0.55 or less.

[0023] (Material for forming the stent body) The stent body 2 can be formed from a resin material (e.g., polyamide, polyurethane, polyethylene, silicone rubber, fluororesin, etc.) that has elasticity, such as radial expandability and contractibility, and flexibility that allows it to easily bend along the insertion path. The stent body 2 can be formed from a thermoplastic resin or a thermosetting resin. Preferably, at least the inner circumferential surface 21 and the outer circumferential surface 22 of the stent body 2 are coated with a material to which bodily fluids do not easily adhere (e.g., a highly biocompatible coating material such as MPC or PMMA). Because bodily fluids mainly flow through the lumen 20, only the surface of the inner circumferential surface 21 may be coated with a material to which bodily fluids do not easily adhere. Alternatively, the outer circumferential surface 22 of the stent body 2 may be coated with a hydrophilic coating. This reduces the coefficient of friction of the surface of the tube stent 1, facilitating insertion into a bodily lumen, and is expected to prevent adhesion of proteins and crystalline components.

[0024] Furthermore, to make it easier to confirm the position of the tip of the tube stent 1 under X-ray imaging, the stent body 2 may be formed by mixing a contrast agent (barium sulfate, bismuth oxide, tungsten, etc.) into the material forming the stent body 2. A marker made of a metal that is radiopaque (e.g., gold, tantalum, platinum-iridium alloy, tungsten, etc.) may be provided on the tip side of the stent body 2. The marker may be provided on the base end side, or in the case of a tube stent equipped with a flap or pigtail, it may be provided closer to the center than the flap or pigtail.

[0025] (How to use) An example of a method of using the tube stent 1 of this embodiment will be described with reference to Figures 4 and 5. Figure 4 is a diagram showing the tube stent 1 being inserted into the bile duct by endoscopic retrograde biliary drainage (ERBD), and Figure 5 is a diagram showing the tube stent 1 placed in the narrowed portion of the bile duct.

[0026] First, a user such as a surgeon inserts the endoscope insertion portion 100 into a body cavity from the patient's mouth or the like, and advances the tip portion 101 of the endoscope insertion portion 100 through the duodenum 200 to the vicinity of the duodenal papilla 201, as shown in Figure 4.

[0027] Next, the user inserts the guide wire 110 into the channel of the endoscope and projects the tip of the guide wire 110 from the opening 101a of the tip portion 101 toward the duodenal papilla 201. Then, the tip of the guide wire 110 is inserted from the duodenal papilla 201 into the bile duct 202. Here, the bile duct 202 is an example of a lumen of the body.

[0028] Next, the user checks the shapes of the duodenal papilla 201 and the narrowed portion 202a of the bile duct 202 under X-ray fluoroscopy and selects a tube stent 1 with an appropriate length. That is, the user selects a tube stent 1 with a length that extends from the duodenal papilla 201 to a position beyond the narrowed portion 202a of the bile duct 202.

[0029] Next, the user inserts a stent delivery catheter (not shown) with the selected tube stent 1 attached to the outside into the channel of the endoscope and advances it along the guide wire 110. Then, the tip of the stent delivery catheter is inserted into the bile duct 202 from the duodenal papilla 201, and the tube stent 1 advances into the bile duct 202 as shown in FIG.

[0030] Next, as shown in Figure 5, when the tip of the tube stent 1 reaches a position beyond the narrowed portion 202a of the bile duct 202, the tube stent 1 is placed there. The tube stent 1 expands radially due to its own expandability, widening the narrowed portion 202a in the radial direction. This allows the flow path of bodily fluids to be secured.

[0031] Although endoscopic retrograde biliary drainage (ERBD) has been described above as a procedure, the present invention may also be applied to other drainage procedures such as endoscopic pancreatic stenting (EPS).

[0032] Furthermore, the present invention is not limited to bile ducts, but can also be applied to other lumens, such as the pancreatic duct and ureter. Here, the pancreatic duct and ureter are examples of bodily lumens. For example, the present invention may be applied to a ureteral stent as a tubular medical tube that helps transport urine from the kidney to the bladder. Possible uses of a ureteral stent include, for example, the following: To prevent ureteral blockage caused by fragments after breaking up kidney stones. To prevent postoperative swelling of the ureter after kidney stone removal. For the treatment of ureteral obstruction due to blood clots, scar tissue, ureteral stones, and inflammatory bowel disease.

[0033] (Effects of the first embodiment) According to this embodiment, the following effects are achieved. (a) In addition to using the lumen 20, which is the same as that of existing resin stents, as the main discharge route, an auxiliary sub-discharge route is provided along the groove 23, so that even if the lumen 20 becomes blocked, it is expected that bodily fluids will be discharged through the sub-discharge route. (b) If the tube stent 1 changes its lumen course due to pressure from a tumor or organ atrophy, causing the tube stent 1 to deform radially, the presence of grooves 23 between the protrusions 24 makes it easy for gaps to remain between the inner wall of the body lumen and the grooves 23. (c) The tube stent 1 may have a plurality of side holes formed in one or both of the distal end and proximal end areas that penetrate the wall of the stent body 2. This allows bodily fluids to flow in and out through the side holes, which is expected to improve the drainage effect. (d) By providing a groove structure on the outer peripheral surface 22 side of the stent body 2, multiple sub-drainage routes for draining body fluids such as bile can be secured, which is expected to extend the placement period. (e) By making the groove 23 spiral, the volume of the sub-drainage route can be increased, which makes it possible to increase the amount of drainage per unit time, and is expected to further extend the retention period. (f) When the tube stent 1 itself is bent or deformed, the protrusions 24 are distorted more than the grooves 23, making it easier to maintain the gap between the grooves 23 and the lumen even in the event of infiltration by tumors, etc., and making it easier to maintain the amount of drainage per unit time. (g) By providing a sub-discharge route between the protrusions 24, the groove 23 can be placed without contacting the lumen or the stent delivery catheter, making the tube stent 1 less likely to be damaged when placed or replaced, and providing a durable tube stent 1. (h) Multiple tube stents 1 with different helical directions may be placed simultaneously. To make this possible, multiple tube stents 1 with different helical directions may be provided as a set, or multiple tube stents 1 with different helical directions may be provided as a set together with a medical device such as a stent delivery catheter. Also, multiple tube stents 1 with the same helical direction may be provided as a set, or multiple or one tube stent 1 with the same helical direction may be provided as a set together with a medical device such as a stent delivery catheter.

[0034] [Second embodiment] 6 is a cross-sectional view corresponding to FIG. 2 of a tube stent according to a second embodiment of the present invention. In this embodiment, a reinforcing layer is added to the first embodiment. The following describes this embodiment, focusing on the differences from the first embodiment.

[0035] The stent body 2 of this embodiment is formed into a tubular shape as a whole, and includes an inner layer 2A having an inner circumferential surface 21, an outer layer 2B provided on the outside of the inner layer 2A and having an outer circumferential surface 22, and a reinforcing layer 3 formed on the outside of the inner layer 2A over the entire length. As in the first embodiment, the outer layer 2B has a plurality of grooves 23 formed on the outside of the outer circumferential surface 22, thereby forming a plurality of (for example, four) protrusions 24 between the grooves 23. As in the first embodiment, the plurality of grooves 23 and protrusions 24 may be formed parallel to the axial direction of the lumen 20, or may be formed spirally.

[0036] The reinforcing layer 3 is configured to include, for example, a coil body formed by spirally winding a linear member, or a braided body formed by weaving linear members. The reinforcing layer 3 may also be configured by combining a coil body and a braided body in layers. The linear member may be, for example, a wire made of a metal (e.g., stainless steel, tungsten steel, titanium-nickel alloy (Ti-Ni), etc.), or a wire made of a non-metal (e.g., nylon monofilament, polyethylene terephthalate (PET) monofilament, polyester monofilament, polyarylate fiber, etc.).

[0037] The inner layer 2A and the outer layer 2B may be formed from the same resin material or different resin materials, such as polyamide, polyurethane, polyethylene, silicone rubber, and fluororesin.

[0038] The diameter d of the lumen 20, the thickness t of the grooves 23, and the depth h of the grooves 23 may be the same as those in the first embodiment. In this case, the inner diameter of the outer layer 2B may be, for example, 0.90 mm or more and 2.00 mm or less. The thickness of the grooves 23 (the thickness of the outer layer 2B) may be, for example, 0.05 mm or more and 0.25 mm or less. Furthermore, the stent body 2 of the first embodiment may be used as the outer layer 2B, and the inner layer 2A and the reinforcing layer 3 may be added thereto.

[0039] (Effects of the second embodiment) The tube stent 1 according to the second embodiment has the same effects as the first embodiment and also has improved kink resistance.

[0040] [Third embodiment] FIG. 7A shows an Amsterdam-type tube stent according to a third embodiment of the present invention, where (a) is a left side view seen from the distal end, and (b) is a longitudinal cross-sectional view of the essential parts. FIG. 7B shows a Tanenbaum-type tube stent according to a third embodiment of the present invention, where (a) is a left side view seen from the distal end, and (b) is a front view of the essential parts. This embodiment is similar to the first embodiment shown in FIG. 1(a), except that one flap 26 is provided on each of the distal and proximal ends. In the case shown in FIG. 7A, the flap 26 is formed by cutting and raising the protrusion 24. 24d in FIG. 7A(b) is a recess after the flap 26 is cut and raised. Two, three, or four flaps 26 may be provided on each of the distal and proximal ends. Alternatively, the flap 26 may be provided on only one of the distal and proximal ends.

[0041] According to the third embodiment, when the tube stent 1 is placed in a lumen of the body, the flap 26 can prevent the tube stent 1 from falling off from the lumen. In the case shown in Fig. 7A, the protrusion 24 is thicker than other parts, so the flap 26 can be easily formed by cutting and raising the protrusion 24. Alternatively, as shown in Fig. 7B, the flap 26 may be formed by attaching a flap mounting member 27 having the flap 26 to the protrusion 24 at the end of the stent body 2 and fixing it by adhesive or the like. [Example]

[0042] Table 1 shows the structures of Examples 1 to 7 and a comparative example. Examples 1a, 2a, 3a, 4a, and 5a correspond to the first embodiment shown in FIG. 1(a). Examples 1b, 2b, 3b, 4b, and 7b correspond to the first embodiment shown in FIG. 1(d). Examples 5a, 5b, and 6b correspond to the second embodiment.

[0043] The outer diameter D1 in Examples 1 to 7 indicates the diameter of the circle (circumscribed circle) 22a circumscribing the four protrusions 24. The outer diameter D2 in Examples 1 to 7 indicates the diameter of the circle (inscribed circle) 22b inscribing the four grooves 23. The diameter d of the lumen 20 in Examples 1 to 4 and Example 7b is equal to the inner diameter of the inner circumferential surface 21. The diameter d in Examples 5 and 6 indicates the inner diameter of the inner layer 2A. The comparative example has a tubular shape with inner and outer circumferential surfaces without grooves or protrusions, and the outer diameter D1 in the comparative example is the diameter of the outer circumferential surface.

[0044] The reinforcing layer 3 was a braided body made of PET monofilament. In Table 1, structures having a reinforcing layer 3 are indicated by "◯" and structures not having a reinforcing layer 3 are indicated by "X". Also in Table 1, cases having a spiral structure of grooves 23 are indicated by the spiral pitch, and cases not having a spiral structure of grooves 23 are indicated by "X".

[0045] The depth h (= h / d) of the groove 23 relative to the diameter d of the lumen 20 means that the greater the depth h of the groove 23 relative to the diameter d, and this indicates that when the tube stent 1 is placed in a curved lumen, at least one sub-exhaust route will be secured without collapsing.

[0046] [Table 1]

[0047] (Evaluation of drainage capacity) 8 is a schematic diagram of an experimental model for evaluating drainage capacity. A simulated lumen 300 simulating a bile duct was positioned vertically, and the stent to be tested was placed inside the simulated lumen 300 so that it was exposed approximately 15 mm from the lower end of the simulated lumen 300. Simulated bile 310 simulating bile was then poured into the simulated lumen 300 from above. Bile is a non-Newtonian fluid, but a yellow-colored glycerin aqueous solution (50%), a Newtonian fluid, was used as the simulated bile 310.

[0048] Table 2 shows the experimental results of the drainage capacity when the lumen 20 is open, and Table 3 shows the experimental results of the drainage capacity when the lumen 20 is closed.

[0049] Figure 9 is a photograph showing the results of an experiment conducted using the experimental model shown in Figure 8. Specifically, Figure 9 is a photograph showing simulated bile 310 adhering to the outer peripheral surface of the tube stent after the simulated bile 310 was poured from above into the experimental model shown in Figure 8. Figure 9(a) shows the tube stent of Example 6b, Figure 9(b) shows the tube stent of Example 7b, and Figure 9(c) shows the tube stent of the comparative example.

[0050] As shown in Figure 9, simulated bile 310 was not attached to the outer peripheral surface of the tube stent of the comparative example, but simulated bile 310 was attached to the outer peripheral surface 22 of the tube stents 1 of Examples 6b and 7b. In other words, it can be seen that simulated bile 310 was not flowing outside the outer peripheral surface of the stent of the comparative example, and that a secondary discharge route did not exist. On the other hand, simulated bile 310 was attached to the outer peripheral surface 22 of the tube stents 1 of Examples 6b and 7b, and it was found that a secondary discharge route was functioning.

[0051] Fig. 10 is a photograph showing the results of an experiment conducted using the experimental model shown in Fig. 8. Specifically, Fig. 10 is a photograph showing simulated bile 310 adhering to the outer peripheral surface of the tube stent after the simulated bile 310 was poured into the experimental model shown in Fig. 8 from above with the proximal upper end of the lumen of the tube stent blocked.

[0052] As shown in Figure 10, simulated bile 310 was not attached to the outer peripheral surface of the tube stent of the comparative example, but simulated bile 310 was attached to the outer peripheral surface 22 of the tube stents 1 of Examples 6b and 7b. In other words, simulated bile 310 was not flowing outside the outer peripheral surface of the tube stent of the comparative example, and it was found that no secondary discharge route existed. On the other hand, simulated bile 310 was attached to the outer peripheral surface 22 of the tube stents 1 of Examples 6b and 7b, and it was found that the secondary discharge route was functioning.

[0053] The experimental results shown in Figure 9 are shown in Table 2, and the experimental results shown in Figure 10 are shown in Table 3. In Tables 2 and 3, the "lumen" of the drainage route indicates the main drainage route, and the "external flow path" indicates a secondary drainage route. "X" indicates that there was no drainage route, "△" indicates that it did not function well as a drainage route, and "○" indicates that it functioned adequately as a drainage route.

[0054] [Table 2]

[0055] [Table 3]

[0056] As can be seen from Tables 2 and 3, when the lumen of the tube stent is patent, all Examples and Comparative Examples function as a drainage route for the lumen. As for the drainage route for the external flow path, the Comparative Example did not function at all, and Example 1a, in which the groove 23 was not formed in a spiral shape, did not function sufficiently, but the other Examples 1b, 2a, 2b, 3a, 3b, 4a, 4b, 5a, and 5b functioned sufficiently.

[0057] 11(a), (b), and (c) are photographs showing a cross section of the tube stent of Example 1b placed in a constricted simulated lumen 300. FIG. 11(a) shows a case where the simulated lumen 300 is compressed from the 12 o'clock direction, causing the infiltration of a tumor or the like from the 12 o'clock direction, making it impossible to distinguish between the protrusion 24' at the 12 o'clock direction and the grooves 23 on either side of it. In this case, the space between the grooves 23 on either side of the protrusion 24 at the 6 o'clock direction and the simulated lumen 300 is not collapsed, so this space is secured as an external flow path 25. FIG. 11(b) shows a case where the simulated lumen 300 is compressed from the 6 o'clock and 9 o'clock directions, causing the infiltration of a tumor or the like from the 6 o'clock and 9 o'clock directions, making it impossible to distinguish between the protrusion 24' at the 6 o'clock direction, the protrusion 24' at the 9 o'clock direction, and the groove 23 between them, resulting in almost complete occlusion of the lumen 20. In this case, the space between the groove 23 on the right side of the protrusion 24 in the 12 o'clock direction and the simulated lumen 300 is not collapsed, and therefore this space is secured as the external flow path 25. Figure 11(c) shows a case in which the simulated lumen 300 is compressed from the 6 o'clock direction, causing the protrusion 24' in the 6 o'clock direction and the grooves 23 on either side thereof to become indistinguishable due to infiltration of a tumor or the like from the 6 o'clock direction and bending of the tube stent 1. In this case, the space between the groove 23 on the right side of the protrusion 24 in the 10 o'clock direction and the simulated lumen 300 is not collapsed, and therefore this space is secured as the external flow path 25.

[0058] (kink resistance) FIG. 12 is a photograph showing an experimental example for evaluating kink resistance with and without a reinforcing layer. When a tube stent is placed in the intrahepatic bile duct (posterior segment), a 20 mm radius and 180° bend are expected, as shown in FIG. 12. In this case, Example 1b, which does not have a reinforcing layer, has a thinner wall than the comparative example (a commercially available resin stent), and therefore exhibits poor kink resistance, resulting in kinking (the area marked with a circle). On the other hand, Example 5b, which has a reinforcing layer 3, did not exhibit kinking (the area marked with a circle). In other words, by adding the reinforcing layer 3 to the inner circumferential surface 21 side of the stent body 2, rigidity against kinking is improved, and rigidity against bending similar to that of existing resin stents, it is possible to ensure a main drainage route and multiple sub-drainage routes even when subjected to strong bending.

[0059] (Variation 1) In the first and second embodiments, the grooves 23 are formed on the outer peripheral surface 22 side, but they may also be formed on the inner peripheral surface 21. This has the effect of maintaining the lumen of the main discharge route.

[0060] (Variation 2) The shape of the tube stent 1 may be a pigtail shape at one end or at both ends. The shape of the tube stent 1 may also be an S-shape, with the distal end curved in an S-shape, or a J-shape. In the first to third embodiments, the tube stent 1 may have a side hole.

[0061] (Variations 3 and 4) 13(a) and 13(b) are perspective views of the essential parts showing groove modifications 3 and 4, respectively. In the first to third embodiments, the groove 23 is formed by partially thinning the wall thickness of the stent main body 2, but in modification 3, as shown in FIG. 13(a), a sub-discharge route is formed by weaving metal or resin linear members 4a and 4b. In modification 4, as shown in FIG. 13(b), a metal or resin linear member 4c is wound in a coil shape around the outer peripheral surface 22 of the stent main body 2. Modifications 3 and 4 also make it possible to form an external flow path outside the outer peripheral surface 22.

[0062] Although the embodiments of the present invention have been described above, the embodiments of the present invention are not limited to the above-described embodiments, and various modifications and implementations are possible. [Explanation of symbols]

[0063] 1...tube stent, 2...stent body, 2A...inner layer, 2B...outer layer, 2a...tip surface, 2b...base end surface, 3...reinforcing layer, 4a, 4b, 4c...linear member, 20...inner cavity, 21...inner peripheral surface, 22...outer peripheral surface, 22a...circumscribed circle, 22b...inscribed circle, 23...groove, 24, 24'...projection, 24a to 24c...corner, 24d...recess, 25...external flow path, 26...flat flap, 27...flap attachment member, 100...endoscope insertion portion, 101...tip portion, 101a...opening, 110...guide wire, 200...duodenum, 201...duodenal papilla, 202...bile duct, 202a...stenosis portion, 300...simulated lumen, 310...simulated bile, D1, D2...outer diameter, d...inner diameter, h...groove depth, p...helical pitch, t...groove thickness, X...longitudinal direction

Claims

1. A tubular stent to be placed in a lumen of a body, a stent body made of resin having a lumen defined by an inner circumferential surface along a longitudinal direction; The stent body has an external flow path formed along its entire length so that, when the tube stent is placed in the lumen, bodily fluid from the body can flow along the longitudinal direction outside the outer circumferential surface of the stent body. Tube stent.

2. The external flow path is a groove formed by partially thinning the wall thickness of the stent body. The tube stent of claim 1.

3. The groove is a plurality of grooves. The tube stent according to claim 2.

4. The plurality of grooves are two or more and five or less grooves formed at equal intervals in the circumferential direction. The tube stent according to claim 3.

5. The plurality of grooves are formed parallel to the axial direction of the inner cavity.

5. The tube stent according to claim 4.

6. The plurality of grooves are formed in a spiral shape.

5. The tube stent according to claim 4.

7. The stent body has a reinforcing layer over its entire length.

7. A tube stent according to claim 5 or 6.

8. the stent body comprises an inner layer having the lumen therein, and an outer layer provided outside the inner layer and having the plurality of grooves formed on its outer peripheral surface, The reinforcing layer is formed between the inner layer and the outer layer. The tube stent according to claim 7.

9. The reinforcing layer is configured to include a coil body formed by spirally winding a linear member, or a braided body formed by braiding the linear member.

9. The tube stent according to claim 8.

10. A tube stent as described in claim 5 or 6, wherein when Vs is the volume over the entire length between a circle circumscribing the protrusion of the thick-walled portion formed by partially thinning the wall thickness of the stent body and one groove, and Vm is the volume over the entire length of the lumen, the following relationship holds: NVs = kVm (where N is the number of grooves and k is 0.8 to 1.2)

11. The ratio of the depth of the groove to the inner diameter of the lumen is 0.025 or more and 0.55 or less.

7. A tube stent according to claim 5 or 6.

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