Patent Publication Number: US-2010114325-A1

Title: Prophylactic Pancreatic Stent

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/107,502, filed Oct. 22, 2008, which is incorporated herein in its entirety. 
    
    
     TECHNICAL FIELD 
     This invention generally relates to stents that are implantable in a vessel or duct within the body of a patient, and in particular to stents that may be used to protect the vessel or duct during a medical procedure. 
     BACKGROUND 
     Minimally invasive medical procedures are performed in various vessels and ducts in the body. In some procedures, access to a vessel or duct may be needed to place prosthetic devices, to obtain a biopsy sample or to otherwise remove tissue material or other substances. 
     Minimally invasive medical procedures are frequently performed in the biliary system. Entry to the biliary system is through the duodenum into Ampulla of Vater leading to the branch for the pancreatic duct or the common bile duct (CBD) and the gall bladder. In most procedures, entry to the CBD is achieved by cannulation using a sphincterotome catheter or an ERCP catheter to gain entry to the bile duct. Typically, a wireguide is preloaded within a lumen of the catheter. Once successful cannulation is performed, the physician may advance the wireguide further into the CBD. The sphincterotome or ERCP catheter may be withdrawn and another device may be advanced over the wireguide into the CBD, such as a biliary stent, a stone extraction balloon or basket, etc. Advancing a catheter/wireguide for entry into the bile duct can be very difficult due to the anatomy of the papilla, the CBD and the pancreatic duct. Often, a physician may accidentally advance the catheter/wireguide into the pancreatic duct. For an inexperienced endoscopist, multiple entries into the pancreatic duct may occur. Single or repeated misplacement of the catheter/wireguide into the pancreatic duct may cause edema or worse trauma that may hinder pancreatic fluid drainage. Injury to the pancreatic duct can lead to post procedural pancreatitis, a very painful and potentially fatal illness. 
     There is a need for a method and a stent that can prophylactically reduce or prevent acute pancreatitis when minimally invasive medical procedures are preformed in the biliary system. In addition, the prophylactic stent may be helpful for inexperienced endoscopists and to reduce the time and complexity of procedures within the biliary system. The stent may be atraumatically placed within a pancreatic duct and remain in place without causing aggravation to the ductal tissue and prevent accidental entry into the pancreatic duct when the bile duct is the intended target. The stent may be temporarily placed and can be removed with little damage or additional irritation to the duct. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a method and a stent having features that resolve or improve on one or more of the above-described drawbacks. 
     The foregoing object is obtained in one aspect of the present invention by providing a stent for prophylactically protecting a duct are provided. The stent includes a non-expandable, generally tubular body having a proximal portion and a distal portion, a lumen extending through at least a portion of the body, a distal opening in the distal portion in fluid communication with the lumen and a proximal opening in the proximal portion in fluid communication with the lumen. The stent further includes a cap portion operably connected to the proximal portion of the body, the cap portion is movable between a non-expanded configuration and an expanded configuration. The non-expanded configuration has a reduced diameter to facilitate advancement into the patient and the expanded configuration has an expanded diameter configured to protect an opening of the internal bodily duct so as to prevent an unintentional entry of an elongate medical device through the opening and into the passageway of the internal bodily duct. 
     In another aspect of the present invention, a method for implanting a prophylactic stent in a duct is provided. The method includes entering a branched ductal system with a wireguide, advancing the wireguide into a first duct of the branched ductal system and advancing a stent over the wireguide. The stent includes a non-expandable, generally tubular body having a proximal portion and a distal portion, a lumen extending through at least a portion of the body, a distal opening in the distal portion in fluid communication with the lumen and a proximal opening in the proximal portion in fluid communication with the lumen. The stent further includes a cap portion operably connected to the proximal portion of the body, the cap portion is movable between a non-expanded configuration and an expanded configuration. The method further includes implanting at least a portion of the distal portion of the stent in the first duct so that the cap portion is in the expanded configuration and protecting an opening in the first duct to inhibit the wireguide from reentering the first duct. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view of a stent according to the present invention; 
         FIG. 1B  is a perspective view of an alternate embodiment of a stent according to the present invention; 
         FIG. 2  is an alternative perspective view of the stent shown in  FIG. 1A ; 
         FIG. 3  is a side view of a stent according to an embodiment of the present invention having a plurality of openings in the body; 
         FIG. 4  is a side view of a stent according to an embodiment of the present invention having a plurality of openings around the cap; 
         FIG. 5A  is a top perspective view of the cap and body of the stent according to the present invention showing a plurality of openings; 
         FIG. 5B  is a side view of the cap and the body of the stent according to an alternative embodiment of the present invention showing a plurality of openings; 
         FIG. 6A  is a side sectional view of an introducer with the stent of  FIG. 1A  therein for delivery; 
         FIG. 6B  is a side sectional view of the introducer shown in  FIG. 6A  with the stent released from the introducer and the cap expanded; 
         FIG. 7A  is a side sectional view of the introducer with the stent of  FIG. 1B  therein for delivery; 
         FIG. 7B  is a side sectional view of the introducer shown in  FIG. 7A  with the stent released from the introducer and the cap expanded and the proximal portion in the angled configuration; 
         FIG. 8  is a diagrammatic view of a wireguide advanced through the pancreatic duct; 
         FIG. 9  is a diagrammatic view of the placement of the prophylactic stent within the pancreatic duct; 
         FIG. 10  is a diagrammatic view of the stent within the pancreatic duct with the cap protecting the entry to the pancreatic duct; and 
         FIG. 11  is a diagrammatic view of the wireguide entering the biliary duct. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The invention is described with reference to the drawings in which like elements are referred to by like numerals. The relationship and functioning of the various elements of this invention are better understood by the following detailed description. However, the embodiments of this invention are not limited to the embodiments illustrated in the drawings. It should be understood that the drawings are not to scale, and in certain instances details have been omitted which are not necessary for an understanding of the present invention, such as conventional fabrication and assembly. 
     As used in the specification, the terms proximal and distal should be understood as being in the terms of a physician delivering the stent to a patient. Hence the term “distal” means the portion of the stent that is farthest from the physician and the term “proximal” means the portion of the stent that is nearest to the physician. 
       FIGS. 1A ,  1 B and  2  illustrate a stent  10  in accordance with embodiments of the present invention. The stent  10  includes a non-expandable, generally tubular body  14  having a proximal portion  20  and a distal portion  30 . The tubular body  14  extends longitudinally along axis A as shown in  FIG. 1A . A lumen  32  extends through at least a portion of the tubular body  14  of the stent  10  between a proximal opening  21  and a distal opening  31 . The proximal portion  20  includes a cap portion  36  and is configured for placement proximal to the pancreatic duct as described in more detail below. One or more retaining members  38  may be included on the tubular body  14 . The retaining members, when present, are configured to help hold the stent  10  in position within the pancreatic duct. One or more openings  42  may be included in the tubular body  14  as shown in  FIG. 3 . The openings  42  are configured to facilitate drainage through the stent  10 . 
     As shown in  FIGS. 1A and 1B , the cap portion  36  extends generally radially outward from the tubular body  14 . The cap portion  36  may be curvilinear and sized and shaped to cover the opening of the pancreatic duct when the stent  10  is placed within the pancreatic duct. The cap portion  36  may be any shape such as the circular shape show in  FIGS. 1A and 1B  or any shape that does not irritate the biliary tree. The cap portion  36  is also sized and shaped so that the stent  10  cannot entirely enter the pancreatic duct and become trapped therein. The cap portion  36  is generally intended to remain external to the pancreatic duct in a bodily cavity and protect the opening to the duct when the tubular body  14  of the stent  10  is placed within the pancreatic duct. The cap portion  36  includes a proximal face  37  shown in  FIG. 1A  and a distal face  39  shown in  FIG. 1B . The distal face  39  is configured to abut the tissue surrounding the opening of the duct. The proximal face  37  is configured to deflect an elongate medical device away from the pancreatic duct and also to inhibit accidental entry of contrast dye into the duct. The cap portion  36  may be domed, having a raised central portion  44  in relation to the periphery  46 . The domed central portion  44  may be centrally positioned on the cap portion  36  or may be asymmetric. The domed central portion  44  may be tapered in a conical or rounded shape to help deflect the wireguide for entering the bile duct as described below. In some embodiments, the cap portion  36  may be generally flat in the central portion  44  as shown in  FIG. 4 . The flat central portion  44  will also be configured to help deflect the wireguide for entering the bile duct and not the pancreatic duct. The periphery  46  of the cap portion  36  extends outward to the extent that the cap portion  36  covers the opening of the pancreatic duct. The periphery  46  may be larger than the opening at the pancreatic duct, but should not be so large that the cap portion  36  interferes with entry into the common bile duct. In some embodiments, the cap portion  36  may include a one-way valve in the proximal opening  21 . The one-way valve may be any kind of valve known to one skilled in the art that will allow pancreatic fluid to drain from the pancreatic duct and will inhibit contrast dye from entering the pancreatic duct once the stent  10  is in position. By way of non-limiting example, the cap portion  36  may have a diameter of about 3-5 mm. Other size diameters for the cap portion  36  are also possible. 
     The proximal portion  20  may include an angled portion  22  that extends at an angle away from the longitudinal axis A as shown in  FIG. 1B  so that the proximal opening  21  is offset from the axis A. This configuration with the angled proximal portion  22  will also help to inhibit entry of the elongate medial device or contrast dye into the pancreatic duct when the prophylactic stent  10  is in position in the duct. As discussed in more detail below, the stent  10  may be deformable for delivery so that the proximal angled portion  22  may be aligned with the distal portion  30  so that the stent  10  may be delivered over a wire guide. The stent  10  is deformable so that the stent  10  will resume the configuration shown in  FIG. 1B  with the angled portion  22  angled away from the axis A and the opening  21  offset from the axis A when the stent  10  is positioned in the duct in the pancreas. 
     The tubular body  14  and the cap portion  36  are configured to facilitate prophylactic protection and drainage of the pancreatic duct into the duodenum. To help facilitate drainage of the pancreatic duct, tubular body  14  and the cap portion  36  may include one or more openings, i.e. the openings  42  in the tubular body as described above. The lumen  32  may extend though the body  14  to the cap portion  36 , for example in by extending to an opening  52  in the central portion  44  of the stent  10 . The cap portion  36  may include a plurality of openings  52 . For example as shown in  FIG. 5A , the cap portion  36  may include the central opening  52  surrounded by a plurality of openings  52  operably connected to the lumen  32  to facilitate drainage from the pancreatic duct. As shown in  FIG. 5B , the plurality of openings  52  may be included in the tubular body  14  above the cap portion  36  and further include a cover  56  that covers the central lumen  32  to protect against accidental entry of a wire guide into the stent  10  any yet still allow drainage of the pancreatic duct through the stent  10  and into the duodenum. In the embodiment shown in  FIG. 5B , the cap portion  36  is sized and shaped to cover and fit against the opening of the pancreatic duct and the cover  56  is sized and shaped to protect the lumen and the entry to the pancreatic duct yet allow drainage from the stent  10  and also allow access to the common bile duct. The cover  56  may have a shorter peripheral extension  58  than the periphery  46  of the cap portion  36 . The cap portion  36  and the cover  56  are flexible and expandable so that the cap portion  36  may be collapsed into a folded configuration for delivery and an expanded configuration when the stent  10  is positioned at the pancreatic duct. The cap portion  36  is also flexible so that the cap portion  36  flexes with the movement of the body and the risk of irritation at the implant site is minimized. 
     In some embodiments, as described above, one or more retaining member  38  may extend outward from the tubular body  14  to help keep the stent  10  in position within the pancreatic duct. The retaining member  38  may be a flap that extends a length of about 4-8 mm from the tubular body  14 . Other lengths for the retaining member may be possible and may depend on the size of the duct opening, the flexibility of the retaining member, the length of the stent and the amount of time the stent  10  is to remain implanted within the duct. The retaining member  38  may be formed from the tubular member  14  with a longitudinal cut in the wall of the tubular member  14 . Alternatively, the retaining member may be formed by molding with the body  14  or addition to the tubular body  14  or any method known to one skilled in the art. The retaining member  38  may be configured for retention of the distal portion  30  of the stent  10  within the duct for several days or weeks and then allow the stent  10  to pass naturally out of the duct. 
     When two or more retaining members  38  are provided, the retaining members  38  may be provided circumferentially or otherwise spaced around the stent  10 . For example, a first retaining member  38  may extend radially outward at a direction about 180° opposite the direction of the curved portion  36  as shown in  FIG. 1 . A second retaining member  38  may extend radially outwardly at about 180° from the first retaining member  38 . The retaining member  38  may be sufficiently flexible to collapse against the tubular body  14  for delivery of the stent  10  and yet have sufficient resiliency to contact the pancreatic duct to hold the stent  10  in place once positioned at the delivery site. 
     The stent  10  may be of any size suitable for implantation into the pancreatic duct and will vary depending on the size of the duct. The stent  10  may have an outer diameter of about 3-10 Fr. The inner diameter of the stent  10  may be about 1-2 mm. Shorter or longer stents may also be used. These sizes are merely exemplary and other sized may be used. The stent may be made from materials so that the stent is soft enough to conform to the curvature of the duct and eliminate or reduce irritation at the implantation site that occurs with a rigid stent, thus reducing the risk of pancreatitis, morphological or ductal changes. The materials should also have sufficient strength to maintain a lumen through the stent when the stent is positioned within the duct. In some embodiments, the stent  10  or a portion thereof may be made from biodegradable materials. Exemplary materials for the stent  10  include, but are not limited to the following, SOF-FLE X ™, a type of polyether urethane, silicone, block co-polymers, urethanes, polyethylene, polystyrene, polytetrafluoroethylene (PTFE), FEP and the like and combinations thereof. In some embodiments, the stent  10  may be formed from biodegradable materials. A number of bioabsorbable homopolymers, copolymers, or blends of bioabsorbable polymers are known in the medical arts. These include, but are not necessarily limited to, polyesters including poly-alpha hydroxy and poly-beta hydroxy polyesters, polycaprolactone, polyglycolic acid, polyether-esters, poly(p-dioxanone), polyoxaesters; polyphosphazenes; polyanhydrides; polycarbonates including polytrimethylene carbonate and poly(iminocarbonate); polyesteramides; polyurethanes; polyisocyantes; polyphosphazines; polyethers including polyglycols polyorthoesters; expoxy polymers including polyethylene oxide; polysaccharides including cellulose, chitin, dextran, starch, hydroxyethyl starch, polygluconate, hyaluronic acid; polyamides including polyamino acids, polyester-amides, polyglutamic acid, poly-lysine, gelatin, fibrin, fibrinogen, casein, collagen. Exemplary non-expandable, tubular stents that may be modified for use with a cap portion include, but are not limited to, a ST-2 SOEHENDRA TANNENBAUM® stent, a COTTON-LEUNG® stent, a COTTON-HUIBREGTSE® stent, a GEENEN® Pancreatic Stent, a JOHLIN® Pancreatic Wedge Stent, or a ZIMMON® Pancreatic (available from Cook Endoscopy, Inc., Winston-Salem, N.C.). 
     The cap portion  36  may be formed from the same or different materials from the body  14 . For example, the cap portion  36  may be formed from polyurethane while the tubular body  14  is formed from polyethylene. Alternatively, the stent  10  may be formed from unitary construction, i.e. where the entire stent if formed from silicone or polyurethane. In some embodiments, the cap portion  36  may include metallic wires within the flexible material. The wires may be formed from any metal known to one skilled in the art that is compatible with implantation and are flexible enough to allow the cap portion  36  to move between the expanded and un-expanded configurations. The cap portion  36  may be connected to the tubular body  14  using any method known to one skilled in the art, for example bonding welding and the like. The cap portion  36  may also be integrally formed with the tubular body  14  when the portions are formed from the same material. The cap  36  may also include a coating to facilitate deflection of the medical device away from the proximal opening  21  of the stent  10 . For example, the cap portion  36  may include a coating to increase lubricity. Alternatively, the cap portion  36  may be formed from a material having an increased lubricity. By way of non-limiting example, the lubricious material may be selected from the following: polymers produced from monomers selected from ethylene oxide; 2-vinyl pyridine; N-vinylpyrrolidone; polyethylene glycol acrylates such as mono-alkoxy polyethylene glycol mono(meth)acrylates, including mono-methoxy triethylene glycol mono (meth)acrylate, mono-methoxy tetraethylene glycol mono (meth)acrylate, polyethylene glycol mono (meth) acrylate; other hydrophilic acrylates such as 2-hydroxyethylmethacrylate, glycerylmethacrylate; acrylic acid and its salts; acrylamide and acrylonitrile; acrylamidomethylpropane sulfonic acid and its salts, cellulose, cellulose derivatives such as methyl cellulose ethyl cellulose, carboxymethyl cellulose, cyanoethyl cellulose, cellulose acetate, polysaccharides such as amylose, pectin, amylopectin, alginic acid, and cross-linked heparin 
     In some embodiments, the stent  10  may include radiopaque markings (not shown) to help with placement of the stent  10  in the duct. In some embodiments, the stent  10  itself may be radiopaque. Some embodiments may include visual markings created by a laser or ink that may be visualized so the stent  10  may be visualized using fluoroscopy or x-ray. Any type of visualization marking known to one skilled in the art may be used with the stent  10 . 
     The stent  10  may be delivered to the pancreatic duct when the physician accidently enters the pancreatic duct with a wireguide when the intended target is actually the bile duct. As discussed above, navigation with a wireguide and a catheter within the biliary tree is difficult. To avoid additional accidental entries into the pancreatic duct during the procedure and to reduce the risk of pancreatitis due to the accidental entry or repeated entry into the pancreatic duct, the wireguide may be left in position within the pancreatic duct and a stent  10  of the present invention may be delivered over the wireguide to the pancreatic duct. The stent  10  may be positioned within the pancreatic duct so that the cap portion  36  prevents further irritation of the pancreatic duct in the event of additional entries into the duct with the wire guide or accidental injection of contrast dye into pancreatic duct. The cap portion  36  is positioned to protect the pancreatic duct and to deflect the wireguide toward the bile duct. In the event the wireguide accidentally enters the lumen  32  of the stent  10 , the tubular body  14  is protective of the duct and the wireguide can be withdrawn and redirected without irritating the pancreatic duct. 
     The stent  10  may be delivered to the implantation site over the wireguide that accidentally entered the pancreatic duct using any delivery system known in the art. The delivery system used will depend on the size of the stent  10  and the materials used to form the stent  10 . The delivery system  100  includes a wireguide  110  that has already entered the pancreatic duct and an introducer catheter  120  that can be advanced over the wireguide  110 . The stent  10  is positioned within the introducer catheter  120  as shown in  FIG. 6A . The introducer catheter  120  may include a pushing catheter  126  and an outer sheath  128  for delivering the stent  10  with the cap portion in the unexpanded configuration for navigation of the catheter to the site. During delivery to the site, the stent  10  is placed over the wireguide  110  and the cap portion  36  of the stent  10  is in the unexpanded configuration. Once the introducer catheter  120  has been removed from the stent  10  at the delivery site, the cap portion  36  assumes the expanded configuration shown in  FIG. 6B  to cover the opening of the pancreatic duct  200 . The wireguide  110  and the introducer catheter  120  have lengths sufficient to extend from the desired location in the patient&#39;s body to the exterior of the patient, as will be understood by one skilled in the art. The delivery system  100  may also include additional lumens. 
     The stent  10  shown in  FIG. 1B  having an angled proximal portion  22  and a proximal opening  21  offset from the axis A may also be delivered using delivery systems known in the art such as the delivery system  100  shown in  FIGS. 6A and 6B . The positioning of the stent  10  is shown in  FIGS. 7A and 7B , where the lumen  32  extends along the wire guide  110  within the introducer catheter  120 .  FIG. 7B  illustrates the angled proximal portion  22  returned to the angled configuration after the wireguide  110  and the introducer catheter  120  are removed from the stent  10 . 
     An exemplary method of delivering and implanting the stent  10  of the present invention will be illustrated with reference to the delivery system  100 . As shown in  FIGS. 8-11 , the delivery system  100  may be used to place the stent  10  in the pancreatic duct  200  of the pancreas  210 . As shown in  FIG. 8 , the wireguide  110  has been accidently advanced from an endoscope  212  through the Ampulla of Vater  214  into the pancreatic duct  200  instead of the common bile duct  220 . Before withdrawing the wireguide  110  from the pancreatic duct  200  and attempting to enter the bile duct, the stent  10  may be positioned within the pancreatic duct  200  to prophylactically protect the duct  200  from further irritation and damage. The wireguide  110  is left in the duct  200  and the stent  10  is advanced over the wireguide  110  and out of the endoscope  212  by the introducer catheter  120 . For reference, the duodenum  222 , the cystic duct  224  and the gall bladder  226  are also shown. The introducer catheter  120  advances the stent  10  into position over the wireguide  110  by pushing the stent  10  distally along the wireguide  110  until the pancreatic duct  200  is reached. The stent  10  may be advanced until the tubular body  14  is positioned within the duct  200 . The cap portion  36  is released from the catheter  120  and assumes the expanded configuration to cover the opening of the duct  200  as shown in  FIG. 9 . The cap portion  36  is positioned external to the duct  200  and covers the opening of the duct  200 . The wireguide  110  is withdrawn from the duct  200  and the stent  10  is left in position as shown in  FIG. 10  to prophylactically protect the pancreatic duct  200  from further irritation and entry by the wireguide  110  or from accidental injection of contrast dye.  FIG. 11  illustrates the wireguide  110  advancing through the Ampulla of Vater  214  and deflecting off the cap portion  36  of the stent  10  and entering into the bile duct  220 . 
     The stent  10  may remain in position for up to about two weeks. Shorter or longer periods of implantation for the stent  10  are also possible. The stent  10  may be pushed out of the duct  200  by natural body function or the stent  10  may be surgically removed. Where the stent  10  or portions thereof are biodegradable, the stent  10  will degrade and be passed by the body. In some embodiments, the tubular body  14  may be degradable and the cap portion  36  may not be degradable. In that instance, the tubular body  14  may degrade so that the cap portion  36  falls off into the duodenum  222  and is passed by the body. 
     The above Figures and disclosure are intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in the art. All such variations and alternatives are intended to be encompassed within the scope of the attached claims. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the attached claims. For example, the invention has been described in the context of the biliary system for illustrative purposes only. Application of the principles of the invention to any other bifurcated lumens or vessels within the body of a patient, including areas within the digestive tract such as the pancreatic system, as well as areas outside the digestive tract such as other vascular systems, by way of non-limiting examples, are within the ordinary skill in the art and are intended to be encompassed within the scope of the attached claims.