TECHNICAL FIELD 
     Embodiments disclosed herein generally relate to a method for placing a plurality of biliary stents across a stricture. More particularly, embodiments relate to a method and device for placing a plurality of biliary stents without requiring re-introduction of a stent delivery catheter. 
     BACKGROUND 
     Endoscopic retrograde cholangiopancreatography (ERCP) is a technique used for viewing and treating the ducts that drain the liver and pancreas. Biliary ducts form a drainage routes into the duodenum from the liver and gallbladder and they join the pancreatic duct, just before they drain into the duodenum about 3 inches from the stomach. The drainage opening is called the papilla (Ampulla of Vater). The papilla is surrounded by a circular muscle, called the sphincter of Oddi. During ERCP, X-ray contrast dye is injected into the bile duct, the pancreatic duct, or both via a catheter disposed through a working channel of an endoscope. 
     Two commonly used types of catheters used during ERCP procedures (particularly where a catheter may be exchanged) are referred to as “long-wire” catheters and “short-wire” catheters. A long-wire catheter is one in which a wire guide lumen is provided through the major length of the catheter. That is, in a catheter configured for use with long-wire procedures, the wire guide lumen extends through more than half, most, or all of the catheter&#39;s length. In catheters for short-wire procedures, the wire guide lumen may not extend the entire length of the catheter. In this type of catheter, the wire guide lumen may extend only from the distal end of the terminal-end device to a point intermediate the distal and proximal ends of the catheter, and often the wire guide extends through less than half or only a very small percentage of the catheter&#39;s length (defined herein as a minor length). This shorter lumen is the only portion of the catheter encompassing the wire guide during a short wire operation. 
     The decreased friction and the lack of a need for a wire guide that is at least about twice as long as the catheter are generally considered advantages of a short-wire catheter, although the pushability of a catheter without a wire guide engaged into a long-wire lumen may be less than that of a long-wire catheter so engaged. Short-wire catheters are often easier to exchange than catheters having the wire guide lumen extending the entire length of the catheter. This is because the wire guide need not be as long as a “long wire” configuration, which requires that a length of the wire guide extending outside the patient&#39;s body be longer than the portion of the catheter extending over the long wire guide in order for a doctor or assistant to maintain a grasp on the wire guide (to avoid undesired movement or displacement thereof). The short wire guide configuration catheters (known also as “rapid exchange catheters) also create less friction during mounting and exchange operations due to the shorter wire guide lumen, leading to a reduced likelihood of displacing the wire guide after it has been positioned, often under radiography, to a desired position/orientation. 
     Stents may be placed into the bile and/or pancreatic ducts to bypass strictures of the duct. These narrowed areas of the bile or pancreatic duct may be caused by—for example—inflammation, scar tissue, or tumors that cause blockage of normal duct drainage. Metal and/or plastic stents may be used, depending upon the medical indications. In some circumstances, it may be useful to provide a plurality of stents that cross a single stricture in generally parallel fashion, such as is shown—for example—in  FIG. 1 . The example of  FIG. 1  shows two plastic biliary stents  197 ,  199  disposed through a biliary duct  182  and protruding through the Ampulla of Vater  184  (not to scale) into the duodenum. Such stents typically are placed by being directed to a target site over and along a guide catheter disposed through the stent lumen. 
     Placement of multiple biliary stents in bile duct stricture can be technically challenging, because difficulties may arise from accessing the stricture with repeated cannulation and guide wire placement. The subsequent exchanges done over a very long guide wire may increase the procedural complexity. In the conventional manner of delivering multiple stents to traverse a single stricture, repeated bile duct cannulation and exchanges are necessary in order to place multiple stents to attain the maximum lumen diameter for the stricture. Direct cannulation with the stent preloaded on stent-delivery catheter without a prior inserted wire guide may be difficult. Although it is possible to use a single wire guide left in place to direct a first (optionally pre-loaded) stent-delivery catheter to a target site, withdraw the stent-delivery catheter, recannulate the stricture, then re-introduce the same (reloaded) or a different (preloaded) stent-delivery catheter for placement of a second stent (repeated for any subsequent stent-placement), it would be advantageous to provide a system and method for serially placing a plurality of stents that would not necessitate the time, effort, and complexity of withdrawing and reintroducing a stent-delivery catheter for second and subsequent stents targeted to traverse a single stricture or to otherwise be delivered along a single wire guide. 
     BRIEF SUMMARY 
     In one aspect, embodiments disclosed herein may include a stent-delivery catheter, as well as methods for introducing a plurality of stents therethrough to a target site in a body passage, using a novel wire-guided technique wherein the stent does not encompass the wire. 
     In certain embodiments, the method may allow generally parallel placement of a plurality of stents during a single procedure, which may be an ERCP procedure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a biliary duct structure traversed by two plastic biliary stents; 
         FIG. 2  shows one embodiment of a dual-lumen stent-delivery catheter; 
         FIGS. 2A-2E  show steps of a method for deploying a stent into a body passage target site with the embodiment of  FIG. 2 ; 
         FIGS. 3A-3E  show steps of a method for deploying a second stent into a body passage target site with the embodiment of  FIG. 2 ; 
         FIGS. 4A-4C  show a long-wire embodiment of a dual-lumen stent-delivery catheter; and 
         FIGS. 5A-5C  show a short-wire embodiment of a dual-lumen stent-delivery catheter. 
     
    
    
     DETAILED DESCRIPTION 
     As used in the specification, the terms proximal and distal should be understood as being from the perspective of a physician operating a device embodiment and method herein for delivering a stent to a patient. Hence, the term “distal” means the portion of the delivery system that is farthest from the physician and the term “proximal” means the portion of the delivery system that is nearest to the physician. Also, as used herein unless otherwise specified, the term “end” refers to a region at and near a proximal or distal terminus, while the word “terminus” is used to refer to the absolute ends of the device defining where its construction ceases. 
     Embodiments are described with reference to the drawings in which like elements are generally referred to by like numerals. The relationship and functioning of the various elements of the embodiments may better be understood by reference to the following detailed description. However, embodiments are not limited to those illustrated in the drawings. It should be understood that the drawings are not necessarily to scale, and in certain instances details may have been omitted that are not necessary for an understanding of embodiments disclosed herein, such as—for example—conventional fabrication and assembly. 
     Various embodiments will be described more fully hereinafter. The invention is defined by the claims, may be embodied in many different forms, and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey enabling disclosure to those skilled in the art. As used in this specification and the claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Visualization of this procedure may be done using radiography and/or ultrasound, as stent construction materials, catheter construction materials, and operating procedures needed for effecting the presently disclosed method are within the skill of those in the relevant art. The method and device embodiments described herein may be used via an endoscope such as—for example—a transesophageal endoscope, percutaneously (via a laparoscope, associated trocar, or other percutaneous access device), in some combination thereof, or via other means, with preferable use being with minimally invasive surgical methods and devices. 
     Embodiments of a device and method for placement of multiple stents (e.g., plastic biliary stents) are described here with reference to  FIGS. 2-3E .  FIG. 2  shows a dual-lumen catheter device  200 . The catheter  200  includes a first lumen configured as a wire guide lumen  202  and a second lumen configured as a stent-delivery lumen  204 , which extends through a major length of the catheter body  206  that defines lateral walls of each lumen. The wire guide lumen  202  may also extend through a major length of the catheter body (e.g., for use in a long-wire procedure) and/or it may include an opening ( 202   a ) through the side of the catheter body only a minor length away from the distal terminus of the catheter body (e.g., for use in a short-wire procedure). As such, the entire length of the wire guide lumen  202  may be directed through and occupy a major length and/or a minor length of the catheter body (i.e., short-wire, long-wire, or dual-use configuration). As is known in the art, a major length wire guide lumen may be provided with a side aperture through the catheter body a minor distance from the distal terminus of the catheter body. This latter configuration is commonly referred to as a “dual use” configuration, because it allows operation in either of a short wire or long wire procedure. 
       FIG. 2A  shows a diagrammatic/schematic illustration of a duct (e.g. such as a biliary duct)  282  with an obstruction shown here as a stricture region  285 . The diagrammatic illustrations provided will be understood by those of skill in the art as generally representative, but actual structures will most likely include far less geometric contours (e.g., a stricture may appear more like the passages shown in  FIG. 1 , the stent(s) may be curved and include one or more pigtails, flared apertures or other features, etc.). A wire guide  210  is shown as already having been introduced to traverse the stricture  285 . In  FIG. 2B , the catheter  200  has been directed along the wire guide  210  (which is disposed through the wire guide lumen  202 ).  FIG. 2B  also shows a proximal end configuration of one embodiment. This is shown as a y-shaped connector  208  with one arm  208   a  in communication with the wire guide lumen  202 , and the other arm  208   b  in communication with the stent lumen  204  (although it should be appreciated that either arm could be configured in communication with either lumen, and different connector or introducer structures may be used within the scope of the present disclosure). A distal length of the catheter  200  is shown as having been directed along the wire guide  210  to a position proximally adjacent of, then having traversed, the stricture  285 . 
     In  FIG. 2C , a stent pusher  228  has been used to advance a polymeric biliary stent  230  through the stent lumen  204  portion traversing the stricture  285  so that the stent  230  traverses the stricture  285  while still within the lumen  204 . It should be appreciated that metallic, metal/polymer, and other stent constructions known in the art or developed in the future may be practiced within the scope of the presently disclosed methods. Preferred stents may include polymeric or metallic stents (including, for example, stents having one or more pigtails, one or more flaps of the type shown in the present non-limiting illustrations, a coiled wire construction, or other features). The stent  230  is alongside but does not at all encompass the wire guide  210 . Next, as shown in  FIG. 2D , the catheter  200  may be withdrawn proximally while the stent pusher  228  and the wire guide  210  are each held in place. In this manner, the catheter  200  may be withdrawn from around the stent  230 , leaving the stent  230  to traverse the stricture  285  and provide a path of fluid communication therethrough. The wire guide  210  also remains in its position (traversing the stricture  285 ) after placement of the stent  230 , as shown in  FIG. 2E . 
     Deployment of a second stent  232  is described with reference to  FIGS. 3A-3E , which deployment method may be used to deploy further stents as well, in a serial manner without having to remove and “reload” a deployment apparatus.  FIG. 3A  shows the deployed first stent  230  as in  FIG. 2E , with the catheter having been rotated so that the stent deployment lumen  204  is no longer aligned with the first stent  230 . Next, as shown in  FIG. 3B , the catheter  200  is again advanced along the wire guide  210  so that a distal end length thereof traverses the stricture  285 . A second stent  232  is advanced through the stent lumen  204  by the stent pusher  228  until—within the confines of the stent lumen  204 —the second stent  232  also traverses the stricture  285 , as shown in  FIG. 3C . 
     In the same manner as was used to deploy the first stent  230 , and as shown in  FIG. 3D , the catheter  200  may be withdrawn proximally while using the stent pusher  228  to hold the second stent  232  in a position traversing the stricture  285 . As such, the second stent  232  is disposed across the stricture  285  alongside the first stent  230  and the wire guide  210  (without encompassing any portion of the wire guide  210 ). As shown in  FIG. 3E , when all desired stents have been placed (e.g., two, three, or more stents as desired have been placed by treating personnel), the catheter  200  and wire guide  210  may be withdrawn leaving the stents  230 ,  232 , et seq in place. As shown in  FIG. 3E , it may be helpful to have the ends of the stents offset from one another to help positioning and alignment of the catheter  200  (e.g., during the procedure shown in  FIGS. 3A-3D ) for stent deployment. Various polymeric stents may be used with the device and method described herein, including those with one or more pigtail features, one or more retention/drain flaps, and/or flared stent designs. It should be appreciated that, in the diagrammatically simplified illustrations provided the stents are shown as occupying less than the full cross-sectional area of the stricture  285 ; however, in actual biological conditions, the stents will most likely occupy and expand a significant cross-section thereof. It should also be appreciated that the second stent (and, if provided, subsequent stents) may be provided—lined up seriatim—in the device lumen, where the pusher  228  engages the proximal-most stent and is used to advance the more distal stents until each is deployed as desired. The stents may include radio-opaque markers and/or radio-opaque construction. 
       FIGS. 4A-4C  show views of the distal end of another catheter embodiment  400 . The face defining the distal terminus  409  is rounded to present an atraumatic, generally domed profile (viewed from the side in  FIG. 4A , and end-on in  FIG. 4B ), which may ease direction of the catheter  400  through an endoscope working channel and/or through a body passage such as, for example, a biliary duct. The stent introducing catheter  400  includes a wire guide lumen  402  that is configured as a long-wire lumen extending longitudinally through a major length of the catheter  400 . The catheter  400  includes a stent delivery lumen  404  that extends through a major length of the catheter body. A distal opening  405  of the stent lumen  404  is disposed along a longitudinal side of the catheter body (rather than, for example, facing out the distal terminus in the manner of the catheter  200  shown in  FIG. 2 ).  FIG. 4C , a longitudinal section view along line  4 C- 4 C of  FIG. 4A , illustrates an example of a polymeric biliary stent  430 , which is shown as already positioned in the stent lumen  404 . A stent pusher  428  (which may be solid or hollow) is disposed proximal of the stent  430 . The stent pusher  428  is configured to pushingly contact and advance the stent  430  through the length of the stent lumen  404 , and to hold it in place while the catheter is retracted (and/or to advance the stent distally) for stent deployment. A transition from a longitudinal length of the stent lumen  404  to the distal opening  405  is curved to provide for smooth exit of the stent  430  from the stent lumen  404 . 
       FIGS. 5A-5C  show another stent delivery catheter embodiment  500 , which is configured for use in a short wire procedure. The face defining the distal terminus  509  is rounded to present an atraumatic profile (shown end-on that may ease direction through an endoscope working channel and/or through a body passage such as, for example, a biliary duct.  FIG. 5C , a longitudinal section view along line  5 C- 5 C of  FIG. 5A , illustrates that the catheter  500  includes a wire guide lumen  502  configured as a short wire lumen extending longitudinally through a minor length of the catheter  500 . As such, a wire guide can be directed through the wire guide lumen  502  with minimal frictional contact. The catheter  500  includes a stent delivery lumen  504  that extends through a major length of the catheter body. A distal opening  505  of the stent lumen  504  is disposed along a longitudinal side of the catheter body (rather than, for example, facing out the distal terminus in the manner of the catheter  200  shown in  FIG. 2 ). 
     Those of skill in the art will appreciate that embodiments not expressly illustrated herein may be practiced within the scope of the claims, including that features described herein for different embodiments may be combined with each other and/or with currently-known or future-developed technologies while remaining within the scope of the claims presented here. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting. And, it should be understood that the following claims, including all equivalents, are intended to define the spirit and scope of this invention. Furthermore, the advantages described above are not necessarily the only advantages of the invention, and it is not necessarily expected that all of the described advantages will be achieved with every embodiment of the invention.
A dual lumen catheter may be provided with one or more stents in a stent-deployment lumen and a wire guide disposed through a wire guide lumen. The wire guide may be directed to a target site in a patient body such as a biliary stricture. The catheter may be directed along the wire guide until it is in or adjacent the target site. A distalmost stent may be advanced out a distal side-facing aperture of the stent-deployment lumen into the target site by a pusher member that advances the stent or that holds the stent in place while the catheter is proximally withdrawn from around the stent. With the wire guide remaining substantially in place, the stent-deployment lumen can be reoriented and the steps repeated to place a second (and, if desired, subsequent) stent(s) next to--and generally parallel with--the first stent.