Abstract:
A device and method for dilation of lumenal stenoses. The device includes a dilator with internal threads. The internal threads of the dilator provide for enhanced ability to cannulate a stenosis by engaging external threads on a wire guide that are complementary to the internal dilator threads.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority to U.S. Provisional Application Ser. No. 60/780,162, filed Mar. 8, 2006, which is incorporated herein by reference in its entirety. 
     
    
     TECHNICAL FIELD  
       [0002]     The present invention relates generally to medical devices, and more specifically to a rotary dilator device useful for dilation of stenotic lumenal occlusions, as well as methods of use for the device.  
       BACKGROUND  
       [0003]     Stenotic lumenal occlusions, whether benign or malignant, may be caused by any of a variety of ailments and may occur in any portion of the gastrointestinal tract. Dilatation of these stenoses is indicated whenever there is associated clinically significant functional impairment or a need to access beyond the stricture for diagnosis or therapy. Several different dilator devices have been used for dilation of digestive tract strictures, including those in the biliary ducts. These dilators can be delivered to strictures in a number of ways depending upon the dilator design and desired operator technique including, for example, using endoscopic, fluoroscopic, and/or wire-directed guidance. Two general classes of dilators are (1) fixed-diameter/push-type dilators and (2) expandable dilators. Each of these design classes includes “through-the-scope” designs and “non-through-the-scope” designs. “Through-the-scope” dilators are designed for use through the accessory channel of an endoscope, such as a duodenoscope. Most “non-through-the-scope” devices are deployed over a wire guide that has been placed with the aid of a subsequently-removed endoscope. Most fixed-diameter/push-type dilators are “non-through-the-scope” devices, except for some designs that are used for pancreaticobiliary applications.  
         [0004]     Generally, dilation of a stenotic lumenal occlusion is accomplished by application of expanding forces against the lumenal stenosis. The fixed-diameter/push-type dilators exert axial as well as radial forces when they are advanced through a stenosis. These fixed-diameter/push-type dilators may be used throughout the gastrointestinal tract and can be passed therethrough via endoscopy, with or without fluoroscopy. Wire-guided through-the-scope dilators typically are passed over a wire guide and through the endoscope accessory channel. Non-through-the-scope wire-guided dilators typically are passed over a wire guide following initial placement of the wire guide using an endoscope, where the endoscope is subsequently removed prior to introduction of the dilator. Fixed-diameter/push-type dilators typically include a blunt rounded tip or an elongated tapered tip that broadens proximally. This type of dilator is typically pushed through the stenosis using a pusher-catheter, such that a smaller profile distal tip first enters the stenotic region, and then the broadening distal portion dilates the stricture as the dilator is advanced therethrough. Some stenoses are resistant to the limited amount of force that may be exerted by this type of dilator (for example, because a stenosis is too highly constricted to permit even the tip of the dilator to enter, or because the material comprising the stenosis has greater resistance than the force that can be exerted through the pusher-catheter).  
         [0005]     Expanding dilators are typically embodied as radially-expanding balloon dilators. These balloon dilators generally are made of low-compliance materials that allow uniform and reproducible expansion to a pre-determined diameter when filled with an inflation fluid. A balloon dilator typically is advanced into a stenosed location and then expanded to dilate the stenosis. However, a balloon dilator, even when uninflated, may be too large to pass through the stenosis enough for effective deployment (by inflating the balloon).  
         [0006]     Threaded-tip stent retrievers have also been used to dilate, for example, highly constricted pancreaticobiliary and esophageal stenotic occlusions that would otherwise allow only passage of a wire guide, and that are resistant to conventional dilation. One exemplary device is the Soehendra® stent retriever, Wilson-Cook Medical, Winston-Salem, N.C., described in U.S. Pat. Nos. 5,334,208 and 5,643,277, each of which is incorporated by reference herein. During an application for stenosis-dilation purposes, the Soehendra® stent retriever is introduced through an endoscope, over a wire-guide to a stenosed target region. The device is rotated such that the threaded exterior of its distal end augers into the stenosis, dilating it. If desired, the device may be withdrawn and another dilation device such as those described above may be used to further dilate the stenotic region.  
         [0007]     Although such a wire-guided screw-tipped device such as a stent retriever may be used to auger through some highly constricted stenoses, other such stenoses may still prove resistant. Therefore, there is a need for a dilator system that has an improved ability to dilate resistant and/or highly constricted (such as, for example, &gt;70% occlusion of a lumenal diameter) stenoses.  
       BRIEF SUMMARY  
       [0008]     In one aspect, the present invention provides a dilator system having an improved ability to pass through and dilate high-grade stenoses. In another aspect, the present invention further relates to methods of using the dilator system.  
         [0009]     A dilator system embodiment of the present invention may include a dilator and a wire guide, with the dilator including an internal threaded surface adjacent its distal end. The wire guide may include a distal, externally threaded surface, with the threads being complementary to the internal threads of the dilator. The dilator may also include an external threaded surface.  
         [0010]     In a method of the present invention, the wire guide may be used for initial cannulation of a stenotic occlusion and preferably is advanced until it engages at least a portion of the stenosis. Then, the dilator may be advanced along the wire guide until its internal threads engage the external wire guide threads. A user may then rotate one of the wire guide or the dilator relative to the other such that the dilator&#39;s internal threaded engagement with the wire guide advances the dilator distally through the stenosis. The external dilator surface, which may be threaded, may then engage the material of the stenosis and exert radial force thereupon to create a more open passage through the stenosis. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIGS. 1A and 1B  illustrate a first embodiment of a dilator system;  
         [0012]      FIG. 1C  illustrates a partial cross-sectional view of a wire guide of the dilator system of  FIGS. 1A-1B ;  
         [0013]      FIGS. 2A and 2B  depict a second embodiment of a dilator system;  
         [0014]      FIGS. 3A and 3B  depict a third embodiment of a dilator system; and  
         [0015]      FIGS. 4A-4D  show a method of using a dilator system of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0016]      FIGS. 1A and 1B  illustrate a first embodiment of a dilator  100  of the present invention. As shown in  FIG. 1A , the dilator  100  includes a torqueable elongate catheter shaft  102 . In the illustrated embodiment, the catheter shaft  102  includes a spiraled stainless steel wire body. A preferred shaft is flexible and efficiently transmits rotational movement from its proximal end to its distal end (i.e., torqueable). Other shaft constructions may be used with the present invention. Any shaft preferably has a lubricious surface (e.g., coated with PTFE) to ease advancement and rotation of the dilator. The proximal end includes a rotational handle  104 , which has a textured surface for ease of use in gripping and rotation.  
         [0017]     The distal end of the dilator  100  has a generally cylindrical end tip  106  that includes external helical threads  108  and preferably is less flexible than the shaft  102 . The outermost diameter of the external threads  108  is substantially the same as the outer diameter of the shaft  102 . The dilator  100  has a lumen  110  extending through its length. (See  FIG. 1B ). In the embodiment illustrated in  FIGS. 1A and 1B , the dilator  100  is shown with a wire guide  120  extending through the lumen  110 . The wire guide  120  has an external helically threaded portion  122 , which extends along a discrete portion of the wire guide length adjacent its distal end. The outermost diameter of the wire guide threads  122  is greater than the outer diameter of the unthreaded portion of the wire guide  120 .  
         [0018]     The wire guide  120  may include an external channel  126  along at least the distal portion of its length. The channel  126  provides a path for introduction of a fluid from a fluid introduction port  111  through the lumen  110  of the dilator shaft  102 , even when the external diameter of the wire guide  120  is nearly the same as the internal diameter of the lumen  110 . The fluid may be, for example, a contrast fluid, a lubricant, a medicative fluid (e.g., a solution or suspension containing a medication such as an anti-inflammatory, an analgesic, or an antibiotic), a solvent material, any mixture thereof, or another desirable fluid. The channel  126  is more clearly shown in  FIG. 1C , which is a partial view of a transverse cross-section taken along line  1 C- 1 C of  FIG. 1A  (the partial view shows only the root portion/minor diameter of the screw-thread  122 , and does not show the protruding/major diameter of the screw thread  122 , nor the portion of the cylindrical end tip  106  substantially surrounding the wire guide).  FIG. 1C  also shows the core  128  and the coating  129  of the wire guide. The core  128  may be, for example, nitinol or stainless steel wire, and the coating  129  may be a polymer or other appropriate material (e.g., PTFE). In another embodiment, a channel may be provided along an interior surface of the lumen  110 , a lumen may be provided through the wire guide with one or more openings to its outer surface, or a second lumen may be provided through the dilator shaft  102  such that a fluid (e.g., a contrast fluid or lubricant) may be directed to the distal end of the shaft  102 .  
         [0019]     The shaft  102  of this or other embodiments may include a radio-opaque material and/or may include radio-opaque markers. Such radio-opaque markers may be positioned at or near the tip and/or along the shaft such that they are useful under fluoroscopic viewing for a determination of, for example, distance of distal advancement or degree of rotation. A distal portion of the shaft  102  may include an electroconductive surface, which provides for electrocautery or electrocoagulation of a surface adjacent the shaft  102 . For example, the threads  108  may comprise an electrocautery surface.  
         [0020]      FIG. 1B  is a detailed longitudinal cross-section of a portion of  FIG. 1A , taken along line  1 B- 1 B, and shows that the dilator lumen  110  includes internal helical threads  112  that complementarily engage the external wire guide threads  122 . The engagement of the internal dilator threads  112  with the external wire guide threads  122  provides for rotating advancement of the dilator  100  relative to the wire guide  120 . Thus, the dilator  100  and wire guide  120  provide a dilator system. The dilator  100  may be configured for introduction through an endoscope or may be configured for “non-through-the-scope” use.  
         [0021]      FIGS. 2A and 2B  illustrate a second embodiment of a dilator  200  of the present invention. As shown in  FIG. 2A , the dilator  200  has a torqueable elongate catheter shaft  202 . In the illustrated embodiment, the catheter shaft  202  includes a body, which is flexible and efficiently transmits rotational movement from its proximal end to its distal end. The body may be made of multifilar tubing, for example, such as that available from Asahi-Intecc (Newport Beach, Calif.). Materials and methods of manufacturing one type of multifilar tubing are described in Published U.S. Pat. App. 2004/0116833 (Kato et al.), the contents of which are incorporated herein by reference. Other shaft constructions may be used within the present invention, and the shaft preferably has a lubricious surface (e.g., coated with PTFE) to ease advancement and rotation of the dilator. The proximal end includes a rotational handle  204 , which has a textured surface for ease of use in gripping and rotation.  
         [0022]     The distal end of the illustrated dilator embodiment  200  has a generally conical end tip  206  that includes external helical threads  208  and is preferably less flexible than the shaft  202  (the term conical as used herein is intended to encompass distal end tip shapes that would have a bullet-shaped, elliptical, or other tapered appearance in longitudinal cross-section). In the illustrated embodiment, the conical tip  206  has a base diameter greater than the outside diameter of the catheter and thereby provides for greater dilation of a stenosis than the embodiment described in  FIGS. 1A-1B . It should be noted that, in certain embodiments, the angle of the conical tapering may be less than is illustrated in  FIGS. 2A-2B  (for example, in a different embodiment, the base diameter of a conical tip may be substantially the same as the external diameter of a catheter to which the tip is mounted). The dilator  200  has a lumen  210  extending through its length. As illustrated in  FIGS. 2A and 2B , the dilator  200  is shown with a wire guide  220  extending through the lumen  210 . The wire guide  220  has an external helically threaded portion  222 , which extends proximally from its distal end along a discrete portion of the wire guide length. The outermost diameter of the wire guide threads  222  is greater than the outer diameter of the unthreaded portion of the wire guide  220 . The threads of the dilator  200  and the wire guide  220  are shown as left-handed threads.  
         [0023]      FIG. 2B  is a detailed longitudinal cross-section of a portion of  FIG. 2A , taken along line  2 B- 2 B, and shows that the dilator lumen  210  includes internal helical threads  212  that complementarily engage the external wire guide threads  222 . The engagement of the internal dilator threads  212  with the external wire guide threads  222  provide for rotating advancement of the dilator  200  relative to the wire guide  220 . The dilator  200  may be configured for introduction through an endoscope or may be configured for “non-through-the-scope” use. If the dilator  200  is configured for “non-through-the-scope” use, then the conical tip  206  may include a larger base diameter than would be permitted to pass readily through the working channel of an endoscope. It should be appreciated that the thread portions of one or both of the wire guide and dilator may be single threaded or multi-threaded (such as, for example, double-threaded or triple-threaded). Embodiments with a multi-threaded portion may provide for greater advancement/retraction distances with fewer rotations of the device.  
         [0024]      FIGS. 3A and 3B  illustrate a third embodiment of a dilator  300  of the present invention. As shown in  FIG. 3A , the dilator  300  has a torqueable elongate catheter shaft  302 . In the illustrated embodiment, the catheter shaft  302  includes a body, which is flexible and efficiently transmits rotational movement from its proximal end to its distal end. The proximal end includes a rotational handle  304 , which has a textured surface for ease of use in gripping and rotation.  
         [0025]     The distal end of the dilator  300  has a generally conical end tip  306  that includes a generally smooth external surface  308  and preferably is less flexible than the shaft  302 . Preferably, the smooth external surface  308  includes a lubricious surface coating (such as, for example, PTFE). In the illustrated embodiment, the conical tip  306  has a base diameter greater than the outside diameter of the catheter. It should be noted that, in certain embodiments, the angle of the conical tapering may be less than is illustrated in  FIGS. 3A-3B  (for example, in a different embodiment, the base diameter of the dilator tip may be substantially the same as the external diameter of a catheter to which the tip is mounted). The dilator  300  has a lumen  310  extending through its length. As illustrated in  FIGS. 3A and 3B , the dilator  300  is shown with a wire guide  320  extending through the lumen  310 . The wire guide  320  has an external helically threaded portion  322 , which extends proximally from its distal end  324  along a discrete portion of the wire guide length. The outermost diameter of the wire guide threads  322  is greater than the outer diameter of the unthreaded portion of the wire guide  320 .  
         [0026]      FIG. 3B  is a detailed longitudinal cross-section of a portion of  FIG. 3A , taken along line  3 B- 3 B, and shows that the dilator lumen  310  includes internal helical threads  312  that complementarily engage the external wire guide threads  322 . The engagement of the internal dilator threads  312  with the external wire guide threads  322  provides for rotating advancement of the dilator  300  relative to the wire guide  320 . The dilator  300  may be configured for introduction through an endoscope or may be configured for “non-through-the-scope” use. If the dilator  300  is configured for “non-through-the-scope” use, then the conical tip  306  may include a larger diameter than would be permitted to pass readily through the working channel of an endoscope. This embodiment provides a potential advantage for certain applications. Specifically, some stenoses comprise living tissue such that it may be preferable not to have an externally threaded dilator surface bitingly engaging the stenosed region. In an application using the embodiment shown in  FIGS. 3A and 3B , the wire guide  320  may be advanced through the stenotic region, and then the dilator  300  may be threadedly advanced along the wire guide  320  through the stenosis, with its generally smooth surface  308  providing dilation forces that are less traumatic to surrounding material than a threaded exterior (e.g., as is illustrated in  FIGS. 1A and 1B ).  
         [0027]      FIGS. 4A-4D  illustrate a method of dilating a stenotic occlusion using the dilator system shown in  FIGS. 1A-1B .  FIG. 4A  shows a vessel  400  with deposited material forming a stenosis  402  that significantly occludes the lumen  404  (e.g., sludge deposits in a biliary duct). As a first step of the method, shown in  FIG. 4B , the wire guide  120  is introduced and passed through the stenosis  402 . The threaded portion  122  of the wire guide  120  preferably traverses the stenosis  402  such that at least part of the threaded portion  122  of the wire guide  120  extends proximally from the stenosis  402 . During this step, the wire guide threads  122  may help a user to rotatingly advance the wire guide  120  through a particularly tight stenosis.  
         [0028]     Next, as depicted in  FIG. 4C , the dilator  100  is advanced over the wire guide  120  to the proximal side of the stenosis  402 . The user then holds the wire guide  120  in place and rotates the dilator  100  relative to the wire guide. As shown in  FIG. 4C , this rotation does two things: (1) the external dilator threads  108  engage the stenosis  402  and, exerting radial force, auger through it in a manner that dilates it; and (2) to the extent the stenosis  402  is resistant to the augering movement of the dilator  100  effected by engagement of the external dilator threads  108  with the stenosis, the engagement of the internal dilator threads  112  (not shown) with the external wire guide threads  122  of the statically-held wire guide provides for axial advancement and retraction of the dilator  100  in a manner that cannulates the stenosis, allowing its dilation. After the dilator  100  is threadedly/rotatingly advanced to about the end of the wire guide threads  122 , the wire guide  120  can be advancingly rotated relative to the dilator  100  to advance the wire guide  120  further through the stenosis  402 . The above steps may then be repeated to dilate the next portion of the stenosis  402 .  FIG. 4D  shows the vessel  400  after the dilator  100  has been advanced completely through the stenosis  402 , after which the dilator  100  and the wire guide  120  have been withdrawn, leaving the stenosis  402  dilated such that the lumen  404  of the vessel  400  is much less occluded (such that, for example, a stent could be placed therein to aid maintenance of lumen patency). In an alternative to this method, the wire guide  120  may be held longitudinally in place and rotated relative to the dilator  100  to advance the dilator  100 . In one preferred embodiment of the alternative method, the dilator  100  will not include external threads 108 .  
         [0029]     It is intended that the foregoing detailed description be regarded as illustrative rather than limiting. Therefore, it is to be understood that the following claims, including all equivalents, are intended to define the spirit and scope of this invention.