Abstract:
A system and method are provided for accessing and cannulating a target mass. The system includes a combined cystotome and access needle that provides for efficient operation. The access needle may be embodied as a polymeric sheath with a piercing stylet configured to extend beyond its distal end. The device embodiments allow a user to access and cannulate a target site such as, for example, a pancreatic pseudocyst with a single device. The device is also configured to allow introduction of a wire guide such that the cannulated target site can readily receive a wire-guided stent, or a stent delivered over the access needle.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application Ser. No. 61/545,343, filed Oct. 10, 2011, which is incorporated herein by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates generally to methods of minimally-invasive surgical methods. More particularly, the invention pertains to a system and method for access to and cannulation of a body structure. 
       BACKGROUND 
       [0003]    The development of minimally invasive methods and devices over recent years has revolutionized the practice of medicine. These methods and devices allow clinicians to perform a wide variety of procedures while minimizing trauma to the patient. Along these lines, there is a need for devices and methods that employ minimally invasive technologies in order to access occluded regions in a mammalian body. 
         [0004]    Cystotomy procedures are used in a variety of surgical procedures. For example, various ailments associated with the biliary tree can be treated by placement of a stent. One example is pancreatic pseudocysts, which may form in the pancreas as a pocket holding necrotic tissue, blood, and/or pancreatic secretions. They may occur, for example, in connection with pancreatitis or as the result of abdominal injury, and are differentiated from true cysts by being contained by a fibrous and/or granular tissue capsule rather than an epithelial lining. Pancreatic pseudocysts may be treated by accessing, cannulating, and placing a drainage stent such as, for example, a pigtail polymer stent into the pseudocyst. Cystotomy may also be used, for example, during treatment and/or removal of accretions (e.g., “stones”) from the urinary bladder. 
         [0005]    Commonly, a pancreatic pseudocyst, or other structure in need of access for diagnostic and/or therapeutic purposes presently requires multiple steps and tools. Typically, one or more cannulation and/or dilator devices must be introduced to open the stricture, penetrate the pseudocyst, or otherwise provide a sufficient path of access for stent-introduction. The present procedure for placement of a drainage catheter into a pancreatic pseudocyst by cystotomy includes several steps that may be implemented during ERCP (Endoscopic retrograde cholangio-pancreatography). 
         [0006]    First a metal access needle often including a stylet through its needle lumen is provided and directed to (and potentially into) the target area. Next the stylet is removed from the metal access needle, and a wire guide is directed through the needle lumen to and/or into the target site. Then, the access needle is removed, being pulled out over the entire length of the wire guide. Next, a separate cystotome is provided, and is directed along the entire length of the wire guide to the target site. A tissue cautery/electrosurgical element disposed at the distal tip of the cystotome is actuated by directing current therethrough to cannulate the target site with sufficient diameter for placement of a stent. Then, the cystotome is removed by being withdrawn along the entire wire guide length, and the drainage stent is directed over the wire guide into the target site. This is a painstaking and time-consuming procedure. 
         [0007]    Therefore, it would be beneficial to provide minimally invasive access devices and methods that will decrease the number of steps taken, the number of items that treating personnel (e.g., physician and assisting personnel) must handle during a procedure, and the amount of time needed to complete a procedure such as, for example, endoscopically placing a drainage stent into a pancreatic pseudocyst. 
       BRIEF SUMMARY 
       [0008]    A device and method are provided including system and method for cannulating a target structure in a patient body. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The invention may be better understood with reference to the following drawings and description. The components in the figures are not necessarily drawn to scale, emphasis instead being placed upon illustrating the principles of the invention. In particular, by way of illustrative example, the components of the embodiments described here preferably will have a closer fit/tolerance than is shown in the drawings. 
           [0010]      FIG. 1  shows an embodiment (in longitudinal section, showing a distal end length) of a system for accessing and cannulating a body structure; and 
           [0011]      FIG. 2  shows another embodiment (in longitudinal section, showing a distal end length) of a system for accessing and cannulating a body structure. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    As used herein, including in the claims, the term “echogenic” is defined as having enhanced echogenicity. Specifically, it is used to refer to materials or portions of materials that are constructed or are treated to have greater reflectivity of ultrasonic waves than standard materials used for a stent, sheath, cannula, catheter, and/or stylet, and to provide an echogenic profile relative to surrounding tissues during use in a patient body to accurately orient and direct the echogenic device portion. It is known in the art that most materials used for a stent sheath, catheter, cannula, or stylet will reflect some ultrasonic waves, but the term “echogenicity,” as used herein includes treating the surface by creating a textured or patterned surface including, for example, one or more of dimples, divots, knurling, ridges, or the like—each of which is known in the art to enhance echogenicity as compared to a smooth surface for a similarly-sized/shaped object, (and/or, when specifically referenced, using a material known to provide an enhanced echogenic profile) configured to provide clear ultrasound visualization at a resolution providing for accurate location and navigation of a device in a body (e.g., of a patient). Echogenic construction may be enhanced by surface texture, but can also be provided by structural inclusions such as embedded bubbles, beads, or other inclusions in a polymer or metal that can provide for a different ultrasound reflectivity than material surrounding them. 
         [0013]    Also, as used herein, the term “needle” refers generally to a tubular cannula that may or may not have a piercing distal tip, and the term “cannula” may refer to a rigid or flexible tubular device that may include a piercing tip. As used throughout unless a special exception is specifically identified, the term “proximal” refers to an end or direction nearer a physician or other person handling an object during normal use (generally, the “handle end”), and “distal” refers to the opposite end (generally, the “tool end”). For purposes of the present application, the term “cystotome” is defined by the structures and limitations of the present description and claims. Generally, a “cystotome” refers to a device for cystotomy of the urinary bladder, but those of skill in the art will appreciate that the device embodiments of the present disclosure will be useful in other procedures for making an incision and/or access aperture through a body structure of (including within) a patient&#39;s body. Drawing figures are not necessarily to scale, as various parts thereof may be magnified or otherwise emphasized to clarify structural features (including that, as one specific example, the proportions of the duodenum and biliary tree structure are not shown to scale, as those of skill in the art will know that the biliary tree is proportionally smaller than shown). 
         [0014]    One embodiment of a system for accessing a body structure is described here with reference to  FIG. 1 , which shows a distal end portion of system components in longitudinal section. The system embodiment provides a combined cystotome and access needle device  100  that provides for a more efficient method of cannulation and access to a body structure such as a pancreatic pseudocyst. Although it is not explicitly illustrated in the drawings, a preferred device body will be configured with sufficient length, flexibility, pushability, and trackability to be operable through a working channel of a gastrointestinal endoscope (e.g., end-viewing and/or side-viewing scopes, including endoscopic ultrasound (EUS) endoscopes). Those of skill in the art will appreciate that several proximal end constructions of a handle and/or other operative proximal end structure may use or readily be adapted from existing devices, and practiced within the scope of the present invention. One or more of the cystotome, access needle sheath, and stylet components in any of the embodiments described below may be configured to include echogenic enhancement(s) for EUS visualization. 
         [0015]    The device  100  includes a cystotome  110  that includes a flexible elongate tubular cystotome sheath body  112  having a distal end. The cystotome body  112  circumferentially defines a cystotome lumen  114  that extends longitudinally through its length. The cystotome  110  also includes a diathermic element  116  configured as a conductive ring that circumferentially defines the distal end of the cystotome  110  at the distal end of the cystotome body  112 . The diathermic element  116  is configured in electrical communication via an electroconductive element embodied here as a wire  117  connected with a proximal region (not shown) of the cystotome that preferably will be configured to transmit energy (e.g., RF energy, electric current) from an electrosurgical power supply. The wire  117  may be electroinsulated. 
         [0016]    The diathermic ring  116  is tapered with a rounded distal transition to the cystotome lumen  114 . More particularly, the shape of the ring  116  may be described as including a tapered external geometry comprising at least one frustoconical length between a proximal diathermic element end and a distal diathermic element end. In some embodiments, the diathermic element  116  may be sized at about 6 Fr to about 10 Fr (about 2 to about 3.33 mm outer diameter), or larger or smaller for various applications. The diathermic element  116  is shown as connecting to the cystotome body by a threaded connection, but it should be appreciated that other connecting means (e.g., one or more of friction-fit, adhesive, sonic welding, or other connecting means) may be used to securely fix the diathermic element  116  to the cystotome body  112 . The cystotome body  112  most preferably is constructed essence of a non-conductive material that will generally prevent conduction from the wire  117  through the body  112 , thereby limiting the exposed conductive surface of the distal portion of the device  110  to the diathermic element. 
         [0017]    An elongate, flexible access sheath, which may be configured as a tubular polymer access needle  120 , is longitudinally and slidably disposed through the cystotome lumen  114 . One suitable polymer for construction of at least a length of the access needle sheath  120  is polytetrafluoroethylene (PTFE). The access sheath  120  includes a needle lumen  124 . The sheath  120  is configured with sufficient length to be advanced beyond the distal end of the cystotome  110  to provide for initial penetration of a target. A stylet  130 , which may be configured as a polymer or a metal alloy stylet, is longitudinally, slidably, and removably through the needle lumen  124 . The stylet  130  preferably includes a distal piercing tip  138 . 
         [0018]    During a method of using the device  100 , an endoscope may be provided and directed to a predetermined location near a target site, such as—for example—a target mass of tissue, to be accessed and cannulated using the device  100 . The stylet piercing tip  138  may be aligned adjacent and distal of the distal end of the access sheath  120 . The device  100  may be directed through a working channel of the endoscope to the target site, and the needle  120  with stylet  130  may be advanced distally (extending past the diathermic element  116 ) to penetrate the target site. The cystotome  110  may then be advanced distally along the needle  120  until the diathermic element  116  contacts the target site around the penetrated locus. Then, the diathermic element  116  may be actuated (e.g., by directing electrosurgical current therethrough) to cannulate the target site). 
         [0019]    The stylet  130  may be removed from the needle sheath lumen  124  and replaced with a wire guide (not shown). Or the needle sheath  120  may be removed from the cystotome lumen  114  and replaced with a wire guide (not shown). The cystotome  110  may be withdrawn proximally along and removed from the needle sheath  120  and/or the wire guide thereafter. Then a drainage stent may be directed along needle sheath  120  and/or the wire guide into the cannulated target site. 
         [0020]    Another embodiment of a system for accessing a body structure is described here with reference to  FIG. 2 , which shows a distal end portion of system components in longitudinal section. The system embodiment provides a combined dual-lumen cystotome and access needle device  200  that provides for a more efficient method of cannulation and access to a body structure such as a pancreatic pseudocyst (e.g., during an endoscopic transgastric pancreatic necrosectomy procedure). 
         [0021]    Although it is not illustrated, a preferred device body will be configured with sufficient length, flexibility, pushability, and trackability to be operable through a working channel of a gastrointestinal endoscope (end-viewing and/or side-viewing, including endoscopic ultrasound (EUS) endoscopes). Those of skill in the art will appreciate that several proximal end constructions of a handle and/or other operative proximal end structure may use or readily be adapted from existing devices, and practiced within the scope of the present invention. 
         [0022]    The device  200  includes a cystotome  210  that includes a flexible elongate tubular cystotome sheath body  212  having a distal end. The cystotome body  212  circumferentially defines a first cystotome lumen  214  that extends longitudinally through its length, and a second cystotome lumen  215  that also extends longitudinally through its length. The cystotome  210  also includes a diathermic element  216  configured as a ring that circumferentially defines the distal end of the cystotome  210  at the distal end of the cystotome body  212 . The diathermic element  216  is configured in electrical communication via an electroconductive element embodied here as a wire  217  that extends through the second cystotome lumen  215  and is connected with a proximal region (not shown) of the cystotome that preferably will be configured to transmit energy (e.g., RF energy, electric current) from an electrosurgical power supply. 
         [0023]    The diathermic ring  216  is domed with a rounded distal transition from the outer surface of the cystotome sheath  210  to the cystotome lumen  214 . More particularly, the shape of the ring  216  may be described as including a domed external geometry comprising at least two radii of curvature between a proximal diathermic element end and a distal diathermic element end. In some embodiments, the diathermic element  216  may be sized at about 6 Fr to about 10 Fr (about 2 to about 3.33 mm outer diameter), or larger or smaller for various applications. The diathermic element  216  is separated from the cystotome lumen by a tubular insulating ring  216   a . The insulating ring  216   a  is shown as connecting to the cystotome body by a threaded connection, but it should be appreciated that other connecting means (e.g., one or more of friction-fit, adhesive, sonic welding, or other connecting means) may be used to securely fix the diathermic element  216  and the insulating ring  216   a  to the cystotome body  212 . The cystotome body  212  most preferably is constructed essentially of a non-conductive material that will generally prevent conduction from the wire  217  through the body  212 , thereby limiting the exposed conductive surface of the distal portion of the device  210  to the diathermic element, and preventing undesired transmission of energy from the wire  217  to the outside of the device and to the contents of the cystotome lumen  214 . 
         [0024]    An elongate, flexible access sheath, which may be configured as a tubular polymer or metallic access needle  220 , is longitudinally and slidably disposed through the cystotome lumen  214 . The access sheath  220  includes a needle lumen  224 . The sheath  220  is configured with sufficient length to be advanced beyond the distal end of the cystotome  210  to provide for initial penetration of a target. A stylet  230 , which may be configured as a polymer or a metal stylet, is longitudinally, slidably, and removably through the needle lumen  224 . The stylet  230  preferably includes a distal piercing tip  238 . Methods of use for this embodiment and variants thereof will be similar to the methods described above with reference to the embodiment of  FIG. 1 . 
         [0025]    A further embodiment may provide a surgical procedure kit that may include an embodiment of  FIG. 1 ,  FIG. 2 , or some variant thereof. Such a kit may further include one or more of at least one wire guide, at least one drainage stent, and/or at least one electrosurgical power supply connector configured to connect an electrosurgical power supply to the electroconductive structure providing electrical communication with the distal diathermic element of the cystotome. 
         [0026]    Those of skill in the art will appreciate that embodiments not expressly illustrated herein may be practiced within the scope of the present invention, 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. 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.