Abstract:
A system for severing lesions within a living body includes a housing defining an interior tissue receiving chamber is coupled to the distal end of an endoscope. At least one snare extends around the ligating band supporting surface so that, when at least one ligating band is received around the ligating band supporting surface, drawing the at least one snare off the ligating band supporting surface releases a corresponding ligating band from the ligating band supporting surface. In addition, a method for severing tissue comprises the steps of introducing into the body an endoscope to which a housing defining an interior tissue receiving chamber is coupled, wherein at least one snare and at least one ligating band extend around the ligating band supporting surface and advancing the distal end of the endoscope into the body until the housing is located adjacent to a first portion of tissue to be severed. The first portion of tissue is then drawn into the interior chamber and a snare is drawn off the distal end of the housing to release a corresponding ligating band from the ligating band supporting surface so that the ligating band and the snare encircle the first portion of tissue.

Description:
The is a continuation of application Ser. No. 08/969,500, filed Nov. 13, 1997. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to the field of tissue ligation, and more particularly to an improved device and method for electrosurgically severing lesions. 
     BACKGROUND OF THE INVENTION 
     A wide variety of lesions, including internal hemorrhoids, polyps, and mucositis, may be treated by ligation. Ligating bands and severing snares are two types of devices commonly used to sever targeted lesions from surrounding tissue. 
     When performing ligating band ligation, a ligating band is initially placed over the targeted lesion or blood vessel section. As a ligating band is typically elastic in nature, the band must be stretched beyond its undeformed diameter before it can be placed over any tissue. After the tissue to be ligated has been drawn within the inner diameter of the ligating band, the band is allowed to return to its undeformed size and therefore apply inward pressure on the section of tissue caught within the band. The effect of the inward pressure applied by the band is to stop all circulation through the targeted tissue, thereby causing the tissue to die. In due course, the body sloughs off the dead tissue and allows it to pass through the body naturally. 
     Ligating band dispensing means are used to facilitate the placement of a single ligating band or a set of ligating bands over the targeted tissue. Two examples of ligating band dispensers are U.S. Pat. No. 5,356,416 to Chu et al. and U.S. Pat. No. 5,398,844 to Zaslavsky et al., both of which are incorporated herein by reference. 
     Alternately, a lesion may be removed through the use of an electrosurgical severing snare. Electrosurgery can be defined as the use of a radio frequency electric current to sever tissue or achieve hemostasis. A high radio frequency is used because a low frequency (i.e., below 100,000 Hz.) will stimulate muscles and nerves and could injure the patient. Electrosurgery is typically performed at frequencies of approximately 500,000 Hz., although frequencies as high as 4,000,000 Hz. may be used. 
     Medical diathermy is similar to electrosurgery in that radio frequency current is passed through the patient&#39;s body. The major difference between these two techniques is the density of the radio frequency electric current; the current density used in medical diathermy is kept low so as to reduce tissue heating and prevent necrosis. 
     There are three surgical effects that can be achieved with electrosurgery. These include electrosurgical desiccation, which is a low power coagulation caused without sparking to the tissue; electrosurgical cutting, where electricity sparks to the targeted tissue and produces a cutting effect; and electrosurgical fulguration, where electricity sparks to the targeted tissue without causing significant cutting. 
     The above-described surgical effects can be accomplished by using either a monopolar or bipolar output. For many applications, however, bipolar output is preferable because the patient return electrode (necessary in monopolar procedures and a common source of accidents) is eliminated, and any desiccation performed is extremely localized because, in a true bipolar operation, only the tissue that is grasped between the two electrodes is desiccated. Bipolar output, however, is poor for cutting or fulgurating, and thus monopolar tools remain commonplace. Severing snares, for example, are almost all monopolar instruments. 
     Three types of electrical current waveforms are typically used in electrosurgery. These include a cutting waveform, which cuts tissue very cleanly but may cause the incised tissue to bleed excessively; a coagulating waveform, which desiccates and fulgurates tissue without significant cutting; and a blended waveform, which is a cutting waveform that as a moderate hemostatic effect. A waveform&#39;s Crest Factor describes the degree of hemostasis that waveform can produce if properly applied. 
     To remove a lesion (or polyp) with an electrosurgical severing snare, a wire snare is looped around the targeted lesion. Next, the lesion is desiccated and is cut through electrosurgically. It is also possible to sever the lesion in a single step. By cutting with a blended current, it is possible to cut through a lesion in one pass without having to worry about bleeding. Alternately, a lesion may be cut through mechanically with a thin snare wire after the blood supply to the targeted tissue has been coagulated and the tissue softened by a desiccation current. 
     After the targeted lesion has been severed from the surrounding tissue, the severed tissue may be aspirated into an endoscope or similar device. In this manner, a sample may be retrieved for further study. Alternately, the severed tissue can be allowed to pass through the body naturally. 
     While bands are more effective in removing tissue while controlling bleeding, snares allow severed tissue to be retrieved and allow a user to cut deeper into the tissue, when increased suction is applied, to ensure, for example, that all diseased tissue is removed at once. 
     Electrosurgical cutting, however, is a difficult technique to master, especially when cutting large or sessile polyps. When using the two step cutting method (i.e., desiccation before cutting) whether the actual cut is to be made mechanically or electrosurgically, a precise amount of desiccation is required. If there is too little desiccation, the stalk may bleed when cut. If there is too much, the stalk may become too hard and dry to cut either mechanically or electrically. It is also exceedingly difficult to master one step cutting, which uses a blended current to ensure sufficient hemostasis. This is especially true when thick snare wires are used or a current with a high Crest Factor is applied. Often it will be very difficult to start cutting a given polyp. Thus, at times it may be desirable to use a pure cutting waveform to get the cut started. However, this may result in serious bleeding because the polyp has not previously been properly desiccated. 
     Currently, if it is desired to alternate between ligating band ligation and the use of electrosurgical snare, one or the other of these two types of instruments must be inserted through the working channel of an endoscope. Finishing with the first device, the user would have to withdraw this device from the endoscope before replacing it with the second device. In treatment of multiple lesions, for example, this process may need to be repeated several times, wasting the user&#39;s time, exposing the instruments to possible contamination during removal, and increasing the time and discomfort associated with the procedure. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a system for severing lesions within a living body which includes a housing defining an interior tissue receiving chamber coupled to the distal end of an endoscope. At least one snare extends around the ligating band supporting surface so that drawing the snare off the ligating band supporting surface releases a corresponding ligating band from the ligating band supporting surface. 
     In addition, the present invention is directed to a method for severing tissue comprising the steps of introducing into the body an endoscope to which a housing defining an interior tissue receiving chamber is coupled, wherein at least one snare and a corresponding ligating band extend around the ligating band supporting surface. The distal end of the endoscope is advanced into the body until the housing is located adjacent to a first portion of tissue to be severed. The first portion of tissue is then drawn into the interior chamber and a snare is drawn off the distal end of the housing to release the corresponding ligating band from the ligating band supporting surface so that the ligating band and the snare encircle the first portion of tissue. The user may then use the snare to sever an outer portion of tissue while the ligating band remains in place on an inner portion thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be more readily understood through the following detailed description, with reference to the accompanying drawings, in which: 
     FIG. 1 is a perspective view of a first embodiment of the present invention; 
     FIG. 2 is a sectional view of the first embodiment through the plane A—A; 
     FIG. 3 is an enlarged detailed viewed of the distal end of the first embodiment through the plane A-B; 
     FIG. 4 is a plan view of the distal end of the first embodiment through a plane perpendicular to the plane A-B, and only showing one snare engaging a ligating band; 
     FIG. 5 a  is a side view of a pull wire/snare assembly used in the first embodiment of the invention; 
     FIG. 5 b  is a side view of the pull wire/snare assembly of FIG. 5 a  with the loop  65   a  electrically coupled to the pull wire  100 ; 
     FIG. 5 c  is a side view of the pull wire/snare assembly of FIG. 5 a  with the loop  65   b  electrically coupled to the pull wire  100 ; 
     FIG. 6 is a perspective view of the first embodiment of the invention showing the invention being used to sever a lesion; 
     FIG. 7 is a cross-sectional view of a second embodiment of the invention; 
     FIG. 8 is a cross-sectional view of the second as taken along line  2 — 2  of FIG. 1; 
     FIG. 9 is a cross-sectional view of a third embodiment of the present invention in which the pull wire  100  extends through the housing  1  from a proximal end to a distal end thereof; 
     FIG. 10 a  is a side view of a connection between a pull wire, a pull wire crank and an r/f energy generator; 
     FIG. 10 b  is a cross-sectional view of the connection of FIG. 10 a  taken along line A—A of FIG. 10 a;    
     FIG. 11 shows a side view of a distal end of a fourth embodiment of the present invention in which each of the snares and pull wires is formed as a single wire; 
     FIG. 12 shows a cross-sectional view of the distal end of FIG. 11 taken along line  12 — 12  of FIG. 11; and 
     FIG. 13 shows a side view of a pull wire for use with the apparatus of FIG.  11 . 
    
    
     DETAILED DESCRIPTION 
     As shown in FIGS. 1 through 6, the present invention comprises a housing  1 , which has a proximal end  5  and a distal end  10 . A lumen  15  extends between the proximal and distal ends  5  and  10 , and may preferably have a generally circular cross-section. A distal aperture  20  is defined at the point where the lumen  15  exits the distal end  10  of the housing  1 . 
     In operation, the housing  1  is attached to the working end  30  of an endoscope  25  by means, for example, of an elastic ring  26  coupled to a proximal end of the housing  1  as is known in the art. The endoscope  25  contains a working channel  35 , which is defined within the endoscope  25  between a proximal end  40  and the working end  30 . The working channel  35  is sized to allow the free passage of instruments from the proximal end  40 , through the working channel  35  to the working end  30 . In this manner, a user using the endoscope  25  can perform procedures on the patient in which the endoscope  25  and the housing  1  have been inserted. 
     The endoscope  25  may be any standard endoscope which is sufficiently long to reach the targeted lesions within the patient&#39;s body. In addition, the elastic ring  26  allows the housing  1  to be attached to endoscopes  25  of various sizes. 
     It may also be preferable to have an external channel  45  located outside the endoscope  25 . As will be discussed later, a first embodiment of the invention includes a pull wire  100  that extends through an entrance port  55  of the external channel  45  to a position proximate an exit port  50  of the external channel  45 . A portion of the pull wire  100  extends beyond the entrance port  55 , so that a user may manipulate the pull wire  100  by applying a force on the exposed portion of the pull wire  100 . By having the pull wire  100  pass through the external channel  45  rather than through the working channel  35  of the endoscope  25 , a user may pass additional instruments, such as a needle  200  (seen in FIG.  6 ), through the working channel  35  of the endoscope  25  and the lumen  15  of the housing  1  without interfering or becoming entangled with the pull wire  100 . 
     Alternatively, as shown in FIG. 9 in the third embodiment, the pull wire  100  may extend through the working channel  35  of the endoscope  25  to directly enter the housing  1 . 
     As seen in FIGS. 1 and 3, one or more ligating bands  60  are disposed about the housing  1  proximate the distal end  10  of the housing  1 . For sake of illustration, the housing  1  is shown in FIG. 1 as holding three ligating bands  60   a-c , although any number of ligating bands  60  may be used. In the first embodiment of the invention, for example, a total of 3-8 or more ligating bands  60  and a corresponding number of severing snares  70  may preferably be used. The numbering of ligating bands  60   a-c  corresponds to the order in which the ligating bands  60   a-c  will be dispensed from the housing  1 . Ligating band  60   a , for example, is located closest to the distal end  10  of the housing  1  and will therefore be the first ligating band  60  to be dispensed from the device. 
     Each ligating band  60   a-c , is partially engaged by a portion of a distal loop  65   a-c  of a respective severing snare  70   a-c . Each distal loop  65   a-c  of the severing snares  70   a-c  extends underneath each ligating band  60   a-c  that is more distal than the corresponding ligating band  60   a-c  which the respective severing snare  70   a-c  is designed to engage, the respective loop  65   a-c  then wraps over the respective band  60   a-c  and passes back under the more distal of the bands  60   a-c  to a snare catch  90 . Distal loop  65   c , therefore, passes underneath ligating bands  60   a  and  60   b , before wrapping around the ligating band  60   c  and passing back underneath ligating bands  60   a  and  60   b  to the snare catch  90 . Each severing snare  70   a-c  also includes a proximal end  75   a-c , which is connected to the pull wire  100  at attachment points  80   a-c.    
     The method by which a distal loop  65   a-c  engages a ligating band  60   a-c  will now be described with reference to distal loop  65   c  and the corresponding ligating band  60   c . The distal loop  65   c  passes from the lumen  15  of the housing  1  through a snare port  85   c . Alternately, a portion of the snare  70   c  exclusive of the distal loop  65   c  may pass through the snare port  85   c , such that the entire distal loop  65   c  is initially outside the housing  1 . First, the loop  65   c  of the proximal-most snare  70   c  is drawn out of the snare port  85   c  so that each of side sections  65   c ′ and  65   c  of the loop  65   c  passes through snare notches  68   c  and  68   c ′ to extend along the sides of the housing  1 . The ligating band  60   c  is then installed over the housing  1  and the side sections  65   c ′ and  65   c ″ are drawn over the ligating band  60   c  to extend around a snare catch  90 . Thereafter, the loop  65   b  of the snare  70   b  is drawn out of the snare port  85   b , so that side portions  65   b ′ and  65   b  of the loop  65   b  pass through corresponding snare notches  68   b ′ and  68   b  to extend along the sides of the housing  1 . The ligating band  60   b  is then installed over the housing  1 , with the loop  65   c  and the side sections  65   b ′ and  65   b  on the distal side of the ligating band  65   c . The loop  65   b  is then drawn over the ligating band  60   b  to extend around the snare catch  90  and the process is repeated with each successive ligating band  60  moving distally along the housing  1 . Although FIG. 1 shows three snares  70  and three ligating bands  60 , those skilled in the art will understand that any number of snares and ligating bands may be employed using this installation procedure. 
     All three distal loops  65   a-c  engage the snare catch  90 . As seen in FIG. 3, distal loop  65   c  has been loaded onto snare catch  90  first, so that distal loops  65   a  and  65   b  can be disengaged from snare catch  90  without becoming entangled with distal loop  65   c . The same goes for distal loop  65   b  with respect to distal loop  65   a . Snare catch  90  is designed so that when a severing snare (e.g.,  70   a ) is engaged, the ligating band  60   a  will be dispensed from the housing  1  over snare catch  90 , without becoming entangled with any of the other distal loops  65   b  or  65   c.    
     As seen in FIG. 4, each of the distal loops  65   a-c  (only distal loop  65   a  is shown) has a corresponding snare port  85   a-c  and a respective pair of snare notches  68   a-c  and  68   a′-c′ . In this manner, each distal loop  65   a-c  can be dispensed from the housing  1  without becoming entangled with any other distal loop  65   a-c , provided the distal loops  65  are dispensed in the proper sequence (i.e., a, then b, then c). Also, snare ports  85   a-c  are preferably slightly recessed proximally from the distal aperture  20 , to increase the angle at which the distal loops  65   a-c  engage snare notches  68   a-c  and  68   a′-c′ . 
     As mentioned earlier, the proximal ends  65   a-c  of the severing snares  70   a-c  are attached to the pull wire  100  at attachment points  80   a-c  at which electrically conducting portions of the distal loops  65   a-c  are exposed, while remaining portions of the distal loops  65   a-c  are electrically insulated except for distal end portions  82   a-c . The severing snare  70   a-c  is attached to a pull wire  100  in such a manner so as to leave an amount of slack  105   b  and  105   c  in proximal ends  75   b  and  75   c . This slack  105   b-c  is useful because when the pull wire  100  is initially engaged, tension is applied to the proximal end  75   a  of severing snare  70   a  first, without being applied to the proximal ends  75   b-c  of severing snares  70   b-c . Instead, as the pull wire  100  moves proximally (to the left in FIG.  2 ), portions of the slack  105   b-c  are taken up before tension is applied to the proximal ends  75   b-c . In this manner, the pull wire  100  may be used to manipulate each of the severing snares  70   a-c  independently of one another. The amount of slack  105   b-c  is preferably selected so that a respective ligating band  60  may be dispensed first by, e.g., one half turn of the crank  112  while a targeted lesion  110  may be severed by the corresponding snare  70  (e.g., snare  70   a ) by a further one half turn of the crank  112 , after which the snare  70   a  is drawn completely through the snare port  85   a  into the housing  1 , before the slack  105   b  associated with the next severing snare  70   b  has been taken up. Thus, the next snare  70   b  and the corresponding ligating band  60  will not be dispensed accidentally immediately after snare  70   a  has been deployed, (i.e., before the housing  1  is positioned adjacent to a second portion of tissue to be resected). Specifically, an amount of slack  105   b  will be selected so that the length of snare  70   b  is substantially equal to the length of the snare  70   a  plus a length equal to a full turn of the crank  112  and the amount of slack  105   c  will be selected so that the length of the snare  70   c  is equal to the length of the snare  70   a  plus two full turns of the crank  112 . 
     As is known in the art, a device such as a pull wire crank  112  as shown in FIGS. 10 a  and  10   b , may be used to apply the necessary force to the pull wire  100  preferably via a stiffened, hooked pull wire  100   a  to dispense the ligating bands  60   a-c  and to manipulate the severing snares  70   a-c . For example, the length of slack  105  may preferably be chosen so that a half turn of the pull wire crank  112  would release a ligating band  60  while a further one half turn of the crank  112  would draw the corresponding snare  70  into the housing  1  to sever the desired portion of tissue. The use of a slightly more rigid pull wire  100   a  also makes the threading of the pull wire  100  through the endoscope easier. 
     A detailed view of the attachment points  80   a-c  of the pull wire  100  is shown in FIGS. 5 a - 5   c . As described above, in order to transfer r/f energy from the proximal end of the endoscope  25  to the snares  70 , the pull wire  100  is formed of electrically conducting material which may be selectively electrically coupled to each of the snares  70   a-c . This is accomplished through the action of slack  105   b-c . Specifically, in an initial configuration, the pull wire  100  is electrically coupled to the loop  65   a  through contact between the contact portion  80   a  of the distal loop  65   a  and a distal contact portion  100 ′ of the pull wire  100  in which the electrical insulation covering the remainder of a distal portion of the pull wire  100  is not present. Of course, an area on the proximal portion of the pull wire  100  also includes a proximal contact portion  100 ″ at which the electrically conducting wire is exposed for coupling to the hooked pull wire  100   a  which is, in turn, coupled to a source of r/f energy. Of course, this source of r/f energy may be activated and deactivated by a user of the device through, for example, a foot switch (not shown). As shown in FIGS. 5 a-c , the distal loop  65   b  is longer than the distal loop  65   a  while the distal loop  65   c  is longer than the distal loop  65   b , etc. Thus, the length of each of the distal loops  65  is increased in a regular progression from the loop  65   a  through the loop corresponding to the ligating band  60  installed proximal-most on the housing  1 . As described above, this increase in length which forms the slack  105   b-c  ensures that only one of the snares  70  and the corresponding ligating band  60  will be activated at a time as the pull wire  100  is drawn proximally. 
     In addition, this slack allows the source of r/f energy (preferably coupled to the proximal contact area  100 ″ of the pull wire  100  via a plug  114  formed on the pull wire crank  112 ) to be coupled to the one snare  70  currently being manipulated by the user. As shown in FIGS. 5 b  and  5   c , the pull wire  100  is formed as a loop of conducting material which extends through each of the loops  65   a-c  so that, as the pull wire  100  is drawn proximally the first loop  65   a  is drawn into the housing  1  and the distal contact portion  100 ′ of the pull wire  100  advances relative to the contact portion  80   b  until the two contacting portions  80   b  and  100 ′ come into contact with each other electrically coupling the loop  65   b  with the source of r/f energy. Similarly, after the user has finished with the snare  70   b , drawing the pull wire  100  further into the housing  1  draws the contacting portion  80   c  further proximally until electrical contact with the distal contacting portion  100 ′ is established. Thus, each of the loops  65  is first electrically linked to the source of r/f energy only as it is deployed from the housing  1 , while the inactive loops  65  which remain in position around the housing  1  are decoupled from the source to prevent injury to surrounding tissue. Of course, the previously deployed snares  70  remain active, but these snares  70  are safely encased within the housing  1 . 
     In use, as shown in FIG. 6 the endoscope is advanced until the distal end is adjacent to a lesion  110  to be ligated. The device may be positioned visually via an optical device (not shown) mounted in the endoscope. After visualizing the lesion  110 , the user then decides whether to perform ligating band ligation, severing snare ligation, or a combination of the two on the targeted lesion  110 . The user may also decide whether to engage the lesion  110  or the vessel wall  115  with a sclerotherapy needle  200 , or other instrument, such as a forceps, basket, or cautery device, which may be passed through the working channel  35  of the endoscope  25  to the lumen  15  of the housing  1 . Because the pull wire  100  preferably passes through the external channel  45 , the working channel  35  is clear for the user to pass such additional instruments therethrough. The user may draw the lesion  110  into the distal aperture  20  under suction or with an instrument such as a forceps and may employ the forceps or suction after engaging the lesion  110  with a ligating band  60   a , so that a tissue sample may be retrieved. 
     After the lesion  110  has been drawn within the housing  1 , the user dispenses a ligating band  60   a  from the housing  1  by applying a force to the pull wire  100  (to the left in FIG.  6 ). The now-dispensed ligating band  60   a  engages lesion  110  and applies an inward force on the lesion  110 , thereby restricting the flow of blood from the vessel wall  115  to lesion  110 . In this manner, the desired level of hemostasis may be achieved and, eventually, the tissue dies and is sloughed off. 
     After the user has drawn the lesion  110  within the housing  1  and has dispensed the ligating band  60   a  from the housing  1 , the distal loop  65   a , which had engaged ligating band  60   a  about housing  1 , is positioned about the stalk  120  of the lesion  110 . Therefore, by drawing the pull wire  100  further proximally, the user pulls the distal loop  65   a  about the stalk  120 , and may sever the lesion  110  either mechanically or electrosurgically. This severing step is preferably accomplished with one continual pull on pull wire  100 , which, if the user elects to sever the lesion  110  electrosurgically, is done while simultaneously applying r/f energy to the snare  70   a  to facilitate cutting and cauterizing the targeted stalk  120 . 
     If the user elects to use only ligating band ligation (i.e., not to use a severing snare), the user simply dispenses the ligating band  60   a  from the housing  1  after drawing the lesion  110  within the distal aperture  20  of the housing  1  by, for example, turning the crank  112  one half turn. Then, the user releases the tissue from the housing  1  and draws the snare  70  into the housing by a further one half turn of the crank  112 . 
     After the lesion  110  has been severed from the vessel wall  115 , the user may continue to apply suction through the working channel  35  to aspirate the lesion  110  through the lumen  15  into the working channel  35  of the endoscope  25 . Alternately, the user may use suction to retain the lesion  110  within the lumen  15  of the housing  1  and then withdrawn the endoscope  25  and housing  1  from the patient. By proceeding in either of these manners, the user may obtain a sample of the lesion that has been severed for pathology evaluation. Alternately, the user may pass an instrument, such as a forceps, through the working channel  35  of the endoscope  25  and retrieve a sample of the lesion  110  for further study, either before or after the lesion  110  has been severed from the vessel wall  115 . 
     Alternately, the user may disengage the suction means to allow the severed lesion  110  to pass through the body naturally. Whether the lesion is completely aspirated through the working channel of the endoscope  25 , or allowed to pass through the body naturally, the user may proceed to treat additional lesions without removing the endoscope  25  from the patient. Of course, if the user desires to treat multiple lesions, the present device must be preloaded with a corresponding plurality of severing snares  70   a-c  and ligating bands  60   a-c , rather than a single snare  70   a  and one ligating band  60   a , as shown in FIG.  6 . When the first lesion  110  has been severed, the user simply positions the housing  1  adjacent to a second lesion  110  and repeats the above described method. 
     A second embodiment of the present invention is illustrated in FIGS. 7 and 8, in which a distal loop  125  of a severing snare  130  is positioned around the housing  1 , but is located behind the ligating band  135  (i.e., is positioned proximally with respect to the band  135 ). The severing snare  130  passes along the endoscope  25  through a sheath  138 , located outside the endoscope  25 . By containing the severing snare  130  and the pull wire (not shown) within the sheath  138 , the working channel  35  remains substantially clear so as to allow a user to pass an additional instrument, such as a needle (not shown) through the working channel  35  and through the lumen  15  without becoming entangled with the severing snare  130  or the pull wire. 
     By applying a force to the pull wire in the distal direction (i.e., to the left in FIG.  8 ), the distal loop  125  is moved toward the distal end  10  of housing  1  and dispenses the ligating band  135  from the housing  1 . As discussed previously, if it is desired to engage a lesion  110  with the ligating band  135 , the lesion is first suctioned into the lumen  15  of the housing  1 . Then, with lesion  110  within the lumen  15 , the ligating band  135  is dispensed to engage the stalk  120  of the lesion  110 . By moving the pull wire further in the distal direction, the user can position the distal loop  125  around the desired portion of the lesion  110  and then retract the pull wire in the proximal direction to tighten the distal loop  125  about the lesion  110  and sever the lesion  110  mechanically or electrosurgically. Movement of the pull wire is preferably controlled by a handle  140  or similar means. 
     In the second embodiment of the invention, it is preferable to use a fairly sturdy distal loop  125  so that a ligating band  135  may be dispensed from the housing  1  when the pull wire is moved in the distal direction. That is, the pull wire must be stiff enough to carry a compressive load from the user to the distal loop  125  sufficient to overcome the friction forces maintaining the ligating band  135  on the housing  1 . 
     An apparatus according to a fourth embodiment of the invention, as shown in FIGS. 11-13, is similar in construction to the previously described embodiments except that a single pull wire  100  is threaded through the device  1  to create a plurality of snares  70  which extend around the housing  1  abutting snares  70   a-c  which are located proximally of an optional proximal end wall  118 . 
     As seen in FIG. 12, an instrument  116 , e.g. a sclerotherapy needle, is present in the working channel  35  as well as the single pull wire  100  which extends through the working channel  35  in the space surrounding the instrument  116  to a first snare port  85   a . The use of a single pull wire  100  allows the working channel  35  to comfortably accommodate an instrument  116  while providing the required control of the snares  70   a-c . In addition, as no channels external to the endoscope are required with this apparatus, the cross-section of the device remains circular and the maneuverability of the device is enhanced. 
     Specifically as shown in FIG. 13, the pull wire  100  of this embodiment includes a first knot  102 , a second knot  104 , a third knot  106 , a fourth knot  105 , a fifth knot  107  and a loop  108 . The pull wire  100  extends through the snare port  85   a  and underneath the ligating band  60   a  so that the knot  102  is located adjacent to a proximal edge of ligating band  60   a . The pull wire  100  then wraps around the housing  1  to form snare  70   a  and passes back under the ligating band  60   a  and through the snare port  85   a  so that the knot  104  is located proximally of the snare port  85   a . The knot  104  and the snare ports  85   a  and  85   b  are sized relative to one another so that the knot  104  may not pass through either of the snare ports  85   a  and  85   b . The pull wire  100  extends from the knot  104  through the snare port  85   b , passes underneath the ligating band  60   a , under the snare  70   a  and under the ligating band  60   b  so that the knot  106  abuts a proximal edge of the ligating band  60   b  and wraps around the housing  1  to form snare  70   b . The pull wire  100  wraps around the housing  1  and passes back under the ligating band  60   b , under the snare  70   a , under the ligating band  60   a  and reenters the snare port  85   b  so that the knot  105  is located on the proximal side of the snare port  85   b . The knot  105  and the snare ports  85   b  and  85   c  are sized relative to one another so that the knot  105  may not pass through either of the snare ports  85   b  and  85   c . Of course, those skilled in the art will understand that, although this embodiment is shown with  3  ligating bands  60   a-c  and  70   a-c , this wrapping pattern may be repeated to create as many snares  70  as are desired until, after the pull wire  100  has passed under the proximal-most ligating band,  60   c  in FIG. 11, the pull wire  100  extends from the knot  107  abutting the proximal edge of the band  60   c , around the housing  1  where, after encircling the housing  1 , the snare  70   c  is formed by tieing a loop  108  around the preceding portion of the pull wire  100 . 
     Those skilled in the art will understand, although FIG. 11 shows the ligating bands  60   a-c  spaced apart, that this is for illustration only. As the single pull wire  100  of this apparatus will transmit energy to all of the snares  70   a-c  when the source of r/f energy is engaged, the snares  70   a-c  should preferably be prevented from damaging adjacent tissue by abutting the ligating bands  60   a-c  against one another. Thus, the snares  70   a-c  will not contact the surrounding tissue. 
     In operation, when a portion of lesion tissue  110  is drawn into the housing  1  and it is desired to deploy the band  60   a , the user turns the crank  112  one half turn as described above and the pull wire and the knot  102  are drawn distally across the housing  1 , pulling the band  601  off of the distal end of the housing  1 . Further rotation of the crank  112  will tighten the snare  70   a  around the lesion  110 , eventually severing the tissue. Once the snare  70   a  has been fully retracted into the snare port  85   a  (knot  102  is sized so that it may pass through the snare port  85   a ), the pull wire  100  straightens out and portion of the pull wire  100  which formed the snare  70   a  no longer forms a loop. The amount of the pull wire  100  that needs to be taken up to fully retract the snare  70   a  also serves the purpose of preventing the premature release of the more proximal bands  60   b - 60   c , etc. When a second portion of lesion tissue  110  has been located and drawn into the housing  1 , the second ligating band  60   b  is released by a further one half turn of the crank  112 . The knot  104  is drawn into the working channel  35  of the endoscope and knot  106  draws the band  60   b  off of the distal end of the housing  1 . Thereafter, the operation of the snare  70   b  and any number of more proximally located snares  70  would be the same as that described for  70   a  and except that the proximal-most snare  70  will tighten like a noose as the pull wire  100  is drawn proximally, sliding through the loop  108 . 
     Still other objects and advantages of the present invention will become readily apparent to those skilled in the art from the above-recited detailed description, wherein only preferred embodiments of the invention has been shown and described. 
     The description of the preferred embodiments is simply by way of illustration of the best mode contemplated for carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modification in various respects, all without departing from the invention. Accordingly, the drawings and descriptions are to be regarded as illustrative in nature, and the scope of the invention is intended to be limited only by the claims appended hereto.