Abstract:
A surgical dilator extractor is introduced into the abdominal cavity through a trocar cannula and expanded, forming a tissue receiving space, at the distal end. The tissue that is to be extracted is then manipulated into the space with a grasper inserted through a lumen in the dilator extractor. The tissue is then removed from the cavity by the surgeon applying a force onto the dilator extractor that insures the elongation of the tissue and temporarily dilates the entry wound to the extent necessary for the tissue to be removed. Alternative embodiments of the surgical dilator extractor and related instrument tool sets and methods for the use thereof also are disclosed.

Description:
RELATED APPLICATIONS 
   This application claims the benefit of U.S. Provisional Application No. 60/261,798, filed Jan. 17, 2001, incorporated by reference herein. 

   BACKGROUND 
   The present invention relates generally to mechanical devices and methods used in laparoscopic surgical procedures to remove organs and excised tissue from internal body cavities. 
   It will be appreciated by those skilled in the art that the use of bags or pouches to remove organs and large tissue specimen during laparoscopic surgical procedures is well known. As described, for example, in U.S. Pat. No. 5,147,371 a pouch is introduced into the abdominal cavity for retrieving gallstones and tissue. The bag is opened and closed using a wire loop as a drawstring. In U.S. Pat. No. 5,192,284 an expandable bag is inserted into the abdominal cavity through a trocar cannula. The bag described in the &#39;284 patent is made of a memory material that is rigid enough to support itself. The bag expands and remains open when it is inserted into the abdominal cavity through the cannula. U.S. Pat. No. 5,480,404 describes a pouch for extracting tissue that is opened and closed by a ratchet mechanism. U.S. Pat. No. 5,341,815 employs shape memory effect metal to open the bag upon insertion through a trocar. U.S. Pat. Nos. 5,681,324 and 5,971,995 describe similar bags and pouches. 
   The pouches described in these patents are useful in containing any bile or gallstones that might otherwise spill into the abdominal cavity during extraction of a torn gallbladder. These type of devices, however, suffer from at least two problems. Since such devices are closed on the distal end, air inside the enclosure tends to balloon the pouches or bags during the extraction process thereby increasing the size or not allowing a full collapse of a bag as it is removed from the wound. Additionally, when the tissue is larger than the wound size it is forced to the bottom of the bag as the radial force of the wound acts on the tissue during extraction. This also increases the size to which the wound must be dilated for removal of the tissue. Tapering the bags toward the distal end helps somewhat to lessen this effect, but the result is not optimal and does not fully address the problem of air trapped in the bag. 
   Since the goal of laparoscopic surgery is to become less invasive by using smaller entry wounds the prior art is of limited value for removing large specimens through, for example 5 mm wounds. When the user pulls on the bag in an attempt to remove it through a small trocar entry wound the specimen is forced to the bottom of the bag by the radial forces exerted by the abdominal tissue or by the forces exerted on the bag from the cannula thus creating a large lump that is often incapable of passing through the wound. The use of this type of extraction bag in these cases often requires de-bulking of the specimen so that the bagged specimen pieces are of such a size that the bag can be extracted through the trocar entry wound, typically 10-12 mm. This is a time consuming process that is not always successful since, for example, large stones may be inside a gallbladder and it also compromises the pathologic examination of the tissue specimen. Alternately the wound size is increased with a scalpel to allow the extraction, thereby lessoning the advantage of the laparoscopic surgery. Additionally, these types of extraction bags add undue complexity to the procedure since they require the use of two ports, one for the bag and the second for a grasper to retrieve the tissue and put it into the bag. 
   U.S. Pat. Nos. 5,190,561 and 5,370,647 to Graber disclose several embodiments of laparoscopic extraction devices that allow a grasper to be inserted into the center of an extractor device so that tissue can be more easily manipulated into the inside of the extractor. In each of the embodiments the extractor is introduced into the abdominal cavity through a specially designed trocar cannula equipped with setscrews to lock the extractor to the trocar cannula. Upon exiting the distal end of the cannula, the distal end of the extractor expands, much like an umbrella. A grasper is then introduced into the abdominal cavity through a lumen in the extractor. The specimen is grasped and pulled into the expanded open distal end of the extractor, a cone shaped device. The grasper is then locked to the cannula using the setscrews. The proximal end of the extractor is equipped with a handle, which is used to pull the extractor and the tissue through the cannula. As the handle is pulled upward “ . . . the enveloping means collapses around the tissue and returns to its pre-deployment.” Thus the enveloping means of Graber &#39;647 is relied on to compress the tissue to a size that allows it to be drawn into the shroud  610 , as shown in FIG.  13 . Thus, the device is not optimally designed to deal with a tissue specimen that will not compress to a point so that it can be drawn through the shroud. 
   The extractor of Graber &#39;647 also has several other disadvantages. The Graber &#39;647 device cannot be used with standard trocars since it utilizes setscrews, not generally available on trocars in current use, to lock it to the trocar, and it utilizes an expensive locking mechanism to lock the grasper to the extractor. In addition, most abdominal laparoscopic procedures are performed with the abdominal cavity insufflated with carbon dioxide. The lumen in the extractor of Graber &#39;647 has no provision for sealing and thus when the extractor is placed through the trocar cannula&#39;s seal, the abdomen would loose its carbon dioxide pressure. The Graber &#39;647 device is removed from the body cavity by an exertion force on the handle of the device. This unduly places rotational and shear forces on the extractor-grasper lever lock and the extractor-trocar setscrews in the case of a trocar cannula that employ screw threads to insure anchorage in the abdominal wall, since these cannula require rather vigorous rotational manipulation to remove them from the abdominal wall. 
   The extractor cover disclosed in the Graber &#39;647 patent is made from “a sturdy waterproof, stain resistant fabric such as treated sailcloth or duck cloth.” These materials are thick and bulky and therefore, are not useful for extractors for less invasive trocar cannula such as 5 mm and smaller devices, since multi-folds of the cover is required for the extractor to pass through small-bore cannula.  FIG. 24  of the &#39;647 patent discloses a thin “baggie,” however, it requires thick leaves  608  and a plunger rod  606  to compress the tissue. The thickness of these unduly complicating features makes the Graber device ill-suited for small cannulas. 
   The embodiment disclosed in  FIG. 12  of the &#39;647 patent teaches the use of a flexible, waterproof web material with an opening mouth so that tissue can enter the rib portion  510 . While this embodiment partially solves the spillage problem it unduly complicates manipulating the tissue inside the extractor and is overly complex in that the extractor cover and the spillage compartment are made of two separate pieces and must be joined by sewing, heat treating, or welding. 
   Laparoscopic removal of the gallbladder has, heretofore, entailed the use of four entry cannula, typically two of which are 10/12 mm in diameter and two of which are 5 mm in diameter. The two 5 mm ports are used to accept instruments such as scissors, graspers, electro-surgery probes, and suction/irrigation devices. The 10/12 mm ports are employed to allow the use of 10 mm endoscopes attached to a camera for viewing the surgical field, to allow a clip applier for ligating vessels and ducts, and to allow the removing of the gallbladder following its excision. 
   In an effort to make the procedure less invasive, 5 mm clip appliers have been developed, such as the one described by Shipp et al. in U.S. Pat. No. 5,858,018. The 5 mm clip applier allows the conversion of one of the two 10/12 mm ports to a third 5 mm port. The remaining 10/12 mm port prior to this invention has been required to accept 10 mm endoscopes and to allow for the removal of the gallbladder, usually through the umbilicus port site. New bright 5 mm endoscopes coupled with more sensitive cameras have been developed that are quite acceptable substitutes for the prior art camera systems. These new developments leave the gallbladder removal through a 5 mm or smaller port as the last obstacle to the full conversion of the process to four much less invasive 5 mm ports. The conversion from two 10 mm and two 5 mm trocars to all 5 mm trocars lowers the entry wounds area by 50 percent, which greatly reduces bleeding and post surgery incisional herniation at the wound sites. 
   What is needed then is a simple, inexpensive device and a simple, easy to use method for rapid removal of tissue, such as a gallbladder, from a wound site that is smaller than the specimen and one that does not require a substantial secondary operation such as grinding the specimen into smaller pieces, or require that the wound be significantly enlarged. 
   SUMMARY OF THE INVENTION 
   The present invention in one embodiment is directed to an expandable dilator extractor that expands upon entry into the abdominal cavity for acceptance of a tissue specimen using a grasper to pull the specimen into the interior of the dilator extractor. The construction of the dilator is such that when a surgeon places an upward force, away from the surface of the abdomen on the deployed dilator, it first causes features inside the tissue space of the dilator extractor to minimize the cross section of the tissue, and thus minimize the wound dilation requirement. This in turn decreases the force required to remove the tissue. The features inside the tissue space of the dilator extractor also preferably grip the tissue so as to keep the tissue in the elongated state and to prevent its motion downward towards the abdominal cavity as the radial forces of the trocar puncture wound act upon it during extraction. Finally, the resulting elongated conical shape forces the trocar puncture wound to expand to allow the larger specimen to be extracted with a minimum of tearing or otherwise permanently enlarging the wound. 
   The present invention also is directed to a method and describes an apparatus for easily removing fluid from tissue, such as bile from a gallbladder, to further reduce the tissue size prior to extraction. 
   In another embodiment, the tissue may be treated to partially dissolve the tissue and thus reduce the extraction force. To reduce yet even further the extraction force, the current invention in another preferred embodiment utilizes a very thin, low friction material in contact with the wound. 
   In another preferred embodiment, the distal end of the cover is open so that no ballooning occurs. Alternatively, the distal end of the cover is drawn up in a drawstring purse fashion. The pursed section is drawn somewhat proximally so that the bottom formed by the purse will serve to retain gallstones and small amounts of bile yet still allows the escape of entrapped gas, thus avoiding ballooning. 
   In another preferred embodiment the cover is allowed to vent by virtue of being constructed of breathable material such as GoreTeX™, or by virtue of appropriately placed venting holes. The dilator extractor of the present invention preferably employs a seal in the form of a valve at the proximal end to insure against loss of peritoneal pressure when a grasper or other tool is inserted or removed through its cannula into the abdominal cavity. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a diagrammatic view of a syringe with a needle, a grasper, a dilator extractor, and a cannula in accordance with one embodiment of the present invention. 
       FIG. 2  is a partial side sectional view of the dilator extractor of  FIG. 1  inserted in the cannula of FIG.  1 . 
       FIG. 3  is a partial side elevation view of the leading end of the dilator extractor of  FIG. 1  in an expanded position. 
       FIG. 4  is a bottom plan view along line  4 — 4  of FIG.  3 . 
       FIG. 5  is an enlarged fragmentary cross sectional view along line  5 — 5  of FIG.  2 . 
       FIG. 6  is a partial side sectional view of the trailing end of a shaft of the grasper of  FIG. 1  with a valve and a seal. 
       FIG. 7  is a partial side elevation view of a pair of jaws at the leading end of a grasper. 
       FIG. 8  is a side elevation view of a grasper, dilator extractor, and cannula inserted in the abdominal wall of a patient, the grasper being inserted in the dilator extractor, the dilator extractor being inserted in the cannula, the dilator extractor and cannula being shown in cross section with the dilator extractor in the expanded position. 
       FIG. 9  is a side elevation view of a syringe, grasper, dilator extractor, and cannula inserted in the abdominal wall of a patient, the grasper being inserted in the dilator extractor, the dilator extractor being inserted in the cannula, the dilator extractor and cannula being shown in cross section with a tissue specimen being aspirated in accordance with the instrumentation and method of the present invention. 
       FIG. 10  is a partial side elevation view of the grasper, dilator extractor, and cannula of  FIG. 9  being withdrawn from the abdominal cavity with the tissue specimen in accordance with the instrumentation and method of the present invention. 
       FIG. 11  is a side elevation view of a grasper and cannula with another embodiment of a dilator extractor of the present invention having tissue engaging protrusions being withdrawn from the abdominal cavity with the tissue specimen. 
       FIG. 12  is a side partial cross sectional elevation view of a grasper and cannula with another embodiment of a dilator extractor of the present invention having a draw cable prior to being drawn in and withdrawn from the abdominal cavity with the tissue specimen. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Reference will now be made in detail to the present preferred embodiments (exemplary embodiments) of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     FIG. 1  shows a tool set  50  having a cannula  100 , a dilator extractor  200 , a grasper  300 , and syringe device  400 . As shown in  FIGS. 1 and 9 , syringe  400  is insertable in grasper  300 , which is in turn insertable in dilator extractor  200 , which in turn is insertable in cannula  100  to form a multi-coaxial assembly for use in laparoscopic surgery. 
   Referring to  FIGS. 2-4  and  8 , dilator extractor  200  is inserted into a pressurized abdominal cavity  60  through the abdominal wall of a patient. Dilator extractor  200  enters through valve  102  at trailing end  106  of cannula  100 . 
   Dilator extractor  200  includes a body  202  having a leading end  204 , a trailing end  206 , a longitudinal axis L, and a lumen  208 . Body  202  includes a dilator  210  at leading end  204  that is movable between an unexpanded position, shown in  FIG. 2 , and an expanded position, shown in FIG.  8 . Trailing end  206  preferably includes a depth-limiting protrusion in the form of shoulder  207 . Shoulder  207  is adapted to limit the depth of insertion of dilator extractor  200  into cavity  60  of the patient. 
   When the trailing end portion of dilator  210  clears leading end  104  of cannula  100 , dilator  210  expands to the expanded position owing to memory elements  212 , thus forming a truncated conical-shaped tissue receiving space  214 , enclosed by a dilator cover  216 . 
     FIG. 2  shows dilator extractor  200  before dilator  210  clears leading end  104  of cannula  100 . Dilator  210  may be preserved in the unexpanded position because of the restraints of a later described retainer  218  or the inner diameter of cannula  100 . In the unexpanded position memory elements  212  are elastically bent inward to permit dilator  210  to have a maximum lateral dimension preferably in the range of 3 mm to 5 mm. Dilator cover  216  is preferably wrapped around memory elements  212  to allow the passage of dilator extractor  200  in the unexpanded position through cannula  100 . 
   In a preferred embodiment, retainer  218  maintains dilator extractor  200  in the unexpanded state. One suitable retainer is straw-shaped and encircles dilator  210 . Retainer  218  extends toward trailing end  206  of dilator extractor  200  terminating into a graspable surface grip  220  proximate trailing end  206 . The composition of retainer  218  is such that it is strong enough to restrain the spring forces of dilator  210 , yet an upward force on graspable surface grip  220  will cause retainer  218  to peel open allowing dilator  210  to expand. By way of example, a suitable strength welded seam in a polyurethane film can accomplish such a peeling feature. 
     FIGS. 3 and 4  show dilator  210  in the expanded position. In a preferred embodiment, flat steel wire is formed to an appropriate expansion angle to form memory elements  212 . Preferably, four such wires are attached to body  202  of dilator extractor  200  using appropriate fasteners or by welding them to body  202 . In alternate embodiments, memory elements  212  may include alternate memory materials such as certain types of polymers and may be integral extensions of dilator extractor  200 . Stamped and rolled stainless steel also would provide a dilator such that the memory elements are integral to the body of the device. 
   Memory elements  212  are preferably parallel to the longitudinal axis of dilator extractor  200  when dilator extractor is in the unexpanded position. As shown in  FIG. 3 , when dilator extractor  200  is in the expanded position, memory elements  212  preferably expand dilator  210  to form an angle A between cover  216  of dilator  210  and the longitudinal axis of dilator extractor  200  of at least 10 degrees, more preferably 20 degrees. 
   Although four longitudinal memory elements  212  are preferred, other forms of memory elements are sufficient for the purpose of expanding dilator  210 . For example, a single memory element may be positioned at leading end  211  of dilator  210  and adapted to run along the circumference of leading end  211 . Other circumferential memory elements may be concentrically included between leading end  211  and leading end  204  of body  202  along dilator  210 . As a further example, a single memory element may form a conical coil adapted to expand dilator  210  in both a longitudinal and axially transverse direction. 
   Once dilator  210  of dilator extractor  200  is in the expanded position as depicted in  FIG. 8 , grasper  300 , in a preferred embodiment, is inserted through channel or lumen  208 , into tissue space  214 , and into cavity  60 . 
   As shown in  FIG. 5 , trailing end  206  preferably includes first and second seals  222 ,  224 , respectively. First seal  222  preferably forms a duckbill “V” shaped valve made of a resilient material that forms a seal when no instrument is inserted into lumen  208 . Second seal  224  is preferably formed of a resilient material containing a through hole  226  in its center. Through hole  226  is preferably smaller than the maximum cross sectional dimension of the instrument that the through hole is adapted to receive and forms a seal when the instrument is inserted into lumen  208 . For example, both seals may preferably be configured to permit the passage of grasper  300  therethrough while inhibiting a loss of pressure from within the patient. It is appreciated that more than or less than two seals may be used without departing from the scope of the present invention. 
   As shown in  FIG. 9 , excised tissue  70  is grasped by jaws  310 ,  312  of grasper  300  and pulled inside conical tissue space  214 . First and second seals  222 ,  224  seal around the outside diameter of grasper  300  so that pressure inside cavity  60  is maintained as grasper  300  and tissue  70  are manipulated. Once tissue  70  is inside conical tissue space  214 , the entire assembly (grasper  300 , dilator extractor  200 , trocar cannula  100 , and tissue  70 ) is ready for extraction. 
   In instances where the tissue specimen is larger than the inside diameter of cannula  100 , such as would usually be the case for a gallbladder specimen with a 5 mm cannula for example, dilator  210  will close somewhat under the influence of the upward force of the surgeon until memory elements  212  and the tissue resilient forces offset the radial forces asserted by the abdominal wall. At this point conical tissue space  214  of dilator extractor  200  will no longer contract and grasper  300 , dilator extractor  200 , and cannula  100  will be locked together in a more or less rigid fashion. This condition is depicted in FIG.  10 . Dilator extractor  200  is constructed in such a manner that application of additional force causes the wedge shape of dilator  210  to begin to increase or dilate the trocar wound in the abdominal wall as the surgeon applies more and more upward force. The larger the specimen, the larger the force necessary to dilate the abdominal wall wound to a size large enough to allow the entire assembly to be removed. The tensile strength of dilator  210  must be adequate to withstand the extraction force. The shape of the trocar puncture wound is important to insure against tearing of the entry wound. A slit entry wound rather than star-shaped entry wound is preferred. 
   Grasper  300 , as shown in FIGS.  1  and  6 - 8 , has a shaft  302  having a leading end  304 , a trailing end  306 , and a lumen  308  through the center of shaft  302  that can be occupied by a hollow needle  402  of syringe device  400 . Shaft  302  includes jaws  310 ,  312  at leading end  304  for grasping tissue therebetween. As shown in  FIG. 7 , jaws  310 ,  312  preferably include surface roughenings such as ridges  314  on the grasping surface of each jaw. As will be appreciated by those of skill in the art, grasper  300  may be adapted to have more than two jaws. For example, a third jaw maybe used to provide a third grasping surface for grasping the tissue. It will be further appreciated that other jaw configurations are possible and within the scope of the present invention. Jaws  310 ,  312  may have a smooth grasping surface, or may have ridges  314 . 
   Shaft  302  preferably has a length in the range of 15 cm to 35 cm and an outside maximum cross sectional dimension of less than 5 mm. Lumen  308  of shaft  302  preferably has an inside maximum cross sectional dimension in the range of 1 mm to 4 mm. 
   As shown in  FIGS. 6 and 8 , trailing end  306  of grasper  300  includes a pair of handles  320  for moving jaws  310 ,  312  relative to one another. Trailing end  306  also preferably includes first and second seals  322 ,  324 , respectively. First seal  322  preferably forms a duckbill “V” shaped valve made of a resilient material that forms a seal when no instrument is inserted into lumen  308 . Second seal  324  is preferably formed of a resilient material containing a through hole  326  in its center. Through hole  326  is preferably smaller than the maximum cross sectional dimension of the instrument that the through hole is adapted to receive and forms a seal when the instrument is inserted into lumen  308 . For example, both seals may preferably be configured to permit the passage of needle  402  therethrough while inhibiting a loss of pressure from within the patient. It is appreciated that more than or less than two seals may be used without departing from the scope of the present invention. 
   Trailing end  306  preferably includes a depth-limiting protrusion for limiting the depth of insertion of grasper  300  into the cavity. The depth-limiting protrusion may be formed as a shoulder, or may form a part of handles  320 . 
   As shown in  FIGS. 1 and 9 , trailing end  406  of needle  402  extends beyond grasper handles  320 , and is fitted with a hypodermic syringe  408 . Needle  402  is movable distally so that it punctures the grasped tissue, for example, a gallbladder. Gallbladders that are distended with bile can thus be drained before extraction by aspirating the bile up through needle  402  and into syringe  408 . Alternately, suction for removing the bile can be supplied from any vacuum source such as an aspirator. 
   This embodiment allows for grasping, tissue manipulation, removal of bile, and extraction all through a single port site. Significantly, one embodiment of needle  402  and grasper  300  allows for the tissue to be firmly grasped by grasper  300  yet needle  402  can still pass through leading end  304  of grasper  300  into the tissue such as a gallbladder where it performs evacuation of the bile. 
   In one preferred embodiment cover  216 , as best shown in  FIGS. 3 and 4 , is preferably made of a laminated, flexible, material that will allow it to be folded and contained in cannula  100  prior to expansion of dilator  210  of dilator extractor  200 . Cover  216  includes an inner surface  228  and an outer surface  230 . 
   Outer surface  230  of cover  216  preferably is made of a material having a low coefficient of friction, such as a low porosity PTFE (polytetrafluoroethylene). Inner surface  228  is preferably made of a material having a high coefficient of friction, such as coarse weave polyester or nylon. It will be appreciated by those skilled in the art that other materials are suitable for providing a coefficient of friction that is higher on inner surface  228  than outer surface  230  and are within the scope of the present invention. Preferably, the coefficient of friction of inner surface  228  is in the range of 0.5 to 1.0. The two materials are preferably laminated together to form a cell migration barrier  232  to avoid viable cancer cells that might be contained in the excised tissue from coming into contact with the trocar site wound. The low friction outer surface  230  of cover  216  minimizes the force required for extraction while the high friction inner surface  228  provides a gripping force on the tissue surface area and thereby minimizes the force transferred to the grasper/tissue interface during the dilation extraction process. The dilation forces acting on the dilator require that the tensile strength of cover  216  is adequate to withstand the friction force exerted by the tissue on inner surface  228 . Bifurcated PTFE and coarse woven polyester with a total thickness of the lamination of approximately 0.005 inches exhibits a tensile strength of about 10,000 PSI. This will accommodate a friction force between the tissue and cover  216  of about 30 pounds without the material of the cover tearing. The upward force placed on the apparatus by the surgeon is divided between cover  216  and the grasper-tissue interface, thus without significant friction between the inside of cover  216  and the tissue, all the extraction force is transmitted to the grasper-tissue interface. 
     FIG. 11  shows an alternate embodiment inner surface  228  of cover  216 . Memory elements  212  are equipped with tissue retaining protrusions such as teeth  234 . Preferably, teeth  234  are generally pointed toward trailing end  206  when dilator  210  is in the expanded position so that as dilator  210  closes around the tissue as shown in  FIG. 11 , teeth  234  bite into the tissue, thus supplying the dominance of the counter acting force to the extraction force rather than the friction of the tissue against inner surface  228  of cover  216 . 
   It will be appreciated by those skilled in the art that other forms of tissue retaining protrusions are suitable for gripping the tissue, for example, tabs, ridges, and knurling. Additionally, the tissue retaining protrusions are preferably uniformly spaced around the longitudinal axis of dilator extractor  200  to provide an even distribution of retaining force against the tissue. Tissue retaining protrusions may also be spaced substantially about the entire area of inner surface  228  of cover  216 . Tissue retaining protrusions may be formed on cover  216 , memory elements  212 , or a combination thereof. Forming tissue retaining protrusions on memory elements  212  provides additional stability when withdrawing the assembly from the wound site. Preferably, the tissue retaining protrusions are adapted to grab the tissue without penetrating it in order to reduce the risk of content spillage from the tissue. 
     FIG. 12  shows another alternate embodiment of the present invention. Dilator  210  preferably includes an elongated cover portion  236  beyond the distal end of memory elements  212 . Elongated cover portion  236  preferably has a hem  238  that at least partially encloses a draw cable  240  at its leading end  242 . Draw cable  240  has a proximal end  244  adapted to lie beyond trailing end  306  of dilator extractor  200  and a distal end  246  adapted to close leading end  242  of elongated cover portion  236 . Distal end  246  of draw cable  240  is fed proximally through dilator extractor lumen  208  and out through seals  222 ,  224 . Preferably, distal end  246  of cable  240  is adapted to circumscribe the perimeter of cover  216  to form at least one loop around the longitudinal axis of dilator extractor  200 , preferably at hem  238 . More than one loop may be formed to provide greater strength for drawing in leading end  211  of dilator  210 . 
   In using draw cable  240 , the tissue is manipulated into tissue space  214 . The surgeon then pulls draw cable  240  proximally, thus drawing in leading end  242  of elongated cover portion  236  like a drawstring purse. The pursed section is drawn somewhat proximally so that the bottom formed by the purse will serve to retain tissue and contents therein such as gallstones and small amounts of bile, yet still allow the escape of entrapped gas, thus avoiding ballooning. 
   Cover  216  of dilator  210  may be breathable or vented to avoid ballooning. Alternatively, vents with valves may be incorporated in the side of body  202  to vent off gases as the tissue is being extracted. 
   Having described the apparatus, methods for its use will now be described. It should be understood that the order disclosed is only preferred and that the steps may be performed in other orders while still being within the scope of the present invention. Additionally, some steps may be repeated as necessary. 
   A preferred method of removing tissue from the abdominal cavity is shown in  FIGS. 8-10 . Cannula  100  is inserted through the abdominal wall and into cavity  60 , which is preferably pressurized. Preferably a cannula having a maximum diameter in the range of 3 mm to 5 mm is used in order to make the procedure less invasive. Dilator extractor  200  is inserted into cannula  100  through seal  102  to a position where leading end  211  of dilator  210  extends beyond leading end  104  of cannula  100 . Dilator  210  is expanded to form tissue extraction space  214 . Grasper  300  is inserted into dilator extractor  200  through seals  222 ,  224  and through lumen  208 . The tissue is grasped by grasper  300  and manipulated into tissue space  214 . If desired, grasper  300  may be locked to dilator extractor  200  to provide more stability. If dilator extractor  210  includes elongated cover portion  236 , the surgeon may pull draw cord  240  at proximal end  244  to draw in elongated cover portion  236 , thus substantially trapping the tissue and any of its contents in tissue receiving space  214 . Next, an upward force is exerted on dilator extractor  200 , dilating the trocar wound such that the tissue is removed from the cavity under the influence of the upward force. 
   Alternately, for tissue containing a fluid such as bile in a gallbladder, additional steps may be included such as suctioning out the fluid prior to the extraction step. For example, needle  402  of syringe device  400  is inserted into grasper  300  through seals  322 ,  324  and through lumen  308  to a position where leading end  404  of needle  402  extends beyond leading end  204  of body  202  of dilator extractor  200 . Fluid is then suctioned from the tissue through needle  402  by syringe  408 . It will be appreciated that vacuum sources other than syringe  408  may be used to aspirate the tissue, for example, an aspirator. It will be further appreciated that aspiration may occur during other phases of the operation prior to the extraction of the tissue from the wound site. For example, needle  402  may be inserted through lumen  208  of dilator extractor  200  and fluid suctioned from the tissue before grasper  300  is inserted or used. 
   To further reduce the extraction force needed to withdraw the assembly with the tissue, the tissue may be treated to at least partially dissolve the tissue or its contents, for example, gallstones of a gallbladder. A syringe may be used to inject a composition capable of dissolving tissue. One example of such a composition is methyl tert-butyl ether. The tissue is treated preferably after fluid is suctioned. It will be appreciated that the tissue may be treated irrespective of any fluid suction. 
   Simulated dilator extractors were built and tested in the abdominal cavity of a swine. Aluminum cones of varying base diameters representing varying tissue sizes simulated the dilator section. Abdominal access for the cones was gained through a 100 mm incision along the midline of the animal. A 5 mm trocar with a single sided cutting tip obturator (rather than the more common three side pyramidal tip) was used to entry the cavity through a circular 5 mm wound located approximately 30 mm to the left of the midline. Each of four simulators consisting of 5 mm cylinders, 100 mm long transitioning into truncated cones with 5 mm diameter tops tapering to bases of 15, 20, 25, 30 mm diameters respectively, were separately tested by inserting them through the access incision. The 5 mm trocar was then inserted into the abdominal cavity, the obturator removed, and the 5 mm simulator tops were then inserted from the distal of the cannula so that they were exposed above the cannula valve. A force gage was then attached to the exposed section. The vertical pull force required to dilate the 5 mm puncture wound so that the cone was total extracted from the animal was then measured with a calibrated force gage. A new 5 mm trocar site was used for each of the four cones. The extraction force is shown in the table below: 
   
     
       
             
             
             
           
         
             
                 
                 
             
             
                 
               Cone Base Diameter, mm 
               Upward Extraction Force, lbs 
             
             
                 
                 
             
           
           
             
                 
               15 
               12 
             
             
                 
               20 
               21 
             
             
                 
               25 
               37 
             
             
                 
               30 
               50 
             
             
                 
                 
             
           
        
       
     
   
   Each measurement was repeated using the same puncture wound to test the extent to which the wound had been torn or permanently stretched. The data indicated that dilation of 2 to 3 times is possible. Up to 20-25 mm the forces are of reasonable magnitude to make the device practical. The minimizing wound size is important to minimizing postoperative hernias and other complications. 
   Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.