to illustrate the principles of the present invention , this specification will discuss the present invention in terms of a continuous flow endoscope system . it is particularly directed to a resectoscope system for use with an electrosurgical throughput device . such devices include known electrodes for cutting , coagulating , cauterizing , or vaporizing tissue . although the present invention will be described with reference to the embodiments shown in the drawings , features of the present invention can be embodied in various different embodiments and alternative types of endoscopes . in addition , any suitable size , shape or type of elements or materials could be used . referring to fig1 - 8 , a resectoscope 10 generally comprises a working element 12 , an assembly of inner and outer sheaths 16 , and a removable telescope 14 . a throughput device 18 may be inserted through the sheath assembly . the throughput device may be any device that interacts with the surgical site into which the distal end of the resectoscope is placed . for example , the throughput device may be a tool , such as an electrode or a fiber optic laser guide . the working element 12 and telescope 14 , in the embodiment shown , are generally representative of a u . s . a . elite system working element and telescope available from circon corporation of stamford , conn . the telescope 14 is removably mounted to the working element 12 , and has a connector 20 for connecting fiber optics in the telescope with a light source by means of a flexible light transmitting cable ( not shown ). the working element 12 generally comprises a frame 22 , a front handle 24 , a movable portion 26 , and a latch assembly 28 . the working element 12 , telescope 14 and throughput devices are well known in the art . in alternative embodiments , any suitable type of working element , telescope and / or throughput device could be used . the moveable portion 26 generally incorporates an electrode locking mechanism 26 a and a portal 26 b for attaching an active cord from the electrosurgical generator to the electrode proximal end ( not shown ). the sheath assembly 16 generally comprises an outer sheath 30 and an inner sheath 32 . the outer sheath 30 generally comprises outer tube 34 . it may include rear end section 36 . the outer tube 34 preferably has a circular cross - section , but other cross sections are possible . for example , it could have a generally oval shape or any other suitable shape for holding the inner sheath 32 or forming inflow or outflow channels . the sheath assembly 16 has a distal tip portion 104 ( discussed in more detail below ). the outer sheath is shown with lateral holes 38 in its front end . the rear end section 36 is attached to the rear of the outer tube 34 . the rear end section 36 has a shield 40 , a connector 42 , a fluid inlet 44 and a fluid outlet 46 . the inner sheath 32 generally comprises inner tube 48 , and may include a frame member 50 and a movable latch 52 . the inner tube is concentrically disposed within outer tube 34 . the inner surface of the inner sheath defines an inflow channel 68 having a main inflow hole 56 . the distal end of the inner tube 48 is a predetermined distance within the outer tube 34 but forward of lateral outflow apertures 38 in the outer tube . the inflow channel 68 forms a path for fluid to pass from the fluid inlet 44 and frame member 50 to the inflow hole 56 in tip portion 104 . the inflow channel may also simultaneously accommodate telescope 14 and device 18 . ( telescope 14 and device 18 are omitted from fig5 ). for improved outflow at a surgical site 1 , the present invention provides a novel design for the distal tip portion 104 of an assembly of outer and inner sheaths . in this respect , the present invention provides one or more novel outflow conduits 100 that are capable of extending into the cavity or area of a surgical site so that they are less likely to be blocked by a tight passage 2 of tissue leading into the site or from debris at the site . in the present invention , one or more outflow apertures 102 are disposed in the outer , lateral surface of the assembly so outflow initiates at a more distal position along the lateral side of the instrument than afforded by the prior devices . looking at fig5 in sheath assembly 16 each aperture 102 initiates in the outer surface of the sheath assembly at a position 106 distal to inflow hole 56 at the distal end of inner sheath 32 . ( the initiation point 106 shown in the drawings is just an example position ; the aperture 102 may initiate anywhere along a line from the distal end of sheath 32 to the inflow hole .) the aperture 102 continues as an outflow conduit 100 communicating with the outflow channel 70 formed between the outer sheath 30 and inner sheath 32 so that fluid may be directed into the outflow channel 70 . accordingly , the outflow conduit extends generally longitudinally within sheath assembly 16 from its initiation point at outflow aperture 102 in the surface of the sheath assembly . the outflow conduit 100 carries fluid proximally beyond the distal end of inner sheath 30 before merging with the outflow channel 70 at position 108 . position 108 preferably is proximally beyond the main inflow aperture 56 to minimize conflict between the fluid dynamics of inflow and outflow . in one possible embodiment , each outflow conduit 100 initiates with an outflow aperture 102 disposed in the outer wall or surface of distal tip portion 104 of outer sheath 30 . each outflow aperture 102 is oriented on a lateral side surface of the outer sheath generally perpendicular to the plane of main inflow hole 56 at the distal end of the sheath assembly 16 . the outflow channel 70 is the space between the concentric sheaths 30 and 32 . however , the outer sheath 30 need not completely surround the inner sheath 32 to form a channel capable of transporting fluids away from the surgical site . for example , the channel 70 could be defined as any geometrical cross - sectional shape of the inner sheath , so long as a fluid flow path is defined . for further example , outflow channel 70 could be defined in an elongate unitary or integral piece of material with a longitudinal partition , creating one or more separate channels for outflow and / or devices . the channels , for example , could run , coaxially , in parallel or otherwise generally longitudinally . the apertures 102 are preferably spaced about the circumference of the outer sheath to provide fluid egress from all positions in a surgical site . the positioning and spacing may be adjusted to suit particular needs . while channel 70 between the outer sheath and inner sheath may be extended to the distal tip of assembly 16 to provide outflow from the surgical site , the laterally positioned outflow apertures 102 and conduits 100 do not substantially increase the outer diameter of the assembly , which would go against principles of minimally invasive surgery . the lateral positioning means that fluid egress needs may be addressed by increasing the total open area in the lateral surface of sheath assembly 16 without significantly adding to the outer diameter of the assembly . the apertures 102 may take any suitable shape or size . as indicated in the figures , a suitable shape is an elongate hole stretching longitudinally along and through the surface of the outer sheath 30 . the novel arrangement of an outflow aperture and conduit overcomes the limitations in the prior art where the lateral outflow apertures are disposed proximal the main inflow aperture . the novel features permit fluid outflow from a position closer to the distal end of the sheath assembly and in front of a main inflow aperture ( e . g . inflow hole 56 ) while maintaining the full aperture of the inner sheath diameter available for the telescope , devices , and inflow of fluid . so - positioned apertures deliver fluid via conduits 100 to a main outflow channel at a position proximal to the main inflow aperture . this outflow system helps avoid conflicting fluid dynamics , while initiating fluid outflow at a position less likely to be impeded by anatomy . in addition to the novel arrangement of outflow conduits 100 , the sheath assembly may also carry conventional outflow holes 38 in a conventional position proximal to the inflow hole 56 at the distal end of sheath 32 . as discussed earlier , in endoscopes used with electrosurgical throughput devices , such as cutting , coagulating , or vaporizing electrodes , the distal tip of the inner or outer sheath assembly may include a dielectric tip portion for electrically insulating the electrode element from the outer and inner sheaths . in general , the dielectrical portion may be a tube - like extension of the outer or inner sheath . for example , in the embodiment shown , outer sheath 30 comprises outer tube 34 and insulative tip element 5 disposed on the distal end of the outer tube 34 . the tip element 5 may be removably or permanently attached or otherwise integrated into the distal end of sheath assembly 16 . it may comprise tip portion 104 in whole or part . the tip 5 is preferably made of a dielectrical material , such as ceramic or a molded plastic or polymer material . the dielectrical tip portion 5 may also take the form of an insulating coating or laminate on the inner and / or outer surfaces of one or both tubes comprising tip portion 104 . the dielectrical tip portion is a design option . for example , in other possible embodiments , such as when the device 18 is a laser , the tip 5 could be comprised of metal and be an integral feature of the inner sheath tube , not a separate part . in addition to what is shown in the figures , dielectric tip portion 5 may take various configurations , such as a partial tube , beak , shield , or any other tip configuration desired tip portion 104 . the dielectric tip element 5 if present , forms the distal end of the sheath assembly 16 . in the prior art , this dielectrical tip element 5 does not provide lateral apertures and / or channels for outflow . therefore , outflow apertures in prior electrosurgical endoscopic devices are not optimally disposed at the distal end of the assembly of the inner and outer sheaths . accordingly , the present invention overcomes the inherent disadvantages of such devices by incorporating lateral apertures 102 and conduits 100 in whole or part in tip element 5 in a tip portion 104 . [ 0052 ] fig8 illustrates features of one possible tip element 5 with outflow apertures 102 . the tip may be formed of ceramic , or any other suitable dielectric material , as noted above . in the embodiment of fig8 the tip element 5 is a hollow , generally cylindrically shaped element . tip element 5 has a plurality of elongate openings 110 disposed in its outer surface for use as outflow apertures 102 and in forming outflow conduits 100 . the openings 1 10 extend longitudinally along arcuate side wall 111 of the element . the openings also have vertical side wall 112 perpendicularly oriented relative to side wall 111 . the tip element 5 may be affixed to the sheath assembly 16 by conventional means such as chemical bonding ( e . g ., epoxy ) or mechanical fastening ( e . g ., swaged or pinned ). in a preferred embodiment , tip element 5 is a complementary size and shape for a close fit within the distal end of sheath 30 . as an example , fig4 and 7 show a mechanical retention means 105 disposed on the outer sheath 30 that mates with an opening or recess 115 in tip 5 to help secure the tip and sheath 30 together . this retention means could be used in conjunction with adhesive to maintain the attachment of the tip and sheath in case the adhesive failed . in the example shown , the retention means comprises a dimpled - in area of tubing . as indicated in fig4 and 5 , the distal end of the outer sheath at tip portion 104 may be slightly larger in diameter than the proximal portion to receive the diameter of tip element 5 . the proximal portion of the element 5 is sufficiently recessed within sheath 30 that the sheath covers a proximal portion of the openings 110 . the exposed portions of the openings 110 comprise outflow apertures 102 ( bounded by arcuate side wall 111 ). the covered portions , in combination with the inner surface of sheath 30 , define outflow conduits 100 . as indicated in figures , there is a reduced or no vertical side wall 112 at the proximal end of openings 110 so that there is a more open end 113 for fluid to flow into the proximally adjacent outflow channel 70 . the size , shape and positioning of the openings 110 may be varied to provide the scope of outflow apertures and conduits contemplated by the other descriptions of each elsewhere herein . as seen in fig5 the present invention may optionally include one or more optional thru - holes 117 disposed in the inner surface of tip 5 and communicating with the outflow conduit at a position just distal a main inflow hole 56 . the thru - holes 115 help remove gas bubbles that may collect at the inflow hole 56 . removal of bubbles helps ensure proper flow conditions and obstructed vision through the telescope . any bubbles pass through a hole 115 into outflow conduit 100 . persons skilled in the art will recognize the foregoing description and embodiments are not limitations , but examples . it will be recognized by persons skilled in the art that many modifications and variations are possible in the details , materials , and arrangements of the parts and steps which have been described and illustrated in order to explain the nature of this invention , and that such modifications and variations do not depart from the spirit and scope of the teachings and claims contained herein .
a sheath assembly for a medical instrument such as an endoscope comprises an outer sheath and inner sheath and novel means for providing out - flow of fluids from a surgical site . the outer sheath is disposed about at least a portion of an inner sheath . the assembly has an outflow aperture disposed in an outer wall at the distal end of the assembly . the outflow aperture is the initiation for an outflow conduit that is generally longitudinally disposed in a distal tip portion of the assembly and communicates fluid to a main outflow channel formed between the outer sheath and inner sheath . in a preferred embodiment , the outflow aperture and conduit are disposed wholly or partially in a dielectric tip element . the novel assembly allows improved outflow by disposing the outflow aperture at a more distal end of the instrument than conventional devices such that the outflow aperture is less prone to blockage by surrounding tissue or debris when used in tight anatomical passages .