referring now to the drawings and particularly to fig1 - 3 thereof , there is shown a retention drainage catheter and inserting stylet therefore in assembled relationship ready for use , the assembly being generally indicated by the reference numeral 10 , the catheter and stylet being generally indicated by the numerals 11 and 12 respectively . the catheter has a distal end generally designated by the numeral 14 , the length of the catheter being such that the distal end 14 can be fully inserted into the bladder while the proximal end 16 still remains outside of the entrance to the urethra . the catheter 11 is constructed as a multi - layer cannula and has an outer layer 18 of relatively soft and pliant latex rubber which is selected to meet the physical requirements set forth above , but principally which must withstand the corrosive effects of urine and withstand the high temperatures of sterilization . an intermediate layer 20 of silicone rubber is disposed within the outer layer 18 , the silicone rubber having greater strength than the latex rubber but otherwise meeting the same physical requirements as the latex rubber . another layer 22 of latex rubber forms an inner layer disposed within the intermediate silicone layer , the inner wall 24 of the inner layer 22 defining a drainage lumen 26 through which urine drains from the bladder . a principal feature of the present invention resides in the provision of a longitudinal drainage opening 30 at the distal end 14 of the catheter . in the conventional catheters , as shown in the prior art cited hereinabove , the catheter is provided with a rounded bullet shaped tip to facilitate insertion of the catheter through the urethra with a minimum of discomfort and risk of trauma , and a laterally opening drainage port is provided adjacent the tip of the catheter . in the present invention , however , the conventional tip has , in effect , been removed and the several layers of the cannula 11 terminate to define the longitudinal opening 30 which is open and unobstructed in order to communicate the interior of the bladder directly with the full cross - sectional area of the drainage lumen 26 rather than through a restricted lateral opening as in the prior art . the manner in which the layers of the cannula terminate to define the opening 30 is best seen in fig4 wherein the inner latex rubber layer 22 terminates abruptly in an annular wall 32 , whereas the intermediate silicone layer 20 and the outer latex layer 18 are both tapered and merge to points adjacent the distal end 14 of the cannula so as to define a smooth , gradually widening portion 34 of the cannula surface from the annular wall 32 to the widest portion of the cannula 11 . the reason for this tapering portion is to provide a smooth , gradually expanding insertion portion of the catheter 11 which cooperates with a gradually widening portion of an inserting stylet to be hereinafter described . it will be apparent that the longitudinal opening 30 provides a wider and less obstructed access from the bladder into the drainage lumen than does the lateral openings in the prior art catheters . the catheter 11 includes means for retaining the distal end 14 thereof within the bladder after the distal end has been passed through the urethra and has entered the bladder . since the juncture of the bladder and the urethra is defined by a sphincter muscle which defines a relatively small opening even when the sphincter muscle is relaxed , it is possible to prevent removal of the catheter by providing the end thereof with an expandable means which overlies a small portion of the bottom of the bladder wall surrounding the sphincter . in the present invention , the preferred means for retaining the catheter in place is the inflatable balloon technique which is well known in the art but which is configurated in the present invention to cooperate in a novel manner with the specific construction of the distal end of the catheter to cause the distal end of the catheter to expand and partly overlie the bottom wall of the bladder . more particularly , the inflatable balloon is a relatively thin layer 36 of latex rubber which is integrally molded or suitably bonded to the outer layer 18 of the cannula at a point 38 downstream from the open end 30 , the point 38 being selected to provide a balloon of suitable size to retain the catheter in place when the balloon is inflated . although the balloon may vary in size depending on the location of the molded or bonded juncture 38 , it is the practice to select a reasonable compromise in the size of the balloon based on two conflicting considerations . one is that the balloon should be as small as possible in order to place the drainage opening as close as possible to the sphincter muscle at the bottom of the bladder to facilitate substantially complete drainage of urine and sedimentary waste material in the bladder . the other consideration is that retention drainage catheters are very often used by elderly people who , for one reason or another , have lost voluntary control of the urinary function and the catheter must remain in place for extended periods of time . due to senility or other factors of mental deterioration of the aged , many of these people have a tendency to try to pull the catheter out without realizing what they are doing , and as a consequence can cause themselves servere injury if the balloon is not large enough to retain the catheter in place even against substantial pulling force . the present invention effectively aleviates both of the aforementioned problems by providing a retaining balloon designed to provide both maximum size for retention purposes and at the same time to keep the drainage opening close to the bottom of the bladder . the ballon layer 36 extends from the molded or bonded juncture 38 to the end of the cannula 11 and has an annular terminal portion 40 which encircles the annular wall 32 of the inner latex layer 18 . the balloon layer 36 is separated from the outer layer 18 of the cannula from the juncture 38 to the annular wall 32 where the balloon layer is either integrally molded or suitably bonded to the annular wall 32 so as to form a fluid - tight seal therewith . it will be noted that the teminal portion 40 of the balloon layer 36 is thicker than the balloon layer and is smoothly rounded for ease of insertion as will more clearly appear hereinafter . in its non - inflated condition , the balloon layer lies flat on the tapered surface of the outer layer 18 and forms the gradually widening portion 34 of the cannula . the balloon is inflated by means of an inflation lumen 42 formed in the silicone layer 20 , the silicone layer being thicker in the area of the inflation lumen than the rest of the layer as best seen in figs . 2 and 3 . with reference to fig1 the inflation lumen 42 extends from a terminus 44 within the balloon layer 36 through the silicone layer 20 to a lateral extension 46 of the outer layer 18 , the lateral extension terminating in a value housing 48 and a fluid injection end 50 . any suitable value member 52 is provided within the valve housing 48 to prevent the escape of the inflation fluid after the balloon layer 36 has been inflated . the silicone layer 20 is provided for the purpose of resisting any tendency of the inflation lumen 42 to expand into the drainage lumen 26 due to the pressure of the inflating fluid within the inflation lumen 42 and the balloon layer 36 . since the silicone rubber is stronger and less flexible than the latex rubber , it is desirable to maintain the silicone layer as thin as possible around its periphery and to thicken the silicone layer only at the location which surrounds the inflation lumen as shown in fig2 and 3 . the catheter assembly 10 includes a stylet 12 which is used to insert the catheter 11 into the urethra , and as a cleaning implement as will be more fully described hereafter . the stylet 12 is an elongated tube formed of a relatively rigid rubber or plastic material which meets the same physical characteristics as the material of the catheter with respect to being susceptable to sterilization , impervious to urine , etc . the stylet is sufficiently rigid so that it can be pushed through the urethra without buckling , and yet is also sufficiently flexible that it will conform somewhat to the configuration of the urethra during the insertion process , although a certain degree of straightening of the urethra during the insertion process in inherent in any catheterization process . the stylet 12 is formed as a rod 54 having a proximal end 56 and a distal end 58 , the length of the rod between the ends 56 and 58 exceeding that of the catheter 11 . the distal end is formed as a smooth rounded tip at the end of a tapered removable end portion 60 of the rod 54 , the rod and the removable end portion being connected together by any suitable means such as the threads 62 or merely a press fit . the rounded end 58 and the taper on the end portion 60 facilitate a smooth sliding passage of the projecting end of the stylet through the urethra . the stylet is also provided with a longitudinal passageway or bore 64 which extends the entire length of the stylet and functions as a limited drainage passageway through which a small amount of urine can flow when the distal end of the stylet enters the bladder . this provides the person inserting the catheter with an indication of when the tip of the stylet enters the bladder , it being known how much further the catheter and stylet must be inserted into the urethra to dispose the distal end of the catheter in the bladder . the end portion 60 is replaced by a suitable brush element 61 such as that shown in fig9 when it is desired to clean the drainage lumen 26 . the stylet and catheter are provided with cooperating abutment means by which the stylet pushes the catheter through the urethra as the stylet is manipulated though the urethra . in the embodiment shown in fig1 a annular boss 66 is formed on the inner surface 26 of the inner latex layer , and a cooperating radial boss 68 is formed on the outer surface of the rod 54 . the abuting engagement of the adjacent surfaces of the bosses 66 and 68 prevents the stylet from passing through the catheter and pulls the catheter through the urethra as the person inserting the catheter pushes on the stylet . it will be recognized that , although the annular boss 66 is formed of the relatively soft latex rubber , there is little likelihood that the radial boss 68 on the stylet will slip past the annular boss 66 during insertion of the catheter due to the fact that the tolerance relationships between the stylet and the catheter inside the drainage lumen 26 are very small , and the radial boss 68 is extremely close to , if not actually in sliding contact with , the inner wall 24 of the drainage lumen 26 . it will also be noted that the boss 66 on the cannula is located substantially at the widest part of the gradually widening portion 34 of the cannula so that as the stylet pushes the catheter through the urethra , only the portion 34 is in advance of the abutting engagement between the catheter and the stylet . the advantage of this arrangement is that substantially the entire portion of the catheter which is not tapered is being pulled through the urethra with the result that there is no tendency for the catheter to buckle or slide back on the stylet during the insertion process . three alternative embodiments of the abutment means between the catheter and stylet are shown in figs . 4 - 6 . in fig4 a multiple step abutment means is shown in which the inner layer 22 of the catheter is provided with an annular boss 70 which defines an abutment wall 72 , and another annular boss or merely a portion 74 of the inner layer 22 of larger diameter from the rest of the inner layer defines another abutment wall 76 spaced rearwardly from the abutment wall 72 . correspondingly on the stylet , a radial boss or merely a portion 78 of the rod 54 which is of reduced diameter from the rest of the rod 54 defines an abutment wall 80 , and a radial boss 82 defines another abutment wall 84 spaced rearwardly from the abutment wall 80 . it will be observed that the two abutment walls 80 and 84 on the stylet are much more widely separated than the corresponding abutment walls 72 and 76 on the catheter , the reason for which will be made clear hereinafter . it will be apparent that if for any reason the forward abutment wall 80 should slip past the forward abutment wall 72 on the catheter , the rearward abutment wall 84 on the stylet wall engage with the rearward abutment wall 76 on the catheter after the stylet has moved forwardly within the catheter a distance equal to the space between the rearward abutment wall 76 on the catheter and the rearward abutment wall 84 on the stylet . thus , the plurality of abutment walls provides an added measure of safety against the stylet passing the single abutment menas shown in fig1 as well as another advantage discussed below in connection with the expansion of the inflatable balloon as shown in fig8 . it well be noted that the rear abutment wall 76 is located substantially at the widest portion of the gradually widening portion 34 of the cannula and the forward abutment wall 72 is located within the gradually widening portion 34 so that only the gradually widening portion of the cannula is pushed ahead of the abutment means during insertion of the cannula regardless of which of the above described pairs of abutment surfaces are in engagement with each other . another form of abutment means is shown in fig5 in which the cooperating abutment surfaces formed on the catheter and stylet are in barb - like configuration to give an added measure of assurance against the stylet abutment surface slipping past the catheter abutment surface and failing to pull the catheter through the urethra . thus , an annular recess 86 is formed on the inner surface 26 of the inner latex layer 22 , and a cooperating radial boss or projection 88 is formed on the outer surface of the stylet rod 54 . as shown in fig5 the recess 86 is wedge shaped , and the projection 88 is correspondingly wedge shaped so that the recess has an abutment surface 90 and the projection has an abutment surface 92 which surfaces engage when the stylet is inserted into the drainage lumen 26 of the catheter . the abutment surfaces 90 and 92 are both slanted forwardly as they extend outwardly so that the recess 86 and projection 88 have a barb - like configuration . although the diameter of the radial projection is larger that the diameter of the drainage lumen 26 , as distinguished from the fig1 and fig . 4 embodiments where the stylet projections do not exceed the diameter of the drainage lumen 26 , there is nevertheless no difficulty in inserting the stylet into the catheter since the inner latex layer 22 is relatively compressible , and the projection 88 simply compresses the material of the layer 22 as it moves through the drainage lumen 26 until the projection moves into the recess 86 . in this embodimemt of the invention , insertion of the stylet into the catheter is further facilitated by inserting the stylet from the distal end of the catheter rather than from the proximal end thereof as would be the direction of insertion for the embodiments shown in fig1 and fig4 . it should be noted that insertion of the stylet in all of the disclosed embodiments is made easier by lubricating the stylet prior to insertion with any suitable sterile lubricant . for the same advantage as pointed out above in connection with the abutment means of fig1 the abutment surfaces of the catheter and stylet are located adjacent the widest part of the gradually widening portion 34 of the cannula . fig6 shows another form of multiple step abutment means similar to that shown in fig4 but having the abutment means configurated as shown in fig5 . the inner layer 22 of the catheter is provided with a forward annular recess 94 which defines an abutment surface 96 and another rearward annular recess 98 which defines another abutment surface 100 spaced rearwardly from the abutment surface 96 . the style is provided with a forward radial projection or boss 102 which defines an abutment surface 104 for engagement with the abutment surface 96 and another rearward annular recess 98 which defines another abutment surface 100 spaced rearwardly from the abutment surface 96 . the stylet is provided with a forward radial projection or boss 102 which defines an abutment surface 104 for engagement with the abutment surface 96 on the catheter and a rearward radial boss or projection 106 which defines another abutment surface 108 for engagement with the abutment surface 100 of the catheter . as in fig5 the projections on the stylet are wedge shaped and the abutment surfaces on both the stylet and the catheter are slanted forwardly as they extend outwardly so that the abutment surfaces have a barb - like cooperation when they engage with each other . it will be noted that the abutment surface 104 and 108 on the stylet are much more widely separated than the corresponding abutment surfaces 96 and 100 on the catheter , as in the fig4 embodiment ; it will also be noted that the annular recess 98 has a uniform diameter over the length of this recess , and the reason for both of these details of construction will be made clear hereinbelow . as with the fig . 4 embodiment , if for any reason the forward abutment surface 104 on the stylet should slip past the forward abutment wall 96 on the catheter , the rearward abutment surface 108 on the stylet will engage the rearward abutment surface 100 on the catheter after the stylet has moved forwardly within the catheter a distance equal to the space between the rearward abutment surface 108 on the stylet and the rearward abutment surface 100 on the catheter , thereby providing the same added measure of safety as discussed above in connection with the fig4 embodiment . again it should be noted that the rearward abutment surface 100 on the cannula is located substantially at the widest part of the gradually widening portion 34 of the cannula and the forward abutment surface 96 is located within the gradually widening portion 34 so that only gradually widening portion of the cannula is pushed ahead of the abutment means during insertion of the cannula regardless of which of the above described pairs of abutment surfaces are in engagement with each other . the present invention provides two unique advantages over any known prior art catheters which advantages are derived from the construction of the embodiments described above and will be more apparent from a description to follow of the manner in which the catheter is used in connection with the insertion and retention of the catheter in the bladder . both of these advantages result from the manner in which the inflatable balloon operates to cause a certain amount of expansion of the distal end of the cannula thereby widening the opening into the drainage lumen and also , in the plural abutment means of the fig4 an fig6 embodiments , allowing a certain degree of freedom of movement of the stylet within the catheter to provide an indication that the balloon has a fact inflated in the bladder and is retaining the catheter in place . with reference to the embodiments shown in fig1 and 5 , the construction and connection of the inflatable balloon 36 , which is the same in both embodiments , causes a certain amount of expansion of the opening 30 at the distal end of the cannula , thus providing a wider opening into drainage lumen to facilitate drainage of waste material over a large area . this expansion results from the forward connection 40 of the balloon 36 to the inner layer 22 of the cannula which causes the balloon to exert a strong radial pull on the end of the inner layer . since the relatively stronger intermediate layer 20 gradually tapers to practically nothing at the end of the cannula , or may terminate altogether before the end of the cannula , this layer offers little or no resistance to the expansion of the forward end of the cannula . as seen in fig7 when the balloon has been fully inflated , the gradually widening portion 34 of the cannula is flared outwardly from approximately the widest part of the gradually widening portion 34 to the end thereof . by providing the other juncture 38 of the balloon 36 with the outer layer 18 of the cannula at the widest point of the gradually widening portion 34 , only that portion 34 of the cannula need be inside the bladder thereby maintaining the balloon relatively flat and the opening 30 as low as possible in the bladder thus promoting maximum drainage of waste material from the bladder . in the embodiments of the invention shown in fig4 and 6 , the expansion effect is enhanced by the construction of the inner layer 22 of the cannula , and in this form of the invention the stylet is utilized to provide an indication that the balloon has inflated . it will be observed that in both of these embodiments the inner layer 22 is thinner in cross - section at least at the location of the rearward abutment surfaces than it is along that portion of the layer 22 within the gradual widening portion 34 of the cannula . the effect of this , as best seen in fig8 is to provide an effective hinge portion of the inner layer about which all three layers of the cannula can bend in response to the radial force exerted on the forward end of the cannula at the terminal portion 40 of the balloon 36 . in these two embodiments , the tapered portion 34 of the cannula bends outwardly far enough to cause the forward abutment surfaces on the cannula to disengage from the forward abutment surfaces on the stylet after the balloon is inflated , thereby allowing the stylet to move forwardly in the cannula until the rearward abutment surfaces on the stylet engage with the rearward abutment surfaces on the cannula . this limited movement of the stylet , which will be relatively free movement in both forward and backward directions , provides a positive indication to the person inserting the catheter that the balloon 36 has in fact inflated within the bladder and that there are no leaks in the balloon or other reason present which would prevent inflation of the balloon .
disclosed is an improved drainage catheter for insertion into and retention in the bladder of the human body , and a novel stylet for use in inserting the catheter through the urethra and into the bladder . the catheter is formed of an elongate flexible cannula having a free and unobstructed open end adapted to be inserted into the bladder to permit drainage of waste material from the bladder and to facilitate the insertion of diagnostic instrumentation into the bladder . the end of the catheter in the bladder can expand to widen the opening and cause the open end to lie lower in the bladder . the stylet is an elongate flexible member adapted to be inserted into the cannula prior to the cannula being inserted into the urethra . the cannula and the stylet have cooperating stop means to prevent the stylet from passing through the cannula beyond a predetermined point so that the stylet can be used to push the cannula through the urethra and insert the open end into the bladder . the stylet has a rounded top which protrudes beyond the open end of the cannula to provide a guide for the cannula in passing through the urethra so as to prevent trauma thereto , the tip being removable so that a cleaning brush element can be attached to the stylet . the cooperating stop means can be arranged such that the cannula will deflect at the stop means on the cannula so that the stylet moves freely to provide an indication that the catheter is properly located and secured within the bladder .