Peritoneal dialysis catheter

A peritoneal catheter comprises a flexible catheter tube carrying porous cuff means to facilitate permanent securance of the catheter to the abdominal wall. The catheter tube defines, in its natural, unstressed condition, a bent segment adjacent the porous cuff means. This permits the catheter to be mounted in a tunnel formed through the abdominal wall in relatively unstressed configuration, with both ends pointing downwardly toward the feet of the patient. In one embodiment, the catheter includes a flange extending circumferentially outwardly of the catheter tube adjacent to the porous cuff means. The flange extends at a nonperpendicular angle relative to the axis of the catheter tube, and the slope of the flange extends transverse the direction of the bent segment. The angled flange, when sutured to the posterior rectus sheath, maintains the catheter tube in the desired tunnel direction within the abdominal wall, with the distal end of the catheter tube pointed properly downwardly toward the pelvic cavity.

TECHNICAL FIELD 
The Tenckhoff catheter is commercially available and widely used with 
patients who must undergo chronic peritoneal dialysis for maintenance in 
the absence of normal kidney function. The catheter is made of silicone 
rubber, and has a pair of porous tissue attachment cuffs in spaced 
relation to each other, so that after implantation of the catheter into 
the abdominal wall, tissue grows into pores of the cuffs, for secure and 
permanent anchoring of the catheter in place. In the article by Tenckhoff 
and Schechter entitled "A Bacteriologically Safe Peritoneal Access 
Device," Trans. Am. Soc. Artif. Intern. Organs 1968; 14:181-187, the 
authors disclosed their new catheter and showed an arcuate subcutaneous 
catheter tunnel, so that both the external and internal end segments of 
the catheter were generally directed in a caudal direction (i.e., 
downwardly, toward the feet of the patient). 
In the practice of installation of such peritoneal catheters, this 
technique is often followed, so that both the outer end of the catheter 
outside of the body and lying over the skin, and the inner end of the 
catheter within the peritoneal cavity, typically point downwardly toward 
the pelvis or feet. 
However, known peritoneal catheters have been molded and cured in generally 
straight configuration, so that their natural, unstressed configuration is 
a straight line, although the catheters are flexible and may be placed in 
other configurations. Accordingly, peritoneal catheters of the prior art 
must be stressed by bending into a substantially U-shape, in order to be 
installed into a curved tunnel through the abdominal wall, which holds the 
catheter in its downward facing, U-shaped position so that both ends of 
the catheter extend downwardly. 
Significant advantages have been found for this arrangement. For example, 
in currently unpublished data by authors including us, it has been 
statistically shown that patients who have downwardly caudally pointing 
outer ends of their peritoneal catheter have fewer days of catheter tunnel 
infection, when compared with patients whose catheter ends point either 
upwardly or in a sideward direction. 
Currently, however, disadvantages of this arrangement also exist. First, it 
appears that the elastic memory of the catheter, which urges it to assume 
its original, unstressed, straight configuration, can cause catheter cuffs 
to be expelled from the tunnel site in a slow, migratory process. This of 
course is most disadvantageous. Secondly, the inner end portion of the 
catheter can migrate upwardly with greater ease, due to the internal 
stresses of the catheter tending to urge it straight. It is undesirable 
for the catheter to migrate upwardly to upper portions of the peritoneal 
cavity, where it is prone to omental wrapping and one way obstruction of 
flow through the catheter. Accordingly, there is a need to keep the inner 
catheter portion positioned in the lower portions of the peritoneal 
cavity, adjacent the pelvis. There is also a need to maintain the desired 
tunnel direction of the catheter within the abdominal wall. 
In accordance with this invention, the above disadvantages are reduced by 
the use of a modified catheter. 
DESCRIPTION OF THE INVENTION 
In one aspect of this invention, a peritoneal catheter comprises a flexible 
catheter tube, which may be made of silicone rubber or equivalent 
material. The tube has a proximal and a distal end portion. The distal end 
portion defines flow port means for fluid communication between the bore 
of the catheter tube and the peritoneal cavity. The catheter also carries 
porous cuff means to facilitate permanent securance of the catheter to the 
abdominal wall. 
In accordance with this aspect of the invention, the catheter tube defines, 
in its natural, unstressed condition, a bent segment adjacent the porous 
cuff means. As the result of this, the catheter can be mounted in a tunnel 
formed through the abdominal wall in relatively unstressed condition, with 
the bent segment being mounted in the tunnel. Hence, the proximal end 
portion of the catheter may extend outwardly from the abdominal wall and 
downwardly from the outer end of the tunnel, while the distal end portion 
of the catheter extends inwardly and downwardly from the inner end of the 
tunnel into the peritoneal cavity. 
Because of the unstressed bent segment, the catheter of this invention 
occupies the desired position where both ends thereof point caudally or 
downwardly, while at the same time the catheter tube is in relatively 
natural, unstressed condition, when compared with prior art catheters 
which have been placed in such a position. Thus, less urging force is 
present in the catheter to cause gradual expulsion of cuffs from the 
tunnel formed in the abdominal wall. Also, less force is present urging 
the distal end portion of the catheter upwardly out of its desired 
position in a lower portion of the peritoneal cavity. 
Additionally, the installed catheter of this aspect of invention can 
exhibit significantly reduced days of tunnel infection which the patient 
must endure, because of the downward pointing aspect of the proximal end 
portion of the catheter. It is believed that downwardly pointing proximal 
end portions of peritoneal catheters permit improved draining from the 
tunnel area in the event of an infection, which can significantly reduce 
the severity of the infection. Also, less contamination of the tunnel site 
takes place because of the migration of sweat and bacteria-laden water 
into the tunnel area, because its outer end points downwardly along with 
the proximal end portion of the catheter. 
It is generally preferred for the bent segment of the catheter to define an 
arc of 90.degree. to 180.degree. so that the proximal and distal end 
portions form an angle to each other that is supplementary to the angle of 
said arc. A "supplementary" angle is an angle which, when combined with 
the arc angle, totals 180.degree.. Accordingly, if the arc of the bent 
segment is 120.degree., the proximal and distal end portions will form an 
angle with each other of 60.degree.. Most preferably, the bent segment 
defines an arc of about 120.degree. to 170.degree.. 
The use of a bent segment which defines an arc makes possible the formation 
of a substantial angle in the catheter, as shown in the drawings, without 
the danger of kinking of the catheter, as might take place if a merely 
angled corner were used rather than an arc. 
The porous cuff means on the catheter may be any conventional cuff used for 
tissue attachment to a catheter. While a single, porous cuff may be used, 
it is preferable to use a pair of spaced, porous cuffs in the manner of 
the well-known Tenckhoff catheter as it is currently commercially 
available. One cuff, hereafter called the exterior cuff, attaches to the 
subcutaneous tissue near the exterior abdominal wall. The other cuff, 
hereafter called the interior cuff attaches within the rectus muscle near 
the posterior rectus sheath. The bent segment of the catheter, as above 
described, is positioned between the interior and exterior cuffs. 
In another aspect of the invention, an outwardly extending flange 
circumferentially surrounds the catheter just below the interior cuff. The 
flange extends in a nonperpendicular relationship relative to the axis of 
the catheter tube, being slanted at an angle less than 90.degree. relative 
to the axis of the catheter. When viewed in the direction of the arcuate 
bend in the catheter, the direction of the slope extends generally 
transverse the direction of the arcuate bend. Preferably, the angle of the 
slope is between about 30.degree. and 50.degree., with the most preferred 
angle being about 45.degree.. 
The direction of the slope of the flange maintains the desired direction of 
the catheter inside the tunnel formed within the abdominal wall. When the 
flange is sloped upwardly to the right, as viewed from the distal end leg 
of the catheter in the direction of the arcuate bend, the catheter is 
intended to maintain a right tunnel implacement, as described in more 
detail below. When the flange is sloped upwardly to the left, as viewed 
from the same perspective the catheter is intended to maintain a left 
tunnel implacement, also as described in more detail below. 
When the angled flange is sutured flat against the posterior rectus sheath, 
the desired tunnel direction of the catheter is maintained within the 
abdominal wall, with the distal end of the catheter pointing in the 
desired caudal direction within the peritoneal cavity.

DESCRIPTION OF SPECIFIC EMBODIMENTS 
Referring to the drawings, catheter 10 is a peritoneal catheter generally 
of the design of a commercially available Tenckhoff catheter, except as 
otherwise described herein. Catheter 10 comprises a flexible catheter tube 
12 which may be made of silicone rubber or any other desired and 
appropriate material. Adjacent the distal end 14 of the catheter, a 
plurality of flow ports 16 are formed in the wall of the catheter, while 
distal end 14 itself may be open as well, for added flow communication 
between the exterior and the bore of catheter 10. 
Proximal end 18 defines an open bore as well for receiving typically a 
titanium adaptor of known design, to provide connection with a transfer 
set or other means for flow communication with peritoneal dialysis 
solution containers. 
A pair of cuffs 20, 22 of known designs are also provided. Outer cuff 20 is 
intended to be positioned within the abdominal wall tunnel within the 
subcutaneous tissue about 2 centimeters from the outer skin. Cuff 22 is 
intended to be positioned adjacent the inner end of the abdominal tunnel, 
near the posterior rectus sheath. The abdominal tunnel may be formed by 
the surgeon when the catheter is installed in the patient's abdomen. 
In accordance with this invention, catheter 10 defines in its natural, 
unstressed condition, a bent segment 24. As shown, bent segment 24 defines 
an arc which may most preferably extend on the order of 
150.degree.-170.degree.. A catheter may be manufactured with such an 
unstressed bend by molding the catheter, or causing it to be cross-linked, 
while in the desired bent position. The bent segment 24 effectively forms 
two legs 15 and 19 in the catheter 10, one leg 15 associated with the 
distal end 14, and the other leg 19 associated with the proximal end 18. 
FIG. 2 illustrates how the catheter may be installed in the peritoneal 
cavity of the patient, with proximal end 18 projecting outwardly from the 
outer end 30 of the tunnel 34 formed by the surgeon in the abdominal wall. 
Distal end 14 of the catheter projects downwardly from the inner end 32 of 
the tunnel formed by the surgeon. Accordingly, since bent segment 24 is 
not as stressed as the catheters of prior art, there is less urging force 
to cause the distal end portion of the catheter to migrate upwardly in the 
peritoneal cavity. 
It is generally preferable for tunnel 34 to be formed on one side of the 
patient, spaced from the midline of said patient. Also, proximal end 18 
may be positioned at a small angle to the midline of the patient. In FIG. 
2, the tunnel 34 is angled so that the exposed proximal end 18 is 
positioned, when viewed by an on-looker, slightly to the left and pointed 
downwardly. This is called a "right tunnel" implacement. 
Alternately (not shown), the tunnel may be angled so that the exposed end 
18 is positioned, when viewed by an on-looker, slightly to the right and 
pointed downwardly. This is called a "left tunnel" implacement. 
A statistical analysis of the frequency and severity of infections made by 
a group, including us, has found that downward external tunnel implacement 
left or right provides the lowest number of days of tunnel infection that 
a patient must endure, when compared with any other position of tunnel 34. 
More particularly, we found that four catheters, installed in patients for 
a total of 2,136 days, in which the outer portions of the tunnels 34 
extended in a direction no more than 45.degree. away from straight down in 
the standing patient, resulted in no tunnel exit site infection at all. 
For catheter installations having higher angles than this from the 
straight down direction, increasing difficulties with tunnel site 
infection were encountered, which grew progressively worse as the angle 
grew larger, and was worst of all when the tunnel site exit pointed 
generally upwardly. FIG. 2 shows an ideal placement of the catheter of 
this invention in the abdomen. 
In FIG. 3, another peritoneal catheter 36 is shown which embodies the 
features of the invention. The catheter 36 is constructed generally like 
the catheter 10 shown in FIG. 1, having distal and proximal ends 14 and 18 
and an intermediate bent section 24. Other structural elements which are 
common to FIG. 1 are also given the same reference numerals as in FIG. 1. 
The catheter 36 shown in FIG. 3 differs from the catheter 10 shown in FIG. 
1 by the inclusion of a flange 38 which is located adjacent to and 
directly below the internal cuff 22. The flange 38 is intended to be 
sutured to the posterior sheath 40 of the rectus muscle 42, as shown in 
FIG. 7. 
A bead 44 is provided below the flange 38. The bead 44 extends within the 
peritoneal cavity (again, see FIG. 7) on the side of the posterior rectus 
sheath 40 opposite to the flange 38. 
In accordance with the invention, the flange 38 is angled in a 
nonperpendicular relationship relative to the axis 13 of the catheter 36. 
As shown in FIG. 4, the angle (designated A in FIG. 4), measured between 
the axis 13 and the flange 38, is generally between about 30.degree. and 
about 50.degree.. As is also shown in FIG. 4, the slope of the flange 38, 
when viewed in side section in the direction of the arcuate bend 24 from 
the distal end leg 15 of the catheter 36, extends in a direction 
transverse the direction of the bend 24 of the catheter 36. 
In FIG. 4, the flange 38 is shown angled sloping upwardly to the right, 
when viewed from the distal end leg 15 in the direction of the arcuate 
bend 24. In this arrangement, the catheter 36 is intended for right tunnel 
implacement, with the exposed proximal end 18 of the catheter 36 angled 
slightly to the right and pointed downwardly, when viewed by an on-looker, 
as shown in FIG. 7. 
Another catheter 46 is shown in FIGS. 5 and 6. This catheter 46, like 
catheter 36, has an angled flange 48. The catheter 46 is identical to the 
catheter 36 (shown in FIGS. 3 and 4), except that the flange 48, when 
viewed from the distal end leg 15 of the catheter 46 in the direction of 
the arcuate bend 24, is angled sloping upwardly to the left, as shown in 
FIG. 6. In this arrangement, the catheter 46 is intended for left tunnel 
implacement, with the exposed proximal end 18 of the catheter angled 
slightly to the left and pointed downwardly, as is shown in FIG. 2. 
When sutured flat against the posterior rectus sheath 40, as shown in FIG. 
7, the angled flange 38 or 48 maintains the desired right or left tunnel 
direction within the abdominal wall. Furthermore, the flange 38 or 48 
maintains the distal end 14 of the catheter pointing in the desired caudal 
direction within the peritoneal cavity. The flange 38 or 48, coupled with 
the arcuate bend 24 of the catheter 36 or 46, prevents migration of the 
catheter during use, maintaining the catheter in the optimal relationship 
within the peritoneal cavity. Tunnel infection is thereby reduced, and 
overall patient comfort improved. 
The above has been offered for illustrative purposes only, and is not 
intended to limit the scope of the invention of this application, which is 
as defined in the claims below.