Low residual bladder catheter

A bladder catheter comprising an elongate tubular body having a proximal portion with a proximal end, a distal portion, preferably between at least about 8 cm and 30 cm, with a distal end and a retaining portion with retaining mechanism disposed between the proximal portion and the distal portion. The tubular body of the bladder catheter further comprises a drainage lumen extending therethrough from a drainage port in the proximal end to at least one opening in the distal portion. The distal end of the catheter preferably comprises a weight. A method of continuously draining urine in a patient, comprising the steps of inserting a bladder catheter according to the present invention into the patient's urethra until the retaining mechanism and distal portion reside within the patient's bladder, actuating the retaining mechanism of the catheter, allowing the distal end of the catheter to fall into the dependent portion and, thereby, draining urine in the dependent portion of the bladder.

BACKGROUND 
Bladder catheters are routinely used for draining the urinary tract of 
patients who are unable to voluntarily urinate and in whom the accurate 
measurement of urine production is necessary. Commonly used bladder 
catheters have a number of problems associated with them. First, they do 
not completely drain the bladder because urine will collect in a dependent 
portion of the bladder, away from apertures in the distal catheter. This 
residual urine, in conjunction with the artificial passage created by the 
catheter, tends to produce urinary tract infections. These infections 
occur within hours to days after the initiation of continuous bladder 
drainage. 
Further, measuring changes in urine output is critical to determining the 
cardiovascular and renal status of severely ill patients. Many of these 
patients are hospitalized in intensive care units and convalesce while 
supine. The supine position promotes collection of residual amount of 
urine in dependent portions of the bladder away from the opening of 
commonly used bladder catheters. In such patients, intermittent movement 
causes the residual amounts of urine to unpredictably contact the drainage 
opening of the catheter. This gives the impression that a large amount of 
urine was produced since the last measurement followed by substantially 
decreased production of urine as the urinary output flows again to the 
dependent portion of the bladder. Similarly, patients on rotating beds for 
the prevention and treatment of bed sores, such as with quadriplegics, 
will also appear to have irregular production of urine due to the 
unpredictable movement of significant amounts of urine to the catheter 
opening as the bed rotates. Thus, the accurate measurement of urine output 
is difficult with commonly used bladder catheters. 
A number of bladder catheters have been developed that attempt to drain 
residual amounts of urine. Some of these have a drainage opening at the 
junction of the bladder and urethra. While some of these designs will 
drain urine when the junction is also the most dependent portion of the 
bladder, they do not drain residual urine from the dependent portions of 
the bladder away from the junction such as when the patient is horizontal. 
Thus, there remains a need for a bladder catheter that will continuously 
drain urine from the dependent portions of a bladder when the patient is 
supine. 
SUMMARY 
The present invention is directed to a bladder catheter that satisfies this 
need. The bladder catheter of the present invention comprises an elongate 
tubular body having a proximal portion with a proximal end, a distal 
portion with a distal end and a retaining portion with retaining 
mechanism. The retaining portion is disposed between the proximal portion 
and the distal portion. The catheter further comprises a drainage lumen 
through the tubular body extending from a proximal port in the proximal 
end to at least one opening in the distal portion. In one preferred 
embodiment, the catheter comprises a weight in the distal portion. In 
another preferred embodiment the distal portion of bladder catheter is 
between about 8 cm and about 30 cm. In still another preferred embodiment, 
the bladder catheter further comprises a support in the distal portion. 
The present invention is also directed to a method of draining urine from a 
patient's bladder comprising the steps of inserting a bladder catheter 
according to the present invention into a patient's urethra until the 
retaining mechanism and distal portion reside within the patient's 
bladder, actuating the retaining mechanism of the catheter, and allowing 
the distal end of the catheter to enter urine in the dependent portion, 
thereby draining the urine from the patient. The method can further 
comprise the step of measuring the urine drained from the patient after 
the allowing step.

DESCRIPTION 
Referring now to FIG. 1, there is illustrated a perspective environmental 
view of a bladder catheter 10 as is known in the prior art. The catheter 
comprises an elongate tubular body 12 having a proximal portion 14 with a 
proximal end 16, a distal portion 18 with a distal end 20 and a retaining 
portion 22 with retaining mechanism 24. The retaining portion 22 is 
disposed between the proximal portion 14 and the distal portion 18. The 
tubular body 12 of the bladder catheter 10 further comprises a drainage 
lumen 26 extending therethrough from a drainage port 28 in the proximal 
end 16 to at least one opening 30 in the distal portion 18. 
In use, the distal end 20 of the bladder catheter 10 is inserted into the 
urethra 32 of a patient 34 and axially slid until the retaining portion 22 
and the distal portion 18 reside within the bladder 36. Urine passing into 
the at least one opening 30 flows through the drainage lumen 26 and exits 
the drainage port 28 in the proximal end 16 of the catheter 10 for 
collection into a drainage bag, not shown. Urine in the dependent portion 
of the bladder 38, however, may not enter the at least one opening 30, 
especially if the patient 34 is supine. 
Referring now to FIGS. 2 and 3, there is illustrated a perspective 
environmental and a fragmentary elevational view, respectively, of a 
catheter 110 embodying features of the invention. The catheter 110 
comprises an elongate tubular body 112 having a proximal portion 114 with 
a proximal end 116, a distal portion 118 with a distal end 120 and a 
retaining portion 122 with retaining mechanism 124. The retaining portion 
122 is disposed between the proximal portion 114 and the distal portion 
118. The tubular body 112 of the bladder catheter 110 further comprises a 
drainage lumen 126 extending therethrough from a drainage port 128 in the 
proximal end 116 to at least one opening 130 in the distal portion 118. 
The tubular body 112 can comprise any of a variety of biocompatible 
materials as are well known to those with skill in the art. The material 
is preferably flexible, but has enough stiffness for axial pushability 
during insertion. In one preferred embodiment the tubular body 112 
comprises rubber. 
The tubular body 112 can be any of a variety of cross-sectional areas and 
lengths such as are suitable for a variety of patients, ranging for 
newborn infants to large adults. In preferred embodiments, the 
cross-sectional area of the tubular body 112 ranges from about 5 Fr. to 
about 30 Fr. In a particularly preferred embodiment, the cross-sectional 
area ranges from about 12 Fr. to about 24 Fr. 
The tubular body 112 can also be any of a variety of axial lengths such as 
are suitable for a variety of patients, ranging for newborn infants to 
large adults. In a preferred embodiment, the axial length of the tubular 
body 112 ranges from about 30 cm to about 75 cm. 
The proximal end 116 of the bladder catheter 110 preferably comprises at 
least one adapter 132 for attaching to a drainage bag, not shown. Further, 
the proximal end 116 of the catheter 110 can comprise an actuator 134 for 
actuating the retaining mechanism 124. For example, when the retaining 
mechanism 124 is an inflation balloon, the actuator 134 comprises an 
adapter for an inflation syringe, not shown, or other inflation devices. 
The length of the proximal portion 114 of the tubular body 112 can be any 
of a variety of lengths such as are suitable for a variety of patients. 
Preferably, the length of the proximal portion 114 is such that it 
comprises no more than approximately about 70% of the length of the 
tubular body 112. In a particularly preferred embodiment, the length of 
the proximal portion 114 comprises between about 60 and about 70% of the 
length of the tubular body 112. 
The retaining portion 122 of the bladder catheter 110 is disposed between 
the proximal portion 114 and the distal portion 118 of the tubular body 
112 and comprises a retaining mechanism 124. The retaining mechanism 124 
can be any of a variety of devices known to those with skill in the art, 
such as reversible expanding prongs, mesh baskets or inflation balloons. 
The length of the retaining portion 122 will depend on the retaining 
mechanism 124 utilized. In one preferred embodiment, the retaining 
mechanism 124 is an inflation balloon as shown in FIG. 2 and the length of 
the retaining portion 122 is about 2.5 cm in the uninflated state. 
The length of the distal portion 118 of the tubular body 112 can be any of 
a variety of lengths such as are suitable for a variety of patients. 
Preferably, the length of the distal portion 118 is such that it comprises 
at least about 25% (twenty-five percent of the length of the tubular body 
112. In a particularly preferred embodiment, the length of the distal 
portion 118 comprises about 25% (twenty-five percent) of the length of the 
tubular body 112. Preferably the distal portion 118 is between about 8 cm 
and about 30 cm. 
The distal portion 118 of the tubular body 112 comprises at least one 
opening 130 communicating with the drainage port 128 via the drainage 
lumen 126. The at least one opening 130 can be of any of a variety of 
shapes, but round or oval is preferred. The at least one opening 130 can 
be circumferentially reinforced to maintain patency. In one preferred 
embodiment, illustrated in FIG. 3, the at least one opening 130 is at 
least two openings. These at least two openings can be staggered axially, 
can be opposingly placed on the distal portion 118 or both. The distal end 
120 of the catheter 110 is preferably tapered to facilitate 
catheterization. 
Further, the distal portion 118 can comprise a weight. Preferably, the 
weight is incorporated into the distal end 120 of the distal portion 118 
of the tubular body 112. The weight tends to cause the distal end 120 of 
the distal portion 118 of the tubular body 112 to submerge into urine 38 
in the dependent portion of the bladder 36, thereby causing urine 38 to 
enter the at least one opening 130 in the distal portion 118. 
The weight can comprise any of a variety of forms and materials. Preferably 
the form is such that it does not increase the cross-sectional area of the 
tubular body 112. 
Referring now to FIG. 4 and 5, there are illustrated elevational views of 
two embodiments of the present invention showing examples of suitable 
configurations for weight, labeled 136 and 142 respectively. FIG. 4 shows 
a weight 136 forming the part of the distal end 120 of the catheter 110 
and secured by a male proximal end 138 of the weight 136 fitting into a 
corresponding female segment 140 of the distal portion 118 of the catheter 
110. FIG. 5 shows a similar arrangement but with the weight 142 covered by 
material 144 forming the distal end 120 of the tubular body 112. This 
later configuration is preferred because it lessens the chance of the 
weight 142 splitting from the catheter 110 body during use. Further, the 
weight can also comprise reinforcing structures, not shown, surrounding 
the at least one opening 130 in the distal portion 118 of the catheter. 
Suitable material for the weight has a higher density than water. 
Preferably, the material is biocompatable and nonreactive to normal 
components of urine. Examples of suitable materials include lead, steel 
and titanium. 
Depending on the length of the distal portion of the catheter 118 and the 
thickness and material of the tubular body 112, the catheter 110 may make 
a sharp bend at the junction of the retaining portion 122 and the distal 
portion 118, or along the distal portion 118. This sharp bend can close 
off the drainage lumen 126, thereby preventing urine flow. In order to 
obviate this problem, the catheter 110 can be provided with a support. 
Preferably, the support comprises a structure integrated into the internal 
wall of the drainage lumen 126 causing any bend in the distal portion 118 
of the catheter 110 to form a gently sloping curve, thereby maintaining 
the patency of the drainage lumen 126. Suitable supports include an 
axially disposed internal rib or a circumferential spiral, extending in 
the tubular body from at least the retaining portion 122 to some or all of 
the distal portion 118. FIG. 6 is a cross-sectional view of the catheter 
110 taken through line 6--6 in FIG. 3 showing a support comprising four 
circumferentially-spaced, axially-oriented internal ribs 146 integrated 
into the tubular body 112. Alternately, one or more axially-spaced, 
circumferential-oriented ribs, not shown, can be incorporated as suitable 
supports. Further, gradually varying wall thickness can be provided for 
the support, also not shown, where the wall is thicker proximal from the 
junction of the retaining mechanism and distal portion, and gradually gets 
thinner distally. Other supports will be equally appreciated by those with 
skill in the art, with reference to the disclosure herein. 
The bladder catheter 110 according to the present invention is used as 
follows. The distal end 120 of the bladder catheter 110 is inserted into 
the urethra 32 of a patient 34 and axially slid until the retaining 
portion 122 and the distal portion 118 reside within the bladder 36. The 
retaining mechanism 124 is then actuated, thereby causing retention of the 
distal portion 118 of the catheter 110 within the bladder 36. 
The relatively long length of the distal portion 118 of the catheter 110 
allows the at least one opening 130 to fall by gravity into the dependent 
portion of the bladder. This allows urine 38 in the dependent portion of 
the bladder 36 to enter the at least one opening 130 and pass into the 
drainage lumen 126 to empty out of the catheter 110 via the proximal port 
128. Drainage occurs through a combination of gravity and siphoning, 
though suctioning can be used as is known by those with skill in the art. 
Urine output is then intermittently measured, such as by collection in a 
drainage bag, not shown. Accurate measurement of urine output is thereby 
accomplished. According to another embodiment of the present invention, 
weight in the distal portion 118 of the catheter 110 assists the distal 
portion 118 to drop into the dependent portion of the bladder increasing 
the accuracy of urine output measurement. When no longer needed, the 
retaining mechanism 124 is unactuated and the catheter 110 slid axially 
outwards. 
Although the present invention has been described in considerable detail 
with reference to certain preferred versions thereof, other versions are 
possible. For example, the catheter 110 can include an anti-bacterial 
coating to inhibit the introduction of infectious organisms into the 
bladder. Therefore, the spirit and scope of the appended claims should not 
be limited to the description of the preferred embodiments contained 
herein.