Overview
Urination (micturition) involves physiological processes
within the urinary tract and the brain. The slight need
to urinate is sensed when urine volume reaches about one-half
of the bladder's capacity. The brain suppresses this need
until a person initiates urination. Neurons in the brain
and in smooth muscle of the bladder govern the detrusor
muscle (layered smooth muscle that surrounds the bladder);
it is not controlled voluntarily. The nervous system stimulates
the detrusor muscle to contract into a funnel shape and
expel urine, once a person initiates urination. Pressure
in the bladder increases and the detrusor remains contracted
until the bladder empties. |
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Once empty, pressure falls
and the bladder relaxes and resumes its normal shape.
If bladder pressure remains high while the bladder is
filling, the bladder contracts erratically. Normally,
the detrusor muscle contracts and relaxes according to the
volume of urine in the bladder and the initiation of urination.
In people with an overactive bladder, the detrusor
muscle contracts spastically, sometimes without a known cause,
which results in sustained, high bladder pressure. People
with the condition typically experience the urgent need to
urinate at inconvenient times and may lose control before
reaching a toilet. Overactive bladder interferes with work,
daily routine, and intimacy; causes embarrassment; and may
diminish self-esteem and quality of life. |
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Incidence and Prevalence
Overactive bladder affects men and women equally. Approximately
20 million people in the United States suffer from the condition.
Though it is not necessarily a result of aging, it most often
affects older people.
Causes
Malfunctioning detrusor muscle in the smooth muscle of the
bladder causes overactive bladder. Identifiable underlying
causes include the following:
- Abdominal
or pelvic trauma or surgery resulting in nerve damage
- Bladder
stones
- Drug
side effects
- Neurological
disease (e.g., multiple sclerosis, Parkinson's disease,
stroke, spinal cord lesions)
Other
conditions can produce symptoms similar to those experienced
with overactive bladder, the most common of which is urinary
tract infection (UTI) in women.
Signs and Symptoms
Three symptoms are associated with an overactive bladder:
- Frequency
(frequent urination)
- Urgency
(urgent need to urinate)
- Urge
incontinence (strong need to urinate followed by leaking
or involuntary and complete voiding)
Treatment
Treatment may include one or more of the following:
- Bladder
retraining
- Medication
- Sacral
Nerve Stimulation
- Surgery
Medications
such as oxybutynin chloride (Tropan XL®) and tolterodine
(Detrusitol®, Terol®) are once-a-day oral medications
for overactive bladder that can improve symptoms in as little
as 2 weeks. These drugs (antimuscarinics) affect the central
nervous system and muscarinic receptors in smooth muscle that
control detrusor muscle. They relax the smooth muscle of the
bladder, which reduces detrusor contraction and subsequent
wetting accidents. In a recent study, participants taking
Tropan XL had 90% fewer accidents, used fewer protective pads,
and experienced 24-hour relief from urgency and loss of control.
Side effects, including dry mouth, constipation, headache,
blurred vision, hypertension, drowsiness, and urinary retention
occur in approximately 50% of those who use the drugs. People
with certain types of kidney, liver, stomach, and urinary
problems, or glaucoma are advised not to take Tropan XL®.
Although there is no evidence that Tropan XL causes birth
defects, pregnant women should not take it without consulting
a physician.
Sacral Nerve Stimulation
Interstime Therapy for Urinary
Control is a reversible treatment for people with urge incontinence
caused by overactive bladder who do not respond to behavioral
treatments or medication. Using an implanted neurostimulation
system, InterStim Therapy sends mild electrical pulses to
the sacral nerve, a nerve near the tailbone in the lower back
that influences bladder control muscles. Stimulation of this
nerve may relieve the symptoms related to urge incontinence.
Prior to implantation, the effectiveness of the therapy is
tested with an external device. For a period of 3 to 5 days,
the patient records voiding patterns with the stimulation.
The test is done on an outpatient basis and the diary is compared
to patterns identified previously to determine if treatment
is effective.
Candidates for InterStim Therapy first undergo a test stimulation
to determine how responsive they are to the therapy. The test
provides information to determine if the device is a viable
treatment option, such as the effect of sacral nerve stimulation
on symptoms and how the patient experiences the stimulation.
If the test is successful, a patient may receive an implanted
InterStim System. The procedure requires general anesthesia.
A lead (a special wire with electrical contacts) is placed
near the sacral nerve and is passed under the skin to a neurostimulator,
which is about the size of a stopwatch. The neurostimulator
is placed under the skin in the upper buttock.
Adjustments to the stimulation can be made at the doctor's
office, with a programming device that sends a radio signal
through the skin to the neurostimulator. An additional programmer
is given to the patient to allow further adjustments to the
level of stimulation, and the system can be turned off at
any time.
Possible adverse effects include the following:
- Change
in bowel function
- Infection
- Lead
movement
- Pain
at implant sites
- Unpleasant
stimulation or sensation
Surgical augmentation of the bladder is
reserved for people who do not benefit from bladder retraining
or medication.
Those who cannot take medication due to medical conditions
or intolerance may find incontinence
management devices helpful. |
