In people with an overactive bladder (OAB), the detrusor muscle (layered smooth muscle that surrounds the bladder) contracts spastically, sometimes without a known cause, which results in sustained, high bladder pressure and the urgent need to urinate (called urgency). Normally, the detrusor muscle contracts and relaxes in response to the volume of urine in the bladder and the initiation of urination.
People with OAB often experience urgency at inconvenient and unpredictable times and sometimes lose control before reaching a toilet. Thus, overactive bladder interferes with work, daily routine, and intimacy; causes embarrassment; and can diminish self-esteem and quality of life.
Urination Urination (micturition) involves 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.
Once urination has been initiated, the nervous system signals the detrusor muscle to contract into a funnel shape and expel urine. Pressure in the bladder increases and the detrusor muscle remains contracted until the bladder empties. Once empty, pressure falls and the bladder relaxes and resumes its normal shape.
Overactive bladder affects men and women equally. The U.S. Department of Health and Human Services has reported that approximately 13 million people in the United States suffer from OAB and other forms of incontinence.
Malfunctioning detrusor muscle in the smooth muscle of the bladder causes overactive bladder. Identifiable underlying causes include the following: Nerve damage caused by abdominal trauma, pelvic trauma, or surgery 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.
Three symptoms are associated with an overactive bladder:
A complete medical history, including a voiding diary; a physical examination; and one or more diagnostic procedures help the physician determine an appropriate treatment plan for overactive bladder.
The medical history includes information about bowel habits, patterns of urination and leakage (when, how often, how severe), and whether there is pain, discomfort, or straining when voiding. The patient's history of illnesses, pelvic surgeries, pregnancies, and medications currently used also supply the physician with information relevant to making a diagnosis. In the elderly, a mental status evaluation and assessment of social and environmental factors may be performed.
A physical examination includes a neurologic status evaluation and examination of the abdomen, rectum, genitals, and pelvis. The cough stress test, in which the patient coughs forcefully while the physician observes the urethra, allows observation of urine loss. Instantaneous leakage with coughing indicates a diagnosis of stress incontinence. Leakage that is delayed or persistent after the cough indicates urge incontinence.
The physical examination also helps the physician identify medical conditions that may be the cause of overactive bladder. For instance, poor reflexes or sensory responses may indicate a neurological disorder.
Examination of the urine may identify medical conditions associated with overactive bladder, such as the following:
If overactive bladder persists after diagnosis and treatment, additional testing may be needed. Urologists perform urodynamic, endoscopic, and imaging tests to obtain a more extensive evaluation of the lower urinary tract to determine a new treatment plan.
Postvoid residual volume (PRV)
This procedure requires catheterization or pelvic ultrasound. The patient voids just before the PRV is measured. This initial void should be observed for hesitancy, straining, or interrupted flow. A PRV less than 50 mL indicates adequate bladder emptying. Repeated measurements of 100 to 200 mL or higher represent inadequate bladder emptying. The clinical setting and the patient's readiness to void may affect the test result; therefore, repeated measurements may be necessary.
Cystometry may be used to measure the anatomic and functional status of the bladder and urethra. The cystometer is an instrument that measures the pressure and capacity of the bladder; thus evaluating the function of the detrusor muscle. Simple cystometry detects abnormal detrusor compliance, but abdominal pressure is not included and the results must be evaluated with caution.
The multichannel, or subtracted, cystometrogram simultaneously measures intra-abdominal, total bladder, and true detrusor pressures. This allows involuntary detrusor contractions to be distinguished from increased intra-abdominal pressure. The voiding cystometrogram detects outlet obstruction in patients who are able to void.
Uroflowmetry identifies abnormal voiding patterns. Urethral pressure profilometry measures the resting and dynamic pressures in the urethra.
Cystoscopy may be performed when urodynamic testing fails to duplicate symptoms, when the patient experiences new symptoms (e.g., cystitis, pain), or when urinalysis reveals a disease process (e.g., menaturia, pyuria). Cystoscopy identifies the presence of bladder lesions (e.g., cysts) and foreign bodies.
X-rays and ultrasound may be used to evaluate anatomic conditions associated with overactive bladder. Imaging of the lower urinary tract before, during, and after voiding is helpful in examining the anatomy of the urinary bladder and urethra.
Treatment may include one or more of the following:
Bladder Training with Timed Voiding
This treatment is used for urge and overflow incontinence. The patient keeps a voiding diary of all episodes of urination and leaking, and the physician analyzes the chart and identifies the pattern of urination. The patient uses this timetable to plan when to empty the bladder to avoid accidental leakage. In bladder training, biofeedback and Kegel exercise help the patient resist the sensation of urgency, postpone urination, and urinate according to the timetable.
Drugs such as oxybutynin chloride (Ditropan XL®) and tolterodine (Detrusitol®, Detrol LA®) are taken orally, once a day, for overactive bladder. They can improve symptoms within 2 weeks. These drugs (antimuscarinics) affect the central nervous system and muscarinic receptors in smooth muscle. They relax the smooth muscle of the bladder, which reduces detrusor contraction and subsequent wetting accidents. In a recent study, participants taking Ditropan 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 glaucoma or certain types of kidney, liver, stomach, and urinary problems are advised not to take Ditropan XL. Although there is no evidence that Ditropan XL causes birth defects, pregnant women should not take it without consulting a physician.
Oxybutynin Transdermal System
The oxybutynin transdermal system (Oxytrol™) is a thin, flexible, clear patch that is applied to the skin of the abdomen or hip, twice weekly, to treat overactive bladder. This treatment delivers oxybutynin continuously through the skin into the bloodstream and relieves symptoms for up to 4 days allowing twice a week dosing.
Patients who have urinary or gastric retention, uncontrolled narrow-angle glaucoma, and those with hypersensitivity to oxybutynin should not use the oxybutynin transdermal system.
Side effects are usually mild and include adverse reactions at the site of application, dry mouth, and constipation.
Sacral Nerve Stimulation
InterStim® therapy is a reversible treatment for people with urge incontinence caused by overactive bladder who do not respond to behavioral treatments or medication. InterStim is an implanted neurostimulation system that sends mild electrical pulses to the sacral nerve, the nerve near the tailbone 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 on an outpatient basis with an external InterStim device. For a period of 3 to 5 days, the patient records voiding patterns that occur with stimulation. The record is compared to recorded voiding patterns without stimulation. The comparison demonstrates whether the device effectively reduces symptoms. If the test is successful, the patient may choose to have the device implanted.
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 can be made at the doctor’s office with a programming device that sends a radio signal through the skin to the neurostimulator. Another programming device is given to the patient to further adjust the level of stimulation, if necessary. The system can be turned off at any time.
Possible adverse effects include the following:
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.