|Classification and external resources|
Overactive bladder (also known as OAB, or Overactive Bladder Syndrome) is a urological condition related to problems with urination. It is an often debilitating and stigmatised syndrome that is not life-threatening and does not always require treatment.
The hallmark symptom of overactive bladder is urgency, but the diagnosis also includes frequent urination, frequent interruptions of sleep because of the need to urinate (nocturia), and urinating unintentionally followed by an urge to continue (urge incontinence). Overactive bladder has many causes which can include diseases such as diabetes, medications such as diuretics, or lifestyle choices such as excessive consumption of caffeine or alcohol. Bothersome urinary symptoms that are related to neurological conditions such as multiple sclerosis are generally treated differently from overactive bladder in people who do not have neurological problems.
People with the condition often have the symptoms for a long time before seeking medical care, and the condition is sometimes identified by caregivers rather than the person with the symptoms. The condition is similar to polyuria and polydipsia and is distinguished from other conditions because the amount of urine passed when there is an urgent need to urinate is relatively small with overactive bladder. Pain while urinating suggests that there is a problem other than overactive bladder.
Management of overactive bladder is addressed in terms of quality of life since it is not a life-threatening problem, and treatment is not always necessary if the treatment would cause more discomfort than the symptoms. The person often keeps a diary tracking urination to help determine whether treatments are working. If the person's quality of life is impaired and behavioral therapies do not work, medications such as anti-muscarinic drugs are used to control the symptoms. Invasive treatment such as surgery to modify spinal nerves is possible but is avoided because of the potential for permanent damage and the nonthreatening nature of the disorder. Overactive bladder is not rare, estimates in population studies vary widely and suggest that from 7-27% of men and 9-43% of women experience these symptoms. Other studies suggest that the condition is more common in men. Many people who have problems have them for less than a year.
There is some controversy about the classification and diagnosis of OAB. Some sources classify overactive bladder into "wet" and "dry" variants depending on whether it is an urgent need to urinate or if it includes incontinence. Wet variants are more common than dry variants. The distinction is not absolute, one study suggested that many classified as "dry" were actually "wet" and that patients with no history of any leakage may have had other syndromes.
Signs and Symptoms
Overactive bladder is characterized by a group of four symptoms: urgency, urinary frequency, nocturia, and urge incontinence. Urge incontinence is not present in the "dry" classification.
Urgency is considered the hallmark symptom of OAB, but there are no clear criteria for what constitutes urgency and studies often use other criteria. Urgency is currently defined by the International Continence Society (ICS), as of 2002, as "Sudden, compelling desire to pass urine that is difficult to defer." The previous definition was "Strong desire to void accompanied by fear of leakage or pain." The definition does not address the immediacy of the urge to void and has been criticized as subjective.
Urinary frequency is considered abnormal if the person urinates more than eight times in a day. This frequency is usually monitored by having the patient keep a voiding diary where they record urination episodes. The number of episodes varies depending on sleep, fluid intake, medications, and up to seven is considered normal if consistent with the other factors.
Nocturia is a symptom where the person complains of interrupted sleep because of an urge to void and, like the urinary frequency component, is affected by similar lifestyle and medical factors. Individual waking events are not considered abnormal, one study in Finland established two or more voids pper night as affecting quality of life.
Urge incontinence is a form of urinary incontinence characterized by the involuntary loss of urine occurring for no apparent reason while feeling urinary urgency as discussed above. Like frequency, the person can track incontinence in a diary to assist with diagnosis and management of symptoms. Urge incontinence can also be measured with pad tests, and these are often used for research purposes. Some people with urge incontinence also have stress incontinence and this can complicate clinical studies.
The etiology of OAB is unclear, and indeed there may be multiple causes. It is often associated with overactivity of the Detrusor urinae muscle, a pattern of bladder muscle contraction observed during urodynamics. It is also possible that the increased contractile nature originates from within the urothelium and lamina propria, and abnormal contractions in this tissue could stimulate dysfunction in the detrusor or whole bladder. Treatments for OAB are usually synonymous with treatments for detrusor overactivity. OAB is distinct from stress urinary incontinence, but when they occur together, the condition is usually known as mixed incontinence.
Diagnosis of OAB is made primarily by ruling out other causes of overactivity of the bladder such as an infection or bladder tumor. The diagnosis is confirmed by cystometry. Additionally, urine culture may be done to rule out infection. The frequency/volume chart may be maintained and cystourethroscopy may be done to exclude tumor and kidney stones. If there is an underlying metabolic or pathologic condition that explains the symptoms, the symptoms may be considered part of that disease and not OAB.
OAB causes similar symptoms to some other conditions such as urinary tract infection (UTI), bladder cancer, and benign prostatic hyperplasia (BPH). Urinary tract infections often involve pain and hematuria (blood in the urine) which are typically absent in OAB. Bladder cancer usually includes hematuria and can include pain, both not associated with OAB, and the common symptoms of OAB (urgency, frequency, and nocturia) may be absent. BPH frequently includes symptoms at the time of voiding as well as sometimes including pain or hematuria, and all of these are not usually present in OAB.
Treatment for OAB includes nonpharmacologic methods such as lifestyle modification (fluid restriction, avoidance of caffeine), bladder retraining or may involve the use of pharmaceutical agents such as antimuscarinic drugs (e.g., darifenacin, hyoscyamine, oxybutynin, tolterodine, solifenacin, trospium, fesoterodine). β3 adrenergic receptor agonists (e.g., mirabegron), and various devices (Urgent PC Neuromodulation System, InterStim) may also be used. Botulinum toxin A (Botox) is approved by the Food and Drug Administration in adults with neurological conditions, including multiple sclerosis and spinal cord injury. Botulinum Toxin A injections into the bladder wall can suppress involuntary bladder contractions by blocking nerve signals and may be effective for up to 9 months. The growing knowledge of pathophysiology of overactive bladder fuelled a huge amount of basic and clinical research in this field of pharmacotherapy. A surgical intervention involves the enlargement of the bladder using bowel tissues, although generally used as a last resort. This procedure can greatly enlarge urine volume in the bladder.
Studies have shown that few people get complete relief from overactive bladder drugs and that all available drugs are no more than moderately effective. A typical person with overactive bladder may urinate 12 times per day. Medication may reduce this number by 2-3 and reduce urinary incontinence events by 1-2 per day.
Epidemiology and prognosis
Earlier reports estimated that about one in six adults in the United States and Europe had OAB. The prevalence of OAB increases with age, thus it is expected that OAB will become more common in the future as the average age of people living in the developed world is increasing. However, a recent Finnish population-based survey suggested that the prevalence had been largely overestimated due to methodological shortcomings regarding age distribution and low participation (in earlier reports). It is suspected, then, that OAB affects approximately half the number of individuals as earlier reported.
The American Urological Association reports studies showing rates as low as 7% to as high as 27% in men and rates as low as 9% to 43% in women. Urge incontinence was reported as higher in women. Older people are more likely to be affected, and prevalence of symptoms increases with age. Many people with OAB symptoms had those symptoms subside within a year, with estimates as high as 39%, but most have symptoms for several years.
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