Overactive Bladder (OAB)

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Overactive bladder (OAB) facts

  • Overactive bladder is an involuntary and sudden contraction of the muscle in the wall of the urinary bladder.
  • Overactive bladder can also result in urinary incontinence, otherwise termed urge incontinence (wet OAB).
  • Overactive bladder is not a normal part of aging.
  • OAB affects both men and women and can significantly impact the quality of life.
  • Many treatments are available for overactive bladder, including pelvic-muscle strengthening, behavioral therapies, medications, neuromodulation, and surgery.

What is an overactive bladder?

Overactive bladder (OAB) is a condition that is characterized by sudden, involuntary contraction of the muscle in the wall of the urinary bladder. This results in a sudden and unstoppable need to urinate (urinary urgency), even though the bladder may only contain a small amount of urine. Key features are the sudden urge to void along with urinary frequency (voiding < 2 hour intervals). Irritating fluids, such as caffeinated beverages (coffee, tea), spicy foods, and alcohol can worsen the symptoms. It is common for those affected to compensate for OAB by toilet mapping, fluid restriction, and timed voiding. There is no pain, burning, or blood in the urine with OAB.

Overactive bladder coupled with urinary leakage (inability to suppress the urge to void) is also referred to as urge incontinence and is a form of urinary incontinence (unintentional loss of urine). Another common type of urinary incontinence is called stress incontinence, which is caused by anatomic weakness in the structures that prevent the bladder from leaking. Such patients will leak with coughing, straining, jumping, or other physical activity that contracts the abdominal muscles. Treatment for stress incontinence is very different than urge incontinence. Stress incontinence is treated with methods that support the weakened support structures, including Kegel exercises, urethral bulking agents, and urethral mesh surgery to strengthen the pelvic floor muscles. In some, there can be a combination of urge and stress incontinence (mixed incontinence). In general, urinary incontinence is more common in women compared to men.

SymptomsOABStress Urinary Incontinence
Urgency (Strong, Sudden Desire to Void)YesNo
Frequency With Urgency (≥ 8 Times/24 Hours)YesNo
Leaking During Physical Activity (For Example, Coughing, Sneezing, Lifting)NoYes
Amounts of Urinary Leakage With Each Episode of IncontinenceLarge (If Present)Small
Ability to Reach the Toilet in Time Following Urge to VoidOften NoYes
Nocturia (Waking to Pass Urine at Night)UsuallySeldom

The overall prevalence of overactive bladder is 13.9%, affecting men and women with equal frequency. Although it can happen at any age, overactive bladder is especially common in older adults. Overactive bladder should not be considered a normal part of aging. The prevalence under the age of 50 is < 10%. After age 60, the prevalence increases to 20%-30%. It is estimated that 60% of patients have dry OAB (no leakage) while 40% have wet OAB.

What are the causes of overactive bladder?

Overactive bladder is typically caused by early, uncontrolled contraction (spasms) of the bladder muscle (detrusor muscle), resulting in an urge to urinate. Overactive bladder is primarily a problem of the nerves and muscles of the bladder that allow for early contraction during the normal relaxation phase of bladder filling. The bladder's contraction in response to filling with urine is one the steps in the normal process of urination. The contraction and relaxation of the detrusor muscle is regulated by the nervous system. Approximately 300 cc of urine in the bladder can signal the nervous to trigger muscles of the bladder to coordinate urination. Voluntary control of the sphincter muscles at the opening of the bladder can hold the urine in the bladder for longer. Up to 600 cc of urine can be contained in a normal adult bladder. For those with OAB, the bladder capacity is typically low (< 200cc).

Overactive bladder typically results from inappropriate contraction of the detrusor muscle regardless of the amount of urine. This could result from problems of the nervous system or other causes.

The common abnormalities of the nervous system that cause overactive bladder are

Other causes include urinary tract infection, bladder stones, urethral strictures, benign prostatic enlargement (BPH), or bladder tumors.

Frequently, no apparent cause of overactive bladder can be determined (idiopathic overactive bladder).

Medically Reviewed by a Doctor on 5/26/2015

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