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Overactive Bladder

2/1/2017 - Julie Zemaitis DeCesare, MD

Editor:  Christopher M. Zahn, MD

Overactive bladder (OAB) is defined as “urinary urgency, typically accompanied by frequency and nocturia, with and without urge urinary incontinence, in the absence of urinary tract infection or other obvious pathology.” OAB impacts approximately 18 million women per year, and accounts for about 7% of all ambulatory visits made by women.

Normal micturition occurs when the smooth detrusor muscle contracts and triggers an automatic relaxation of the urethral sphincter muscles. In cases of overactive bladder, the detrusor muscle contracts when the bladder is not full, often at random occurrences. This triggers the patient to feel the sudden urge to void with resultant episodic incontinence, although not all women with OAB will have actual urinary leakage. Most patients describe an overwhelming urge to void with difficulty getting to the bathroom in time to void. Frequency and nocturia are also common symptoms.

Initial evaluation of this condition includes the following: complete history, bladder diary, physical exam (including the assessment of the pelvic support, urethral mobility, and provoked incontinence), urinalysis, and post void residual. Multichannel urodynamic studies should be reserved for complex cases in which an initial office diagnosis is unclear.

Initial treatment involves non-invasive lifestyle and behavior modifications. These include physical therapy with or without biofeedback, bladder training, and dietary modifications, including fluid restriction, avoidance of caffeine, and weight loss. Timed voids may also decrease episodes of incontinence.

First-line pharmacologic treatment is anti-muscarinic medications. It is reasonable to start with these agents in well-counseled patients who decline behavior or lifestyle modifications. The mechanism of action on the bladder is uncertain. It is generally accepted that these medications inhibit efferent nerves of the bladder. Excessive or discordant release of acetylcholine promotes excessive detrusor contractions and symptoms of overactive bladder. Thus, blockage of acetylcholine will theoretically decrease the detrusor contractions. These medications also increase the storage capacity of the bladder and reduce urgency symptoms. Common agents include propantheline, oxybutynin, and tolterodine tartrate. Side effects are problematic and include dry mouth, constipation, and somnolence. Less common effects include nausea, dry eyes, and headache. There is evidence that these medications only have a minimal effect on the amount of voiding episodes, which is one of the most bothersome symptoms.

Additional treatments have been described for OAB. Botulinum Toxin A injections have shown promise. However, overtreatment can lead to urinary retention. Acupuncture has been effective in clinical applications. Mirabegron is a relatively new pharmacological agent that acts as a B3 receptor agonist, leading to relaxation of the detrusor muscle to increase capacity. The side effect profile is similar to placebo. Nerve modulators, including posterior tibial nerve stimulation and sacral neuromodulation, have also been shown to promote relief from OAB. Neuromodulation is usually reserved for patients with recalcitrant urgency urinary incontinence who have not responded to other measures.

Further Reading:

Urinary incontinence in women. Practice Bulletin No. 155. American College of Obstetricians and Gynecologists. Obstet Gynecol 2015;126:e66–8.

Olivera C, Meriwether K, El-Nashar S, Grimes C, Chen C, Orejuela F, Antosh D. et al. Nonantimuscarinic treatment for overactive bladder: a systematic review. Am Obstet Gynecol 2016;215:34-57.

Initial Approval:  January 2017

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