Pathophysiology: the varieties of bladder overactivity

Overactive bladder (OAB) is the most common term currently used in clinical medicine to describe a complex of lower urinary tract symptoms (LUTS) with or without incontinence. The symptoms usually include urgency, frequency, nocturia, troublesome or incomplete emptying, and, occasionally, pain. Causes of bladder overactivity include neurologic illness or injury, bladder outlet obstruction, urethral weakness, detrusor hyperactivity and impaired contractility in elderly patients, emergence of new voiding reflexes, and so-called idiopathic bladder overactivity. Most clinicians agree that effective treatment for OAB symptoms should be guided by a basic assessment of patients for these contributing factors. However, it is not at all certain that outcomes are significantly improved by diagnostic precision. This is in part because of the ubiquity of LUTS in the setting of the various common lower urinary tract disorders: stress incontinence, outlet obstruction, and neurologic illness or injury. The ubiquity of LUTS would imply that they are caused by common mechanisms and, theoretically at least, would be amenable to a single form of effective therapy. Conversely, the limited kinds and number of LUTS and the limited representation of lower urinary tract structures in the central nervous system may mean that several different causes produce similar symptoms, but these are not amenable to a single form of effective therapy. Future research directions should keep each possible explanation in mind as new knowledge about lower urinary tract function and possible intervention continues to emerge.