Role of cystometry in evaluating patients with overactive bladder.

Overactive bladder (OAB) can be caused by a variety of conditions. We believe that cystometrography (CMG) is an essential part of the diagnostic evaluation, both in defining underlying pathophysiology and directing treatment. Essential to the diagnosis of OAB syndrome is some combination of urinary frequency, urgency, urge incontinence, and pain. CMG can be thought of simply as a provocative test to determine whether bladder filling, involuntary detrusor contractions, or low bladder compliance in fact reproduces any of these symptoms, and whether the symptoms abate when the bladder is empty or when the pressure decreases. At another level, the CMG has been likened to "the reflex hammer" of the lower urinary tract and, as such, provides important neurologic information. Finally, the voiding phase of the CMG is an essential component of the detrusor pressure/uroflow study, which is the only accurate method of diagnosing urethral obstruction and impaired detrusor contractility. Both of these conditions can coexist with detrusor overactivity. The treatment of OAB depends on the underlying cause. We believe that only by understanding the particular cystometric characteristics of patients with OAB can we determine the appropriate treatment. Urodynamic testing should serve as an essential part of therapy and guide future research in diagnosis and management.