There is very little information about what is “normal” in terms of voiding frequency. Overactive bladder (OAB) is frequently defined in studies of pharmacologic agents as more than eight voids per 24 hours, a definition that was based on the 95th percentile of voids in a small sample of Scandinavian women (13). Data from a broader sample of women in the United States suggest that the median number of voids per day is eight, and 95% of so-called normal women void 12 or fewer times per day (14).
Overactive detrusor function is defined as a urodynamic diagnosis characterized by involuntary detrusor contractions during the filling phase, which may be spontaneous or provoked. It is divided into neurogenic detrusor overactivity, resulting from a relevant neurologic condition and idiopathic detrusor overactivity, when there is no clear cause (15).
The term overactive bladder syndrome is defined as urinary urgency, usually accompanied by frequency and nocturia, with or without urgency urinary incontinence, in the absence of urinary tract infection or other obvious pathology (8). It is often referred to as OAB-dry when women with these symptoms do not leak urine, and OAB-wet when it is accompanied by incontinence. It is important to note that a woman with severe urgency and a sense of impending leakage who remains dry may have the exact same bladder pathology as one with severe urgency and concomitant leakage. A woman with a strong urethral sphincteric mechanism may be able to avoid leakage during uninhibited bladder contractions, and although one with a strong sphincter may remain dry, she still may be disturbed by the urgency and impending sense of leakage.
Mixed Incontinence As implied by the name, women with mixed incontinence have symptoms of both stress and urge urinary incontinence. Younger women are more likely to have stress incontinence alone, whereas in older women mixed and urge incontinence predominate. In a review of 15 population-based studies of women of all ages with urinary incontinence, a median of 49% (range 24% to 75%) had stress urinary incontinence, 21% (range 7% to 49%) had urge urinary incontinence, and 29% (range 11% to 61%) had mixed urinary incontinence (16).
Functional incontinence is more common in elderly women and refers to incontinence that occurs because of factors unrelated to the physiologic voiding mechanism. A woman who cannot get to the bathroom quickly enough may often become incontinent. Functional incontinence can be related to such factors as decreased mobility, musculoskeletal pain, or poor vision. Factors leading to transient urinary incontinence are, as the name implies, medically reversible conditions. A useful mnemonic to help remember these factors is DIAPPERS (17,18) (Table 26.2). These factors argue strongly for the inclusion of a thorough medical evaluation as part of the workup of any patient with urinary incontinence.
Table 26.2 Reversible Causes of Incontinence
From Resnick NM, Yalla SV. Management of urinary incontinence in the elderly. N Engl J Med 1985;313: 800–805, with permission.
to the outside (19). Such cases are diagnosed at birth. Before the advent of modern reconstructive surgery, these infants usually died very early in life from sepsis.