Bladder storage and bladder emptying involve the interplay of the sympathetic and parasympathetic nervous systems. The modulation of these activities appears to be inﬂuenced by a variety of nonadrenergic, noncholinergic neurotransmitters and neuropeptides, which fine tune the system at various facilitative and inhibitory levels in the spinal cord and higher areas of the central nervous system (5–7). Neuropathology at almost any level of the neurourologic axis can have an adverse effect on lower urinary tract function.
Micturition Micturition is triggered by the peripheral nervous system under the control of the central nervous system. It is useful to consider this event as occurring at a micturition threshold, a bladder volume at which reﬂex detrusor contractions occur. The threshold volume is not fixed; rather, it is variable and can be altered depending on the contributions made by sensory afferents from the perineum, bladder, colon, rectum, and input from the higher centers of the nervous system. The micturition threshold is, therefore, a ﬂoating threshold that can be altered or reset by various inﬂuences.
The spinal cord and higher centers of the nervous system have complex patterns of inhibition and facilitation. The most important facilitative center above the spinal cord is the pontine-mesencephalic gray matter of the brainstem, often called the pontine micturition center, which serves as the final common pathway for all bladder motor neurons. Transection of the tracts below this level leads to disturbed bladder emptying, whereas destruction of tracts above this level leads to detrusor overactivity. The cerebellum serves as a major center for coordinating pelvic ﬂoor relaxation and the rate, force, and range of detrusor contractions, and there are multiple interconnections between the cerebellum and the brainstem reﬂex centers. Above this level, the cerebral cortex and related structures exert inhibitory inﬂuences on the micturition reﬂex. Thus, the upper cortex exerts facilitative inﬂuences that release inhibition, permitting the anterior pontine micturition center to send efferent impulses down the complex pathways of the spinal cord, where a reﬂex contraction in the sacral micturition center generates a detrusor contraction that causes bladder emptying.
A normal lower urinary tract is one in which the bladder and urethra store urine without pain until a socially acceptable time and place arises, at which point voiding occurs in a coordinated and complete fashion. Lower urinary tract disorders include disorders of storage (such as urinary incontinence), emptying (such as urinary hesitancy and retention), and sensation (such as urgency or pain). Current definitions for these disorders are depicted in Table 26.1.
Definitions Defining urinary incontinence would seem an easy task: women who leak urine must be “incontinent.” A joint report from the International Urogynecological Association and the International Continence Society made recommendations on the terminology of female pelvic ﬂoor dysfunction in an attempt to update the definitions by a female-specific approach and clinically based consensus. This report defined incontinence as “the complaint of any involuntary leakage of urine” (8). This definition does not take into account the wide variation in this symptom and the disruption it causes. For example, half of young nulliparous women report occasional minor urine leakage; for most this is neither a bother nor a symptom for which they would seek treatment. At the other extreme, 5% to 10% of adult women have severe leakage daily. These women often dramatically alter their lives because of leakage, curtailing activities, social outings, and intimacy. Many suffer marked deterioration in self-esteem. In between these two extremes lies another one-third of adult women who report leakage at least weekly, but without the same degree of life-altering severity as the women previously noted.