and disabilities, such as insomnia, falls, depression, caregiving, and nursing-home placement.10,21 The indirect costs of UI are associated with a significant decrease in health-related quality of life, especially in women. Other “costs” of UI are difficult to measure but are significant. These include the consequences of social withdrawal or isolation resulting from the perceived stigma of UI or from the fear of leakage or odor.22–24
Bladder Anatomy and Physiology
The anatomy and physiology of the bladder are complex, but a basic understanding of these topics is essential in order to appreciate the various types of UI and their management.25,26 Figure 1 illustrates the basic anatomic structures and nervous system “wiring” involved in bladder function, including the detrusor muscle, the internal and external sphincters (bladder neck and proximal urethra, respectively), and their neurological components.
Figure 1
Bladder anatomy and physiology.
Reduced activation of the sympathetic nervous system (SNS) results in relaxation of the detrusor muscle, closure of the sphincter, and bladder filling. When the volume of urine in the bladder reaches 200 to 400 mL, the sensation of urge to void is relayed via the spinal cord to the brain centers. Voluntary voiding (micturition) involves the parasympathetic nervous system and the voluntary somatic nervous system. Influences from these systems cause contractions of the detrusor muscle and corresponding somatic nervous activity, leading to sphincter relaxation.26–31
Etiology and Risk Factors
Multiple factors, including age-related physiological changes, may result in or contribute to the various syndromes of UI. Both genitourinary and non-genitourinary factors may contribute to incontinence in aging patients. Age-related functional changes in the urinary tract (detrusor overactivity, impaired bladder contractility, decreased pressure in urethra closure, atrophy of urethral areas, and prostatic hypertrophy) may contribute to UI.32 In women, risk factors for these genitourinary changes include multiple or complex vaginal deliveries, high infant birth weight, a history of hysterectomy, and physiological changes related to the transition to postmenopause. Smoking, a high body mass index, and constipation are also associated with an increased risk of UI.33–37
Pathophysiological causes of UI include lesions in higher micturition centers, in the sacral spinal cord, and in other neurological areas as well. UI may also be associated with numerous comorbidities, such as Parkinson’s disease, Alzheimer’s disease, cerebrovascular disease,