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Urinary incontinence may be caused by anatomic, physiologic, and/or pathologic factors. Often several interacting factors contribute to the condition, especially in the elderly. Urinary incontinence may be acute and transient (as in pregnancy or during a urinary tract infection) or chronic, and is classified based on symptoms or cause.
Urinary incontinence results when the pressure in the bladder exceeds that of the urethra. Uninhibited contractions of the detrusor are a frequent cause, but incontinence may also be the result of inappropriate relaxation of the urethra. The term "overactive bladder" is used to describe involuntary contractions of the detrusor muscle. The symptoms associated with overactive bladder are urge urinary incontinence, urgency, and frequency. Urgency is classified into two types:
- motor urgency - which arises from overactive detrusor function
- sensory urgency - in which the sensation of urge is not associated with detrusor contractions. Urge urinary incontinence is one of the most disturbing symptoms of overactive bladder and is characterized by a strong desire to void that is associated with an involuntary loss of urine.
Two primary bladder abnormalities can cause overactive bladder and urge urinary incontinence. The more common is detrusor instability, in which patients have involuntary detrusor contractions that are nonneuropathic or of unknown origin. There is no general consensus regarding the cause of detrusor instability although both a myogenic and neurologic basis have been suggested. The other common cause of overactive bladder is detrusor hyperreflexia-characterized by involuntary detrusor contractions resulting from damage to the nervous system from known neurologic conditions, such as stroke, spinal cord lesions, or multiple sclerosis.
In addition to urge urinary incontinence, other urinary incontinence subtypes include stress, mixed (urge and stress), overflow, functional, and reflex incontinence. Stress incontinence is typified by involuntary loss of urine during coughing, sneezing, laughing, or during physical activities that increase intra-abdominal pressure. Mixed incontinence is not unusual, particularly in older women; generally one symptom (either urge or stress incontinence) is predominant and more bothersome to the patient. Overflow incontinence is the involuntary loss of urine as a result of an
over distended bladder, which may occur in cases of urinary obstruction. When incontinence is caused by chronic impairment of physical and/or cognitive functioning, the term "functional incontinence" is used. "Reflex incontinence" describes urine loss that occurs without any warning or sensory awareness.
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