What Causes Urinary Incontinence?
There are many possible causes for being incontinent of urine, and sometimes several causes are occurring at the same time. Diagnosis and therapy are more difficult when more than one cause is present, but the cause or causes of incontinence must be identified to provide effective treatment.
Stress incontinence occurs during physical activity; urine leaks out of the body when the abdominal muscles contract, leading to an increase in intra-abdominal pressure (for example, when sneezing, laughing, or even standing up from a seated position). Stress incontinence is most commonly caused when the urethra (the tube from the bladder to the outside of the body) is hypermobile because of problems with the muscles of the pelvis. A less common cause of stress incontinence is a muscle defect in the urethra known as intrinsic sphincter deficiency. The sphincter is a muscle that closes off the urethra and prevents urine from leaving the bladder and passing through the urethra to the outside of the body. If this muscle is damaged or deficient, urine can leak out of the bladder. Some people may have both.
Stress incontinence is the most common type of bladder control problem in younger and middle-aged women. In some cases, it is related to pregnancy and childbirth. It may also begin around the time of menopause. Stress incontinence affects 15% to 60% of women and can affect young and older people. It is especially common in young female athletes who have never given birth, and it occurs while they are participating in sports.
People with urge incontinence cannot hold their urine long enough to get to the toilet in time; it is also called an overactive bladder. Healthy people can have urge incontinence, but it is often found in elderly people or in those who have diabetes, stroke, Alzheimer's disease, Parkinson's disease, or multiple sclerosis.
Urge incontinence occurs due to overactivity of the bladder wall muscle (the detrusor). Urge incontinence may be caused by a problem with the muscle, with the nerves that control the muscle, or both. If the cause is unknown, it is called idiopathic urge incontinence. Overactive bladder, or urge incontinence, without neurologic causes is called detrusor instability, meaning the muscle itself contracts inappropriately.
Risk factors for urge incontinence include aging, obstructions to urine flow (such as an enlarged prostate), and consumption of so-called bladder irritants (such as coffee, tea, colas, chocolate, and acidic fruit juices).
Mixed incontinence is caused by a combination of stress and urges incontinence. In mixed incontinence, the muscle controlling the outflow of the bladder (the sphincter) is weak, and the detrusor muscle is overactive. Common combinations involve hypermobile urethra and detrusor instability.
Overflow incontinence occurs because the bladder is too full and urine passively leaks or overflows through the urinary sphincter. This can occur if the flow of urine out of the bladder is constricted or blocked (bladder outlet obstruction), if the bladder muscle has no strength (detrusor atony), or if there are neurologic problems. Common causes of bladder outlet obstruction in men include benign prostatic hyperplasia (BPH or nonmalignant enlargement of the prostate gland), prostate cancer, bladder (vesical) neck contracture (narrowing of the outlet from the bladder due to scarring or excess muscle tissue), and urethral narrowing (strictures). Bladder outlet obstruction can occur in women with significant pelvic organ prolapse (such as a prolapsed uterus). It may even occur after surgery to correct incontinence (such as the sling or bladder neck suspension procedures); this is called iatrogenic-induced overflow incontinence.
Some common neurologic causes of overflow incontinence include herniated lumbar disc, diabetes-related bladder problems, and other nerve problems (peripheral neuropathy). Less common causes of overflow incontinence include AIDS, neurosyphilis, and genital herpes affecting the perineal area (perineal neurosyphilis).
This type of incontinence occurs when a person is unable to reach the toilet in time due to a physical or mental impairment. For example, a person with severe arthritis may not be able to unbutton his or her pants quickly; also someone with Alzheimer's disease or another type of brain dysfunction may not be able to plan a trip to the bathroom.
Conditions that can worsen or contribute to the different types of incontinence include constipation or stool impaction, diabetes, hypertension, tobacco use, and obesity. Further, taking certain medications (such as some antidepressants, estrogens, diuretics, and sleep medications) may worsen incontinence.
An infrequent cause of bladder incontinence (usually acute) is a condition termed cauda equina syndrome. It is caused by significant narrowing of the spinal canal that may be caused by trauma, disc herniation, spinal tumors, inflammation, infections, or after spinal surgery. The incontinence often occurs acutely and may be accompanied by bowel incontinence, groin numbness, and loss of strength and/or sensation in the lower extremities. This condition is a medical emergency; if pressure on the nerves is not removed quickly (within about 48 hours of initial symptoms), permanent nerve damage with function loss may occur. Most clinicians suggest that the earliest interventions have the best outcomes.