Urinary control relies on the finely coordinated activities of the smooth
muscle tissue of the urethra and bladder, skeletal muscle, voluntary inhibition,
and the autonomic nervous system.
Urinary incontinence can result from anatomic, physiologic, or pathologic
(disease) factors. Congenital and acquired disorders of muscle innervation
(e.g., ALS, spina bifida, multiple sclerosis) eventually cause inadequate
urinary storage or control.
Acute and temporary incontinence are commonly caused by the following:
- Limited mobility
- Medication side effect
- Urinary tract infection
Chronic incontinence is commonly caused by these factors:
- Birth defects
- Bladder muscle weakness
- Blocked urethra (due to benign prostate hyperplasia, tumor, etc.)
- Brain or spinal cord injury
- Nerve disorders
- Pelvic floor muscle weakness
Of the several types of urinary incontinence, stress, urge, and mixed
incontinence account for more than 90% of cases. Overflow incontinence is more
common in people with disorders that affect the nerve supply originating in the
upper portion of the spinal cord and older men with benign prostate hyperplasia
(BPH). The primary characteristics of these types are as follows:
loss during physical activity that increases abdominal pressure (e.g.,
coughing, sneezing, laughing)
loss with urgent need to void and involuntary bladder contraction (also called detrusor instability)
- Mixed—both stress and urge incontinence
dribbling of urine; bladder never completely empties
Incidence and Prevalence
The U.S. Department of Health and Human Services reported in 1996 that
approximately 13 million people in the United States suffer from urinary
incontinence. The condition is far more prevalent in women than men. In the
general population aged 15 to 64 years old, 10-30% of women versus 1.5-5% of men
are affected. At least 50% of nursing home residents are affected. Of that
number, 70% are women.
Urge incontinence is characterized by a sudden uncontrollable urge to urinate
and frequent urination. It is often necessary to use a bathroom as frequently as
every 2 hours, and bed-wetting is common.
With urge incontinence, the bladder contracts and squeezes out urine
involuntarily. Sometimes a large amount of urine is released. Accidental
urination can be triggered by
- sudden change in position or activity,
- hearing or touching running water, and
- drinking a small amount of liquid.
Two bladder abnormalities commonly cause urge incontinence. The most common
is a neurogenic bladder (overactive type), which is caused by brain or
spinal cord injury or disease that interrupts nerve conduction above the sacrum
and results in loss of bladder sensation and motor control. There are several
neurological diseases and disorders associated with a neurogenic bladder,
including the following:
- Alzheimer's disease
- Diabetes mellitus
- Multiple sclerosis
- Parkinson's disease
- Ruptured intervertebral disk
- Traumatic brain or upper spinal-cord injury
- Tumors located in the brain or spinal cord
Chronic urinary tract infection, bladder stones, and polyps can irritate the
bladder and cause detrusor muscle instability, leading to urge
incontinence. Detrusor muscle instability without a known cause is also common.
It has been suggested that, in these cases, an unidentified dysfunction in
muscle or nerve tissue is responsible.
Diuretics increase the amount of urine released from the body. They
are commonly used to treat hypertension (high blood pressure) and edema (fluid
build-up in the body). Rapid-acting diuretics increase the urgency and frequency
of urination in some people, especially the elderly and bedridden. Modifying
dosage may alleviate symptoms.
People with stress incontinence lose urine involuntarily during physical
activities that put pressure on the abdomen. This type of incontinence is often
seen in women after they reach middle age. A weak pelvic floor and a poorly
supported uretheral sphincter cause stress incontinence. Activities commonly
associated with stress incontinence include the following:
- Rising from a chair or bed
Stress incontinence occurs when the bladder neck and urethra do not close
properly. When these structures move down and bulge (herniate) through weakened
pelvic floor muscles, they are said to be hypermobile. Herniation, or
cystocele, changes the angle of the urethra, which causes it to remain open
and allow urine to leak out. There are three classifications of stress
Type I — The bladder neck and urethra are open and slightly
hypermobile, and the urethra moves down less than 2 cm when stressed. Type I
patients have little or no sign of cystocele.
Type II — The bladder neck and urethra are closed and hypermobile, and
the urethra moves down more than 2 cm when stressed. Patients who have cystocele
inside the vagina have Type IIA stress incontinence. When cystocele is outside
the vagina, it is classified as Type IIB.
Type III (severe) — The urethral sphincter is very weak (called
intrinsic sphincter deficiency).
In this condition, patients never feel the urge to urinate, the bladder never
empties, and small amounts of urine leak continuously. Overflow incontinence is
prevalent in older men with an enlarged prostate and is rare in women.
Signs and Symptoms
Symptoms include the following:
- Bladder never feels empty
- Frequent nighttime urinate
- Inability to void, even when the urge is felt
- Urine dribbles, even after voiding
Conditions that may lead to overflow incontinence include the following:
- Benign prostate hyperplasia (BPH; enlarged prostate)
- Neurogenic bladder (underactive)
- Urinary stones
Overflow incontinence is a common symptom of benign prostate hyperplasia.
The prostate is located directly beneath the bladder and in front of the rectum.
The upper portion of the urethra passes through the prostate, so when the gland
becomes enlarged it may obstruct the passage of urine through the urethra.
Neurogenic bladder associated with overflow incontinence is caused by
the loss of sensation of bladder fullness due to damage or obstruction of sacral
nerves (located in the five vertebrae above the sacrum). This may result from
certain types of surgery on the spinal cord, sacral spinal tumors, or birth
defects. It also may be a complication of various diseases such as diabetes
mellitus and polio.
Tumors and urinary stones can block the urethra and cause
Diagnosis involves identifying the type and severity of the disorder.
Depending on the information gained from a standard medical history and physical
examination, urologists may prescribe one or more diagnostic procedures to make
an accurate diagnosis and develop an effective treatment plan.