Stress incontinence

Alternative names:

fallen bladder; loss of pelvic support; urinary incontinence

Definition:

An involuntary loss of urine that occurs at the same time that internal abdominal pressure is increased, as with coughing, sneezing, laughing, or physical activity.

Causes, incidence, and risk factors:

NORMAL URINATION:
The ability to hold urine and maintain continence is dependent on normal function of the lower urinary tract, the kidneys, and the nervous system. Additionally, the person must possess the physical and psychological ability to recognize and appropriately respond to the urge to urinate.

The process of urination involves two phases: 1) the filling and storage phase, and 2) the emptying phase. Normally during the filling and storage phase, the bladder begins to fill with urine from the kidneys. The bladder stretches to accommodate the increasing amounts of urine. The first sensation of the need to urinate occurs when approximately 200 milliliters of urine is stored. The healthy nervous system will respond to this stretching sensation by alerting you to the need to urinate while also allowing the bladder to continue to fill. The average person can hold approximately 350 to 450 milliliters of urine. The ability to fill and store urine properly requires a functional sphincter (muscle controlling output of urine from bladder) and a stable bladder wall muscle (detrusor).

The emptying phase requires the ability of the detrusor muscle to appropriately contract to force urine out of the bladder. Additionally, the body must also be able to simultaneously relax the sphincter to allow the urine to pass out of the body.

STRESS INCONTINENCE:
Stress incontinence is a storage problem in which the strength of the urethral sphincter is diminished, and the sphincter, reacting to the increased pressure from the abdomen, is not able to prevent urine flow. Storage problems may occur as a result of weakened pelvic muscles that support the bladder, or because of malfunction of the urethral sphincter. Prior trauma to the urethral area, neurological injury, and some medications may weaken the urethral closure. Sphincter weakness may occur in men following prostate surgery or in women after pelvic surgery. Stress incontinence may be seen in women who have had multiple pregnancies, or who have pelvic prolapse (protrusion of the bladder, urethra, or rectal wall into the vaginal space), with a cystocele, cystourethrocele, or rectocele. Additionally, women with low estrogen levels may have stress incontinence due to decreased vaginal muscle tone.

Studies have documented that about 50% of all women have occasional incontinence, and as many as 10% have regular incontinence. Nearly 20% of women aged 75 or over experience daily incontinence. The risk increases with advancing age, obesity, chronic bronchitis, asthma, and childbearing.