Stress incontinence is a bladder storage problem in which the strength of the urethral sphincter is diminished, and the sphincter is not able to prevent urine flow when there is increased pressure from the abdomen.

Stress incontinence may occur as a result of weakened pelvic muscles that support the bladder and urethra, or because of malfunction of the urethral sphincter. Prior trauma to the urethral area, neurological injury, and some medications may weaken the urethra.

Sphincter weakness may occur in men following prostate surgery or in women after pelvic surgery. Stress incontinence is often seen in women who have had multiple pregnancies and vaginal childbirths, or who have pelvic prolapse (protrusion of the bladder, urethra, or rectal wall into the vaginal space), with cystocele, cystourethrocele, or rectocele.

Studies have documented that about 50% of all women have occasional urinary incontinence, and as many as 10% have regular incontinence. Nearly 20% of women over age 75 experience daily urinary incontinence.

Stress urinary incontinence is the most common type of urinary incontinence in women. Risk factors for stress incontinence include female sex, advancing age, childbirth, smoking, and obesity. Conditions that cause chronic coughing, such as chronic bronchitis and asthma, may also increase the risk of stress incontinence.

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 ml 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 550 ml of urine. The ability to fill and store urine properly requires a functional sphincter muscle, controlling output of urine from the bladder, and a stable bladder wall muscle (the detrusor muscle).

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.