Dr. med. Dirk Manski

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Stress Urinary Incontinence in Women: Epidemiology and Etiology

Definition of stress urinary incontinence

The International Continence Society (ICS) defines urinary incontinence as "the complaint of any involuntary loss of urine". Stress urinary incontinence is urine leakage, which is associated with increased abdominal pressure and insufficient urethral sphincter mechanism. The main symptom of stress incontinence is the loss of urine on exertion, sneezing, or coughing.

Epidemiology of stress urinary incontinence

Vaginal deliveries are a risk factor for stress urinary incontinence:

The prevalence of incontinence in nulliparous women is around 10%, after cesarean section 16%, and in women with vaginal deliveries up to 21%. Comparative studies between cesarean sections and vaginal deliveries found a different prevalence of stress incontinence: 7% (cesarean sections) vs. 12% (vaginal deliveries).

Further risk factors:

Age [see the following table], pelvic surgery, adipositas, COPD, and estrogen deficiency.

Prevalence of urinary incontinence.
Age Women Men
15–44 years 5–7% 3%
45–64 years 8–15% 3%
>65 years 10–20% 7–10%

Etiology and Pathogenesis of Stress Urinary Incontinence

Components of the bladder sphincter mechanism:

Components of the bladder sphincter are the urethral closure pressure caused by the sphincter muscles and active and passive pressure transmission during the elevation of abdominal pressure.

Urethral closure pressure:

Urethral closure pressure is mainly created by the external sphincter muscle (striated muscle) and internal sphincter muscle (smooth muscle) [see section bladder anatomy].

Passive pressure transmission:

If the abdominal pressure rises, additional pressure is transmitted on the bladder sphincter without muscle contraction of the pelvic floor. Passive pressure transmission is enabled by the connective tissue suspension of the urethra, bladder, and vagina.

Active pressure transmission:

If the abdominal pressure rises, contraction of the striated muscles of the pelvic floor and bladder sphincter causes an increase in urethral closure pressure.

Causes of Stress Urinary Incontinence:

Any defect causing a reduced urethral closure pressure or impaired pressure transmission with rising abdominal pressure will cause stress urinary incontinence. The most common causes of stress incontinence are a hypermobile urethra and an intrinsic sphincter deficiency (hypotonic urethra).

Hypermobile urethra:

The caudal displacement of the urethra due to rising abdominal pressure into the extra-abdominal compartment leads to a lack of passive pressure transmission, opening of the bladder neck, and, thus, stress urinary incontinence.

The stability of the suburethral connective tissue is a crucial factor for continence under stress. Vaginal deliveries increase the risk of stress urinary incontinence due to damage to the connective tissue, muscle tearing, and the innervation of the pelvic floor and sphincter muscles. The defects also lead to pelvic floor deficiency and prolapse of the pelvic organs.

Pelvic organ prolapse is a clinical sign of stress urinary incontinence but may also mask incontinence. The prolapse may cause kinking and obstruction of the urethra. An excessive kinking of the urethra may lead to residual urine and urinary retention. After correction of prolapse, incontinence may become clinically relevant. The effect of hysterectomy on stress incontinence is controversial.

Intrinsic sphincter deficiency :

Insufficiency of the urethral sphincter, regardless of the cause, is called intrinsic sphincter deficiency.

Chronic elevated abdominal pressure:

Diseases or circumstances that elevate the abdominal pressure aggravate existing stress urinary incontinence, e.g., COPD, obesity, or carrying heavy loads.

Integral theory of stress urinary incontinence by Petros and Ulmsten:

The integral theory of stress urinary incontinence by Petros and Ulmsten relates symptoms to anatomical defects of the pelvic region. The vagina acts like a hammock under the urethra and bladder and plays a central role in pressure transmission and in preventing urge symptoms. The proximal urethra is the zone of critical elasticity; this elasticity is essential for bladder filling. Scarring of the proximal urethra causes urgency. Depending on the location of the pelvic floor defects, various symptoms and therapeutic consequences may be distinguished, see the following table:

Integral theory of stress incontinence (Petros and Ulmsten, 1990): description of anatomical defects with clinical symptoms and therapeutic consequences.
Level III Level II Level I
Location Lesion between the bladder neck and symphysis Lesion between the bladder neck and cervix or hysterectomy scar Lesion between cervix or hysterectomy scar and os sacrum
Defective structures Ligamentum pubourethrale, pubococcygeus muscle Arcus tendinous fascia pelvis Cardial ligaments and uterosacrcal ligaments
Signs and Symptoms Stress incontinence Stress incontinence, cystocele Residual urine, urge symptoms, rectocele or enterocele
Treatment Pubovaginal slings (TVT, TOT) Colporrhaphia anterior Colporrhaphia posterior, sacrocolpopexy

Index: 1–9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


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  Deutsche Version: Belastungsinkontinenz der Frau