Stress urinary incontinence

Definition

• Sudden involuntary leakage of urine during activities that raise intra-abdominal pressure, such as exertion, sneezing, coughing, laughing or straining.
• Urine leaks when the pressure in the bladder exceeds the urethral closure pressure.

Classification

• Pathophysiologically, urethral hypermobility with descent of the bladder neck due to weakened supports is distinguished from intrinsic sphincter deficiency.

Occurrence & epidemiology

Epidemiology

• More than 60% of women experience urinary incontinence during their lifetime, more often after childbirth and with increasing age; in a US survey of over 15,000 women about 25% reported stress-only incontinence.
• Stress urinary incontinence is one of the most common types of incontinence in women.

Aetiopathogenesis

Why stress incontinence develops

• Basic mechanism: the urethral closure pressure falls below the bladder pressure during exertion.
• Structural correlate: the suburethral support from fascia, ligaments, and the levator ani no longer supports the bladder neck.
• Risk factors: vaginal births, macrosomic babies, obesity, chronic cough, oestrogen deficiency, heavy physical labour.

Aetiology and pathogenesis

• The primary support of the bladder neck and urethra is the levator ani muscle complex.
• Risk factors in women include pregnancy, multiple vaginal births, menopause and obesity; further modifiable factors are smoking and chronic constipation.

Clinical features

More facts from the study questions

• Stress incontinence accounts for about half of all cases.
• The mixed form accounts for about one third.
• An intrinsic sphincter deficiency is the correlate of a rigid, hypomobile urethra.
• The underlying mechanism of urge incontinence is involuntary contractions of the bladder muscle (detrusor vesicae muscle) during the filling phase.
• Risk factors for stress incontinence include vaginal births, macrosomic infants, obesity and chronic cough.

• Leakage occurs during activities that raise pressure, such as coughing, sneezing, laughing or exertion.
• Pelvic organ prolapse, common after menopause or childbirth, is often associated with stress incontinence.

Diagnosis

• A bladder diary is a valuable aid; in the cough stress test with a full bladder, leakage from the urethra at the moment of coughing confirms stress incontinence.
• In the Q-tip test, an angle change of 30° or more on straining indicates urethral hypermobility.
• Urodynamic assessment includes post-void residual measurement, urethral pressure profile and leak point pressure; a maximum urethral closure pressure below 20 cmH2O is associated with intrinsic sphincter deficiency.
• An abdominal leak point pressure below 60 cmH2O suggests intrinsic sphincter deficiency or a short functional urethral length, values above 90–100 cmH2O stress incontinence due to hypermobility.
• In the pad test, urine loss is quantified by weighing a pad before and after specified activities; in the one-hour test a weight gain of 1 g is considered significant.

Keep learning in the app

Further reading (selection)

1. StatPearls: Stress Urinary Incontinence (NCBI Bookshelf)
2. Clinical Evaluation of Urinary Incontinence (J Midlife Health 2018, PubMed Central)
3. Relationship between Q-Tip Test and Urethral Hypermobility on Perineal Ultrasound (J Clin Med 2023, PubMed Central)
4. DocCheck Flexikon, Harninkontinenz

Cross-references