Describe the types of incontinence, causes, evaluation and management.

Leakage coincides exactly with the rise in pressure, without urgency.

Definition

Urinary incontinence is the involuntary loss of urine that is objectively demonstrable and a social or hygienic problem. Stress urinary incontinence (sui) is the involuntary leakage of urine on effort or exertion (coughing, sneezing, lifting) due to a rise in intra-abdominal pressure exceeding the urethral closure pressure (urethral sphincter incompetence).

Stress Urinary Incontinence - Mechanism

Types of Urinary Incontinence

• Stress incontinence — leakage on raised intra-abdominal pressure.
• Urge incontinence — leakage preceded by urgency, from an overactive (detrusor) bladder.
• Mixed — features of both stress and urge.
• Overflow — dribbling from a chronically over-distended bladder (retention).
• Continuous (true) — from a fistula (vesicovaginal/ureterovaginal).

Causes / Risk Factors of Sui

Childbirth and pelvic-floor injury (the chief cause — denervation and weakening of the supports), multiparity, menopausal oestrogen deficiency, obesity, chronically raised intra-abdominal pressure (chronic cough, constipation), genital prolapse and previous pelvic surgery.

Pathophysiology

Continence depends on the urethral closure pressure exceeding the bladder pressure. Sui results from urethral hypermobility (loss of the supports of the bladder neck, so that a rise in intra-abdominal pressure is transmitted unequally to the bladder but not the urethra) and/or intrinsic sphincter deficiency (a weak urethral sphincter), allowing leakage when abdominal pressure rises.

Evaluation

• History — circumstances, frequency, severity and impact; a bladder diary.
• Examination — demonstrate leakage on the cough stress test, assess prolapse and pelvic-floor tone; a Q-tip test for urethral hypermobility.
• Investigations — urinalysis/culture (exclude infection), a pad test, post-void residual urine, and urodynamic studies (to confirm sui and exclude detrusor overactivity before surgery); cystoscopy if indicated.

Management

• Conservative (first line) — pelvic-floor muscle (Kegel) exercises, weight reduction, treatment of cough/constipation, bladder training, vaginal oestrogen in post-menopausal women, and a continence pessary; duloxetine in selected cases.
• Surgical — for failure of conservative treatment: the mid-urethral sling (tension-free vaginal tape, TVT / transobturator tape, TOT) is the standard, and Burch colposuspension is an abdominal alternative; periurethral bulking agents for the frail.

WHY Stress Incontinence Is a Mechanical Failure

The key to understanding stress urinary incontinence is why the leak occurs on coughing but not at rest — which reveals it as a mechanical, not a bladder, problem. Continence during a rise in intra-abdominal pressure depends on the bladder neck and proximal urethra being held in their normal position above the pelvic floor, so that any pressure transmitted to the bladder is transmitted equally to the urethra, and the pressure gradient is unchanged. The urethra is supported by the pubourethral ligaments and the endopelvic fascia, resting on the hammock of the levator ani. When these supports are damaged — typically by childbirth, and unmasked later by the oestrogen loss of the menopause — the bladder neck becomes hypermobile and descends below the pelvic floor when the woman coughs, so that the abdominal pressure is transmitted to the bladder but not to the urethra: the intravesical pressure momentarily exceeds the urethral closing pressure, and urine escapes. Hence the leak is painless, immediate, small in volume, coincident with the cough or sneeze, and unaccompanied by urgency. Understanding that this is a failure of support, not of the bladder muscle, explains why the surgical cure is to restore support beneath the mid-urethra, and why it is quite different from urge incontinence.

WHY It Must Be Distinguished from Urge Incontinence

A distinction of great practical importance is why stress and urge incontinence must be separated before any treatment is offered — because their treatments are entirely different and each is useless (or harmful) for the other. In stress incontinence, urine leaks with a rise in abdominal pressure (coughing, sneezing, laughing, lifting), there is no warning, no urgency, and the volume lost is small — the problem is a failure of urethral support. In urge incontinence (overactive bladder/detrusor overactivity), the woman feels a sudden, overwhelming, uncontrollable need to void and leaks a large volume on the way to the toilet, with frequency and nocturia — the problem is an unstable, involuntarily-contracting detrusor. The treatments follow accordingly: stress incontinence is treated by pelvic-floor (Kegel) exercises, weight loss, and — if these fail — surgery to support the mid-urethra (a mid-urethral sling, or a Burch colposuspension); urge incontinence is treated by bladder training and antimuscarinic drugs or mirabegron. Operating on a woman whose real problem is an overactive bladder will not cure her and may make her worse. Many women have mixed incontinence, and urodynamic studies are used where the picture is unclear.

• Stress incontinence: involuntary leakage on a rise in intra-abdominal pressure (cough, sneeze, laugh, lift) — no urgency, small volume.
• Cause: loss of support to the bladder neck and urethra (childbirth, menopause, obesity, chronic cough) → urethral hypermobility.
• Distinguish from urge incontinence (detrusor overactivity: sudden urgency, large-volume leak, frequency, nocturia) — the treatments are entirely different.
• Assess with a stress test, Q-tip test, pad test and urodynamics where the picture is mixed or unclear.
• Treat with pelvic-floor (Kegel) exercises, weight loss and local oestrogen first; surgery — mid-urethral sling (TVT/TOT) or Burch colposuspension — if these fail.