Theories of female stress incontinence
- Loss of urethral support / urethral hypermobility
- Intrinsic sphincter deficiency
Urethral hypermobility
Female urethra is supported laterally by attachments to endopelvic fasciae and ATFP, anteriorly by pubourethral ligaments and posteriorly by anterior vaginal wall
Pressure transmission theory
- Oldest theory – SUI prevented by urethra’s intra-abdominal position with increases in pressure in abdomen transmitted to urethra
- If proximal urethra and bladder neck descend infra-abdominally as in prolapse, loss of this pressure transmission and constriction leads to SUI
- Restoration of continence by replacing proximal urethra and bladder neck back to intra-abdominal position i.e., MMK procedure and colposuspension
Hammock hypothesis
- SUI prevented by the posterior compression of anterior vaginal wall and lateral fascial attachments at times of increased intra-abdominal pressure
- Restoration of continence relies on recreating posterior urethral support and allowing compression, and repositioning of urethra may not be necessary
Integral theory
- Site of maximal continence is mid-urethra at pubourethral ligaments – during storage phases, anterior force from pubococcygeus pull vagina up against pubourethral ligaments, and backwards forces push on vagina and bladder neck.
- Laxity in the vaginal wall and surrounding structures loses this site of maximal continence, and also may cause inappropriate stretch receptor activation causing urgency.
- Restoration of continence relies on mid-urethral repositioning (i.e., mid urethral slings)
Intrinsic sphincter deficiency
Some women with excess urethral hypermobility and loss of pelvic supports retain continence, and some women with no hypermobility have SUI
ISD implies a neural or structural issue, typically a fixed urethra with little intrinsic closure function (classically “pipestem” urethra)
- Typically diagnosed on urodynamics with low VLPP < 60 cm H20
- Treatment for ISD alone may be bulking agents or pubovaginal sling
- Usually a degree of ISD and hypermobility combined
- Often seen after previous surgeries or radiation
Risk factors for SUI
- Age
- Aged care facility
- Pregnancy, giving birth, and parity
- SUI increases whilst pregnant, then decreases from 3 months post-partum
- Caesarean less associated with SUI cf. vaginal birth
- Bigger babies increase risk SUI
- Multiparity increases risk
- Race – increased SUI in Caucasians > African American
- Hormonal therapy
- Oral oestrogens increase risk of SUI, topical oestrogen does not
- SUI more prevalent during menopause
- Obesity
- Pelvic surgery or radiation (conflicting evidence re: hysterectomy)
- Vigorous activity
- Smoking
- Unclear re: SUI – definitely more urgency and frequency
Vaginal delivery leads to SUI
- Stretch injury to supportive ligaments and fasciae
- Relative ischaemia to pelvic tissues due to compression
- Damage to pelvic nerves from compression
- Damage to pelvic musculature and pelvic floor
- Direct injury to urinary tract due to long labour and ischaemia
Work-up of SUI
History & examination.
Usual investigations – urine culture, ultrasound/PVR, bladder diary, ICIQ, pad weights.
In the ‘index’ patient – further advanced investigations such as UDS and cystoscopy can be omitted.
The following change an index patient to a ‘complicated’ patient:
- Significant pelvic organ prolapse
- Mixed incontinence or concern for concurrent overactivity
- Elevated PVR
- Recurrent or persistent SUI
- Prior surgical interventions
- Prior mesh
- Obese
- Neurological conditions
- Advanced age
- Previous radiation or malignancy
Who should get a cystoscopy?
- Haematuria or microscopy
- Unexplained pyuria
- Recurrent UTIs
- Previous surgery and potential foreign body i.e., mesh
- Any concern about potential lower tract abnormality
Who should get urodynamics?
EAU – “Preoperative urodynamics in women with uncomplicated, clinically demonstrable SUI does not improve outcomes of surgery … do not routinely carry out UDS when offering treatment for uncomplicated SUI”
- “Perform UDS if the findings may change the choice of invasive treatment”
AUA – “May omit UDS for the index patient desiring treatment when SUI is clearly demonstrated”
“May perform UDS in non-index patients”
RCTs (including VALUE trial, 2012 NEJM) have failed to show benefit for UDS prior to uncomplicated SUI treatment.
Who should definitely get UDS:
- Previous anti-incontinence or prolapse surgery
- Concurrent significant prolapse
- Significant voiding dysfunction or high residuals
- Mixed symptoms and significant urgency / OAB
- SUI has not been objectively confirmed
- Diagnostic dilemma – doubt or clarity regarding diagnosis (‘equivocal symptoms’)
- Neurological conditions
Arguments for routine UDS:
- Diagnosis of DO may be found in a quarter of cases
- Patient education and ‘buy in’
- UDS may show different picture to history – bladder is an unreliable witness
- Justification of surgical intervention and decide on procedure, help counsel on potential complications
- Medicolegal
Urodynamics for SUI
- Prolapse needs to be reduced – can ‘mask’ SUI
- Assess for compliance, DO
- Urodynamic stress incontinence (previously called genuine stress urinary incontinence) – involuntary leak during filling phase, with increased abdominal pressure, in the absence of detrusor contraction
- VLPP should be performed ideally around 200 – 250 mL
- Lowest leak point pressure counts – gradual Valsalva, or ‘small cough, medium cough, big cough’
- Leak point pressure < 60 – 65 cm H2O diagnostic of ISD
- Leak point pressure > 100 cm H2O diagnostic of urethral hypermobility
- Fluoro findings:
- Descent of the bladder neck with abdominal pressure – supportive of hypermobility
- Urethral pressure profile (UPP)
- Recording pressures along length of urethra with bladder at rest
- Maximal urethral closure pressure (MUCP) is maximal urethral pressure minus detrusor pressure
- Functional urethral length – length of which urethral pressure > detrusor pressure
- MUCP < 20 cm H2O thought to be confirmatory of ISD, and associated with worse outcomes of colposuspension