Stress Urinary Incontinence (SUI)

From Berek & Novak's Gynecology, Chapter 29 - Urinary Tract

1. DEFINITION

2. EPIDEMIOLOGY & INCIDENCE

• Urinary incontinence affects approximately 25-45% of adult women, with prevalence increasing with age.
• SUI is the most common type of urinary incontinence in women, followed by mixed and urgency types.
• Prevalence of SUI: approximately 10-30% of adult women in the general community.
• The condition carries significant economic impact - costs of urinary incontinence in the United States exceed $19.5 billion annually, with the majority spent on routine care (absorbent products, laundry, routine health visits).
• Quality of life impact: UI affects physical activity, social interactions, emotional well-being, and sexual function. Women with urinary incontinence are more likely to experience depression and anxiety, and to avoid exercise and social activities.
• Studies suggest that fewer than 50% of women with urinary incontinence seek medical care, often attributing symptoms to a "normal" part of aging.

3. ETIOLOGY & PATHOPHYSIOLOGY

Normal Continence Mechanism

1. Anatomical support of the bladder neck and proximal urethra by the pubocervical fascia and arcus tendineus fascia pelvis
2. Intact urethral sphincter (intrinsic sphincter mechanism)
3. Urethral pressure exceeding bladder/intravesical pressure at all times during filling

Two Principal Mechanisms of SUI

• Most common mechanism
• Weakness of the pelvic floor support structures (pubocervical fascia, levator ani, pubourethral ligaments) leads to descent and rotation of the bladder neck and proximal urethra during increases in intra-abdominal pressure
• The urethra falls below the pelvic floor and intra-abdominal pressure is not transmitted equally to the bladder and urethra - net result: bladder pressure exceeds urethral pressure and leakage occurs
• The "hammock hypothesis" (DeLancey): the posterior vaginal wall and its fascial attachments act as a supportive layer; when this is deficient, the urethra cannot be compressed against a stable backstop

• The sphincter mechanism itself is intrinsically damaged, regardless of mobility
• Results in a poorly functional, "open" or "lead-pipe" urethra at rest
• Clinically: leakage with minimal activity or even at rest
• Associated with: prior urethral/pelvic surgery, pelvic radiation, neurological disease, aging
• Urodynamically defined: Abdominal Leak Point Pressure (ALPP) < 60 cm H₂O or Maximum Urethral Closure Pressure (MUCP) < 20 cm H₂O
• Carries a worse surgical prognosis than pure hypermobility

Mixed Mechanism

4. RISK FACTORS

Obstetric / Reproductive Factors

• Vaginal delivery is the most important modifiable risk factor - associated with pudendal nerve injury, levator ani muscle damage, and fascial tears
• Each vaginal delivery increases risk; forceps delivery confers higher risk than spontaneous vaginal delivery
• Parity: multiparity significantly increases risk compared to nulliparity
• Macrosomia (birth weight >4 kg) and prolonged second stage of labor

Demographic / Constitutional

• Age: prevalence increases with age - neuromuscular changes, hormonal changes, collagen changes
• Obesity (BMI > 30): one of the strongest modifiable risk factors; weight loss reduces incontinence episodes significantly
• Race: White women have higher rates of SUI; Black women are more likely to have urgency incontinence
• Genetics: family history and connective tissue disorders (Ehlers-Danlos)

Hormonal

• Menopause / estrogen deficiency: thinning of urethral mucosa, reduced coaptation
• The urethra and bladder trigone are estrogen-sensitive tissues

Anatomical / Surgical

• Prior pelvic surgery (hysterectomy - increases risk ~2-fold)
• Pelvic organ prolapse (common co-morbidity)
• Previous incontinence surgery (failure, recurrence)

Other

• Chronic straining (constipation, chronic cough, heavy lifting)
• Neurological diseases affecting lower urinary tract innervation
• Medications (alpha-blockers can worsen SUI)

5. DIAGNOSIS

A. History & Symptoms

• Type of leakage (stress, urgency, continuous, nocturnal)
• Onset, duration, severity (number of pads/day, pad weight)
• Aggravating factors (cough, sneeze, exercise, walking, urge)
• Voiding dysfunction (hesitancy, poor stream, incomplete emptying)
• Pelvic organ prolapse symptoms (bulge, pressure)
• Bowel symptoms, sexual dysfunction
• Obstetric history, menopausal status
• Current medications, prior treatments

• ICIQ-SF (International Consultation on Incontinence Questionnaire - Short Form)
• UDI-6 (Urogenital Distress Inventory)
• IIQ-7 (Incontinence Impact Questionnaire)
• PFDI / PFIQ (Pelvic Floor Distress Inventory / Impact Questionnaire)
• Sandvik Severity Index

B. Voiding Diary / Bladder Diary

• Minimum 3-day diary (ideally 5-7 days)
• Records: fluid intake, time/volume of voids, leakage episodes, associated activity, pad use
• Assesses: functional bladder capacity, frequency, nocturia, urgency episodes
• Essential for distinguishing SUI from urgency incontinence and for baseline assessment

C. Physical Examination

• BMI, mobility, cognitive function, fluid intake habits

• Inspect for pelvic organ prolapse using POP-Q staging
• Assess vaginal atrophy/estrogenization
• Urethral hypermobility: cotton swab (Q-tip) test - straining deflection >30° from horizontal is positive (though less used now)
• Palpate pelvic floor (levator ani) for tone, tenderness, voluntary contraction

• Fill bladder to ~300 mL, ask patient to cough vigorously - observe for simultaneous urine leakage (synchronous = SUI; delayed = detrusor overactivity)
• Should be performed in both supine and standing positions

D. Urinalysis & Urine Culture

• First-line investigation in all patients
• Rule out urinary tract infection (can mimic/exacerbate incontinence), hematuria (malignancy), glucosuria (diabetes)
• Treat any UTI before proceeding with further evaluation

E. Post-Void Residual (PVR)

• Measured by ultrasound or catheterization within 20 minutes of voiding
• Normal: < 50 mL (definitely normal) to < 100 mL
• PVR > 200 mL: significant retention - evaluate for voiding dysfunction
• Elevated PVR can indicate overflow incontinence mimicking SUI

F. Pad Test

• 1-hour pad test (ICS): patient performs standardized activities with a pre-weighed pad; weight gain > 1 g = positive
• 24-hour pad test: more representative of daily life; > 4 g/24 hrs = positive
• Objectively quantifies leakage severity

G. Urodynamic Studies (UDS)

• Non-invasive measurement of voiding flow rate
• Normal: Qmax > 15-20 mL/s, bell-shaped curve
• Reduced flow may suggest obstruction or detrusor underactivity

• Measures intravesical pressure (Pves), abdominal pressure (Pabd), and calculated detrusor pressure (Pdet = Pves - Pabd) during bladder filling
• Normal filling: little or no change in Pdet (compliant bladder), no involuntary contractions
• Detects: detrusor overactivity (involuntary contractions), reduced compliance, sensory abnormalities
• Capacity measured:
  • First desire to void
  • Strong desire to void
  • Maximum cystometric capacity
• Valsalva/Cough Test during filling: demonstrates USI - leakage with increased Pabd in absence of Pdet rise

• Patient performs Valsalva; the abdominal pressure at which leakage first occurs is recorded
• ALPP < 60 cm H₂O: ISD (severe)
• ALPP 60-90 cm H₂O: mixed/intermediate
• ALPP > 90 cm H₂O: primarily hypermobility

• Measures pressure along the length of the urethra at rest and during stress
• Maximum Urethral Closure Pressure (MUCP) = Pura - Pves
• MUCP < 20 cm H₂O = ISD
• Pressure Transmission Ratio (PTR): increment in urethral pressure on stress as a percentage of simultaneously recorded increment in intravesical pressure (normal >1 in the proximal urethra)

• Evaluates detrusor contractility during voiding
• Distinguishes detrusor underactivity from bladder outlet obstruction

• Assesses pelvic floor/sphincter neuromuscular activity

H. Imaging

• Pelvic/Bladder Ultrasound: assesses PVR, bladder wall thickness, urethral mobility (ultrasound Q-tip equivalent)
• MRI Pelvis (dynamic/defecography MRI): for complex prolapse + incontinence cases
• Fluoroscopic Urodynamics (Videourodynamics): gold standard for complex/neurogenic cases - simultaneously visualizes anatomy and records pressures

I. Cystourethroscopy

• Indicated when: hematuria, recurrent UTI, suspected fistula, foreign body (mesh), prior pelvic surgery
• Not routine in uncomplicated SUI
• Evaluates: urethral coaptation, bladder mucosa, trigone, ureteric orifices

6. MANAGEMENT

A. CONSERVATIVE (NON-SURGICAL) MANAGEMENT

1. Lifestyle Modifications (First-Line)

• Weight loss: reduces intra-abdominal pressure; randomized trials show significant reduction in incontinence episodes with even modest weight loss (5-10% body weight)
• Fluid management: avoid excessive fluid intake; caffeine reduction (caffeine is a bladder irritant and may worsen urgency component)
• Constipation treatment: reduces chronic straining
• Smoking cessation: reduces chronic cough
• Timed voiding: helps regulate bladder habits

2. Pelvic Floor Muscle Training (PFMT) - Kegel Exercises

• First-line treatment for SUI, urgency UI, and mixed UI
• Mechanism: strengthening of the levator ani and urethral sphincter complex
• Protocol: performed correctly with physiotherapist guidance; typically 3 sets of 8-12 sustained contractions (8-10 seconds each) per day; continued for minimum 3-6 months
• Evidence: Cochrane review shows women treated with PFMT are significantly more likely to report cure or improvement vs. no treatment; NNT ~3 for significant improvement in SUI
• Prerequisite: patient must be able to identify and correctly contract the pelvic floor muscles (digital examination or biofeedback to confirm)
• Biofeedback-assisted PFMT: uses vaginal or rectal pressure sensors to provide visual/audio feedback; improves adherence and technique
• Supervised PFMT is significantly more effective than self-directed programs
• PFMT is also effective in the peripartum period (antenatal and postnatal) for prevention

3. Mechanical Devices

• Continence Pessaries (incontinence ring pessary, incontinence dish): support the bladder neck; useful in women who are not surgical candidates or who prefer non-surgical management; also used for pre-surgical trial to confirm SUI
• Urethral Inserts (Femsoft insert): occlusive devices placed in the urethra; can cause UTI/urethritis; used situationally
• External devices (urethral patches): adhesive foam patch over urethral meatus

4. Electrical and Magnetic Stimulation

• Electrical stimulation (E-stim) via intravaginal or anal electrode
• Magnetic stimulation (M-stim): extracorporeal, targets pudendal nerve and pelvic floor
• Evidence not well-established; reserved for specialized centers

B. PHARMACOLOGICAL MANAGEMENT

1. Alpha-Adrenergic Agonists

• Mechanism: stimulate alpha-adrenergic receptors in the urethral smooth muscle - increase urethral tone
• Examples: ephedrine, pseudoephedrine, phenylpropanolamine
• Limitations: non-specific, systemic side effects (hypertension, cardiac effects, CNS stimulation); phenylpropanolamine withdrawn due to risk of hemorrhagic stroke
• Not FDA-approved for SUI; rarely used

2. Duloxetine (SNRI)

• FDA-approved for depression and chronic pain; not approved for SUI (approved in Europe for SUI at 40 mg twice daily)
• Mechanism: dual serotonin and norepinephrine reuptake inhibition at the sacral spinal cord (Onuf's nucleus) - increases sphincter striated muscle tone during filling; also increases bladder storage
• Evidence: shown to be equally effective as PFMT in one study; reduces leakage episodes by ~50% vs ~50% for placebo in trials
• Side effects: nausea (most common, ~25%), fatigue, insomnia, somnolence, dizziness, blurred vision - limit use as first-line
• Role: second-line, especially in women not suitable for or awaiting surgery, or with mixed UI

3. Imipramine (Tricyclic Antidepressant)

• Dual action: anticholinergic (relaxes bladder) + alpha-agonist (constricts urethra)
• Particularly useful in mixed UI (stress + urgency components)
• Side effects: anticholinergic (dry mouth, constipation, urinary retention, cognitive effects), cardiac arrhythmias

4. Estrogen

• Systemic (oral/transdermal) HRT is contraindicated for treatment of UI
• WHI and HERS trials demonstrated that systemic estrogen WORSENS incontinence
  • HERS: OR for worsening incontinence = 1.5; OR for new SUI = 1.7; OR for new UUI = 1.5
  • More pronounced negative effect for stress than urgency incontinence
• Topical (vaginal) estrogen: may improve urethral coaptation and reduce urgency/frequency; does NOT reliably treat SUI but can be used as adjunct, particularly in postmenopausal women with atrophy

C. SURGICAL MANAGEMENT

1. Mid-Urethral Slings (MUS) - GOLD STANDARD for SUI

• A polypropylene mesh tape is placed tension-free at the mid-urethra (NOT at the bladder neck)
• During increased abdominal pressure, the tape acts as a "backboard" - the urethra is kinked/compressed against the tape, restoring continence
• No tension is applied; the mesh integrates with periurethral connective tissue over time

• Cure rates: 85-90% at 1 year for TVT; 80-85% for TOT
• Long-term data (11-year follow-up): ~77% subjective cure for TVT
• TVT vs. TOT: Equivalent overall cure rates; differences in complication profile

• Retropubic (TVT): bladder perforation (most common - 3-5%, usually recognized intraoperatively by cystoscopy), bowel injury (rare), major vessel injury (rare), postoperative voiding dysfunction/retention, de novo urgency (5-15%)
• Trans-obturator (TOT/TVT-O): groin/thigh pain (more common than TVT, usually transient), lower risk of bladder injury, tape erosion, obturator nerve injury

2. Retropubic Colposuspension (Burch Procedure)

• Historical gold standard; now largely replaced by MUS
• Open or laparoscopic approach
• Technique: the periurethral vaginal wall is sutured to Cooper's ligament (iliopectineal ligament) bilaterally, elevating and stabilizing the bladder neck and proximal urethra
• Outcomes: Cure rate ~80-90% at 1 year; declines over time (~70% at 5 years, ~55% at 10 years)
• Burch vs. TVT: Multiple RCTs and a Cochrane review show equivalent cure rates at 1 year; TVT has lower morbidity (shorter OR time, less blood loss, shorter hospital stay, quicker recovery)
• Advantage: avoids mesh; preferred in women with mesh concerns or concurrent laparotomy/hysterectomy
• Complications: voiding dysfunction, de novo detrusor overactivity, pelvic organ prolapse (particularly enterocele - over-rotation of the vaginal axis), wound complications

3. Pubovaginal Sling (Autologous Fascial Sling)

• Uses a strip of the patient's own rectus fascia (or fascia lata) placed at the bladder neck
• Preferred for ISD (ALPP < 60 cm H₂O) and in women with mesh contraindications (prior mesh erosion, desire to avoid synthetic materials)
• Provides both support (backboard) and compression (slight tension applied)
• Outcomes: Cure rates ~80-90% for ISD; slightly higher rates of voiding dysfunction and retention compared to MUS
• Higher morbidity than MUS: longer operative time, wound morbidity, postoperative pain
• In the SISTEr trial (Albo et al., NEJM 2007): Burch vs. autologous fascial sling - the fascial sling had significantly higher success rates (47% vs. 38%) but higher complications (voiding dysfunction 14% vs. 2%)

4. Injectable Bulking Agents (Periurethral/Transurethral Injections)

• Substances injected periurethrally or transurethrally at the mid-urethra or bladder neck to bulk the urethral lumen and improve coaptation
• Agents used: Macroplastique (polydimethylsiloxane), Coaptite (calcium hydroxyapatite), Bulkamid (polyacrylamide hydrogel), Deflux (dextranomer/hyaluronic acid)
• Indications: Women who are poor surgical candidates (elderly, multiple comorbidities), desire to avoid major surgery, ISD without significant hypermobility
• Outcomes: Less effective than MUS (30-50% cure at 1 year); effect wanes over time; multiple injections often required
• Advantages: minimally invasive, office-based or outpatient, reversible, no mesh
• Complications: UTI, urinary retention (transient), local reaction, migration of particles

5. Artificial Urinary Sphincter (AUS)

• Used almost exclusively in women when other methods have failed and in cases of severe ISD
• Rarely used in women (more common in men post-prostatectomy)
• A silicone cuff is placed around the urethra/bladder neck; operated by a control pump in the labia

6. Laparoscopic Colposuspension

• Laparoscopic version of the Burch procedure
• Equivalent cure rates to open Burch but with less morbidity
• More technically demanding; not widely practiced since MUS became predominant
• COLOSUS trial: showed laparoscopic Burch equivalent to TVT at 2 years

D. MANAGEMENT OF SPECIAL SITUATIONS

• Treat the predominant symptom first
• PFMT and bladder training address both components
• Pharmacotherapy (anticholinergics/beta-3 agonists) for the urgency component
• Surgery addresses SUI but may not improve urgency component (de novo urgency can occur post-MUS)

• PFMT is first-line; antenatal PFMT reduces risk of postpartum incontinence
• Surgery is deferred until completion of childbearing

• Combined repair: MUS + prolapse repair (vaginal or laparoscopic)
• Prolapse can mask SUI - "occult SUI" unmasked after prolapse reduction (pessary test or prolapse reduction test before surgery)
• Pre-surgical urodynamics is especially important

• Re-evaluation with urodynamics essential
• Consider ISD as a contributing mechanism
• Options: repeat MUS (with care regarding mesh burden), autologous fascial sling, bulking agents, AUS

• Conservative management preferred
• Surgical risk-benefit analysis; anesthesia risk
• Continence pessaries are an excellent option

• Often ISD-dominant
• Autologous sling or AUS preferred; MUS outcomes less predictable
• Urodynamics essential

SUMMARY TABLE: Management Algorithm for SUI

KEY EXAM POINTS (Postgraduate Level)

1. Definition: SUI = involuntary leakage on effort/exertion/cough/sneeze; confirmed urodynamically as USI (leakage without detrusor contraction).
2. Two mechanisms: Urethral hypermobility (most common) vs. Intrinsic Sphincter Deficiency (ISD, ALPP < 60 cmH₂O or MUCP < 20 cmH₂O).
3. ISD markers: Prior urethral surgery, radiation, neurology; "lead-pipe" urethra; worse surgical prognosis.
4. Q-tip test: Deflection > 30° = urethral hypermobility.
5. Urodynamics before surgery: Especially for mixed incontinence, prior failed surgery, voiding dysfunction, or neurological disease.
6. PFMT: First-line, supervised, minimum 3-6 months. Cochrane review: significant cure/improvement over no treatment.
7. Estrogen (systemic): CONTRAINDICATED - worsens SUI (WHI, HERS data); topical only as adjunct.
8. Duloxetine: SNRI, works at Onuf's nucleus (S2-S4); NOT FDA-approved for SUI; comparable to PFMT in trials; significant side effects (nausea).
9. TVT vs. TOT: TVT has higher bladder injury risk; TOT has higher groin pain risk; TVT preferred for ISD. Mandatory cystoscopy after TVT.
10. Burch colposuspension: Historical gold standard; open or laparoscopic; sutures to Cooper's ligament; risk of enterocele; equivalent to TVT at 1 year.
11. Autologous fascial sling: Best for ISD, mesh contraindications; SISTEr trial showed higher success but higher voiding dysfunction vs. Burch.
12. Bulking agents: For poor surgical candidates or ISD without hypermobility; 30-50% cure; not durable.
13. Occult SUI: Always reduce prolapse (pessary test) before urodynamics/surgery to unmask.