Definition: involuntary loss of urine

Classification based on symptoms vs. pathophysiology

• Urodynamics required to correlate symptoms with voiding physiology
• Symptoms
  • Stress urinary incontinence (SUI) - leakage during increased abdominal pressure (sneezing, lifting, etc.)
  • Urge urinary incontinence (UUI) - leakage a/w sudden compelling desire to void
  • Mixed - SUI + UUI
    • Treating SUI first (eg sling) will fix UUI in 50% of cases
  • Unaware incontinence (without urge or stress); nocturnal enuresis; continuous incontinence (e.g. from fistula)
• Pathophysiology
  • Urethral vs. extra-urethral (e.g. fistula)
  • Intrinsic sphincter deficiency (ISD) - SUI in the absence of a detrusor contraction
  • Urethral hypermobility - increased abdominal pressure → excessive descent of bladder neck and urethra (2/2 pelvic floor weakness), lack of urethral coaptation. a/w ISD and SUI
  • Detrusor overactivity (DO) - involuntary detrusor contractions during the filling phase (diagnosed by filling cystometry) (neurogenic/hyperreflexia vs. idiopathic/instability)
  • Low bladder compliance - progressive rise in intravesical pressure during filling
  • Urinary retention - leakage from overflow incontinence

Voiding dysfunction can be categorized by...

Physiology of voiding

• Bladder filling - sympathetic (β3) stimulation / parasympathetic (M3) inhibition to reduce detrusor tone
  • Onuf's nucleus (S2-S4 pudendal motor neurons) innervate the sphincter 
  • Guarding reflex: inhibit PNS / activate SNS / activate Onuf's nucleus -> promote bladder filling
• Bladder emptying - sympathetic inhibition, parasympathetic stimulation
  • Detrusor distension → activate voiding reflex (spinal reflex through PMC). PMC inhibits Onuf's nucleus -> voiding
  • Frontal cortex (when mature) should inhibit voiding/PMC until desired, otherwise PMC activation → reflex voiding
    • Babies have spastic bladders/reflex voiding because frontal cortex is not mature
  • PMC = pontine micturition center = Barrington's nucleus

• Sympathetic (β3, α1): T10-L2 -> hypogastric n. -> inferior pelvic plexus
• Parasympathetic (M3): S2-S4 -> pelvic n. -> inferior pelvic plexus
• Somatic (N): S2-S4 -> pudendal n.
• *Suprasacral cord leads to detrusor sphincter dyssynergia (DSD) with risk of 'hostile bladder' and outlet obstruction
• ~ 10% of MS will also have DSD
• MSA - impaired contractility with poor compliance, while PD has more detrusor overactivity

AUA symptom score (AUASS) (same as IPSS): 1-7 (mild), 8-19 (mod), 20-35 (severe)

History:

• Precipitating factors
• Severity (number of pads/day, wetness of the pad when changed)
• Voiding symptoms (urgency, frequency, nocturia, intermittent/weak/hesitant stream, etc.)
• OB history (G/P/A, type of delivery)
• GU conditions: stricture, STDs, UTIs, etc.
• Hx of pelvic surgery
• Neuro disease/symptoms (e.g. MS, stroke)
• Fluid consumption (type and amount)
• Medications

Physical exam

• Pelvic/prostate exam
  • Pelvic exam: check during relaxed + cough/Valsalva
  • Atrophic vaginitis, urethral hypermobility, diverticulum, cystocele, enterocele/uterine prolpase, rectocele
  • Urethral hypermobility: Cotton swab test - insert lubricated cotton swab into urethra; if swab axis Δ > 30° from rest to strain = hypermobility
  • Check for urine leak during cough
• Neuro exam may include: perineal sensation, anal sphincter tone, bulbocavernosus reflex (BCR)
  • **hide** BCR (squeezing glans/clitoris → anal sphincter contraction) mediated through S2-S4 pudendal nerve. Absent in 30% of normal women
• Rectal exam - stool impaction
• Lower extremity edema (increased urine production when recumbent at nighttime)

• UA/cx (glucosuria, infxn)
• PVR - retention
• Voiding diary (fluid consumption, void volume, incontinence episodes, urinary sx, BMs)
• Urodynamics if diagnosis unclear, empiric therapy unsuccessful, or considering surgical intervention
• Further workup - cysto, imaging

Behavioral

• Voiding diary, timed/scheduled voiding q2-3h
• Pelvic floor muscle training (e.g. Kegels set of 10 x 6-8s, 3x/day) should be offered as first-line therapy for SUI/UUI/mixed incontinence
• Avoid excessive fluid intake; avoid bladder irritants (caffeine, alcohol, spicy/acidic food)
• Weight loss
• Avoid constipation

Urge incontinence:

• Anticholinergics, B3 agonist (Mirabegron), Botox, Interstim

Stress incontinence:

• Urethral sling (urge incontinence may persist in 20-30%)

For mixed incontinence:

• Anticholinergics improve UUI about 50% of the time, do not improve SUI
• Sling improves SUI > 90% of the time, but can increase UUI 50% too!
  • 15% risk of de novo OAB with sling though