Overview
Overactive Bladder Syndrome (OAB)
1. Clinical Overview
Summary
Overactive bladder (OAB) is a symptom syndrome characterised by urinary urgency, usually with frequency and nocturia, with or without urgency incontinence, in the absence of urinary tract infection or other pathology. It can be "wet" (with incontinence) or "dry" (without).
Key Facts
| Aspect | Detail |
|---|---|
| Definition | Urgency ± frequency ± nocturia ± incontinence |
| Underlying Mechanism | Detrusor overactivity (involuntary contractions) |
| OAB Dry | Urgency without incontinence |
| OAB Wet | Urgency with incontinence |
| First-Line | Bladder training + lifestyle modification |
Clinical Pearls
- Urgency is key: The defining symptom - sudden compelling desire to void
- "Latchkey incontinence": Classic scenario - leaking when putting key in door
- Exclude UTI first: Always dipstick/MSU before diagnosing OAB
- Anticholinergics in elderly: Avoid due to cognitive effects
2. Epidemiology
Prevalence
| Population | Prevalence |
|---|---|
| Overall adults | 10-15% |
| Age >5 years | 30% |
| Gender | Similar or slight female predominance |
Risk Factors
| Risk Factor | Notes |
|---|---|
| Age | Increases with age |
| Obesity | |
| Caffeine/alcohol | Bladder irritants |
| Neurological disease | MS, stroke, Parkinson's |
| Previous pelvic surgery |
3. Pathophysiology
Normal vs OAB
Normal Filling:
Bladder Fills → Detrusor Relaxes → First Sensation → Urge → Voluntary Void
OAB:
Bladder Fills → INVOLUNTARY Detrusor Contractions → Urgency → Incontinence (if not suppressed)
Causes
| Category | Examples |
|---|---|
| Idiopathic | Most common |
| Neurogenic | MS, stroke, spinal cord injury, Parkinson's |
| Bladder outlet obstruction | BPH (secondary DO) |
| Infection/irritation | UTI, bladder stones |
4. Clinical Presentation
Core Symptoms
| Symptom | Definition |
|---|---|
| Urgency | Sudden compelling desire to void, difficult to defer |
| Frequency | > voids per day |
| Nocturia | Waking ≥1 time to void |
| Urgency incontinence | Involuntary leakage with urgency |
Distinguishing OAB from Stress Incontinence
| Feature | OAB | Stress Incontinence |
|---|---|---|
| Key symptom | Urgency | Leakage with exertion |
| Trigger | Sound of water, key in door | Cough, sneeze, exercise |
| Volume leaked | Moderate-large | Small spurts |
| Warning | Strong urge | None |
5. Clinical Examination
Assessment
| Component | Purpose |
|---|---|
| Abdominal | Palpable bladder (retention) |
| Pelvic | Exclude prolapse, masses |
| Neurological | Lower limb, perineal sensation |
| Cough stress test | Exclude concurrent SUI |
Red Flags
| Finding | Action |
|---|---|
| Haematuria | Exclude malignancy |
| Pelvic mass | Imaging |
| Neurological signs | MRI spine |
6. Investigations
First-Line
| Test | Purpose |
|---|---|
| Urinalysis / MSU | Exclude UTI |
| Bladder diary (3 days) | Frequency, volumes, leakage |
| Post-void residual | Exclude retention |
Second-Line
| Test | Indication |
|---|---|
| Urodynamics | Confirm detrusor overactivity |
| Cystoscopy | Haematuria, recurrent UTI |
7. Management
Lifestyle Modifications
| Intervention | Details |
|---|---|
| Caffeine reduction | Coffee, tea, cola |
| Fluid modification | 1.5-2L/day |
| Weight loss | If BMI elevated |
| Smoking cessation |
Bladder Training
- Schedule voiding - gradually increase intervals
- Goal: void every 3-4 hours
- Duration: 6+ weeks
- Urgency suppression techniques
Pharmacotherapy
| Drug Class | Examples | Notes |
|---|---|---|
| Anticholinergics | Solifenacin, tolterodine, oxybutynin | Avoid oxybutynin in elderly |
| Beta-3 agonist | Mirabegron | No anticholinergic SEs, watch BP |
| Combination | Anticholinergic + Mirabegron | If monotherapy fails |
Anticholinergic Side Effects
- Dry mouth
- Constipation
- Blurred vision
- Cognitive impairment (especially elderly - avoid oxybutynin)
Third-Line (Specialist)
| Treatment | Details |
|---|---|
| Botox injection | OnabotulinumtoxinA into detrusor; lasts 6-9 months |
| Sacral neuromodulation | Implanted device |
| PTNS | Percutaneous tibial nerve stimulation |
8. Complications
| Complication | Notes |
|---|---|
| Quality of life impairment | Social isolation |
| Skin breakdown | Incontinence-associated dermatitis |
| Falls | Rushing to toilet (elderly) |
| UTI | Pad use, incomplete emptying |
| Depression/anxiety |
9. Prognosis & Outcomes
| Intervention | Success Rate |
|---|---|
| Bladder training | 50-80% improvement |
| Anticholinergics | 60-70% improvement |
| Botox | Effective in refractory cases |
| Overall | Chronic condition requiring ongoing management |
10. Evidence & Guidelines
| Organisation | Key Points |
|---|---|
| NICE NG123 | Bladder training first, anticholinergic caution in elderly |
| ICS | Standardised terminology |
| EAU | European guidelines |
11. Patient / Layperson Explanation
What is overactive bladder? It's when your bladder squeezes too often, giving you a sudden strong urge to go to the toilet. You might feel like you need to go very frequently, get up at night, or sometimes not make it in time.
What causes it? Often we don't know the exact cause. It can happen with age, after stroke, or with conditions like MS or Parkinson's.
How is it treated?
- Lifestyle changes: Cut down on caffeine, don't drink too much or too little
- Bladder training: Learning to hold on a bit longer, gradually
- Medication: Tablets that relax the bladder muscle
- Specialist treatments: Botox injections, nerve stimulation
Will it get better? Most people find significant improvement with treatment. It's very common - you're not alone.
12. References
- NICE NG123. Urinary Incontinence and Pelvic Organ Prolapse. 2019.
- Gormley EA, et al. AUA/SUFU OAB Guideline. 2019.
- Abrams P. ICS Standardisation Report on Terminology. 2002.