Overactive bladder (OAB) is a symptom syndrome — urinary urgency, usually with frequency and nocturia, with or without urgency incontinence, in the absence of infection or obvious pathology — and is distinct from detrusor overactivity (a urodynamic observation).
Definitions and Pathophysiology
- Urgency is a sudden compelling, hard-to-defer desire to void; UUI is leakage with/just before urgency. OAB can coexist with SUI; SUI with "OAB dry" is not MUI.
- Three pathophysiologic hypotheses: neurogenic (loss of inhibition / re-emergence of primitive reflexes / afferent sensitization), myogenic (increased spontaneous excitation and propagation), and integrative (local contractions spreading via various routes).
Epidemiology
Prevalence ~12% (EPIC). Both sexes are similar, but men have more "OAB dry" and women more "OAB wet." Storage LUTS impact quality of life more than other LUTS.
Diagnosis and Evaluation
The 2017 CUA OAB guideline mandates four steps: history/physical, urinalysis, a questionnaire, and a voiding diary (the frequency-volume chart is the principal objective tool for frequency/nocturia). Screen for occult neurologic disease (new OAB with ED/tremor). Bladder pain syndrome is distinguished by pain (urgency in OAB does not include pain), pain rising with filling, more consistent voided volumes, and the ability to defer voiding.
Management
- Observation is acceptable once conditions requiring treatment are excluded.
- Conservative (≥6 weeks, ideally 3 months): weight loss, smoking cessation, reduced caffeine/fluid/alcohol, pelvic-floor training, and bladder retraining.
- Pharmacologic: an antimuscarinic if no contraindication (avoid in narrow-angle glaucoma, impaired gastric emptying, history of retention; consider cognition) — try at least two antimuscarinics for ≥4 weeks each; then mirabegron if antimuscarinics fail/aren't tolerated. Acute retention in men on antimuscarinics ± an α-blocker is up to 3%.
- Third-line/surgical (after confirming DO on UDS if needed): intradetrusor onabotulinumtoxinA, sacral neuromodulation, or percutaneous tibial nerve stimulation; augmentation cystoplasty is no longer recommended in adults. Two main UDS diagnoses associate with OAB — DO and increased filling sensation — though DO may be absent (especially in women) and present in asymptomatic patients.
Self-Test
1. How does OAB differ from detrusor overactivity? OAB is a symptom syndrome (urgency ± incontinence, with frequency/nocturia); detrusor overactivity is a urodynamic observation of involuntary contractions.
2. What four assessments are mandatory in OAB evaluation (2017 CUA)? History/physical, urinalysis, a questionnaire, and a voiding diary.
3. What distinguishes bladder pain syndrome from OAB? Painful symptoms, pain rising steadily with filling, more consistent voided volumes, and the ability to defer voiding.