What is Overactive Bladder (OAB)?
Overactive bladder is a clinical syndrome defined by urinary urgency—a sudden, compelling desire to urinate that is difficult to defer—usually accompanied by increased daytime urinary frequency and nocturia, with or without urgency urinary incontinence, in the absence of urinary tract infection or other obvious pathology. 1
Core Defining Features
Urgency is the hallmark symptom that must be present to diagnose OAB. 1 This is not simply a strong desire to void, but rather an overwhelming, sudden urge that the patient finds difficult to postpone. While urgency alone can define OAB, the condition typically presents with a constellation of associated symptoms:
Primary Symptoms
- Urgency (required): Sudden compelling desire to void that is difficult to defer
- Frequency: More than 7 voids during waking hours (though this varies with fluid intake, sleep hours, and comorbidities) 1
- Nocturia: Waking one or more times at night to void; ≥3 episodes typically causes moderate to major bother 1
- Urgency urinary incontinence (UUI): Involuntary urine leakage associated with urgency (present in some but not all patients) 1
Critical Diagnostic Distinctions
OAB is a diagnosis of exclusion—you must rule out urinary tract infection, hematuria, and other obvious pathology before making this diagnosis. 1 The condition specifically excludes patients with neurologic causes of bladder dysfunction (non-neurogenic OAB). 1
What OAB is NOT:
- Nocturnal polyuria: Large volume nighttime voids (>20-33% of 24-hour urine output depending on age) due to excessive nighttime urine production from cardiac/vascular disease or sleep disorders—not OAB 1
- Polydipsia: Many small voids throughout the day due to excessive fluid intake 1
- Neurogenic bladder: Symptoms from multiple sclerosis, spinal cord injury, Parkinson's disease, or other neurologic conditions
Clinical Presentation
Patients typically report that symptoms are bothersome enough to affect their quality of life, though many suffer for extended periods before seeking care due to embarrassment. 1 Sometimes a caregiver or partner recognizes the problem and prompts the patient to seek evaluation. 1
The symptoms can manifest as:
- OAB-dry: Urgency and frequency without incontinence
- OAB-wet: Urgency and frequency with urgency incontinence episodes
Underlying Mechanism
While the exact pathophysiology remains incompletely understood, OAB likely involves multiple mechanisms including increased bladder smooth muscle excitability, abnormal spread of excitation through the bladder wall, heightened sensory nerve activity, and altered central nervous system processing of bladder signals. 2 The International Continence Society definition implies detrusor overactivity (involuntary bladder contractions), though this is not required for clinical diagnosis. 1
Prevalence and Impact
OAB affects over 10% of the general population, with prevalence increasing with age (12.4% in those over 40 years in Japanese studies). 3, 4 The condition substantially impairs quality of life, affecting social function, physical activity, and psychological well-being. 2, 4
Initial Evaluation Requirements
According to the 2024 AUA/SUFU guidelines, the initial office evaluation must include: 5
- Medical history with comprehensive bladder symptom assessment
- Physical examination
- Urinalysis to exclude microhematuria and infection (dipstick or microscopic; urine culture if urinalysis suggests infection/hematuria)
Post-void residual (PVR) measurement should be obtained in patients with emptying symptoms, history of urinary retention, enlarged prostate, neurologic disorders, prior incontinence/prostate surgery, or long-standing diabetes. 5