Prof. Giacomo Novara โ Urology, University of Padua
OAB (OverActive Bladder) โ Frequency-urgency syndrome
The desire to void that arises physiologically as the bladder fills and distends beyond a certain threshold. It is controllable, deferrable, and proportional to bladder volume.
A sudden, compelling desire to void that is difficult or impossible to defer, arising even with a poorly filled bladder. It is the symptomatic correlate of involuntary detrusor contractions during the filling phase.
Under normal conditions, the detrusor contracts only during voluntary voiding. In OAB, the detrusor generates involuntary contractions during the filling phase. This reduces the functional capacity of the bladder (the threshold at which urgency arises: 150โ250 mL instead of the normal 300โ400 mL), while anatomical capacity (400โ500 mL) remains intact. The bladder is not structurally smaller โ it is functionally less capacious.
Urgency + urgency urinary incontinence. More frequent in women due to the shorter urethra and lower urethral resistance.
Urgency + frequency/nocturia without leakage. More common in untreated males due to higher urethral resistance.
The equal sex distribution is a key feature that excludes prostatic involvement in OAB pathogenesis. Other causes of LUTS mimicking OAB must always be excluded: bladder neoplasm (especially CIS), distal ureteral calculus, urinary tract infection, urethral stricture, neurological causes.
The diagnosis of OAB is clinical: it is based on symptoms reported by the patient, without the need for urodynamic testing at initial evaluation. Clinical trials of antimuscarinics and beta-3 agonists were conducted on the basis of clinical, not urodynamic, diagnosis.
Assessment of urgency, daytime and nocturnal frequency, incontinence episodes. IPSS for overall lower urinary tract symptoms.
To exclude urinary tract infection, glycosuria (diabetes), microhaematuria (bladder neoplasm), crystalluria (urolithiasis).
The patient records, for 3 days (not necessarily consecutive), the time and volume of each void. Essential for distinguishing true OAB (reduced functional capacity) from polyuria of any cause (normal functional capacity). Ask for time and volume only: the more you ask, the less you get.
Excludes associated pathology. Post-void residual in OAB is generally low; if elevated, the diagnosis should be reconsidered.
Not mandatory at first assessment. Indicated before second-line treatments or in cases of diagnostic uncertainty. Demonstrates involuntary detrusor contractions during filling (detrusor overactivity).
Inexpensive, free of side effects, and frequently underestimated. Should be offered to all patients before any pharmacological treatment.
Target: diuresis โค1,500 mL/day. Bear in mind that fruit and vegetables contain 60โ70% water. Dispel the myth that "drinking plenty is always good."
Nocturia โ shift hydration to the morning and early afternoon. Herbal teas and soups in the evening worsen nocturia: "have your tea at five o'clock, like the English."
Tea, coffee, cola drinks, and beer have an additional diuretic effect. Reduce consumption in the evening hours.
Diuretics taken in the evening โ switch to morning or early afternoon dosing. Discuss with the cardiologist whether substitution with another antihypertensive class is feasible.
Antimuscarinics and beta-3 agonists are both moderately effective: they reduce urgency and incontinence episodes by approximately 0.5 per day compared with placebo. They are not miracle drugs โ but the effect is real and clinically appreciated by patients who respond.
The SYNERGY trial demonstrated that combination therapy (solifenacin + mirabegron at full doses) is statistically superior to monotherapy. However, the additional clinical benefit is very modest: approximately 0.2 fewer incontinence episodes per 24 hours compared with antimuscarinic monotherapy alone. In practical terms: for every 5 days of combination therapy, one fewer incontinence episode compared with monotherapy.
If behavioural and pharmacological therapy is inadequate, urodynamic testing should be performed to confirm detrusor overactivity before proceeding to second- or third-line treatments.
Endoscopic injections of botulinum toxin into the bladder wall (15โ20 injection sites, avoiding the trigone), under light sedation. The toxin blocks the SNAP-25 protein, inhibiting acetylcholine release at detrusor cholinergic junctions.
Efficacy: markedly superior to antimuscarinics โ three times more effective than placebo in reducing incontinence. Significant quality-of-life improvement.
Duration: approximately 6โ9 months of efficacy. Symptoms then gradually return. Can be repeated indefinitely: patients with 10โ15 injections over the years maintain a sustained response.
Main adverse effect: urinary retention in 7โ10% of cases (quote ~10% to the patient to be safe). The patient must be willing to perform clean intermittent catheterisation if required. Those who do not accept this risk are not candidates for the procedure. Retention resolves as the drug effect wanes (within a few months).
Cost: covered by the National Health Service โ an important advantage over oral drugs.
Percutaneous placement of an electrode in the S3 sacral foramen, connected to a subcutaneous neurostimulator (similar to a cardiac pacemaker). Mechanism of action not fully elucidated but demonstrated to be effective.
Two-stage procedure: first, electrode implant with an external neurostimulator for a 2โ4-week trial; if the response is positive, permanent generator implant in the gluteal or abdominal pocket.
Advantages over botulinum toxin: no retention risk, no need for self-catheterisation โ ideal for patients who do not accept that risk.
Disadvantages: very high cost (single manufacturer: Medtronic). The battery depletes periodically and must be replaced. Cost-effectiveness analysis is unfavourable compared to botulinum toxin.
Non-responders to botulinum toxin: neuromodulation is the main alternative, although some patients do not respond to this either.
Reserved for cases refractory to all previous therapies. The bladder is augmented with an ileal segment (augmentation cystoplasty), or โ more commonly in patients with associated chronic pelvic pain โ cystectomy with urinary diversion is performed (as for bladder carcinoma).
Both are major surgical procedures with risks related to intestinal use (metabolic and infectious complications). After cystoplasty, many patients require clean intermittent catheterisation. Incidence: 1โ2 cases per year even at high-volume centres.
Botulinum toxin and sacral neuromodulation have comparable efficacy in randomised trials. The choice depends on:
Fluid restriction, timed hydration schedule, review of concomitant medications. Reassessment with voiding diary.
If unsatisfactory: optimise dosage, switch formulation (extended release, patch), or combine. Follow-up at 3 months.
To confirm detrusor overactivity before proceeding to invasive treatments.
First choice for second-line therapy. Effective, NHS-covered, repeatable. Inform the patient of the self-catheterisation risk (~10%).
Alternative to botulinum toxin or after treatment failure. Costly, with no retention risk.
Augmentation cystoplasty or cystectomy with diversion. Only in cases refractory to all of the above.