[When is a urodynamic investigation indicated for overactive bladder?]

Overactive bladder (OAB) is generally not disease specific. Symptoms are frequency, nocturia, and urgency with or without urge incontinence. The prevalence of 16.6%, evaluated in six European countries, is surprisingly high. Causes for overactive bladder are an increase of sensory stimulation and/or a decrease of sensory threshold of the bladder or a disproportion between strength of afferent stimulation and central inhibition of micturition reflex resulting in detrusor overactivity. Overactive bladder is a symptom-based diagnosis. Urodynamics is an important diagnostic tool in daily routine. Urodynamics encompasses a spectrum of different techniques and is more than just cystometry. Simple cystometry or video cystometry should be carried out after evaluation with a frequency volume chart, flow rates, and residuals, mostly by ultrasound. Urodynamic observations should never be discussed separately but always together with history, symptoms, signs, and pathological findings. It is not necessary to perform a filling and voiding cystometry in each patient with symptoms and signs of overactive bladder. Indications for cystometry are prior to invasive therapy or where previous medical or surgical therapy has failed, after pelvic surgery or pelvic irradiation, in patients with signs or symptoms suggestive of an emptying disorder, in neurological disorders, or where there is any doubt about the diagnosis. Diagnostic evaluation of geriatric patients with overactive bladder can usually be accomplished with a basic assessment while invasive procedures should be the exception.