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What are the symptoms of an overactive bladder?

With an overactive bladder the detrusor muscle contracts spontaneously during filling and the person feels a sudden and strong urge to urinate

The defining symptom of an overactive bladder (OAB) is Urgency[1] which is defined by the International Continence Society (ICS) as being:

‘the complaint of a sudden compelling desire to pass urine, which is difficult to defer’

Usually the person gets little or no warning.

Overactive bladder syndrome[1] is defined by the ICS as being:

‘Urgency, with or without urge incontinence, usually with frequency and nocturia’.

So the person with OAB must have urgency, but they may also have:

  • Frequency of more than seven times a day
  • Urge incontinence (OAB wet) where urgency results in actual leakage of urine, usually on the way to the toilet
  • Nocturia (waking to pass urine during the main sleep period))

What is the detrusor muscle?

Normally the detrusor muscle is relaxed during bladder filling and contracts only when voluntary voiding is initiated.

With OAB the detrusor muscle contracts spontaneously during filling and the person feels a sudden and strong urge to void. They may not reach the toilet in time.

Strong detrusor contraction can empty the bladder completely, so urine floods out and runs down the person’s leg. This is a feature of urgency urinary incontinence (UI) as compared to stress UI, where small volume leaks and squirts occur.

Detrusor muscle contractions occur spontaneously at low urine volumes (eg 50-80ml), or on provocation (eg cold weather, hearing running water, key in the lock syndrome, vibrations such as sitting on a bus). There is a failure to inhibit the reflex arc and the higher control centres fail to suppress the urgency, but the actual cause of why this happens is not fully understood.

OAB symptoms are unpredictable and can be very debilitating but most can be effectively treated[2].


1. Glossary of terminology. International Continence Society. [Cited 24 August 2018]. Available from:

2. Kinsey D, Pretorius S, Glover L, Alexander T. The psychological impact of overactive bladder: A systematic review. Journal of Health Psychology 2016;21(1);69–81. [Cited 23 August 2018] Available from:

© Association for Continence Advice. CC BY-NC 4.0
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Understanding Continence Promotion: Effective Management of Bladder and Bowel Dysfunction in Adults

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