How is an overactive bladder diagnosed?

Overactive bladder (OAB) is a symptom complex of urinary urgency, with or without urge incontinence, frequency and nocturia. There are different types of OAB and urodynamics can help to diagnose the cause of bladder dysfunction.

Clinical practice points. In practice a clinical diagnosis of OAB is made based on clinical symptoms the patient describes. Your treatment decisions will be based mainly on what the person tells you. This is why it is so essential to listen to your patient and to ask the right questions.

Key symptoms

To identify OAB look for indications of these symptoms, including:

• Urgency — on an urgency scale of 0-4, where 4 is highest
• Frequency — more than seven voids a day, could be several times an hour
• Low voided volumes — 20, 50, 100, 150ml or less (resulting in decreased bladder capacity)
• If OAB wet — variable-sized wet patches because unstable bladder contraction can happen at any level of bladder filling
• Nocturia — night-time waking to void
• Poor stream — (constantly voiding of small volumes)
• Feeling of incomplete bladder emptying — bladder not filling effectively
• Reduced fluid intake
• Concentrated urine
• Constipation

Patients are encouraged to fill in a bladder diary. A sample bladder diary is available for you to view in PDF format.

Aggravating factors include:

• Caffeine
• Alcohol
• Anxiety/fear
• Constipation

Types of OAB

OAB is a clinical diagnosis. It may be separated into idiopathic, neurogenic and sensory urgency.

Idiopathic

Idiopathic OAB (of unknown cause) forms the majority of cases.

Neurogenic

Neurogenic OAB arises from the nervous system. Neurological lesions resulting from strokes, Alzheimer’s disease, multiple sclerosis, spinal cord injuries, Parkinson’s disease and others cause a loss of inhibitory impulses from the frontal cortex of the brain.

The sacral reflex arc becomes more dominant, resulting in frequent, spontaneous contractions of the detrusor muscle during the filling phase.

There is increased sensory input from the bladder, such as urinary tract infection, faecal impaction, prostatic enlargement, bladder stones, bladder tumours.

Sensory urgency

Sensory urgency often presents after an individual has had a urinary tract infection. At low levels of bladder filling, perhaps only 25ml, the person experiences a strong urgent desire to void, feels that their bladder is full, rushes to the toilet but can only pass a small volume of urine with a poor stream.

This could occur 3-4 times an hour, resulting in a daytime frequency of 20+ times. In most cases there is no wetting.

In most cases this is a daytime problem only (no nocturia) and the person will void a normal volume in the morning of 300-400ml. Sensory urgency can be very effectively and quickly treated, with an explanation about what is happening, and advice about bladder training.

The person has the bladder capacity but is receiving the wrong messages.

Urodynamics investigation

Urodynamics are clinical investigations undertaken to assess how the bladder and urethra are storing and releasing urine.

They help to diagnose the cause of bladder dysfunction. Urodynamic studies (UDS) use clinical procedures such as cystometry and uroflowmometry to investigate and measure different aspects of bladder functioning.

The investigations look at muscle function, mechanics, and nerve responses of the bladder and urinary tract. UDS can tell if a person is experiencing OAB because of detrusor overactivity (DO), which is sub-divided into neurogenic detrusor overactivity (NDO) or idiopathic detrusor overactivity (IDO).