Introduction

Conventional (laboratory) cystometry is the ‘gold standard’ in measuring bladder function. However, it is a static test and is considered ‘nonphysiological’, involving rapid retrograde filling of the bladder in a laboratory setting, which does not always allow reliable reproduction of symptoms. Ambulatory urodynamic monitoring (AUM), using micro-tip pressure transducers and a digital solid-state recorder, is a useful additional test for women in whom conventional urodynamics fails to reproduce or explain the lower urinary tract symptoms of which they complain. This system allows information to be recorded digitally, downloaded and reviewed at the end of the test. The trace can then be expanded or compressed without loss of information.

Differences between AUM and conventional cystometry

AUM is performed in accordance with the International Continence Society (ICS) Standardisation of Ambulatory Urodynamic Monitoring.

‘Ambulatory’ refers to the nature of the urodynamic monitoring rather than the mobility of the subject and, although it records the same measurements as conventional urodynamics, it differs principally from conventional cystometry in the following ways:

1. □ AUM is performed over a longer period of time (4 hours) and allows more than one cycle of bladder filling and voiding.

2. □ It utilises natural bladder filling (a standard fluid intake, such as 200ml half-hourly, is recommended).

3. □ It takes place outside the urodynamics laboratory.

4. □ Its portability allows reproduction of a patient's normal activities of daily living more easily. These may include manoeuvres designed specifically to identify the presence of involuntary detrusor or urethral activity or to provoke incontinence.