Ambulatory Urodynamics

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Functional Urology Unit, Casa Madre Fortunata Toniolo, Bologna, Italy

Conventional urodynamics is a “nonphysiological” test, since it involves a retrograde rapid filling of the bladder in a laboratory setting which does not always allow a reliable reproduction of patient symptoms.

Conversely, ambulatory urodynamic monitoring (AUM) analyzes the bladder and urethral function in the condition of everyday life.

The ICS defines AUM as “any functional test of the lower urinary tract predominantly utilizing natural filling the urinary tract and reproducing subject’s normal activity.”

The main differences of AUM from conventional urodynamics can be summarized as follows:

The study is performed over a longer period of time, usually 4 h, and allows more than one cycle of bladder filling and voiding.
It utilizes a natural bladder filling (a standard fluid intake of 200 ml half-hourly is recommended).
It takes place outside the urodynamic laboratory.
Normal activities of daily living (specific maneuvers to provoke detrusor overactivity or incontinence are suggested) are reproduced more easily.

AUM has a specific indication in those cases in which conventional urodynamics fail to clarify the patient complaints providing a second-line investigational modality to standard urodynamic methods.

11.1 Equipment

The equipment of AUM has been miniaturized over the years and with the advent of air-charged catheters the recording has become easier. The system includes:

The recording unit
The event sensors (pressure, EMG, leakage)
A uroflowmeter
A desktop/laptop computer
Software to download and analyze the recorded data

The recording unit must be lightweight and portable to allow freedom of movement. It should have a facility to mark events on the traces to allow a better interpretation of the recordings (Fig 11.1).

Figure 11.1

Wireless Bluetooth AUM unit (Courtesy of MMS)

In any case, a bladder diary written by the patient should always be recommended during test.

The recorder should have the ability to be connected to a uroflowmeter, preferably by a wireless technology, to allow simultaneous recording of pressure and flow.

Pressure transducers are usually solid-state 7-Fr bladder and rectal catheters. Recently air-charged catheters have been introduced. The advantage of these catheters over the fluid-filled type is that they are at less risk of movement artifacts and don’t need adjustment of reference point.

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