URODYNAMIC APPARATUS

Typical Number in Hospital: 1

Cost Bands: 6

References:

Some disorders of the bladder and urethra, especially those resulting in urinary incontinence or retention, are investigated in a special urodynamic clinic which may be in the urology, gynaecology or X-ray department. The main apparatus is a multichannel chart recorder with additional equipment which may include a uroflowmeter, profilometer, catheter puller, and X-ray fluoroscope. The multichannel recorder may include the functions of a cystometer, urethral pressure profile recorder and electromyograph.

Typical urodynamic tests may include:

1. Cystometry. The bladder is filled through a urethral catheter while recording the pressure generated within the bladder. Often the net contribution to pressure from the bladder muscle itself is recorded by electronically subtracting the pressure in the rectum from the total pressure in the bladder.

2. Urometry. The flow rate during normal bladder emptying is plotted on the chart recorder. The total volume voided is also calculated.

3. Profilometry. A plot of pressure along the urethra is recorded using an external pressure transducer with a slow infusion through the urethral catheter, or a tiny pressure transducer may be mounted on the recording catheter. The catheter may be moved along the urethra using a catheter puller.

4. Urethral pressure transmission tests. Pressures recorded from the rectum are subtracted from the pressures detected at various points along the urethra during coughing or straining. The relative changes in the two pressures are used to assess the ability of the urethra to close in response to high abdominal pressures.

5. Fluid bridge test. Penetration of urine into the upper part of the urethra during coughing and straining can be detected by pressure measurements, or by leakage into a catheter opening into the urethra, or by electrical impedance measurements between two metal rings mounted on the urethral catheter.

6. Electromyography. The action of muscles in and around the urethra may be recorded during the tests using electrodes mounted on the urethral catheter, using needle electrode inserted into the muscles, or from surface electrodes on the perineum.

7. Cystoscopy. Direct viewing of the inside of the bladder and urethra via a cystoscope or urethroscope can sometimes provide additional information about urodynamic function.

8. Fluoroscopy. The bladder is filled with an X-ray contrast medium and viewed during filling, during straining and coughing, and during emptying. Diagnostic information is obtained from the shape of the bladder base and from visualization of the entry of contrast medium into the urethra.

In many cases a video tape recording is made of the X-ray image of the bladder and urethra overlayed with the pressure, EMG and flow recordings.