270

Practical Urology: EssEntial PrinciPlEs and PracticE

Videocystometrography (Cystometry + Cystourethrography)

diameter saline-filled plastic pressure catheter

If appropriate radiological facilities exist, the

inserted into the sub-terminal site hole is gently

inserted into the bladder and the two catheters

bladder can be filled with contrast media thus

then disengaged. The bladder is filled via the

allowing the simultaneous screening of the blad-

10 F catheter which is removed prior to the void-

der and outflow tract during filling and voiding

ing phase leaving the fine catheter in situ.

to be conducted (cystourethrography). When

Alternatively a 6, 7, or -8 Fr dual-lumen catheter

these two procedures are combined this results

can be used which avoids the need to use two

in the gold standard investigation, the videocys-

catheters and then disengage them. The intra-

tometrogram or videourodynamic study. Radio-

vesical pressure can also be measured via a

logical screening provides valuable additional

suprapubic route. The bladder can be drained of

anatomical information on the appearance of

urine and this initial residual volume recorded,

the bladder,the presence of vesicoureteric reflux,

alternatively the study can be carried out by

the degree of support to the bladder base during

filling on top of the initial residual and calculat-

coughing and by itself is more than adequate for

ing the residual at the end of the study by

the diagnosis of sphincteric competence, and/or

subtraction.

the level of any outflow obstruction in the lower

The intra-abdominal pressure is measured

urinary tract on the voiding phase. This infor-

via a pressure recording rectal catheter, inserted

mation, along with the accompanying pressure

10–15 cm above the anal verge, but may also be

flow tracings, can be recorded on a video tape

inserted into the vagina or a stoma. The patient

allowing subsequent review and discussion. The

is asked to cough to check for dampening of the

majority of patients can be adequately investi-

signal, this is repeated throughout the procedure

gated using the simpler urodynamic techniques

as a quality control method (a cough should

described including simple cystometry. Video-

increase both intra-abdominal pressure and

cystometry is however essential for the adequate

intra-vesical pressure but only show as a blip on

assessment of complex cases where equivocal

the detrusor trace). The catheters are then con-

results have been obtained from simpler inves-

nected to the transducers. The most common

tigations, for the definition of neuropathic

transducers are fluid filled and rely on faultless

disorders, and in situations where there has

positioning of transducer and meticulous fluid

been an apparent failure of a previous surgical

height referencing. Artifacts may be caused by

procedure.

air within the system,dampening waves or kinks

Technique for Videocystometrography/Cystometry: The

within tubing, blocking readings. These must be

detrusor pressure is estimated by the automatic

eliminated. All systems are zeroed at atmo-

subtraction of rectal pressure (as an index of

spheric pressure. For catheter mounted trans-

intra-abdominal pressure) from the total blad-

ducer, the reference point is the transducer itself.

der pressure (intra-vesical pressure), thus

For external transducers, the reference point is

removing the influence of artifacts produced by

the level of the superior edge of the symphysis

abdominal straining. During this study notice is

pubis. Newer air charged transducers remove

taken of the initial bladder residual, the bladder

this need and are gaining popularity but still

volume at the time of the patient’s first sensation

need to be validated. The two pressure measure-

of filling, the final tolerated bladder volume and

ment lines are then connected to the transduc-

the final residual volume after voiding.

ers incorporated in the urodynamic apparatus.

Patients, excluding those with indwelling

The lines are flushed through, great care being

catheters, are asked to void into a flowmeter to

taken to exclude all air bubbles from both the

allow measurement of a free flow rate. Next, a

tubing and transducer chambers. Contrast

fluid-filled rectal catheter is introduced into the

medium or saline (in a “non-video” study) at

rectum, the end of the tube being protected with

room temperature is then instilled into the blad-

a finger stall to prevent fecal blockage, (a slit is

der at a predetermined rate under the control of

cut in this to prevent tamponade producing arti-

a peristaltic pump. Medium and fast fill (50–

factual results during the study).With the patient

100 mL/min) is used routinely, although slower

in the supine position, the external urethral

filling rates (10–25 mL/min) approaching the

meatus is cleaned with antiseptic solution.

physiological range are mandatory in the assess-

A 10Ch Nelaton filling catheter with a 1 mm

ment of the neuropathic bladder.