280

Practical Urology: EssEntial PrinciPlEs and PracticE

blockade of the prostate). In this context it is

far from satisfactory. Urethral pressure profi-

notable that in recent years it has been

lometry although useful in the assessment of

increasingly recognized that an important

sympatholytic agents in drug trials is not appro-

component of prostatic obstruction results

priate as a diagnostic technique. The dynamic

from smooth muscle contraction within the

evaluation of urethral sphincter function by the

pathologically enlarged prostate.

use of anal or skin mounted electrodes is inac-

curate. Accurate electromyographic evaluation

of the urethral sphincter is possible with a con-

Detrusor–Urethral Dyssynergia

centric needle electrode but it is a painful inves-

tigation and cannot be carried out during

In detrusor–urethral dyssynergia there is syn-

voiding.

chronous contraction of the detrusor and urethra.

It can be subdivided depending upon the struc-

tures involved into detrusor–bladder neck dys-

Urethral Pressure Measurement

synergia and detrusor–sphincter dyssynergia.

Detrusor–Bladder Neck Dyssynergia

At rest the urethra is closed and this must be

recognized when interpreting the results of ure-

This refers to a detrusor contraction in the

thral pressure studies. The urethral pressure and

the urethral closure pressure are therefore ideal-

presence of incomplete bladder neck opening

ized concepts which represent the ability of the

on micturition. It is not uncommon in the gen-

urethra to prevent leakage. In current urody-

eral population, and is a common cause of

namic practice, the urethral pressure is mea-

voiding dysfunction in younger males. It is

sured by a number of different techniques,which

thought to be a congenital abnormality, and

do not always yield consistent values. Not only

commonly presents in the third and fourth

do the values differ with the method of mea-

decades of life.

surement but there is often lack of consistency

for a single method. For example the effect of

Detrusor–Sphincter Dyssynergia

catheter rotation when urethral pressure is mea-

sured by a catheter mounted transducer and the

Detrusor–sphincterdyssynergia(DSD)describes

considerable artifacts which automatically result

from the introduction of any catheter into the

a detrusor contraction occurring at the same

urethra.

time as an involuntary contraction of the ure-

thral or periurethral striated smooth muscle.

Obstructive overactivity of the striated ure-

Technique

thral sphincter muscle may occur in the absence

of detrusor contraction, but is not DSD. This

Measurements may be made at one point in the

condition is uncommon in the general popula-

tion, it affects women in particular and is most

urethra over a period of time,or at several points

commonly seen in association with polycystic

along the urethra consecutively forming a ure-

ovary disease.

thral pressure profile (UPP).

Detrusor–sphincter dyssynergia is usually

At rest the urethral pressure profile denotes

associated with neurological disorders, com-

the intra-luminal pressure along the length of

monly supraspinal lesions, and the diagnosis

the urethra. All systems are zeroed at atmo-

needs to be treated with caution in the absence

spheric pressure. For external transducers the

of a documented neurological deficit.

reference point is the superior edge of the sym-

physis pubis. For catheter mounted transducers

the reference point is the transducer itself. Intra-

Complex Urodynamic Investigation

vesical pressure should be measured to exclude

a simultaneous detrusor contraction. The sub-

traction of intravesical pressure from urethral

The current techniques available for the investi-

pressure produces the urethral closure pressure

gation of urethral sphincteric dysfunction are

profile.