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VALSALVA
LEAK POINT PRESSURE IN THE EVALUATION OF STRESS URINARY INCONTINENCE
T.M. LANE, P.J.R.
SHAH
Institute
of Urology and Nephrology, London, England
ABSTRACT
Videourodynamics
probably represents the most precise method of classifying stress urinary
incontinence and without doubt is our preferred investigation of choice.
It both confirms the demonstrable loss of urine from the urethra during
a stress manoeuvre (when the vesical pressure exceeds urethral pressure
in the absence of a detrusor contraction) and the severity of sphincteric
dysfunction once the diagnosis of SUI has been established. Whilst few
would argue with the importance of the videourodynamic examination it
does necessitate simultaneous fluoroscopic examination of the lower urinary
tract as well as multi-channel urodynamics. These facilities are not always
readily available. Given that cystometrograms and urethral profilometry
fail to provide the requisite information regarding the bladder neck and
proximal urethra there arose the need for an easily reproducible method
(not requiring access to more complex and expensive equipment) which could
identify sphincteric dysfunction.
Observations during thousands of urodynamics
demonstrated that 76% of those classified as having type III SUI (intrinsic
sphincter deficiency) were recorded as having consistently low leak point
pressures (less than 60 cm H20). The significance of this lies principally
in the ease with which Valsalva leak point pressure (VLPP) can be established
with only basic urodynamic equipment and without necessary recourse to
formal videourodynamic examinations. It has over the last few years evolved
as an easily performed and reliable test to determine the ability of the
urethra to resist the expulsive force of the bladder generated by increased
intra-abdominal pressure. The VLPP represents the lowest bladder pressure
at which urethral leakage occurs during a prompted stress manoeuvre. It
represents a dynamic test, which documents the abdominal pressure required
to induce incontinence.
Perhaps a more convincing attestation to
the potential clinical utility of VLPP represents the change in values
before and after anti-incontinence procedures. Bladder neck collagen injection
for example results in an elevation in VLPP measures, which is commensurate
with the clinical improvement in symptoms.
Given the VLPP utility in identifying pre-operatively
those patients in whom there is an appreciable level of sphincter dysfunction
then it offers the opportunity (even for those without ready access to
videourodynamics examinations) for improved selection of patients for
particular (and appropriate) surgical interventions aimed at dealing with
urethral coaptation with or without bladder neck re-approximation.
Key words:
urinary incontinence, urodynamics, diagnosis, urethra, bladder
Braz J Urol, 26: 420-425, 2000
INTRODUCTION
The
term valsalva (or abdominal) leak point pressure (VLPP) represents a measure
of the intravesical pressure that is required to overcome urethral resistance
during a stress manoeuvre such as coughing or straining. As a dynamic
test, it is a reflection of the stress competence of the urethra, which
ultimately mirrors its ability to resist abdominal pressure as an expulsive
force (1). Detrusor leak point pressure (DLPP) by contrast is the pressure
at which detrusor stretch or contraction generates sufficient force to
induce involuntary urinary leakage. Whilst the latter has found importance
in its ability to predict upper tract deterioration (2) in those with
neuropathic bladders (an integral part in the pressure-based management
of such patients) VLPP has found increasing utility as a simple surrogate
for the more complex videourodynamics (VCMG) in that it provides an indication
as to the extent to which intrinsic sphincter dysfunction (ISD) is responsible
for incontinence.
THE EVOLUTION OF
VALSALVA LEAK POINT PRESSURE
The
inability of the anterior repair to make a significant long-term contribution
to the management of stress urinary incontinence (SUI) saw its eventual
demise. An era of more accurate patient selection and the more efficacious
retropubic procedures was soon ushered in and was reflected by ever-improving
clinical outcomes. There remained however a significant proportion of
patients, who despite adequate bladder-neck re-approximation, continued
to have SUI. In this group of patients sphincteric dysfunction appeared
as a recurrent feature in those failing surgical intervention. Poor urethral
closing pressures (in those performing urethral profilometry) was a frequently
noted finding with maximal urethral closure pressures (MUCP) inevitably
below 20 cm H0 (3). As such MUCP measurements of less than 20 cm H20 became
widely (and perhaps erroneously) regarded as a measure of intrinsic sphincter
deficiency.
ISD
represents an inability of the urethra to maintain mucosal coaptation
either at rest or in the presence of minimal physical stress and consequently,
incontinence results. Bladder neck suspension procedures in patients with
ISD unsurprisingly have a high incidence of failure because the underlying
pathology is that of urethral dysfunction and poor coaptation (none of
which are addressed by re-approximation). Stress incontinence (as a result
of bladder neck descensus) by contrast develops because of a pressure
transmission discrepancy between the bladder neck and urethra and is therefore
appropriately managed by bladder neck suspension.
The
role of MUCP measurements has until recently (especially in the Gynaecological
literature) been regarded as an appropriate investigation in those with
suspected ISD. Unfortunately, data, which appeared to suggest that a low
MUCP was diagnostic of ISD, was (for the large part) entirely retrospective
and based on a series of patients investigated following failed retropubic
procedures (4). MUCP estimation involves the automated withdrawal of a
microtip transducer through the urethra and recording the highest value
obtained. Unfortunately however the procedure is more an evaluation of
urethral sphincter function at rest and consequently represents a measure
of the passive resistance of the urethra (5). It critically fails to provide
information about the function of the bladder neck and proximal urethra.
Perhaps the greatest denial of ISD classification by urethral profilometry
is that the patient is not required to become incontinent during the study
and as such has been widely criticised by the International Continence
Society (ICS) as a means of establishing the diagnosis (6). As a static
study, it has been seen to correlate better with age than any other parameter.
It has an increasingly limited role in the assessment of SUI.
Videourodynamics
in our view represents the most precise method of classifying stress urinary
incontinence and without doubt is our preferred investigation of choice.
It both confirms the demonstrable loss of urine from the urethra during
a stress manoeuvre (when the vesical pressure exceeds urethral pressure
in the absence of a detrusor contraction) and the severity of sphincteric
dysfunction once the diagnosis of SUI has been established. Whilst few
would argue with the importance of the videourodynamic examination it
does necessitate simultaneous fluoroscopic examination of the lower urinary
tract as well as multi-channel urodynamics. These facilities are not always
readily available. Given that cystometrograms and urethral profilometry
fail to provide the requisite information regarding the bladder neck and
proximal urethra there arose the need for an easily reproducible method
(not requiring access to more complex and expensive equipment) which could
identify sphincteric dysfunction.
Observations
made by Edward McGuire during thousands of videourodynamic examinations
(7) demonstrated that 76% of those classified as having type III SUI (intrinsic
sphincter deficiency) were recorded as having consistently low leak point
pressures (less than 60 cm H20). The significance of this lies principally
in the ease with which VLPP can be established with only basic urodynamic
equipment and without necessary recourse to formal VCMG. It has over the
last few years evolved as an easily performed and reliable test to determine
the ability of the urethra to resist the expulsive force of the bladder
generated by increased intra-abdominal pressure (1). The VLPP represents
the lowest bladder pressure at which urethral leakage occurs during a
prompted stress manoeuvre. It represents a dynamic test, which documents
the abdominal pressure required to induce incontinence. The DLPP by contrast
documents the pressure at which leakage occurs driven by detrusor pressure.
Swift & Ostergard (8) have shown a poor correlation between MUCP and
ALPP (even to the extent that some patients with high MUCP values obtained
at urethral profilometry leaked during stress manoeuvres and were subsequently
recorded as having low VLPP values). Perhaps a more convincing attestation
to the potential clinical utility of VLPP represents the change in values
before and after anti-incontinence procedures. Bladder neck collagen injection
for example results in an elevation in VLPP measures, which is commensurate
with the clinical improvement in symptoms. MUCP measures however remain
unaltered and to our knowledge fail to show a consistent improvement by
any procedure designed to correct SUI.
Given
the VLPPs utility in identifying pre-operatively those patients in whom
there is an appreciable level of sphincter dysfunction then it offers
the opportunity (even for those without ready access to VCMG) for improved
selection of patients for particular (and appropriate) surgical interventions
aimed at dealing with urethral coaptation with or without bladder neck
re-approximation.
MEASUREMENT OF
VALSALVA LEAK POINT PRESSURE
There
is often considerable variability in the method of VLPP estimation and
as such, there has been increasing concern over the lack of standardisation
between units. Nevertheless, most investigators in the field adhere to
basic principles. Patients are generally positioned in the sitting or
standing position and intra-vesical pressure recorded via a 10-Fr microtip
pressure transducer catheter in the bladder. Intra-abdominal pressure
is monitored via a rectal probe. The bladder is filled with saline or
contrast material at a rate of 50 ml/min to a volume of 200 ml (or approximately
one half the expected functional capacity). The patient is then instructed
to make an increasing expulsive effort against a closed glottis (a progressive
Valsalva manoeuvre) until leakage is demonstrated. We generally repeat
the procedure and the lowest increase in vesical pressure, which results
in leakage is designated the VLPP. In the absence of fluoroscopy urethral
leakage has to be confirmed by direct vision and so appropriate patient
positioning to facilitate this is essential. The corresponding pressure
at the time of leakage is most accurately recorded by using an event marker
generally available on even basic urodynamic equipment.
In
the absence of leakage during a progressive valsalva manoeuvre the patient
is requested to cough. However, determining an accurate VLPP during a
cough is often difficult and is therefore generally tried only after a
valsalva manoeuvre has failed to demonstrate incontinence. If vigorous
coughing is ultimately necessary to cause leakage the VLPP is inevitably
high.
As
is readily apparent a variety of technical aspects of the procedure may
influence the values obtained and accordingly there is justified concern
over the reproducibility of measurements. The influence of bladder volumes
on VLPP for example has been investigated by some authors. Faerber (9)
determined the effects of vesical volume on the VLPP in an attempt to
determine the optimum volume for VLPP determination. Previously Theofrastous
& Miklos (10,11) had reported that VLPP decreased significantly with
increasing vesical volume. After an elegant study Faerber concluded that
vesical volumes of between 200-300 ml provided the most appropriate classification
in the majority of women with SUI and that volumes in excess of 300 ml
had the potential to incorrectly classify type I or type II incontinence.
Catheter
size used during VLPP estimation has similarly been cited as a possible
confounding factor in the effort to standardise values between units (11).
The catheter in effect acts as a barrier to urethral leakage and accordingly
makes urine loss more difficult to provoke. This in turn raises the recorded
level of VLPP. Some authors have proposed using an intra-vaginal catheter
to estimate abdominal pressures (and with some success by Miklos et al.,
ref. 11) which has enabled lower VLPP measurements to be obtained.
Provocation
testing is similarly poorly standardised. VLPP measurements obtained by
provocation coughing as compared to a progressive valsalva manoeuvre are
inevitably higher regardless of the difficulties in recording an accurate
VLPP. Our own preference is for a graduated valsalva manoeuvre, which
obviates some of the difficulties arising during cough-induced leakage.
However, if this fails to demonstrate incontinence we recommend a ‘six-cough’
test. As with the progressive valsalva manoeuvre the patient is asked
to cough with increasing force so as to record the lowest possible intra-abdominal
pressure to cause leakage.
Pelvic
prolapse can be a serious impediment to accurate VLPP estimation. Undiagnosed
prolapsing tissue may act to dissipate the expulsive force on the urethra.
It emphasises the pivotal role of an adequate pelvic examination despite
the increasing reliance on urodynamics for a precise diagnosis. Prolapse
necessitates manual reduction and repeat VLPP estimation to obviate the
occlusive influence on the urethra. Frequently surgery is undertaken to
correct pelvic prolapse only to reveal an underlying SUI and low VLPP.
Non-physiological positioning may similarly have a role in values obtained
as will the effect of co-existing detrusor instability and poor bladder
compliance. Whilst our own preference for video-urodynamics is clear those
undergoing VLPP estimation in the absence of lower urinary tract fluoroscopy
should undergo a filling cystometrogram prior to VLPP measurement.
CLINICAL UTILITY
OF VALSALVA LEAK POINT PRESSURE
It
is important to remember that less than half of those patients presenting
with the complaint of urine loss with coughing, sneezing and other exertional
activities ultimately have a diagnosis of SUI (12). Whilst SUI represents
a powerfully emotive symptom and sign, it ultimately remains a urodynamic
diagnosis. Blaivas & Olssen (13) emphasise the distinction between
SUI due to anatomical factors (such as urethral hypermobility) and sphincter
related problems (type III or ISD). The recommended procedure for ISD
is a sling procedure (cadaveric or sheath harvest) or newer modalities
such as the tension-free vaginal tape (TVT). Bulking agents such as collagen
and Macroplastique remain a minimally invasive alternative. Under such
circumstances there is a 95% success rate for a sling procedure and 65%
success for urethropexy. Because it is the failure of the urethra to co-apt
normally in ISD, suspension procedures (which do not address this deficiency)
have a high incidence of failure and consequently are not recommended
in this sub-group of patients. Unfortunately clear cut distinctions between
urethral hypermobility and ISD rarely exist in clinical practice. For
us it would seem a reasonable assumption that there exists a spectrum
of bladder neck mobility which can co-exist independently with a spectrum
of ISD in patients with demonstrable SUI. If the urethra leaks then it
undoubtedly has a degree of pathology, the degree of pathology being on
a continuum. VLPPs may have utility in establishing a ranking on that
continuum (14). When combined with a negative filling cystometrogram and
physical examination the VLPP adds significantly to the incontinence evaluation
by assessing the presence and magnitude of ISD. At the very least it identifies
those who might benefit from video-urodynamics where this is not routinely
available. A VLPP of 60 cm H20 or less indicates a significant degree
of ISD whereas a VLPP of 90 cm H20 or more is normally associated with
urethral hypermobility (given a history of SUI). There will of course
be intermediate values and in these cases there is likely to be an element
of hypermobility and ISD co-existing. If combined with a standard Blaivas
classification more confident recommendations might eventually prove possible.
For example, where there is significant bladder neck descent (type II)
and the VLPP is high, a standard suspension procedure is advised. In type
III SUI where there is both descensus of the bladder neck and a low VLPP,
then a sling procedure is the treatment of choice. Alternatively, when
there is minimal descensus (and a low VLPP) injectables such as collagen
or Macroplastique to the bladder neck might suffice.
Given
that patients are often only recognised as having ISD after a failed retropubic
procedure the importance of the VLPP is self-evident. It is even more
important if one considers that those who have had three or more failed
operations have only a success rate of 33% with further anti-incontinence
procedures. The first operation is always (or should be always) the best
opportunity for cure and if the VLPP can secure the appropriate patient
selection for particular interventions then this can only further improve
outcomes.
Whilst
the clinical use of VLPP has gained widest acceptance in the role of female
incontinence assessment it has found similar use in the investigation
of post-prostatectomy incontinence and myelodysplasia (15). Here one can
frequently demonstrate open dysfunctional internal sphincters that leak
and low abdominal pressures. VLPP estimation can in these cases equally
define and quantify the defect in the urethral sphincter function and
so modify treatment protocols accordingly.
VALSALVA LEAK POINT
PRESSURE IN THE CLASSIFICATION OF STRESS URINARY INCONTINENCE
There
exist 2 important components in the pathophysiology of SUI. Urethral hypermobility
and sphincteric weakness. Urethral hypermobility (perhaps best assessed
with a Q-tip test) is a difficult concept to define in that there exists
at least three different kinds of hypermobility (as defined by fast-scan
magnetic resonance imaging) none of which have a clear-cut relationship
with the degree of sphincteric weakness. Sphincteric weakness by contrast
exists as a spectrum of dysfunction. Given that in the patient with SUI
he or she must by definition have a weak urinary sphincter then VLPP measurement
represents the most accurate means of formally assessing this. Blaivas
(16) now recommends that the term ISD is put on hold (since all patients
with sphincteric incontinence have a weak sphincter) and that stress incontinence
simply be classified by two parameters: VLPP and the degree of hypermobility.
Stress urinary incontinence therefore should be regarded as having 2 categories,
sphincteric incontinence (urinary incontinence that occurs in the absence
of detrusor contraction) and stress hyperreflexia (urinary incontinence
during stress that is accompanied by an involuntary detrusor contraction).
In sphincteric incontinence only 2 parameters need be considered: a description
of the urethral hypermobility and a measure of the VLPP.
For
those previously unfamiliar with the concept of VLPP, it should be apparent
that its importance in the assessment of SUI can only increase further.
From its humble beginnings as a useful adjunct in the selection of surgical
interventions it is set to become a fundamental tenet in the understanding
and classification of the incontinent patient. The concept of ISD by contrast
now appears somewhat dated and far from individuals being labelled as
having a sphincteric weakness, all patients will be assumed to have a
degree of incompetence the extent of which is graded by the VLPP. Ultimately
however the true extent of the clinical applicability of VLPP will depend
on the ability of investigators to provide reproducible results that allow
accurate comparisons to be made between centres. In turn, this requires
standardisation of the technical aspects of VLPP determination so that
confidence in the significance of recorded values can be assured.
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______________________
Received: March 17, 2000
Accepted: April 12, 2000
_______________________
Correspondence address:
Julian Shah
Institute of Urology and Nephrology
University College London
Bland Sutton Institute
48 Riding House St
London W1P 7PN, England
Fax: + + (71) 673-7076
E-mail: rmsqjus@ucl.ac.uk
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