Int Urogynecol J (2012) 23:269–277 DOI 10.1007/s00192-011-1585-y
REVIEW ARTICLE
Normal urodynamic parameters in women Part II—invasive urodynamics Wally Mahfouz & Tala Al Afraa & Lysanne Campeau & Jacques Corcos
Received: 3 May 2011 / Accepted: 6 October 2011 / Published online: 20 October 2011 # The International Urogynecological Association 2011
Abstract Introduction and hypothesis This literature review, providing reference ranges of normal variability in urodynamic parameters, is the second part of a two-part article. The first part addresses non-invasive urodynamics (UDS), while the second part addresses invasive techniques. Methods Data were obtained through MEDLINE from articles published between January 1956 and February 2011, International Continence Society meeting abstracts, and standardization reports. Search terms included cystometry, urethral pressure profilometry, leak point pressure, video UDS, normal volunteer, pressure flow studies, and electromyography. Results Normal values varied widely in the literature. However, with the help of clinical data, it was possible to define “normality” ranges for most of the different parameters. Conclusions Urodynamic evaluation of lower urinary tract (LUT) function is not a physiological test. However, it is still the best available tool for LUT function assessment. Even if normality in UDS can be defined, tests must always be interpreted against patient characteristics, complaints, and symptoms. Keywords Urodynamics . Normal volunteer . Cystometry . Pressure flow study . Urethral pressure profilometry . Electromyography (EMG) W. Mahfouz : T. Al Afraa : L. Campeau : J. Corcos Department of Urology, Jewish General Hospital, McGill University, Montreal, Quebec, Canada J. Corcos (*) Department of Urology, Jewish General Hospital, 3755 Côte Sainte-Catherine, Montreal, QC H3T 1E2, Canada e-mail:
[email protected]
Introduction Non-invasive urodynamics (UDS) consists of tests [voiding diaries, flowmetry, post-void residual (PVR) estimation and pad tests], which do not require any patient manipulation. In contrast, invasive UDS warrants the insertion of catheters, transducers, and/or needle sets into patients. While non-invasive tests are useful tools for screening (i.e., flowmetry) or diagnosis (i.e., voiding diaries), invasive tests are necessary to confirm the diagnosis and refine the findings. The invasiveness of these tests raises the problem of their nonphysiological recording. Acknowledging their limitations, such tests must always be interpreted by an experienced urologist with knowledge of recording conditions and patients’ complaints and symptoms.
Method Data were obtained from various sources, including MEDLINE search via PubMed, for articles published between January 1956 and February 2011, International Continence Society (ICS) meeting abstracts and Standardization Committee reports as well as the bibliographies of retrieved articles and book chapters. The key terms searched were UDS, cystometry, urethral pressure profilometry, leak point pressure, PVR urine, video UDS, normal volunteer, pressure flow studies, and electromyography (EMG). Based on a literature review, we report normal UDS values and ranges in women. Limits Such a review, gathering together results from normal volunteers as well as patients, and trying to define
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normality have limits. The heterogeneity of the population, the absence of standardized technical methods for some testings, and the frequent absence of gender and age consideration in the interpretation of data, are many limiting factors for such articles. Taking this into consideration, we hope that future research in urodynamics will address this heterogeneity by studying a large cohort of normal volunteers to conform or modify our findings. Cystometry The principal aim of cystometry is to reproduce patient symptoms and relate them to any synchronous urodynamic events [1]. During the filling phase, abdominal and bladder pressures are recorded via rectal and urethral catheters, respectively, whereas detrusor pressure (Pdet) is calculated by subtracting abdominal pressure from bladder pressure. Initial resting abdominal and bladder pressures are 5–20 cm H2O in the supine position, 15–40 cm H2O in the sitting position, and 30–50 cm H2O in the standing position [2]. Pdet in an empty bladder varies between 0 and 10 cm H2O in 90% of cases [3]. Normal Pdet during bladder filling at a rate of 50–60 ml/s should be 40 ml/cm H2O. Wyndaele [10] conducted a urodynamic study of 30 volunteers (20 male and 10 female volunteers), and found that compliance was higher in female than in male volunteers, with normality exceeding 100 ml/cm H2O. The ICS [5] recommends two standard points for measuring bladder compliance: detrusor pressure at empty bladder and at maximum bladder capacity or immediately before the start of any detrusor contraction that causes significant leakage. Both points are measured excluding any detrusor contraction. Wahl et al. [13, 14] developed another method for measuring bladder compliance that they claimed was more accurate and practical, especially in children. They standardized bladder compliance according to a complex mathematical formula. 3. Detrusor stability during bladder filling The absence of involuntary detrusor contractions is considered to be normal and is defined as “stable detrusor activity” [10, 15]. Uninhibited detrusor contractions occur in 10–18% of asymptomatic volunteers and do not need any further evaluation in asymptomatic patients [10, 16]. Advance in ambulatory UDS has complicated discussion of DO, which has been shown to arise in 60% of asymptomatic women undergoing ambulatory UDS [17]. The significance of these DO in normal volunteers is not very well understood as shown by the study looking for correlation with other variables in this population. The mere absence of documented overactivity on cystometrograms (CMG) does not rule out its existence. Up to 40% of patients with urge incontinence do not show DO on CMG [18]. The 1988 ICS report [8] differentiated types of detrusor storage function, as determined by filling cystometry, into:
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Fig. 1 The normal cystometrogram curve has two phases: a filling phase, including all normal parameters during the storage phase (first sensation, detrusor function, bladder compliance, and capacity) and a voiding phase on pressure flow study
(a) normal detrusor function, which allows filling with little or no change in pressure and no involuntary phasic contractions despite provocation, and (b) overactive detrusor function, which is urodynamic observation characterized by involuntary detrusor contractions during the filling phase and may be spontaneous or provoked [19]. DO has a variety of patterns on urodynamic tracing. The 2002 ICS report [5] describes two types: (a) phasic DO, defined by its characteristic waveform, which may or may not lead to urinary incontinence, and (b) terminal DO, classified as a single involuntary detrusor contraction occurring at cystometric capacity, which cannot be suppressed and causes incontinence often resulting in complete bladder emptying [17].
Table 1 Normal reported cystometric parameters during filling in females
The first ICS report [20, 21] stated that, in order to diagnose “detrusor instability,” the contraction should be at least 15 cm H2O. However, it was subsequently realized that involuntary detrusor contractions of 10
given permission to void [5]. This volume includes both the amount voided and residual urine left after the void (PVR) [17]. Normal cystometric capacity varies widely, but is normally between 300 and 500 ml, with higher values in men than in women [10]. Wyndaele [10] conducted a urodynamic study of 30 volunteers (20 male and 10 female), with a mean age of 24 years, and reported wide variability of normal ranges. Bladder capacity was found to be larger in men than in women, ranging from 300 to 550 ml. Summary The bladder should have constantly low pressure that usually does not reach more than 6–10 cm H2O above baseline at the end of filling (end-filling pressure), and there should be no involuntary contractions, with normal first sensation ranging between 100 and 250 ml, bladder compliance between 30 and 100 ml/cm H2O, and maximum bladder capacity between 450 and 550 ml. Pressure flow (P/Q) P/Q study simultaneously measures Pdet and flow rate during voiding. P/Q assessment is considered to be the gold standard for quantifying and grading bladder outlet obstruction (BOO) and differentiating between BOO and detrusor underactivity [22–28]. P/Q data can be plotted on pressure flow nomograms to classify patients as being either obstructed or not obstructed and, at the same time, grade the severity of obstruction. Different types of nomograms have been developed. The most common in clinical practice are ICS nomogram [22], Abrams–Griffiths nomogram, Schafer nomogram, bladder contractility nomogram, urethral resistance factor, and the composite nomogram [17], but these nomograms are used in men only. During P/Q assessment, several parameters are recorded, including detrusor opening pressure, maximum detrusor pressure (Pdet.max), Pdet at maximum flow (Pdet :Qmax ), minimum detrusor pressure during voiding, maximum flow rate (Qmax), voided volume (VV), and PVR. The ICS has defined the following terms in the interpretation of P/Q [3,
5]. Pre-micturition pressure is intravesical pressure just before the onset of isovolumetric detrusor contraction. Detrusor opening pressure is Pdet recorded at the onset of measured flow, which tends to be elevated in patients with infravesical obstruction. Opening time is the time that elapses from the initial rise in Pdet to the onset of flow through the urethra. However, because flow rate is measured at a downstream location (i.e., flowmeter outside the urethra), flow rate measurement is slightly delayed from bladder pressure measurement. This flow delay, generally between 0.5 and 1 s, should be factored into the analysis [29]. Pdet :Qmax is the magnitude of detrusor contraction when flow rate is at its maximum [5]. Pdet.max is the maximal pressure recorded regardless of flow. This pressure can exceed pressure at maximal flow if the bladder is contracting isometrically against a closed outlet. Isometric detrusor pressure is obtained by mechanical obstruction of the urethra or by active contraction of the distal sphincter mechanism during voiding. Post-micturition contraction (after contraction) is a reiteration of detrusor contraction after flow has ceased, and its magnitude is typically greater than that of micturition pressure at maximal flow. After contractions are not well-understood, but they seem to be more common in patients with unstable or hypersensitive bladders [30]. PVR is the volume of urine remaining in the bladder immediately after voiding. Although the test situation often leads to inefficient voiding and falsely elevated residual urine, the absence of residual urine does not exclude infravesical obstruction or bladder dysfunction [17]. Wyndaele [10] attempted to define what can be considered as normal parameters by urodynamics in 38 healthy adult volunteers (28 men and 10 women) with a mean age of 24 years. Free flow rate, water cystometry, and P/Q assessment were performed in all of them. Micturition bladder pressure was higher in men than in women, reflecting higher outflow resistance in men, but Pdet was not statistically different between the sexes. Flow time was significantly longer, and Qmax was significantly lower during P/Q evaluation than during free flow rate measurement in both sexes. There was no residual urine at all in the
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majority of volunteers estimated by urethral catheter, but six men and three women had
