∗ From Abrams P, Blairvas JG Stanton SL, et al: Int Urogynecol J 1991;1:45-58.The International Continence Society (ICS) established a committee for the standardization of terminology of lower urinary tract function in 1973. Five of the six reports from this committee, approved by the Society, have been published ( ). The fifth report on “Quantification of urine loss” was an internal ICS document and appears, in part, in this document.
These reports are revised, extended, and collated in this monograph. The standards are recommended to facilitate comparison of results by investigators who use urodynamic methods. These standards are recommended not only for urodynamic investigations carried out on humans but also during animal studies. When using urodynamic studies in animals, the type of anesthesia used should be stated. It is suggested that acknowledgment of these standards in written publications be indicated by a footnote to the section ( ) “Methods and Materials” or its equivalent, to read as follows: “Methods, definitions and units conform to the standards recommended by the International Continence Society, except where specifically noted.”
Urodynamic studies involve the assessment of the function and dysfunction of the urinary tract by any appropriate method. Aspects of urinary tract morphology, physiology, biochemistry, and hydrodynamics affect urine transport and storage. Other methods of investigation such as the radiographic visualization of the lower urinary tract are a useful adjunct to conventional urodynamics. This monograph concerns the urodynamics of the lower urinary tract.
The clinical assessment of patients with lower urinary tract dysfunction should consist of a detailed history, a frequency/volume chart, and a physical examination. In urinary incontinence, leakage should be demonstrated objectively.
The general history should include questions relevant to neurological and congenital abnormalities as well as information on previous urinary infections and relevant surgery. Information must be obtained on medication with known or possible effects on the lower urinary tract. The general history should also include assessment of menstrual, sexual, and bowel function and obstetric history.
The urinary history must consist of symptoms related to both the storage and the evacuation functions of the lower urinary tract.
The frequency/volume chart is a specific urodynamic investigation recording fluid intake and urine output per 24-h period. The chart gives objective information on the number of voidings, the distribution of voidings between daytime and nighttime, and each voided volume. The chart can also be used to record episodes of urgency and leakage and the number of incontinence pads used. The frequency/volume chart is very useful in the assessment of voiding disorders and in the follow-up of treatment.
Besides a general urological and, when appropriate, gynecological examination, the physical examination should include the assessment of perineal sensation, the perineal reflexes supplied by the sacral segments S2-S4, and anal sphincter tone and control.
Procedures Related to the Evaluation of Urine Storage
Cystometry is the method by which the pressure–volume relationship of the bladder is measured. All systems are zeroed at atmospheric pressure. For external transducers, the reference point is the level of the superior edge of the symphysis pubis. For catheter-mounted transducers, the reference point is the transducer itself. Cystometry is used to assess detrusor activity, sensation, capacity, and compliance.
Before starting to fill the bladder, the residual urine may be measured. However, the removal of a large volume of residual urine may alter detrusor function especially in neuropathic disorders. Certain cystometric parameters may be significantly altered by the speed of bladder filling (see Compliance, Section The Detrusor during Voiding ).
During cystometry, it is taken for granted that the patient is aware, unanesthetized, and neither sedated nor taking drugs that affect bladder function. Any variations should be specified.
The following details should be given:
Access (transurethral or percutaneous).
Fluid medium (liquid or gas).
Temperature of fluid (state in degrees Celsius).
Position of patient (e.g., supine, sitting, or standing).
Filling method may be by diuresis or catheter. Filling by catheter may be continuous or incremental; the precise filling rate should be stated. When the incremental method is used the volume increment should be stated. For general discussion, the following terms for the range of filling rate may be used:
Up to 10 mL/min is slow fill cystometry (“physiological” filling).
10 to 100 mL/min is medium fill cystometry.
More than 100 mL/min is rapid fill cystometry.
The following details should be given:
Fluid-filled catheter: specify number of catheters, single or multiple lumens, type of catheter (manufacturer), size of catheter.
Catheter tip transducer: list specifications.
Other catheters: list specifications.
Cystometric terminology is defined as follows:
Intravesical pressure is the pressure within the bladder.
Abdominal pressure is taken to be the pressure surrounding the bladder. In current practice, it is estimated from rectal or, less commonly, extraperitoneal pressure.
Detrusor pressure is that component of intravesical pressure that is created by forces in the bladder wall (passive or active). It is estimated by subtracting abdominal pressure from intravesical pressure. The simultaneous measurement of abdominal pressure is essential for the interpretation of the intravesical pressure trace. However, artifacts on the detrusor pressure trace may be produced by intrinsic rectal contractions.
Bladder sensation . Sensation is difficult to evaluate because of its subjective nature. It is usually assessed by questioning the patient in relation to the fullness of the bladder during cystometry.
Commonly used descriptive terms include:
First desire to void .
Normal desire to void : defined as the feeling that leads the patient to pass urine at the next convenient moment, but voiding can be delayed if necessary.
Strong desire to void : defined as a persistent desire to void without the fear of leakage.
Urgency: defined as a strong desire to void accompanied by fear of leakage or fear of pain.
Pain (the site and character of which should be specified). Pain during bladder filling or micturition is abnormal.
The use of objective or semiobjective tests for sensory function, such as electrical threshold studies (sensory testing), is discussed under Sensory Testing (see Section Sensory Testing ).
The term “capacity” must be qualified as follows:
Maximum cystometric capacity , in patients with normal sensation, is the volume at which the patient feels he or she can no longer delay micturition. In the absence of sensation, the maximum cystometric capacity cannot be defined in the same terms and is the volume at which the clinician decides to terminate filling. In the presence of sphincter incompetence, the maximum cystometric capacity may be significantly increased by occlusion of the urethra, e.g., by Foley catheter.
The functional bladder capacity , or voided volume, is more relevant and is assessed from a frequency/volume chart (urinary diary).
The maximum (anesthetic) bladder capacity is the volume measured after filling during a deep general or spinal/epidural anesthetic, specifying fluid temperature, filling pressure, and filling time.
Compliance indicates the change in volume for a change in pressure. Compliance is calculated by dividing the volume change (ΔV) by the change in detrusor pressure (Δ Pdet ) during that change in bladder volume (C = ΔV/Δ Pdet ). Compliance is expressed as milliliters per centimeters of water pressure (see also Compliance, Section The Detrusor during Voiding ).
Urethral Pressure Measurement
The urethral pressure and the urethral closure pressure are idealized concepts that represent the ability of the urethra to prevent leakage (see Section Urinary Incontinence ). In current urodynamic practice, the urethral pressure is measured by a number of different techniques that do not always yield consistent values. Not only do the values differ with the method of measurement, but there is often lack of consistency for a single method (e.g., the effect of catheter rotation when urethral pressure is measured by a catheter mounted transducer).
Intraluminal urethral pressure may be measured:
At rest, with the bladder at any given volume.
During coughing or straining.
During the process of voiding (see Section Urethral Pressure Measurements during Voiding ).
Measurements may be made of one point in the urethra over a period, or at several points along the urethra consecutively forming a urethral pressure profile (UPP).
Two types of UPP may be measured in the storage phase :
Resting urethral pressure profile with the bladder and subject at rest.
Stress urethral pressure profile with a defined applied stress (e.g., cough, strain, Valsalva).
In the storage phase, the urethral pressure profile denotes the intraluminal pressure along the length of the urethra. All systems are zeroed at atmospheric pressure. For external transducers, the reference point is the superior edge of the symphysis pubis. For catheter-mounted transducers, the reference point is the transducer itself. Intravesical pressure should be measured to exclude a simultaneous detrusor contraction. The subtraction of intravesical pressure from urethral pressure produces the urethral closure pressure profile .
The simultaneous recording of both intravesical and intraurethral pressures is essential during stress urethral profilometry.
The following details should be given:
Infusion medium (liquid or gas).
Rate of infusion.
Stationary, continuous, or intermittent withdrawal.
Rate of withdrawal.
Position of patient (supine, sitting, or standing).
The following details should be given:
Open catheter: specify type (manufacturer), size, number, position, and orientation of side or end hole.
Catheter-mounted transducers: specify manufacturer, number of transducers, spacing of transducers along the catheter, orientation with respect to one another; transducer design, e.g., transducer face depressed or flush with catheter surface; catheter diameter, and material. The orientation of the transducer(s) in the urethra should be stated.
Other catheters, e.g., membrane, fiberoptic-specify type (manufacturer), size, and number of channels as for microtransducer catheter.
Measurement technique: For stress profiles, the particular stress employed should be stated, e.g., cough or Valsalva.
Recording apparatus: Describe type of recording apparatus. The frequency response of the total system should be stated. The frequency response of the catheter in the perfusion method can be assessed by blocking the eyeholes and recording the consequent rate of change of pressure.
Terminology referring to profiles measured in storage phase ( Fig. A.1 ) is defined as follows:
Maximum urethral pressure is the maximum pressure of the measured profile.
Maximum urethral closure pressure is the maximum difference between the urethral pressure and the intravesical pressure.
Functional profile length is the length of the urethra along which the urethral pressure exceeds intravesical pressure.
Functional profile length (on stress) is the length over which the urethral pressure exceeds the intravesical pressure on stress.
Pressure “transmission” ratio is the increment in urethral pressure on stress as a percentage of the simultaneously recorded increment in intravesical pressure. For stress profiles obtained during coughing, pressure transmission ratios can be obtained at any point along the urethra. If single values are given, the position in the urethra should be stated. If several pressure transmission ratios are defined at different points along the urethra, a pressure “transmission” profile is obtained. During “cough profiles,” the amplitude of the cough should be stated if possible. Note: The term “transmission” is in common usage and cannot be changed. However, transmission implies a completely passive process. Such an assumption is not yet justified by scientific evidence. A role for muscular activity cannot be excluded.
Total profile length is not generally regarded as a useful parameter.
The information gained from urethral pressure measurements in the storage phase is of limited value in the assessment of voiding disorders.
Quantification of Urine Loss
Subjective grading of incontinence may not indicate reliably the degree of abnormality. However, it is important to relate the management of the individual patients to their complaints and personal circumstances as well as to objective measurements.
To assess and compare the results of the treatment of different types of incontinence in different centers, a simple standard test can be used to measure urine loss objectively in any subject. To obtain a representative result, especially in subjects with variable or intermittent urinary incontinence, the test should occupy as long a period as possible, yet it must be practical. The circumstances should approximate to those of everyday life, yet be similar for all subjects to allow meaningful comparison. On the basis of pilot studies performed in various centers, an internal report of the ICS (5th) recommended a test occupying a 1-h period during which a series of standard activities was carried out. This test can be extended by further 1-h periods if the result of the first 1-h test was not considered representative by either the patient or the investigator. Alternatively, the test can be repeated having filled the bladder to a defined volume.
The total amount of urine lost during the test period is determined by weighing a collecting device such as a nappy, absorbent pad, or condom appliance. A nappy or pad should be worn inside waterproof underpants or should have a waterproof backing. Care should be taken to use a collecting device of adequate capacity. Immediately before the test begins, the collecting device is weighed to the nearest gram.
Typical Test Schedule
Test is started without the patient voiding.
Preweighed collecting device is put on and first 1-h test period begins.
Subject drinks 500 mL sodium-free liquid within a short period (maximum 15 min), then sits or rests.
Half-hour period: subject walks, including stair climbing equivalent to one flight up and down.
During the remaining period, the subject performs the following activities:
Standing up from sitting, 10 times.
Coughing vigorously, 10 times.
Running on the spot for 1 min.
Bending to pick up small object from floor, five times.
Wash hands in running water for 1 min.
At the end of the 1-h test the collecting device is removed and weighed.
If the test is regarded as representative, the subject voids and the volume is recorded.
Otherwise the test is repeated preferably without voiding.
If the collecting device becomes saturated or filled during the test, it should be removed and weighed and replaced by a fresh device. The total weight of urine lost during the test period is taken to be equal to the gain in weight of the collecting device(s). In interpreting the results of the test, it should be born in mind that a weight gain of up to 1 g may be due to weighing errors, sweating, or vaginal discharge.
The activity program may be modified according to the subject’s physical ability. If substantial variations from the usual test schedule occur, this should be recorded so that the same schedule can be used on subsequent occasions.
In principle, the subject should not void during the test period. If the patient experiences urgency, then he or she should be persuaded to postpone voiding and to perform as many of the activities in Section Typical Test Schedule (5a-e) as possible to detect leakage. Before voiding, the collection device is removed for weighing. If inevitable voiding cannot be postponed, then the test is terminated. The voided volume and the duration of the test should be recorded. For subjects not completing the full test, the results may require separate analysis, or the test may be repeated after rehydration.
The test result is given as grams urine lost in the 1-h test period in which the greatest urine loss is recorded.
Provided that there is no interference with the basic test, additional procedures intended to give information of diagnostic value are permissible. For example, additional changes and weighing of the collecting device can give information about the timing of urine loss; the absorbent nappy may be an electronic recording nappy so that the timing is recorded directly.
Presentation of Results
The following details should be given
Physical condition of subject (ambulant, chairbound, bedridden).
Relevant medical conditions of subject.
Relevant drug treatments.
In some situations the timing of the test (e.g., in relation to the menstrual cycle) may be relevant.
Findings . Record weight of urine lost during the test (in the case of repeated tests, greatest weight in any stated period). A loss of less than 1 g is within experimental error, and the patients should be regarded as essentially dry. Urine loss should be measured and recorded in grams.
Statistics . When performing statistical analysis of urine loss in a group of subjects, non-parametric statistics should be employed because the values are not normally distributed.
Procedures Related to the Evaluation of Micturition
Measurement of Urinary Flow
Urinary flow may be described in terms of rate and pattern and may be continuous or intermittent. Flow rate is defined as the volume of fluid expelled via the urethra per unit time. It is expressed in mL/s.
The following details should be given:
Patient environment and position (supine, sitting, or standing).
By diuresis (spontaneous or forced: specify regimen).
By catheter (transurethral or suprapubic).
Type of fluid.
The following details should be given:
Solitary procedure or combined with other measurements.
The terminology referring to urinary flow is defined as follows:
Continuous flow ( Fig. A.2 ):
Voided volume is the total volume expelled via the urethra.
Maximum flow rate is the maximum measured value of the flow rate.
Average flow rate is voided volume divided by flow time. The calculation of average flow rate is only meaningful if flow is continuous and without terminal dribbling.
Flow time is the time over which measurable flow actually occurs.
Time to maximum flow is the elapsed time from onset of flow to maximum flow.
The flow pattern must be described when flow time and average flow rate are measured.
Intermittent flow ( Fig. A.3 ):
The same parameters used to characterize continuous flow may be applicable if care is exercised in patients with intermittent flow. In measuring flow time, the time intervals between flow episodes are disregarded.
Voiding time is total duration of micturition, i.e., includes interruptions. When voiding is completed without interruption, voiding time is equal to flow time.
Bladder Pressure Measurements during Micturition
The specifications of patient position, access for pressure measurement, catheter type, and measuring equipment are as for cystometry (see Section Cystometry ).
The terminology referring to bladder pressure during micturition is defined as follows ( Fig. A.4 ).
Opening time is the elapsed time from initial rise in detrusor pressure to onset of flow. This is the initial isovolumetric contraction period of micturition. Time lags should be taken into account. In most urodynamic systems, a time lag occurs equal to the time taken for the urine to pass from the point of pressure measurement to the uroflow transducer.