WEDNESDAY SEPTEMBER 5 – 8AM TO 12PM
SESSION III
WORKSHOP 25
TITLE
TYPE
CHAIR
ROOM
DESCRIPTION
Ultrasound for the pelvic floor: more than a handy gizmo?
Interactive Seminar
Margaret Sherburn
SPEAKERS
Margaret Sherburn
Jennifer Kruger
Judith Thompson
Chantale Dumoulin
The aim of the workshop is to provide health care
professionals the necessary confidence and knowledge to
use transabdominal and transperineal real-time ultrasound
in their practice. The four main objectives are to: 1.
Demonstrate best practice in the use of transabdominal and
transperineal ultrasound for clinical practice; 2. Demonstrate
the use of ultrasound to quantify changes in hiatal
dimensions of levator ani from pre- to post pelvic floor
muscle training; 3. Demonstrate how to use ultrasound to
help patients localise the pelvic floor muscles; and 4. Use
case studies to illustrate the use of ultrasound in the clinic.
2D Real-time ultrasound imaging for the pelvic floor
Margaret Sherburn PhD FACP
Specialist Continence and Women‟s Health Physiotherapist
Department of Physiotherapy, The University of Melbourne, Australia
Physiotherapy, Royal Women‟s Hospital, Melbourne
Transabdominal ultrasound approach to image the pelvic floor muscles.
Ultrasound imaging technology has the potential for precise assessment, feedback and
measurement of the musculo-skeletal system and in particular, the pelvic floor muscles
(PFM). The use of this technology in imaging of the pelvic floor muscles to assess their
function and response to treatment programs is a more recent application of real-time
ultrasound. It is important to note the difference in the use of ultrasound for feedback
rather than diagnostics, and therefore the terminology used; „real-time‟ or „rehabilitative‟
rather than „diagnostic‟ ultrasound.
The advantages of trans-abdominal ultrasound to image the pelvic floor are that it is
user-friendly and intuitive, with an easy to interpret visual image for patient feedback of
pelvic floor muscle activity. The disadvantages are that sources of unreliability are both
the operator and the patient. In addition, there is no bony landmark in the field of view
against which to measure absolute values for PF displacement. Therefore all
displacement values are relative to the resting position of the PFM for that patient.
Normative values for PF displacement will therefore be difficult to define, and at this
stage of our understanding, clinical comparisons must remain intra-patient rather than
inter-patient.
Validity, and intra-tester and inter-tester reliability have been tested for the application of
trans-abdominal ultrasound in imaging the PFM. It has been validated against the „gold
standard‟ of digital vaginal assessment. A correct PFM contraction is a displacement of
the base of the bladder towards the top (anterior) and left or right (cephalic) of the
monitor screen in equal proportion. An overactivity of puborectalis appears as a more
vertical movement on the screen; ie an anterior draw. Inter- and intra-rater reliabilities
have also been tested. Transabdominal ultrasound was shown to be very reliable, with
ICC scores of r=0.81 - 0.89 for intra-rater reliability, and r=0.86 - 0.88 for inter-rater
reliability [1] despite there being no bony landmark from which to take a measure.
What is known about the utility of transabdominal real-time ultrasound:
The lift is not equal to pelvic floor muscle „strength‟, other factors such as fascial laxity
and bony diameters play a part in the lift. Yet, the lift increases after a training program.
Ultrasound feedback is as effective as digital feedback for learning how to do a PFM
contraction [2]. This makes PFM examination more accessible for patients who cannot
access a pelvic floor physiotherapist, or who cannot tolerate a digital examination.
US measures depend on test position, with greater displacements in standing compared
to lying and sitting. US has high acceptability in all examination positions compared to
vaginal examination [3].
PFM displacement with instruction to contract PFM is significantly greater than the
displacement on instruction to contract the PFM and TrA, and to that of TrA instruction
alone. In addition, there was an unexpected finding that 30% depressed the PFM on
instruction to elevate [4],
Imaging technique
Patient position:
• Any of crook-lying, supine, sitting, standing
• Ensure position is standardised
• Cannot compare US measurements taken in different positions
• Displacement values in standing are higher than in horizontal positions
Patient preparation:
A bladder filling protocol is required
• 2 hours before examination, empty the bladder
• Then drink between 500-750mls
• Finish drinking 30 min before scanning and do not void before scan
Lower abdomen is exposed to the upper edge of the pubic symphysis.
Have ultrasound gel and tissues ready.
Machine preparation
• Curved linear array 2-5MHz probe
• lower Hz for those with a large abdomen, and up to 5MHz for a patient
with little abdominal fat
• Choose B-mode for imaging, M-mode for measuring
• Place gel covered probe supra-pubically in the sagittal or transverse plane
• Adjust gain - for clear definition of grey scale
• Adjust depth - fill screen allowing for tissue movement
• Adjust focus zones - position & number (1 or 2)
• Midline placement very important for measurement reliability in sagittal plane.
• Use the navel as an external landmark
• palpate the pubic symphysis and place the probe directly above and
resting on it
• Use bladder outlet or endometrium of uterus as an internal landmark,
• turn probe to the transverse plane, and alter the probe angle to visualise
bladder outlet. Pivot the probe on that point to get back to sagittal plane
for scanning
• Patient performs the activity requested
Muscle parameters that can be measured:
a) Lift: a measure of „strength‟
Measure perpendicular to movement of bladder wall OR use x/y coordinates
Measure displacement in mm
b) Lift over time: a measure of „endurance‟
Measure amount of time lift remains above baseline in secs (as above) on „cine
loop‟ in b- mode OR use m-mode
c) Repeated lifts: an alternate measure of „endurance‟
Measure the number of lifts per unit time
OR
Measure the average decrease in amount of displacement over time
•
•
•
For visual feedback, allow the patient to view the screen to see the effect of the
exercise/activity until learning occurs.
For measurement, follow the instructions according to the model of US machine
you are using
• Use either B-mode or M-mode
Save & record results
1. Sherburn, M., et al., Investigation of transabdominal real-time ultrasound to
visualize the muscles of the pelvic floor. Aust J Physiother, 2005. 51(3): p. 167170.
2. Galea MP, Tisseverasinghe S, Sherburn M, Phillips B. Motor skill training of the
pelvic floor muscles using visual versus tactile feedback 2006 ICS 2006
abstract #682
3. Frawley, H.C., et al., Reliability of pelvic floor muscle strength assessment using
different test positions and tools. Neurourol Urodyn, 2006. 25(3): p. 236-42.
4. Bo, K., M. Sherburn, and T. Allen, Transabdominal ultrasound measurement of
pelvic floor muscle activity when activated directly or via a transversus abdominis
muscle contraction. Neurourol Urodyn, 2003. 22(6): p. 582-8.
Ultrasound - utility and evidence
Jenny Kruger PhD
Postdoctoral Fellow
Auckland Bioengineering Institute
University of Auckland, New Zealand
Background
The term „Ultrasound‟ refers to very high frequency sound waves (>2MHz). The
soundwaves are longitudinal compression waves which are modified by the medium
through which they travel. The more dense the material the faster the sound will travel.
Acoustic impedance is a term which describes the difference in properties between two
contiguous structures. The higher the acoustic impedance the brighter the image. Bone
has high acoustic impedance, producing a bright or hyperechoic image. Water and fat
have a low acoustic impedance thus the image appears darker hypoechoic or anechoic.
Images are produced in shades of gray on a black background, known as grayscale or B
mode imaging. The soundwaves are generated from the transducer head which also
then records echoes from structures which they encounter1.
1.1 Transducers:
The transducer heads differ mainly by how the crystals are arranged within it i.e. annular
array, linear array, curvilinear, etc., which in turn influences the depth, angle of
penetration and field of view1. The crystals are piezoelectric elements which vibrate
when subjected to electrical stimulation. Temporal characteristics of send/receive cycle
in transducer allow for real time images (4D) to be produced. Different transducers are
used for different imaging tasks: Obstetric and abdominal ultrasound - 2-5MHz curved
array transducer, or transvaginal probes with a frequency of ≥5MHz. 3.5-7MHz with a
wide field of view are used for 3D imaging. Linear array transducers are used for
abdominal scanning.
1.2 Ultrasound machines:
There are many different varieties and abilities of ultrasound machines, from simple 2D
(B mode) imaging to very expensive machines that integrate image planes to produce
rendered volume images and allow acquisition of real time 4D imaging. The image
produced on the screen consists of multiple scan lines, which can be adjusted by
adjusting the frame rate. Optimal real time imaging relies on high frame rates. Certain
elements of the image can be adjusted on the screen; most commonly using the „depth‟
button which allows deeper structures to be visualized by often with a loss of resolution.
The gain button adjusts the brightness of the image, and „focus‟ allows the focusing on a
particular area.
Utility:
Ultrasound has been available for many years, although other imaging modalities such
as computed tomography and MRI have been used to evaluate the pelvic floor. The
advantage of ultrasound is that there is no ionizing radiation; it is cost effective and easy
to use. Off line analysis has also hugely increased accessibility. It has proved to be
comparable to MRI in most situations and better for real time acquisition2 3
Transperineal ( translabial) or transvaginal ultrasound is the most common method for
investigating pelvic floor disorders4. This approach enables the entire pelvic floor muscle
area to be visualized, and if using a 3D ultrasound machine, the boundaries of the
muscle can be seen in the axial orientation – previously the domain of Magnetic
resonance imaging.
2.1 2D/B Mode ultrasound imaging
Usually readably available, and easy to use. Only need a simple machine with cine loop
capabilities, and a 3.5- to 6-MHz curved array transducer. Patient is usually examined in
the supine position, knees comfortably flexed after voiding. The transducer is covered in
a glove or condom for hygienic reasons. Ultrasound gel applied to the transducer then
placed firmly on the perineum in the midsagittal orientation (Figure 1). Still widely used4-6
Clinical use of 2D ultrasound




Figure 1: 2D Pelvic floor ultrasound.
AC- anal canal, PR- puborectalis
muscle. Dotted line =AP diameter of
hiatus


Good modality for use as biofeedback.
Measure the anterior-posterior diameter from
edge of symphysis pubis to ano-rectal angle at
rest, on contraction and on valsalva
Assess movement of the bladder neck during
cough and valsalva ( cine loop)
Assess activation ( or not) of the pelvic floor
muscle prior to cough
Assess any damage to insertion site of the
puborectalis muscle. ( easier on 3D imaging)
Assess any changes in these parameters after
physiotherapy
2.2. 3D/4D Ultrasound
3D ultrasound popularized by obstetric scanning – proved very suitable for pelvic floor
muscles. Involves the integration of 2D sectional images into rendered volume images,
and allow access to the axial plane4. Require a minimum of a curved array volume
transducer (8-4MHz) with a wide angle of acquisition (≥70°). Protocol as for 2D. Use
the symphysis pubis as reference point during movement.
Clinical use of 3D/4D ultrasound:


Figure 2: Standard acquisition screen of 3D pelvic floor image
1, Coronal, 2, Midsagittal, and 3, axial planes and 4, rendered
axial plane (ie, semitransparent representation of all pixels in
box [region of interest] seen in1- 2). P, puborectalis muscle; R,
rectum, S, symphysis pubis; U, urethra; V, vagina.




Useful for biofeedback. Easy
to visualize the entire
muscle.
Measure ap diameter,
transverse diameter and
hiatal area at rest, on
contraction and valsalva.
Highly reproducible7-9
Able to look for signs of levator
damage using tomographic
imaging (TUI)(Figure 3)
TUI examines the insertion site
of puborectalis in individual
slices, at predetermined
intervals10
Diagnosed pf damage
(avulsion) affects pf muscle
strength11
Off line analysis greatly
increased utility. Able to
access other opinion.
Figure 3: Typical right-sided levator defect (*) measuring about 2
cm in (dorsoventral) width and at least 1.75 cm in (craniocaudal)
depth as it is apparent in all 8 slices.
Dietz, H.P. Pelvic floor ultrasound; a review (2010) AJOG
202(4) 321-334
Handy Tips for transperineal ultrasound scanning:
1. Make sure there are no air bubbles under the condom/glove and use plenty of
ultrasound gel. If there are air bubbles you will see bright lines at the top of the
image
2. Press transducers quite firmly against the perineum, there should be little ‘gap’
between the transducer head and edge of the symphysis.
3. Always try to keep the symphysis in your picture. It is the reference point –
sometimes difficult if there is a prolapse of ballooning of the hiatus.
4. If there is prolapse, try and not to hold it back with the probe during a valsalva
5. Make sure the patient does an effective valsalva. Really PUSH!! (for at least 6
secs)
References:
1. Chudleigh T, Thilaganathan B, editors. Obstetric Ultrasound. How, Why and When. Third ed.
Edinburgh: Elsevier, 2004.
2. Kruger JA, Heap SW, Murphy BA, Dietz HP. Pelvic Floor Function in Nulliparous Women Using
Three-Dimensional Ultrasound and Magnetic Resonance Imaging. Obstetrics &
Gynecology March 2008;111(3):631-38.
3. Majida M, Braekken IH, Bo K, Benth JS, Engh ME. Validation of three-dimensional perineal
ultrasound and magnetic resonance imaging measurements of the pubovisceral muscle
at rest. Ultrasound Obstet Gynecol 2010;35(6):715-22.
4. Dietz HP. Pelvic floor ultrasound: a review. Am J Obstet Gynecol 2010;202(4):321-34.
5. Athanasiou S, Chaliha C, Toozs-Hobson P, Salvatore S, Khullar V, Cardozo L. Direct imaging of
the pelvic floor muscles using two-dimensional ultrasound: a comparison of women
with urogenital prolapse versus controls. BJOG: An International Journal of Obstetrics
and Gynaecology 2007;114(7):882-88.
6. Costantini S, Nadalini C, Esposito F, Valenzano MM, Risso D, Lantieri P, et al. Perineal
ultrasound evaluation of the urethrovesical junction angle and urethral mobility in
nulliparous women and women following vaginal delivery. Int Urogynecol J Pelvic Floor
Dysfunct 2005;16(6):455-9.
7. Yang SH, Huang WC, Yangs SY, Yang E, Yang JM. Validation of new ultrasound parameters for
quantifying pelvic floor muscle contraction. Ultrasound in Obstetrics & Gynecology
2009;33(4):465-71.
8. Braekken IH, Majida M, Ellstrom-Engh M, Dietz HP, Umek W, Bo K. Test-retest and intraobserver repeatability of two-, three- and four-dimensional perineal ultrasound of pelvic
floor muscle anatomy and function. Int Urogynecol J Pelvic Floor Dysfunct
2008;19(2):227-35.
9. Braekken IH, Majida M, Engh ME, Bo K. Test-retest reliability of pelvic floor muscle
contraction measured by 4D ultrasound. Neurourol Urodyn 2009;28(1):68-73.
10. Dietz HP, Shek KL. Tomographic ultrasound imaging of the pelvic floor: which levels matter
most? Ultrasound Obstet Gynecol 2009;33(6):698-703.
11. Dietz HP, Shek C. Levator avulsion and grading of pelvic floor muscle strength. Int Urogynecol
J Pelvic Floor Dysfunct 2008;19(5):633-6.
Real time Ultrasound Assessment of Pelvic Floor Muscle Function
Judith Thompson PhD FACP
Specialist Continence and Women‟s Health Physiotherapist
Body Logic Physiotherapy, 215 Nicholson Road, Shenton Park, Perth, Western Australia
School of Physiotherapy, Curtin University, Perth, Western Australia
Evaluation of pelvic floor muscle (PFM) function is necessary to teach PFM exercises and to
evaluate the effectiveness of PFM training programs. An accurate diagnosis of the PFM
dysfunction is essential to allow targeted intervention. The focus of clinical physiotherapy
assessment to date has been on the assessment of voluntary PFM contractions (Bo and
Sherburn 2005), but the voluntary activation of the PFM does not always reflect the functional
activation of the PFM (Wijma, Tinga et al. 1991; Bo and Stien 1994; Peschers, Vodusek et al.
2001; Devreese, Staes et al. 2007; Thompson, O'Sullivan et al. 2007). Differences in the
voluntary and reflex activation of the PFM have been demonstrated in both continent (Bo and
Stien 1994; Peschers, Vodusek et al. 2001) and incontinent women (Wijma, Tinga et al. 1991;
Deindl, Vodusek et al. 1994; Barbic, Krajli et al. 2003; Devreese, Staes et al. 2007; Thompson,
O'Sullivan et al. 2007). In asymptomatic women, there is an unconscious, reflex contraction of the
PFM simultaneously with, or prior to, increases in intra-abdominal pressure (IAP) (Constantinou
and Govan 1982; Shafik, Doss et al. 2003), such as coughing (Deindl, Vodusek et al. 1994;
Neumann and Gill 2002; Barbic, Krajli et al. 2003), Valsalva (Bo and Stien 1994; Shafik, Doss et
al. 2003) and sit ups (Bo and Stien 1994) this functional activation of the PFM and co-activation
with the abdominal muscle is essential for continence and pelvic organ support. This reflex PFM
activation has been shown to be altered in women with stress urinary incontinence during
postural manouvres (Smith, Coppieters et al. 2007; Smith, Coppieters et al. 2007) and coughing
(Madill, Harvey et al. 2010; Madill and McLean 2010). Therefore it is important to develop clinical
tests that investigate the unconscious activation of PFM during functional manoeuvres as well as
the capacity to consciously contract the PFM. Ultrasound can be used to assess the reflex
activation of the PFM and as biofeedback to retrain this supportive action during functional tasks
(Thompson, O'Sullivan et al. 2007).
Ultrasound has the advantage for physiotherapists in that it allows a dynamic real-time
assessment of functional activation of the PFM in as close as “real life” situation as possible. It is
non-invasive (abdominal) or minimally invasive (perineal) and the images generated have a
strong biofeedback effect for both therapist and patient. Ultrasound is suitable for use in men,
women and children and Transabdominal (TA) ultrasound is particularly useful to give direct
objective assessment of PFM function in populations where vaginal examination (VE) or digital
rectal examination(DRE) may not be desirable (Thompson, O'Sullivan et al. 2005).
The most common methods of ultrasound used by physiotherapists in the clinic are 2D
Transperineal (TP) and Transabdominal (TA) ultrasound. TP ultrasound is an established reliable
method of evaluating women with incontinence (Dietz 2004), the advantages are that it allows
good visualization of bladder neck, urethra and vagina and measurements of bladder neck
movement during PFM contraction and Valsalva manoeuvre are made from a fixed bony
landmark, the pubic symphysis, making it more reliable for comparisons between subjects. The
disadvantages of TP are that it requires specific training and practice to perform the technique
consistently, the measure is more complex and time consuming to calculate, the images rendered
require experience to interpret and the location of the probe on the perineum is more invasive
than TA approach and may limit some functional manouevres. TA ultrasound is totally
noninvasive method of PFM assessment and has become popular clinically and is used by
physiotherapists worldwide. There are several advantages of TA ultrasound for physiotherapists;
the technique involves only one measure and therefore it is quick and easy in a clinical situation,
the probe placement does not restrict movement of the lower limbs, the technique is easy to
perform in different functional positions and it is totally non-invasive so that the patient does not
need to undress making it available to a wider population of clients- such as those attending
Pilates or for musculo-skeletal physiotherapy. There are however some disadvantages; a
confounding variable is that movement of the bladder base does not always reflect movement at
the bladder neck and in some instances it may actually reflect outward movement of the
abdominal wall instead due to lack of a bony reference point (Thompson, O'Sullivan et al. 2005).
In situations where there is no or minimal movement of the bladder base during functional tasks it
is difficult to assess if there is increased rest tone of the PFM or there is minimal movement due
to a well supported pelvic floor with good fascial support or that the PFM. Where ever possible
ultrasound assessment should be done in conjunction with a digital VE or DRE (with consent) to
accurately assess the resting tone and strength of the PFM.
When comparing the TP and TA ultrasound, there is a significant amount of agreement between
both methods of ultrasound for the direction of movement of the bladder neck and the bladder
base during functional manoeuvres with 94% agreement during abdominal curl up and 100%
agreement during Valsalva (Thompson, O'Sullivan et al. 2007). Transperineal ultrasound was
more sensitive in detecting differences between continent and incontinent women in bladder neck
movement during functional tasks when compared with TA ultrasound detecting differences in
bladder base movement during the same tasks (Thompson, O'Sullivan et al. 2007).
In initial studies TP ultrasound was shown to be more reliable than TA US during functional
manoeuvres with interclass correlation (ICC) and standard error of measurement (SEM) for
Valsalva TP 0.87(0.16), TA (sagittal view) 0.51 (0.35) (Thompson, O'Sullivan et al. 2005) and
abdominal curl TP 0.79(0.33), TA(sagittal view) 0.53(0.41) (Thompson, O'Sullivan et al. 2007).
However in a follow up study comparing the transverse and sagittal views using TA ultrasound
with experienced operator improved reliability for TA ultrasound similar to TP ultrasound has been
recorded (unpublished data). Very good reliability of TA ultrasound (transverse view) (ICC 0.92)
has been reported for measurements during active straight leg raise tasks (O'Sullivan, Beales et
al. 2002)..
In conclusion, the use of ultrasound clinically for physiotherapists is growing: TP ultrasound is
more reliable than TA ultrasound due to the fact that the measurements are taken from a fixed
bony marker, this makes it more suitable for comparisons between subjects as valuable outcome
measure for research purposes. On the other hand TA ultrasound is useful as a noninvasive
biofeedback tool for PFM assessment in a wider population. It is quick and easy to use in a
clinical situation however precaution should be taken to use firm probe placement and
standardize the technique used to minimize measurement errors.
References
Barbic, M., B. Krajli, et al. (2003). "Compliance of the bladder neck: importance of activity pattern
of levator ani muscle and content of elastic fibers of endopelvic fascia." Neurourol
Urodyn 22: 269-276.
Bo, K. and M. Sherburn (2005). "Evaluation of female pelvic-floor muscle function and strength."
Phys Ther 85(3): 269-282.
Bo, K. and R. Stien (1994). "Needle EMG registration of striated urethral wall and pelvic floor
muscle activity patterns during cough, Valsalva, abdominal, hip adductor, and gluteal
muscle contractions in nulliparous healthy females." Neurourol Urodyn 13(1): 35-41.
Constantinou, C. and D. Govan (1982). "Spatial distribution and timing of transmitted and reflexly
generated urethral pressures in healthy women." Jnl of Urology 127: 964-969.
Deindl, F., D. Vodusek, et al. (1994). "Pelvic floor activity patterns: comparison of nulliparous
continent and parous urinary stress incontinent women. A kinesiological EMG study." Brit
J Urology 73: 413-417.
Devreese, A., F. Staes, et al. (2007). "Incontinent women have altered pelvic floor muscle
contraction patterns." J Urol 178(2): 558-562.
Dietz, H. P. (2004). "Ultrasound imaging of the pelvic floor. Part I: two-dimensional aspects."
Ultrasound Obstet Gynecol 23(1): 80-92.
Madill, S., M.-A. Harvey, et al. (2010). "Women with stress urinary incontinence demonstrate
motor control differences during coughing." Journal of Electromyography and Kinesiology
20(5): 804-812.
Madill, S. and L. McLean (2010). "Intravaginal pressure generated during voluntary pelvic floor
muscle contractions and during coughing: the effect of age and continence status."
Neurourology and Urodynamics 29(3): 437-442.
Neumann, P. and V. Gill (2002). " Pelvic floor and abdominal muscle interaction: EMG activity
and intra-abdominal pressure." Int Urogynecol Jnl Pelvic Floor Dysfunct 13: 125-132.
O'Sullivan, P., J. Beales, et al. (2002). "Alterations of motor control in subjects with impaired
lumbopelvic stability during the active straight leg raise test." Spine 27(1): 1-8.
Peschers, U. M., D. B. Vodusek, et al. (2001). "Pelvic muscle activity in nulliparous volunteers."
Neurourol Urodyn 20(3): 269-275.
Shafik, A., S. Doss, et al. (2003). "Etiology of the resting myoelectric activity of the levator ani
muscle: physioanatomic study with a new theory." World J Surg 27(3): 309-314.
Smith, M. D., M. W. Coppieters, et al. (2007). "Postural activity of the pelvic floor muscles is
delayed during rapid arm movements in women with stress urinary incontinence." Int
Urogynecol J Pelvic Floor Dysfunct 18(8): 901-911.
Smith, M. D., M. W. Coppieters, et al. (2007). "Postural response of the pelvic floor and
abdominal muscles in women with and without incontinence." Neurourol Urodyn 26(3):
377-385.
Thompson, J., P. O'Sullivan, et al. (2005). "Assessment of pelvic floor movement using
transabdominal and transperineal ultrasound." Int Urogynecol J Pelvic Floor Dysfunct
16(4): 285-292.
Thompson, J., P. O'Sullivan, et al. (2007). "Comparison of transperineal and transabdominal
ultrasound in the assessment of voluntary pelvic floor muscle contractions and functional
manoeuvres in continent and incontinent women." International urogynecology journal
and pelvic floor dysfunction 18(7): 779-786.
Thompson, J. A., P. B. O'Sullivan, et al. (2007). "Comparison of transperineal and transabdominal
ultrasound in the assessment of voluntary pelvic floor muscle contractions and functional
manoeuvres in continent and incontinent women." Int Urogynecol J Pelvic Floor Dysfunct
18(7): 779-786.
Wijma, J., D. Tinga, et al. (1991). "Perineal ultrasound in women with stress incontinence and
controls: the role of the pelvic floor muscles." Gynecol Obstet Invest(32): 176-179.