Ultrasound modalities for assessment female lower urinary tract and
pelvic floor structures (part2)
Introduction
Modalities of sonographic urethrocystography
I-Transabdominal sonography
II-Endosonography
Procedures
A- Endoanal (Transrectal sonography)
B-Vaginal ultrasonography
(Vaginosonography)
C-Intraurethral ultrasound
III-Introital
sonography
IV- Perineal ultrasound (PU) (Perineosonography, Dynamic
transperineal sonourethrocystography, Translabial, Vulvar or TP-USG)
IV- Perineal ultrasound
(PU) (Perineosonography, Dynamic transperineal sonourethrocystography, Translabial,
Vulvar or TP-USG)
Given the difficulties of demonstrating the
urethrovesical junction by semi-invasive vaginal and rectal scanning, a method
has been devised for the sonographic visualization of the BN region. Kohorn in
1986 described perineal sonography (PU), using linear array ultrasound (3.5-5
MHz) placed in the perineal region and performed this technique as an
alternative to conventional UCG in the investigation of female urinary
incontinence (Kohorn et al, 1986). Unlike vaginosonography
and rectosonography perineal scanning does not alter topographic relationships,
and the transducer position is not affected by straining (Gordon et al,
1989).
Perineal ultrasound as part of the
diagnostic work-up for stress urinary incontinence and genitourinary prolapse
allows for the morphological and dynamic assessment of the LUT (Sendag
et al, 2003). Perineal
sonography provides similar information to that obtained by radiographic
procedures (Kohorn et al, 1986 and Gordon et al, 1989). Perineal
ultrasound is an effective, well tolerated and affordable diagnostic procedure (Beco,
2001). It is undoubtedly extremely useful in assessing
anatomic-functional disorders (Sadovsky, 1997). It appears
to hold promise as noninvasive and accurate methods of evaluating the position
and mobility of the urethrovesical junction and proximal urethra in incontinent
women (Kohorn et al, 1986, Bhatia et al, 1987, Koelbl et al, 1991 and
Schaer et al, 1995 I).
Perineal
ultrasound is a simple and easy to learn method for pelvic floor evaluation. It
has the advantages of offering greater comfort and safety for the patient,
whose BN movement and BN closing or opening at stress can be precisely,
visualized and assessed. Information provided by perineal ultrasound testing is
so important that it could expect this method to become an obligatory Para clinical test in preoperative evaluation of patients
complaining of SUI, as well as uterovaginal prolapse, in the future (Schaer
et al, 1995 I, Peschers et al, 1997 and Dietz et al, 2001 I).
Urogynaecology
perineal ultrasound examination seemed strongly to support diagnosis of genuine
SUI (Sendag et al, 2003). Descent
of urethra, bladder outlet and BN hypermobility can be quantified
against infero-posterior margin of the symphysis pubis. The cervix, cul-de-sac
and rectum can usually be visualized with translabial ultrasound (Creighton et al 1992). Exoanal (perineal)
ultrasound provides information on normal anatomy and on defects of the anal
sphincter (Peschers et al, 1997).
Its
main advantage is that it can be holding on the perineum during coughing and
the Valsalva’s maneuver so that the whole movement can be watched. Perineal
ultrasonography clearly demonstrates movement of the whole pelvic floor. Minor
degree of both anterior and posterior vaginal wall prolapse could be seen and
quantified. Correlation with
the International Continence Society prolapse assessment system is good (Creighton et al, 1992, Dietz et al, 2001 I and Dietz et al, 2001 II).
Certain
disadvantages of PU may contribute to the observed discrepancies. A large
bowel-filled prolapse, i.e. an enterocele or rectocele, may result in
incomplete imaging of the cervix and vault, especially if these structures
remain high. Furthermore, transducer pressure may result in an underestimation
of severe prolapse. However, none of these disadvantages would impact on the
most likely application of the method, which is the clinical audit of
procedures designed to cure female POP (Dietz et al, 2001 I).
Technique of
perineal ultrasound
With
a curved array real time ultrasound scanning machine and the probe placed sagittal
onto the vulva, symphysis, bladder, urethra and the pelvic floor can be
visualized in one frame, while the patient in supine or standing position (Wijma
et al, 1991).
Increasing the bladder
filling volume does not affect the measurement values, but funneling can be
seen well with higher bladder volumes. The best overall image quality was
obtained at 300ml. A comparison between coughing and the Valsalva maneuver
showed that during coughing, the BN descends less and remains closer to the
symphysis than with the Valsalva maneuver (Schaer et al, 1996 II).
Parameters of
perineal ultrasound
1-Bladder neck localization 'position'
and mobility assessment at rest, straining and pelvic floor contraction: For BN localization, a rectangular (X-Y) coordinate system is used,
with inferior border of symphysis pubis as reference point. The x-axis is
constructed by drawing a line between the superior and inferior border of the
symphysis (central line of the symphysis). The y-axis is constructed
perpendicular to the x-axis at the inferior symphysis border. Dx is defined as
the distance (mm) (the horizontal or backwards displacement) between BN and the
y-axis (Dy) is defined as the distance (mm) (the vertical or downwards
displacement) between BN and the x-axis. For exact localization of the BN, it
measures the upper and ventral point of the urethral wall at the immediate
transition into the bladder (Schaer et al, 1996 II) (figures 1, 2 and 3).
Figure 1: Measurement
method for perineal ultrasound testing: Dx: distance between y axis and bladder
neck; Dy: distance x axis and bladder neck (Quoted from Schaer et al.,
1996 II).
Figure 2: BN position at rest, in the standing position in a
patient suffering from SUI: Dx 3.6mm and Dy 26.7mm (Quoted from Meyer et
al, 1996).\
Figure 3: BN position with straining, in the standing position;
same patient as in figure 21: Dx 17.8mm and Dy 15.9mm (Quoted from Meyer
et al, 1996).
Correlation between the
importance of backward and downward displacement is strong, making superfluous
a two-dimensional coordinate system for routine BN position/mobility
assessment. No significant correlations were found between the extent of BN
mobility in supine and standing positions in terms of backwards and downwards
displacement in parous patients (Meyer et al, 1996).
A- Bladder neck position at rest
In
almost all studies the BN position is defined as a distance or an angle, with
the line going from the BN to the inferior border of the symphysis pubis (Mouritsen
et al, 1993). Vesical neck position is determined by the
supportive structures which are mainly composed of striated muscle and
connective tissue (DeLancey, 1986). The BN is
significantly lowered at rest in parous women than in those who have an
elective cesarean delivery and in nulliparous women (Peschers et al,
1996).
B- Bladder neck mobility with straining
The BN is mobile in
normal continent nulliparous women (Peschers et al, 2001 II). In continent nulliparous
females, it is found that the mean vertical movement was 5.3+/-2.4mm and for
horizontal movement did not exceed 11.2mm (Brandt et al, 2000). Antenatal BN mobility is known to be
associated with postpartum SUI (Reed, 2004).
BN
mobility was significantly increased after both spontaneous and instrumentally
assisted vaginal delivery (Peschers et al, 1996 and Meyer
et al, 1998). Spontaneous
vaginal delivery significantly increased the degree of BN descent during
coughing (Wijma et al, 2003). A BN descent of more than 1cm on Valsalva correlates
with SUI (Bergman et al, 1989). Parous patients with SUI
showed significant BN hypermobility compared to nulliparous patients in the
supine position, in which the backwards and downwards displacements were 15mm
(Dx, backwards displacement) and 11mm (Dy, downward displacement),
respectively. A cut-off limit of more than 14mm of backward BN displacement
correlates with SU incontinent patient
(Meyer et al, 1996). Bladder neck mobility
is associated with GSI compared to the continent nulliparous women (Demirci
et al, 2001). The distance
between UVJ and the pubis was more on the backward displacement in stress
incontinent women as compared to the continent women and UVJ passed down the
pubic symphysis in 63% of SU incontinent cases during stress (Demirci et
al, 1996 and Sendag et al, 2003).
During
Valsalva’s maneuver, patients with SUI show greater caudal mobility of the vesical
neck, which becomes more significant as the degree of SUI increases. Dorsal
mobility is also greater in patient with SUI although this parameter is of no
use to quantify the degree of SUI (Fernandez et al, 1998).
C- Bladder neck mobility with pelvic
floor contraction
On
PU findings during pelvic floor contraction confirmed that BN descent is
related to pelvic floor relaxation and BN elevation to pelvic floor contraction
(Wise et al, 1992). Decreased BN elevation is another feature of
altered pelvic floor function after childbirth. The ability to elevate BN
depends on the strength of pelvic floor muscle and on integrity of the
connection of the urethra to the pelvic floor muscle (Sampselle, 1990).
2- Bladder neck
opening and funneling
It
is an opening of BN and proximal urethra in the absence of either detrusor
contraction or an increase in intra abdominal pressure. This definition is
differs from ''funneling" when BN open in patients as they perform a
Valsalva's maneuver or when the bladder is at maximum capacity (English
et al, 1999).
Bladder neck opening at rest
The presence of open BN
at rest is considered an echo graphic sign of intrinsic sphincteric
incompetence (Fernandez et al, 1998). Striated muscle was
lost at the BN and along the dorsal wall of the urethra as women aged (Perucchini
et al, 2002). Nulliparous women with an open BN and filled the bladder
to cystometric capacity would be more likely to have SUI after childbirth (Chapple
et al, 1989).
Bladder neck
funneling
Funneling
is diagnosed when an opening of the proximal urethra, seen as two sharp lines
representing the internal limits of the urethral wall is detected (Schaer
et al, 1995 I). Internal urinary meatus must open
for UI to occur. The fact that it is pushed open by increases in abdominal
pressure does not always mean that urine escapes from distal urethra. It is
found BN funneling in 51% of continent women. It is possible for abdominal
pressure to open internal urinary meatus while distal urethra is held closed. The distal sphincter mechanism largely controlled
continence during stress (Versi et al, 1990). Bladder neck funneling can be detected with PU in near one-half of SU
incontinent women (Fink et al, 1996).
3- Rotational angel (RA or straining angle)
Rotation (RA
or Gamma) angle is
the angle between the axis of the symphysis and the connecting line between
urethrovesical junction and lower borderline of the symphysis (difference between the angle during
Valsalva minus the angle during rest) (Martan et al, 1998). Applicability
of perineal sonography in anatomical evaluation of BN in women with and without
GSI showed that if 28° or 13mm were used as cut-off point for RA and descent of
BN (Chen et al, 1997).
If
the difference of gamma angle during contraction of the muscles of the pelvic
floor and Valsalva’s maneuver is more than 30 degrees during 40th
week of gestation or 3-5 days after delivery (when this mobility is even
greater), then the women is liable to develop the stress type of incontinence
and it is recommend to use Kolpexin after the puerperium for exercise and
strengthening of the muscles of the pelvic floor (Martan et al, 1996).
Hypersensitive
bladder and control (with no LUTS) groups had a significantly higher BN
position at rest and during stress, a lesser rotational angle of the BN, a
lower prevalence of BN funneling and cystocele formation, and lesser mean
bladder wall thickness than the other diagnostic groups (Yang and Huang,
2002).
4- Posterior urethrovesical
angle (PUVA beta)
This
angle has important roles in GSI pathophysiology (Alper et al,
2001). It is measured as one
side is formed by the urethral axis, the other side by at least one third of
the bladder base near the BN (Green, 1975). Posterior urethrovesical angle (beta angle) was found to be
significantly different between the women with SUI and continent women both at
rest and on straining (Sendag et al, 2003).
Pelvic floor
movement
Levator function is
evaluated using translabial ultrasound: cranioventral displacement of BN is
utilized to quantify levator activity (Dietz et al, 2003). The
contraction of the pelvic floor muscles stabilizes the vesical neck in
nulliparous women (Peschers et al, 2001 I).
The pelvic floor moves on
a pivot around the anterior, inferior border of the symphysis, with the BN,
bladder and posterior perineum moving downwards and forwards on increasing
intra abdominal pressure. This movement is seen to some degree in all women but
is much more marked in women with prolapse and/or SUI (Creighton et al,
1992).
A-Movement of
the anterior pelvic structures
In
stress incontinent women there is good correlation between the findings of the
gynecological and perineal sonographic examinations (Fink et al, 1996).
B-Movement of the posterior pelvic structures
A rectocele can be seen as
an area of brighter echo in the posterior pelvic floor and shows a rectocele in
a patient at rest (Creighton et al, 1992) (Figure 4).
Figure 4 (a) Perineal ultrasound scan of a rectocele at rest. The
anterior inferior border of the symphysis and the Foley balloon are marked with
crosses. Two arrows indicate the limits of the rectocele. (b) Diagram showing
the symphysis, Foley balloon, bladder and vagina outlined in white (Quoted
from Creighton et al, 1992).
Ultrasound
contrast medium
Contrast medium is
available for ultrasound investigation. For visualization of urethrovesical
junction, an echogenic contrast medium (Echovist) is administered
transurethrally and PU is performed. Women are examined in upright position at
rest and during Valsalva’s maneuver. With the subject in upright position, the
contrast medium lay at lowest point of the bladder and resulted in a reverse
picture of bladder base and BN and clear visualization of these structures.
When BN, urethra or bladder base are not visible with plain PU they are seen
when ultrasound contrast medium is used (Schaer et al, 1995 II).
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