Ultrasound modalities for assessment female lower urinary tract and pelvic floor structures (part2)
Modalities of sonographic urethrocystography
A- Endoanal (Transrectal sonography)
B-Vaginal ultrasonography (Vaginosonography)
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).