Translabial ultrasound can objectively quantify uterovaginal prolapse. The inferior margin of the symphysis pubis serves as a convenient (if arbitrary) line of reference against which the maximal descent of bladder, uterus, cul de sac and rectal ampulla on Valsalva manoeuvre can be measured.
Figure 1 shows a three compartment prolapse, with the uterus leading. Findings have been compared to clinical staging and the results of a standardized assessment according to criteria developed by the International Continence Society, with good correlations shown for the anterior and central compartments (Dietz et al., 1999). There seems to be a strong association with symptoms of prolapse, provided a maximal Valsalva is generated (Blain et al., 2008).
The two main forms of cystocele- cystourethrocele and cystocele with intact retrovesical angle- are easily differentiated (see Figure 2 and Video 1). There are substantial differences between those two forms of cystocele, with the former associated with stress incontinence and an intact levator, the latter with prolapse, voiding dysfunction and levator trauma (Eisenberg et al., 2010).
Uterine prolapse is more difficult to identify, due to the iso- echoic appearance of the uterine cervix. At times nabothian follicles simplify identification, but even without those a prolapsing uterus can be identified (see Video 2).
While there may be poorer correlation between posterior compartment clinical assessment and ultrasound, not the least due to variable rectal filling, it is possible to distinguish between ‘true’ and ‘false’ rectocele, i.e., a defect of the rectovaginal septum and perineal hypermobility without fascial defects (Fig. 3).
True rectoceles may be present in young nulliparous women (Dietz et al., 2005), but are more common in the parous. In some women they clearly arise in childbirth (Dietz and Steensma, 2006). From imaging experience to date, fascial defects seem to almost always be found in the same area, i.e., very close to the anorectal junction, and most commonly are transverse. Many are asymptomatic. Routine posterior repair often results in reduction or distortion of such defects, without effecting closure.
Hopefully the ability to differentiate between different forms of posterior compartment descent will allow better surgical management in the future, not the least because enterocele (see Video 3) can easily be distinguished from rectocele. Occasionally, a clinical rectocele may turn out to be evidence of rectal intussusception, a much more complex abnormality, which is not uncommon amongst prolapse patients and strongly associated with abnormal pelvic floor structure and function (Rodrigo et al., 2011). Most recently, it appears that Colorectal surgeons are starting to use the technique to complement or replace defecography, and perineal ultrasound can also be used for exo-anal imaging of the anal sphincter- see the colorectal page.
Disadvantages of the method include incomplete imaging of bladder neck, cervix and vault with large rectoceles and the possible underestimation of severe prolapse due to transducer pressure. Occasionally, apparent anterior vaginal wall prolapse will turn out to be due to a urethral diverticulum , or a paravaginal cyst (see Other Pathology).
Figures 4 and 5 show histograms and receiver operator curves for cystocele and rectocele, defining cut-offs for the ultrasonic diagnosis of ‘significant cystocele/ rectocele on the basis of prolapse symptoms in patients with single- compartment prolapse. According to this data, cystoceles reaching more than 10 mm below the inferior margin of the symphysis pubis are likely to be symptomatic, and the same is true for rectoceles descending 15 mm or more below this line.
Figure 6 demonstrates the appearance of a silicone ring pessary in the three orthogonal planes. There is total reflection and refraction of incident ultrasound waves due to the smooth surface of the pessary, resulting in complete absence of echoes from within or behind the pessary.
Video 3: A rectoenterocele in a patient with 3rd degree posterior compartment prolapse. The enterocele is to the left, the rectocele to the right in the midsagittal plane (left image).
Figure 1: Prolapse quantification in the mid-sagittal plane. The reference line is placed through the inferior symphyseal margin. From: Dietz et al., Pelvic Floor Ultrasound. Springer London, in print.
Figure 2: The distinction between cystoure-throcele (open retrovesical angle) and cysto- cele with intact RVA. From: Dietz, Ultrasound Obstet Gynaecol 2006; 28: 629-634
Figure 3: The distinction between true rectocele (i.e., a defect of the rectovaginal septum) and perineal hypermobility (excess distensibility of levator/ RV septum. From: Dietz, Ultrasound Obstet Gynaecol 2006; 28: 629-634
Figure 4: Histogram and receiver operator curve for ‘significant’ cystocele as diagno-sed on the basis of prolapse symptoms.
Figure 5: Histogram and receiver operator curve for ‘significant’ rectocele as diagno-sed on the basis of prolapse symptoms.
Figure 6: A silicone ring pessary as imaged in the three orthogonal planes. There is only a small specular echo as most of the ultra-sound is refracted, causing appearances that may be mistaken for a cystic structure.
Video 1: Third- degree cystocele with marked urethral kinking.
Video 2: Second- degree uterine prolapse after Perigee transobturator repair of a third-degree cystocele.