Pelvic Floor Disorders: Surgical Approach

6. Pelvic Floor Ultrasonography

Giulio A. Santoro , Sthela Murad-Regadas, Luigi Causa and Anders Mellgren

(1)

Department of Surgery, Pelvic Floor Unit, Regional Hospital, Treviso, Italy

Giulio A. Santoro

Email: giulioasantoro@yahoo.com

Abstract

The pelvic floor is a complex, three-dimensional (3D) mechanical apparatus that has been artificially divided in three different regions: anterior, middle, and posterior compartments. However, urinary (urinary incontinence, voiding dysfuntion, cystocele), genital (uterine prolapse, vaginal vault prolapse, enterocele), and anorectal abnormalities (fecal incontinence, obstructed defecation, rectocele, intussusception, dyssynergia) are frequently associated in women with pelvic floor dysfunction [1]. Although patients may present with symptoms that involve only one compartment, 95% of patients have abnormalities in all three compartments [2]. As a consequence, the specialist (urologist, gynecologist, gastroenterologist, and colorectal surgeon) approaching the pelvic floor should not have vertical vision confined to their area of interest, but a transverse, multicompartmental vision, always taking into consideration that pelvic floor disorders rarely occur in isolation.

6.1 Introduction

The pelvic floor is a complex, three-dimensional (3D) mechanical apparatus that has been artificially divided in three different regions: anterior, middle, and posterior compartments. However, urinary (urinary incontinence, voiding dysfuntion, cystocele), genital (uterine prolapse, vaginal vault prolapse, enterocele), and anorectal abnormalities (fecal incontinence, obstructed defecation, rectocele, intussusception, dyssynergia) are frequently associated in women with pelvic floor dysfunction [1]. Although patients may present with symptoms that involve only one compartment, 95% of patients have abnormalities in all three compartments [2]. As a consequence, the specialist (urologist, gynecologist, gastroenterologist, and colorectal surgeon) approaching the pelvic floor should not have vertical vision confined to their area of interest, but a transverse, multicompartmental vision, always taking into consideration that pelvic floor disorders rarely occur in isolation.

The diagnostic evaluation has a fundamental role in identifying all pelvic floor dysfunctions and providing adequate information for management, taking into consideration the consequences of therapy on adjacent organs and avoidance of sequential surgeries. The increasing availability of ultrasound equipment in the clinical setting, and the recent development of 3D and four-dimensional (4D) ultrasound, have renewed interest in using this modality to image the pelvic floor anatomy as a key to understanding dysfunction. Ultrasound has several important advantages over other imaging modalities (defecography, cystography, magnetic resonance), including the absence of ionizing radiation, relative ease of use, minimal discomfort, cost-effectiveness, relatively short time required, and wide availability. A “multicompartmental” ultrasonographic assessment, using a combination of different modalities (endovaginal sonography, endoanal ultrasound, and transperineal ultrasound), provides a comprehensive evaluation of this region [3]. The clinical relevance of this “integrated approach” is to reduce inappropriate surgical treatments and high rates of postoperative failures.

6.2 Ultrasonographic Techniques

6.2.1 Transperineal Ultrasonography

Transperineal ultrasonography (TPUS) is performed with the patient placed in the dorsal lithotomy position, with hips flexed and abducted, and a convex transducer positioned on the perineum between the mons pubis and the anal margin (perineal approach). Imaging is performed at rest, during maximal Valsalva maneuver and during pelvic floor muscle contraction [4]. Conventional convex transducers (with frequencies of 3–6 MHz and field of view of at least 70°) provide two-dimensional (2D) imaging of the pelvic floor. In the midsagittal plane, all anatomical structures (bladder, urethra, vaginal walls, anal canal, and rectum) between the posterior surface of the symphysis pubis and the posterior part of the levator ani are visualized (Fig. 6.1). Using 3D transabdominal probes developed for obstetric imaging (RAB 8-4, GE Healthcare Ultrasound, Milwaukee, Wis, USA; AVV 531, Hitachi Medical Systems, Tokyo, Japan; V 8-4, Philips Ultrasound, Bothell, Wash, USA; 3D 4-7 EK, Medison, Seoul, South Korea), 3D-TPUS and 4D-TPUS can be performed [56]. These transducers combine an electronic curved array of 4–8 MHz with mechanical sector technology, allowing fast motorized sweeps through the field of view. An advantage of this technique, compared with the 2D mode, is the opportunity to obtain tomographic or multislice imaging in order to assess the entire puborectalis (PR) muscle and its attachment to the pubic rami (Fig. 6.2). It is also possible to measure the diameter and area of the levator hiatus, and to determine the degree of hiatal distension on Valsalva maneuver [7]. 4D imaging involves real-time acquisition of volume ultrasound data, which can then be visualized instantly in orthogonal planes or rendered volumes.

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Fig. 6.1

Two-dimensional transperineal ultrasonography. Midsagittal view of normal female pelvic floor, including the symphysis pubis, the urethra and bladder, the vagina and uterus, the rectum, and the anal canal. Posterior to the anorectal junction, the puborectalis (PR) muscle is visualized as a hyperechogenic structure

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Fig. 6.2

Three-dimensional transperineal ultrasonography. Axial view of normal female pelvic floor, including the symphysis pubis (SP) and pubic rami (PR), the urethra (U) and bladder (B), the levator ani (LA), and the anal canal (AC)

6.2.2 Endovaginal Ultrasonography

Endovaginal ultrasonography (EVUS) is performed with the patient placed in the same position as that adopted for TPUS. It may be performed with a high multifrequency (9–16 MHz), 360° rotational mechanical probe (type 2050, B-K Medical, Herlev, Denmark) or with a radial electronic probe (type AR 54 AW, 5–10 MHz, Hitachi Medical Systems) [8]. The difference between these two transducers is that the 3D acquisition is free-hand with the electronic transducer, whereas the mechanical transducer has an internal automated motorized system that allows an acquisition of 300 aligned transaxial 2D images over a distance of 60 mm in 60 s, without any movement of the probe within the tissue. The set of 2D images is reconstructed instantaneously into a high-resolution 3D image for real-time manipulation and volume rendering. An advantage of 3D compared with the 2D mode is the opportunity to obtain sagittal, axial, coronal, and any desired oblique sectional image. The 3D image may be rotated, tilted, and sliced to allow the operator to vary infinitely the different section parameters, and to visualize and measure distance, area, angle, and volume in any plane. The 3D volume can also be archived for offline analysis on the ultrasonographic system or on a PC with the help of dedicated software [8].

6.2.3 Endoanal Ultrasonography

Endoanal ultrasonography (EAUS) is performed with the same probes adopted for EVUS [9]. During examination, the patient may be placed in a dorsal lithotomy, left lateral, or prone position. However, irrespective of patient position, the transducer should be rotated so that the anterior aspect of the anal canal is superior (12 o’clock position) on the screen, the right lateral aspect is to the left (9 o’clock), the left lateral aspect is to the right (3 o’clock), and the posterior aspect is inferior (6 o’clock). The recording of data should extend from the upper aspect of the PR muscle to the anal verge. The mechanical rotational transducer allows automatic 3D acquisition.

6.3 Ultrasonographic Anatomy

Evaluation of the complex anatomy and function of the pelvic floor may require more than one ultrasonographic modality. TPUS, EVUS, and EAUS may provide complementary information, and often multicompartmental scanning is needed to obtain a complete overview [3].

6.3.1 Pelvic Floor Structures

3D-EVUS performed with 360° field-of-view transducers provides a topographical overview of pelvic floor anatomy [8]. Four levels of assessment in the axial plane can be defined (Fig. 6.3). At the highest level (level I), the bladder base can be seen anteriorly and the inferior third of the rectum posteriorly. Level II corresponds to the bladder neck, the intramural region of the urethra, and the anorectal junction. Level III corresponds to the midurethra and the upper third of the anal canal. At this level, the levator ani can be visualized as a multilayer hyperechoic sling coursing laterally to the vagina and posteriorly to the anal canal, and attaching to the inferior pubic rami anteriorly. Biometric indices of the levator hiatus can be measured [11]: (a) the anteroposterior diameter, from the inferior border of the symphysis pubis to the 6 o’clock inner margin of the levator ani; (b) the laterolateral diameter, measured at the widest part, perpendicular to the anteroposterior diameter; (c) and the area, calculated as the area within the levator ani inner perimeter enclosed by the inferior pubic rami and the inferior edge of the symphysis pubis. At the lowest level (level IV), the superficial perineal muscles (bulbospongiosus, ischiocavernosus, and superficial transverse perineal muscles), the perineal body, the distal urethra, and the middle and inferior thirds of the anal canal can be visualized. At this level, the anteroposterior diameter of the urogenital hiatus, corresponding to the symphysis pubis-perineal body distance, can be determined.

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Fig. 6.3

Three-dimensional endovaginal ultrasonography. Four standard levels of assessment of the normal female pelvic floor: levels I-IV. A, anal canal; B, bladder; BCM, bulbocavernosus muscle; PB, pubic bone; PVM, pubovisceral muscle; R, rectum; STP, superficial transverse perinei muscle; U, urethra. (Reproduced from [10], with permission)

Pelvic organ descent is usually assessed with 2D-TPUS [6]. A midsagittal view, obtained with an acquisition angle of 70° or more, will include the symphysis pubis, the urethra and bladder, the vagina and uterus, the rectum, and the anal canal. Posterior to the anorectal junction, the PR muscle is visualized as a hyperechogenic structure (Fig. 6.1). 3D-TPUS provides the following additional information in the reconstructed axial plane [7] (Fig. 6.2): levator hiatus dimensions, determined in the plane of minimum anteroposterior dimensions; PR muscle dimensions, determined in the plane of maximum muscle thickness; qualitative assessment of the PR muscle and its insertion on the inferior pubic ramus. Biometric indices of the levator hiatus at rest determined in nulliparous women by Santoro et al. [11] using 3D-EVUS (anteroposterior diameter 4.84 cm, laterolateral diameter 3.28 cm, hiatal area 12 cm2) were comparable to the results reported by Dietz et al. [7] using 3D-TPUS (anteroposterior diameter 4.52 cm, laterolateral diameter 3.75 cm, hiatal area 11.25 cm2). The main advantage of external (transperineal) over internal (endovaginal) sonographic imaging of the levator ani is that maneuvers such as Valsalva and pelvic floor muscle contraction allow its functional assessment. Ballooning of the hiatus, i.e., excessive distensibility of the levator ani, is defined as an increase in hiatal area to > 25 cm2 on Valsalva maneuver, and its visualization generally requires full development of pelvic organ prolapse (POP) [12]. Quantitative assessment of muscle trauma is greatly facilitated by tomographic ultrasound [13].

6.3.2 Anterior Compartment

Assessment of the anterior compartment is performed with 2D-TPUS [4] (Fig. 6.1). Measurements in the midsagittal plane, performed with the patient at rest or during functional maneuvers, include [14]: bladder wall thickness or detrusor wall thickness (normal value, up to 5 mm); postvoid residual bladder volume; bladder-symphysis distance, measured between the bladder neck and the lower margin of the symphysis pubis (this measurement enables assessment of the position and mobility of the bladder neck, using the difference between values obtained at rest and on Valsalva; there is no definition of ‘normal’ for bladder neck descent, although a cut-off of 25 mm has been proposed to define hypermobility); urethral length, measured from the bladder neck to the external urethral orifice; retrovesical angle, the angle between the posterior wall of the bladder and the longitudinal axis of the urethra (normal value, 90–120°); proximal urethral rotation (change in angle between proximal urethra and central symphyseal axis) on Valsalva; and descent of the most inferior aspect of a cystocele relative to the symphysis pubis.

6.3.3 Central Compartment

Assessment of the central compartment is performed with 2D-TPUS [4] (Fig. 6.1). In the midsagittal section, an unusually low cervix is isoechoic, its distal margin evident as a specular line, and it often causes acoustic shadowing. In the same section, it is possible to visualize the corpus uteri and determine whether it is enlarged, retroverted, or anteverted. Dynamic 2D-TPUS allows evaluation of uterine descent that may result in compression of the rectal ampulla, explaining symptoms of obstructed defecation. Imaging of vault descent is more difficult, because the vaginal wall is often obscured by a descending rectocele or enterocele.

6.3.4 Posterior Compartment

The anal canal is generally imaged by 3D-EAUS [9]. This method is firmly established as one of the cornerstones of a colorectal diagnostic work-up [15]. With EAUS, the anal canal is divided into three levels of assessment in the axial plane (Fig. 6.4). (1) The upper level corresponds to the hyperechoic sling of the PR muscle and the concentric hypoechoic ring of the internal anal sphincter (IAS). In males, the deep part of the external anal sphincter (EAS) is also identified at this level. (2) In the middle level, the complete ring of the superficial EAS (concentric band of mixed echogenicity), the conjoined longitudinal layer, the complete ring of the IAS and the transverse perinei muscles are visualized. (3) The lower level corresponds to the subcutaneous part of the EAS. 3D-EAUS is useful in assessing the anatomical characteristics of the anal canal [9]. The muscles of the lower and upper parts of the anal canal are different. At its upper end, the PR muscle anchors the sphincter complex to the pubic rami. Anteriorly, the circular fibers of the deep part of the EAS are not recognizable in females, whereas in males the EAS is symmetrical at all levels of the anal canal. The IAS is not completely symmetrical, either in thickness or at its distal end. It can be traced superiorly into the circular muscle of the rectum, extending from the anorectal junction to approximately 1 cm below the dentate line. In the intersphincteric space, the smooth longitudinal muscle conjoins with striated muscle fibers from the levator ani, particularly the puboanalis, and a large fibroelastic element derived from the endopelvic fascia to form the conjoined longitudinal layer.

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Fig. 6.4

Three-dimensional endoanal ultrasonography. Three standard levels of assessment of the normal anal canal: levels I-III. EAS, external anal sphincter; IAS, internal anal sphincter; PR, puborectalis muscle. (Reproduced from [10], with permission)

6.4 Clinical Applications

6.4.1 Urinary Incontinence

Urinary incontinence has been defined by the International Urogynecology Association and the International Continence Society as ‘involuntary loss of urine’ [16]. This condition is exceptionally common, with more than 40% of women over the age of 40 years estimated to experience it. The most common types are: stress urinary incontinence (SUI), defined as involuntary loss of urine during increased abdominal pressure, thought to be due to a poorly functioning urethral sphincter muscle (intrinsic sphincter deficiency) or to hypermobility of the bladder neck or urethra; and urge urinary incontinence (UUI), defined as involuntary urinary leakage accompanied or immediately preceded by urgency, due to detrusor overactivity [16]. Ultrasonography can provide essential information in the management of SUI [5]. Tunn et al. [17] recommended measurement of the retrovesical angle with TPUS in patients with SUI. For quantitative evaluation of urethral mobility, Valsalva maneuver is preferable to the cough test. In patients with SUI or UUI, funneling of the internal urethral meatus may be observed on Valsalva and sometimes even at rest. Marked funneling has been shown to be associated with poor urethral closure pressures. TPUS allows comprehensive evaluation of many abnormalities of the female urethra, such as urethral diverticula, abscesses, tumors, and other urethral and paraurethral lesions [5].

Ultrasonography also allows evaluation of tapes used in anti-incontinence surgery, whose improper positioning or dislodgement may be associated with failed surgery (Fig. 6.5). Dietz et al. [18] performed 3D-TPUS to assess the effectiveness of suburethral slings (tension-free vaginal tape, intravaginal slingplasty, and suprapubic arch sling system). All three tapes were visualized by ultrasound and showed comparable short-term clinical and anatomical outcomes. Ultrasound is particularly useful in the assessment of postoperative voiding dysfunction. The minimum gap between implant and symphysis pubis on maximal Valsalva maneuver seems to be the single most useful parameter in the postoperative evaluation of suburethral tapes, as it is associated negatively with voiding dysfunction and positively with both SUI and UUI. Occasionally, sonographic findings will suggest tape perforation (partial or complete), with the implant found within the rhabdosphincter muscle, or even crossing the urethral lumen. At times it is necessary to divide an obstructive tape, and ultrasound can help in locating the tape, as well as in confirming tape division postoperatively.

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Fig. 6.5

Two-dimensional transperineal ultrasonography. Midurethra (U) tape (T). B, bladder

6.4.2 Fecal Incontinence

Fecal incontinence (FI) is defined as the involuntary loss of feces (liquid or solid stool), and anal incontinence is defined as the involuntary loss of flatus or feces [16]. Intact musculature, including the PR muscle, IAS, and EAS, is a prerequisite for fecal control, as is a functioning nerve supply to these muscles. Other factors contributing to continence include stool consistency, rectal sensitivity and capacity, and anorectal angle. Any impairment of one or more of these factors may result in FI. Anal sphincter defects and pudendal nerve damage occurring during vaginal delivery are by far the most common causes of FI, consequently making this problem more prevalent in women than men. In patients with FI, it is fundamental to establish the underlying pathophysiology in order to choose the appropriate therapy (e.g., dietary adjustments, medication, biofeedback, sphincter repair, artificial bowel sphincter, graciloplasty, sacral nerve stimulation, and injection of bulking agents) [19]. EAUS has become the gold standard for morphological assessment of the anal canal [15]. It can differentiate between incontinent patients with intact anal sphincters and those with sphincter lesions (defects, scarring, thinning, thickening, and atrophy) [9]. Tears are identified by interruption of the circumferential fibrillar echo texture (Fig.6.6). Scarring is characterized by loss of normal architecture, with an area of amorphous texture that usually has low reflectivity. Two scoring systems have been proposed to define the severity of anal sphincter damage. Starck et al. [20] introduced a specific score, with 0 indicating no defect and 16 corresponding to a defect >180° involving the whole length and depth of both sphincters. Noderval et al. [21] described a simplified system for analyzing defects: the maximal score of 7 denotes defects in both the EAS and the IAS exceeding 90° in the axial plane and involving more than half of the length of each sphincter. The presence of a sphincter defect, however, does not necessarily mean that it is the cause of the FI, as many people have sphincter lesions without having symptoms of incontinence. On the other hand, patients with FI and an apparently intact sphincter may have muscle degeneration, atrophy, or pudendal neuropathy. Ultrasonography also allows evaluation of anti-incontinence surgery (sphincter repair, graciloplasty, bulking agent injection) [3].

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Fig. 6.6

Three-dimensional endoanal ultrasonography. Combined anterior damage of the external (EAS) and internal anal sphincters (IAS) from the 10 o’clock to the 2 o’clock position

6.4.3 Levator Ani Injuries

Levator avulsion is the disconnection of the muscle from its insertion on the inferior pubic ramus and the pelvic sidewall, whereas tears may occur in any part of the muscle. Avulsion is a common consequence of overstretching of the levator ani during the second stage of labor and occurs in 10–36% of women at the time of their first delivery [21]. 3D-EVUS and 3D-TPUS may be utilized to document major levator trauma [31213] (Fig. 6.7). Defects are usually visualized most clearly on maximal pelvic floor muscle contraction.

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Fig. 6.7

Three-dimensional transperineal ultrasonography. Tomographic ultrasound, showing a right-side levator ani avulsion. (Reproduced from [10], with permission)

Tomographic ultrasound imaging is particularly useful [13]. The functional and anatomical consequences of levator ani avulsion are considerable, with a reduction in muscle strength of about one-third and marked alteration of anatomy. The main effect of avulsion is probably due to enlargement of the levator hiatus, but avulsion may also be a marker for other forms of trauma, such as damage to connective supporting structures (uterosacral ligaments and endopelvic and pubocervical fascia), which are currently difficult to detect by imaging [22]. An enlarged levator hiatus, whether congenital or due to irreversible overdistension or avulsion injury, may result in excessive loading of ligamentous and fascial structures, which may, over time, lead to connective tissue failure and the development of prolapse [22]. Patients with, compared with those without, a levator ani defect are 2.3 times more likely to have a significant cystocele, and four times as likely to have uterine prolapse. It seems that, compared with any of the other components of the levator ani, trauma to the PR component is most significant in affecting both the size of the hiatus and the symptoms and signs of prolapse.

6.4.4 Anterior Compartment Prolapse

Anterior compartment prolapse, or ‘cystocele’, is common in women and may cause symptoms such as pelvic heaviness, the sensation of a lump, and voiding difficulty. Cystocele frequently coexists with other disorders involving the central and the posterior compartments, such as uterine prolapse, rectocele, and enterocele [16]. Dynamic 2D-TPUS demonstrates downwards displacement of the urethra and the presence of cystocele in the midsagittal plane during maximal Valsalva maneuver [23] (Fig. 6.8). There are two basic types of cystocele: cystourethrocele, in which both bladder base and urethra form one smooth surface, and ultrasound shows an open retrovesical angle over 140° and isolated cystocele, in which the retrovesical angle remains intact and the lowermost point of the bladder is clearly below the bladder neck. Cystourethrocele is associated with SUI, while isolated cystocele is associated with symptoms of prolapse and with voiding dysfunction. Comparative studies have shown good correlation between TPUS and radiological methods [24].

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Fig. 6.8

Two-dimensional transperineal ultrasonography. Midsagittal view of multicompartmental prolapse, appearing as displacement of the pelvic organs below the referral line (red line, horizontal to the inferior margin of the symphysis pubis SP)

Ultrasonography also allows evaluation of mesh implants for anterior compartment prolapse [3]. This is particularly useful considering that complications such as support failure, mesh erosion, and chronic pain are not uncommon. Polypropylene meshes are less visible on X-ray and magnetic resonance imaging, but highly echogenic. Sonographic imaging can determine the position, extent, and mobility of implants, helping with the assessment of surgical techniques and determination of functional outcome. Mesh may be visualized in the anterior vaginal wall, dorsal to the trigone and posterior bladder wall. 3D-TPUS has demonstrated that often the implanted mesh is nowhere near as wide as it is supposed to be, and this finding has been interpreted as evidence of mesh shrinkage, ‘contraction’, or ‘retraction’. A more likely explanation is that the mesh did not remain flat but folded up on itself, either during the implantation process or immediately after closure. Surgical technique seems to play a role, since fixation of mesh to underlying tissues results in a flatter, more even appearance. Moreover, ultrasonography may uncover complications such as dislodgement of anchoring arms [3].

6.4.5 Middle Compartment Prolapse

Uterine prolapse is defined as downwards displacement of the uterus beyond the halfway point of the vagina. Vaginal vault prolapse refers to descent of the vaginal apex in a patient who has had a hysterectomy, and is commonly associated with enterocele or sigmoidocele. Continued descent of the apex of the vagina may result in complete eversion of the vagina [16]. These conditions are usually obvious clinically, but dynamic 2D-TPUS can demonstrate the effect of the descending uterus on the bladder neck, urethra, or anorectum, explaining symptoms of voiding dysfunction or obstructed defecation [23].

6.4.6 Posterior Compartment Prolapse

Posterior compartment prolapse includes rectocele, rectal intussusception, rectal prolapse, enterocele, and perineal descent [16]. Symptoms that can be related to these disorders include obstructed defecation, such as incomplete evacuation, straining at stool and vaginal digitation [16]. Several modalities have been employed to identify and quantify posterior compartment prolapses. To date, defecography has been the gold standard for evaluation of this condition. However, dynamic TPUS has been shown to demonstrate rectocele, enterocele, and rectal intussusception with images comparable with those of defecography [6]. Rectocele is measured as the maximal depth of the protrusion beyond the expected margin of the normal anterior rectal wall (Fig. 6.8). On radiological imaging, a depth of < 2 cm is considered within normal limits; rectocele should be considered moderate if the depth is 2–4 cm, and large if it is > 4 cm. On sonographic imaging, a herniation of a depth of over 10 mm has been considered diagnostic [6]. Rectal intussusception may be detected as an invagination of the rectal wall into the rectal lumen during maximal Valsalva maneuver. The intussusception may also be observed to enter the anal canal or be exteriorized beyond the anal canal [6]. Enterocele is diagnosed ultrasonographically as a herniation of bowel loops into the vagina (Fig. 6.8). It can be graded as: small, when the most distal part descends into the upper third of the vagina; moderate, when it descends into the middle third of the vagina; or large, when it descends into the lower third of the vagina [6]. Enterocele may also coexist with rectocele. A comparative clinical study found poor agreement between defecation proctography and TPUS in the measurement of quantitative parameters. However, when ultrasound imaging revealed a rectocele or rectal intussusception, there was high likelihood of this diagnosis being confirmed on proctography [6]. Other studies have shown better agreement between sonographic and radiological assessment. Steensma et al. [25] reported good agreement between 3D-TPUS and defecography for detecting enterocele. On the other hand, other studies have suggested that defecography overdiagnoses these abnormalities. Perniola et al. [26] suggested that ultrasonography should not replace defecography in clinical practice, but that it should be performed as an initial examination or screening method in patients with defecatory disorders.

A new ultrasonographic technique (echodefecography, EDF) to evaluate posterior compartment prolapses has been developed by Murad-Regadas et al. [2728]. This is a 3D dynamic anorectal ultrasonographic modality performed with the same 360° rotating transducer used for EAUS. The standardization of the technique, parameters, and values of EDF makes the method reproducible [28]. EDF was shown to correlate well with conventional defecography and was validated in a prospective multicenter study [28]. Following rectal enema, patients are examined in the left lateral position. Images are acquired by four automatic scans and analyzed in the axial, sagittal, and, if necessary, in the oblique plane. Scan 1 (at rest position without gel): the transducer is positioned at 5.0–6.0 cm from the anal margin. It is performed to visualize the anatomic integrity of the anal sphincter musculature and to evaluate the position of the PR and EAS at rest. The angle formed between a line traced along the internal border of the EAS/PR (1.5 cm) and a line traced perpendicular to the axis of the anal canal is measured. Scan 2 (at rest-straining-at rest without gel): the transducer is positioned at 6.0 cm from the anal verge. The patient is requested to rest for the first 15 s, strain maximally for 20 s, then relax again, with the transducer following the movement. The purpose of the scan is to evaluate the movement of the PR and EAS during straining, identifying normal relaxation, nonrelaxation or paradoxical contraction (anismus). The resulting EAS/PR positions (represented by the angle size) are compared between scans 1 and 2. Normal relaxation is recorded if the angle increases by a minimum of 1°, whereas paradoxical contraction (anismus) is recorded if the angle decreases by a minimum of 1°. Nonrelaxation is recorded if the angle changes less than 1° (Figs. 6.9 and 6.10); Scan 3: the transducer is positioned proximally to the PR (anorectal junction). The scan starts with the patient at rest (3.0 s), followed by maximum straining with the transducer in fixed position (the transducer does not follow the descending muscles of the pelvic floor). When the PR becomes visible distally, the scan is stopped. Perineal descent is quantified by measuring the distance between the position of the proximal border of the PR at rest and the point to which it has been displaced by maximum straining (PR descent). Straining time is directly proportional to the distance of perineal descent. Even with patients in the lateral position, the displacement of the PR is easily visualized and quantified. On EDF, normal perineal descent during straining is defined as a difference in PR position of ≤ 2.5 cm and perineal descent > 2.5 cm. The normal range values were established by comparing EDF with defecography [29]. Scan 4: following injection of 120–180 mL ultrasound gel into the rectal ampulla, the transducer is positioned at 7.0 cm from the anal verge. The scanning sequence is the same as in scan 2 (at rest for 15 s, strain maximally for 20 s, then relax again, with the transducer following the movement). The purpose of the scan is to visualize and quantify all anatomical structures and functional changes associated with voiding (rectocele, intussusception, grade II or III sigmoidocele/enterocele). In normal patients, the posterior vaginal wall displaces the lower rectum and upper anal canal inferiorly and posteriorly, but maintains a straight horizontal position during defecatory effort. If rectocele is identified, it is classified as grade I (< 6.0 mm), grade II (6.0–13.0 mm), or grade III (> 13.0 mm) (Fig. 6.11). Measurements are calculated by first drawing two parallel horizontal lines along the posterior vaginal wall, with one line placed in the initial straining position, and the other line drawn at the point of maximal straining. The distance between the two vaginal wall positions determines the size of the rectocele. Intussusception is clearly identified by observing the rectal wall layers protruding through the rectal lumen. No classification is used to quantify intussusceptions (Figs. 6.12 and 6.13). Grade II or III sigmoidocele/enterocele is recognized when the bowel is positioned below the pubococcygeal line (on the projection of the lower rectum and upper anal canal).

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Fig. 6.9

Three-dimensional echodefecography. Sagittal plane: a angle measured at rest position (lines), b increased angle (normal relaxation) during straining (lines). EAS, external anal sphincter; IAS, internal anal sphincter; PR, puborectalis muscle

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Fig. 6.10

Three-dimensional echodefecography. Sagittal plane: a angle measured at rest position (lines), b decreased angle (anismus) during straining (lines). EAS, external anal sphincter; IAS, internal anal sphincter; PR, puborectalis muscle

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Fig. 6.11

Three-dimensional echodefecography using gel into the rectum. Sagittal plane: a patient without rectocele, b grade III rectocele (arrows). EAS, external anal sphincter; IAS internal anal sphincter; PR, puborectalis muscle

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Fig. 6.12

Three-dimensional echodefecography using gel into the rectum. a Axial plane: anterior intussusception (arrows), b Sagittal with coronal plane: without rectocele and anterior intussusceptions (arrows)

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Fig. 6.13

Three-dimensional echodefecography using gel into the rectum. a Axial plane: anterior and right-side intussusceptions (arrows). b Sagittal with coronal plane: grade II rectocele and anterior and right side intussusceptions (arrows)

6.4.7 Pelvic Floor Dyssynergia

Pelvic floor dyssynergia, also known as anismus, spastic pelvic floor syndrome, or paradoxical PR syndrome, is a phenomenon characterized by a lack of normal relaxation of the PR muscle during defecation [30]. However, an involuntary (reflex) contraction of the levator ani is common, especially in young nulliparae, and it is thought to be part of a generalized defensive reflex, implying that false-positive findings in asymptomatic women may well be common in stressful clinical settings. Dyssynergia is associated with symptoms of obstructed defecation and incomplete emptying. The diagnosis of dyssynergia may be suggested by tests of anorectal physiology (electromyography and manometry); however, proctography and dynamic magentic resonance defecography have an important diagnostic role [30]. Various radiological abnormalities have been described, including prominent puborectal impression and acute anorectal angulation during straining and defecation. Dynamic TPUS may also have a role in documenting pelvic floor dyssynergia [3]. During Valsalva maneuver, the anorectal angle becomes narrower, the levator hiatus is shortened in the anteroposterior dimension, and the PR muscle thickens as a result of contraction. This sonographic finding may help to choose biofeedback therapy and in evaluating the results after treatment.

6.5 Discussion

The ultrasonographic multimodalities (EVUS, EAUS, TPUS, and EDF) integrated approach to the pelvic floor provides an accurate anatomical assessment of patients with UI, FI, and POP [3]. Division into anterior, middle, and posterior compartments has led to fragmentation of assessment: the anterior compartment containing the urethra and bladder has been the realm of the urologist and urogynecologist, who use TPUS as their modality of choice for scanning; the middle compartment containing the uterus and reproductive organs has been the domain of gynecologists, who use mainly EVUS for assessment; and the posterior compartment containing the small and large bowels and the anorectum belonged to the colorectal surgeons, who prefer EAUS and EDF [16]. This artificial division of the pelvis fails to recognize the close anatomical relationship of these compartments. Dysfunction of one of the compartments influences the structure and function of another. For this reason imaging should evolve from assessment involving a single compartment, with the inherent limitations, to an “integrated approach” for multicompartmental evaluation [3].

Combining different modalities has the potential to complement the advantages, overcome the limitations of each of these tools, and substantially improve the clinical management of pelvic floor disorders (PFDs). Care of women with PFDs begins with an understanding of the unique musculofascial system that supports the pelvic organs. The principles underlying reconstructive surgery are either restoration of normal anatomy and thereby a presumed return to normal function, or creation of compensatory anatomical mechanisms [1]. To date, decisions have been based on clinical assessment, which has a limited role in evaluating the morphological changes leading to PFD. Obstructed defecation, FI, UI, and voiding dysfunction are frequently concurrent issues in patients with POP, suggesting a more widespread PFD affecting both support and sphincter function, and requiring more specific investigation. Moreover, it is often unclear as to whether, or to what degree, given symptoms are related to the degree of prolapse [1]. It is, therefore, important to make an accurate preoperative assessment, yet there is controversy concerning the role of diagnostic testing in selecting treatment for PFD. Several studies have looked specifically at the clinical utility of imaging investigations, with varying results [3132]. The greatest utility of ultrasonography in patients with POP is to identify not just the clinical manifestation (cystocele, uterine prolapse, rectocele, or enterocele) but the underlying anatomical and functional abnormalities of the pelvic floor muscles and connective tissues. Levator ani damage, avulsion defects, abnormal levator ani contractility, pathologically enlarged levator hiatus (ballooning), and anal sphincter lesions may be diagnosed on TPUS, EVUS, and EAUS [3]. Ultrasonography also has the advantage of enabling evaluation of function of the pelvic floor with various dynamic maneuvers. Perniola et al. [26] suggested that ultrasonography should be performed as an initial examination in patients with defecatory disorders. Positive findings on ultrasound may avoid more invasive tests, whereas negative findings require confirmation by defecation proctography. In patients with UI, ultrasonography can provide useful information on the anatomy and function of the lower urinary tract. Urethral mobility, urethral vascularity, funneling of the internal urethral meatus, bladder neck descent, and bladder wall thickness may be evaluated on TPUS [45]. In addition, ultrasonography allows evaluation of anti-incontinence procedures and helps in understanding their failure. In patients with FI, EAUS has been recommended by the International Urogynecological Association/International Continence Society joint report as the gold standard investigation to identify anal sphincter injury [16].

In conclusion, the goal of pelvic surgery is to relieve patient symptoms and to restore anatomy and function whenever possible. There is no doubt that the additional knowledge gained from multicompartmental ultrasonography of the pelvic floor, with a systematic “integrated” approach, will improve our chances of actually reaching this goal. Imaging findings are already leading to either modification or a choice of specific operative procedures, and current research is being directed toward the impact of imaging on patient outcomes, in both the short and the long term.

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