Can the rectovaginal septum be visualized by transvaginal three-dimensional ultrasound?

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1 Ultrasound Obstet Gynecol 2011; 37: Published online 10 January 2011 in Wiley Online Library (wileyonlinelibrary.com). DOI: /uog.8896 Can the rectovaginal septum be visualized by transvaginal three-dimensional ultrasound? H. P. DIETZ Sydney Medical School Nepean, Penrith, Australia KEYWORDS: 3D ultrasound; female pelvic organ prolapse; rectocele; rectovaginal septum; vaginal ultrasound ABSTRACT Objective The rectovaginal septum (RVS) is described as a layer of connective tissue separating the anorectum from the vagina. RVS defects are thought to be responsible for rectocele formation. This study attempted to visualize the RVS with transvaginal three-dimensional (3D) ultrasound. Methods Fifty-two women were interviewed and underwent clinical examination and pelvic floor ultrasound examination. Two-dimensional (2D) translabial imaging was used to assess for rectocele on maximal Valsalva maneuver. Transvaginal volume ultrasound data were archived and analyzed 6 9 months later, by an observer blinded to clinical data. 3D volumes were assessed for the presence of a hyperechoic layer between the vaginal muscularis and internal anal sphincter/anorectal muscularis. Data were analyzed relative to clinical findings, symptoms and the 2D ultrasound diagnosis of a rectocele. Results Forty-six volume ultrasound datasets could be analyzed. On clinical examination, 20 women were found to have a rectocele ( Stage 2). On translabial ultrasound there were 28 (61%) women with true rectocele i.e. pocketing of the rectal ampulla. On 3D ultrasound a hyperechogenic layer between vaginal and anorectal muscularis was identified in all but one patient. Gaps in this layer were identified in 10 (22%) women. There were no consistent associations between clinical findings of posterior compartment descent or sonographically detected rectocele and RVS thickness or extent, or the finding of a gap in the RVS on 3D imaging. Conclusions The RVS may be identifiable with static transvaginal 3D ultrasound, but this method does not seem to yield any information that correlates with clinical or translabial 2D ultrasound findings of posterior vaginal wall prolapse. Copyright 2011 ISUOG. Published by John Wiley & Sons, Ltd. INTRODUCTION The rectovaginal septum (RVS) is a controversial structure. Some consider it a potential space, others a distinct anatomical entity. When considered the latter, it is taken to be synonymous with the rectovaginal fascia or Denonvillier s fascia of the female, also termed the rectogenital septum 1. It is described as a layer of connective tissue connecting the paracervical ring and/or cardinal/uterosacral ligament complex with the perineal body 2, separating the anorectum from the vagina and preventing herniation of the rectal ampulla into the vagina 3. Aigner et al. 1 agree that the RVS is identified as a clearly defined plate in the coronal plane consisting of fibrous connective tissue and longitudinal muscle fibers between the rectum and the vagina, but claim that it connects the perineal body to the longitudinal muscle layer of the ventral rectal wall 1. Cullen Richardson 4 also describes the RVS as a strong sheet of connective tissue, containing dense collagen, some strands of smooth muscle, and a very dense network of heavy elastin fibers. It is thought to support the posterior compartment analogous to the pubocervical fascia in the anterior compartment 5. It occupies an oblique coronal plane between the two lateral aspects of the levator ani muscle, to which it is connected laterally, and the pelvic sidewall. It is located in immediate proximity to the posterior vaginal wall 2. Depending on the structure and function of the levator ani, it is the only substantial structure that stands between the intra-abdominal pressure of the rectal ampulla and the atmospheric pressure of the lower posterior vagina below the levator hiatus. Correspondence to: Prof. H. P. Dietz, Obstetrics and Gynaecology, Nepean Clinical School, University of Sydney, Nepean Hospital, Penrith NSW 2750, Australia ( hpdietz@bigpond.com) Accepted: 17 November 2010 Copyright 2011 ISUOG. Published by John Wiley & Sons, Ltd. ORIGINAL PAPER

2 Rectovaginal septum 349 On surgical dissection, it is possible to isolate a connective tissue layer between the vaginal skin and the anorectal muscularis (Figure 1). This structure is easily missed, i.e. divided together with vaginal skin and muscularis, unless great care is taken. Hydrodissection seems particularly helpful in this respect. Defects of the RVS are thought to be responsible for rectocele formation, i.e. herniation of the anterior wall of the rectal ampulla into the vagina 3. They are supposed to be transverse, in the midline or lateral, although it is possible that some defects observed by the gynecological surgeon are in fact artifactual, i.e. a product of dissection rather than pre-existing. Proponents of the defect-specific approach to rectocele repair hold that this procedure is best performed by closing all apparent defects and by approximating the detached RVS margin to the paracervical ring and the uterosacral ligaments. It is not surprising that some anatomists doubt its existence as a separate, surgically useful structure, given that many gynecological surgeons have never consciously seen the RVS, considering it part of the vaginal wall. Our inability to directly image the RVS and to determine its integrity preoperatively has clearly hampered surgical progress in this field. Imaging by defecation proctography 6 and translabial 7 ultrasound can demonstrate a true rectocele, i.e. a diverticulum of the rectal ampulla that herniates into the vagina, and it is generally assumed that this implies a defect of the RVS, but direct imaging would be far preferable, especially in order to define the exact location and extent of defects in this structure. The RVS was recently described as a hyperechogenic structure sandwiched between the vaginal and rectal muscularis, in a case report on sonorectovaginography after instillation of fluid into the peritoneal cavity 8.The present study was an attempt to directly visualize the RVS with the help of high-frequency transvaginal threedimensional (3D) ultrasound. METHODS A total of 52 women with symptoms of pelvic floor dysfunction were seen consecutively in a tertiary urogynecological unit between January and May They underwent standardized (local, non-validated) interview, clinical examination (International Continence Society Prolapse quantification (ICS POP-Q)), multichannel urodynamic testing and pelvic floor imaging (while supine and after voiding) with a BK Pro Focus system, an 8802 convex array (4.3 6 MHz) used translabially, and an 8848S transvaginal 6.5-MHz 3D probe (Bruel & Kjaer Australia, North Ryde, New South Wales, Australia). This vaginal probe integrates both a 6.5-cm linear transducer for longitudinal views (as used in this study) and a convex array for transverse views. An external mover allows 3D acquisition via a magnetic clip-on collar, allowing an acquisition angle of up to 179, during an acquisition time of up to 30 s. Two-dimensional (2D) translabial imaging was used to assess for rectocele as described previously 9. Transvaginal volume ultrasound data were then acquired with the maximum acquisition angle of 179, utilizing the transducer s linear array. The acquisition time was kept under 15 s to reduce motion artifacts. Volumes were archived on the system s hard disk and analyzed 6 9 months later, using the software BK 3D View Version (Bruel & Kjaer Australia), on a PC in order to guarantee blinding to all clinical data, since the offline analysis was performed by the same person who performed the clinical assessment. 3D volumes were assessed for the presence of a hyperechoic layer between the hypoechoic vaginal muscularis and the internal anal sphincter/anorectal muscularis (Figure 2). This layer was described as being present or absent, and as being contiguous or discontinuous, and its thickness and extent cranial and caudal of the anorectal junction were measured centrally at the level of the anorectal junction. Figure 3 shows a patient in whom this layer was partially absent, interpreted as a defect of the RVS. Data were then analyzed in comparison with clinical findings, symptoms and the sonographic diagnosis of pocketing of the rectal ampulla extending into the vagina. Figure 1 Rectovaginal septum (arrows), as identified on intraoperative dissection of the posterior vaginal wall. Figure 2 Anal canal, rectal ampulla and rectovaginal septum (RV septum) as imaged on transvaginal three-dimensional ultrasound. The left aspect of the image is cranial and the right is caudal. IAS, internal anal sphincter; POD, pouch of Douglas; PR, puborectalis.

3 350 Dietz Figure 3 Sonographic defect (arrows) of the rectovaginal septum (RVS). PR, puborectalis. Ethics approval was obtained for retrospective analysis of data obtained during routine clinical assessment (SWAHS HREC 09 16). Statistical evaluation was undertaken using SPSS 12 for Windows (SPSS Inc., Chicago, IL, USA) and Minitab V13 for PC (Minitab Inc., State College, PA, USA). Two-sample t-tests and chi-square tests were used for statistical analysis, the former after normality testing (Kolmogorov Smirnov). Repeatability of categorical parameters was tested using Cohen s kappa, intraclass correlation (absolute agreement definition, single measurements) and Bland Altman analysis for bias and limits of agreement. P < 0.05 was considered statistically significant. On clinical examination, 20 women were found to have significant posterior compartment descent ( Stage 2). On 2D translabial ultrasound there were 28 (61%) women with true rectocele, i.e. pocketing of the rectal ampulla into the vagina, of at least 10 mm in depth. On 3D ultrasound a hyperechogenic layer between vaginal and anorectal muscularis was identified in all but one patient, and its mean thickness was 1.1 (range, ) mm. This layer extended on average from 16.8 (range, ) mm below to 28.5 (range, ) mm above the anorectal junction, and in many women it extended beyond the field of vision. Gaps in this layer were identified in 10 (22%) women. The intraobserver repeatability data on a series of 20 arbitrarily selected patients (measurements repeated after 2 weeks, with observer blinded to previous results) are given in Table 1. Most numerical measurements were of moderate to poor repeatability. The finding of a gap in the RVS had a kappa of 0.5, signifying only moderate repeatability. There were no consistent associations between clinical findings of posterior compartment descent or a sonographically detected rectocele on the one hand, and RVS thickness or extent, or the finding of a gap in the RVS on the other (Table 2). In fact, presence of a gap on 3D transvaginal ultrasound was negatively associated with a significant rectocele on clinical examination (P = 0.016, chi-square test). The one patient in whom no RVS could be identified showed no significant clinical rectocele and a perfect posterior compartment on ultrasound. RESULTS From the 52 patients included in this study, 46 volume ultrasound datasets that could be analyzed were retrieved; six datasets were either corrupted or had not been archived appropriately. All subsequent data relate to this group of 46 women. The mean age at assessment was 55 (range, 29 82) years. Thirty-eight (83%) women presented with stress incontinence, 39 (85%) with urge incontinence and 14 (30%) with symptoms of prolapse. Symptoms of obstructed defecation, such as incomplete bowel emptying, vaginal digitation and straining at stool, were reported by 27 (59%) women. 89% were vaginally parous (median, 3 (range, 0 5) births). Sixteen (35%) had undergone a hysterectomy. One patient reported a previous posterior repair. DISCUSSION The RVS or rectovaginal fascia is a highly controversial structure. DeLancey, the foremost anatomist in the field of pelvic floor reconstruction, has stated that he doubts the existence of the RVS as a surgically useful structure 10. On the other hand, it forms the basis for a defectspecific approach to posterior compartment prolapse repair 4. Unfortunately, the surgical techniques designed to utilize the RVS for rectocele repair have not always been well described. As a result, it is not always clear from the literature as to what authors actually mean when they claim to be following a defect-specific or site-specific approach 11 15, and a number of different approaches seem to be subsumed under this term. To be more precise, it has been variously claimed that Table 1 Intraobserver repeatability of transvaginal three-dimensional ultrasound assessment of the rectovaginal septum Parameter ICC (95% CI) or kappa Bias LOA Vaginal mucosal thickness 0.89 ( ) to 1.1 Rectovaginal septum thickness 0.48 ( ) to 1.0 Anorectal muscularis thickness 0.62 ( ) to 0.7 Extent of septum above anorectal junction 0.52 ( ) to 18.8 Extent of septum below anorectal junction 0.23 ( ) to 15.9 Gaps in rectovaginal septum 0.5 ICC, intraclass correlation (two way mixed, absolute agreement definition); LOA, limits of agreement.

4 Rectovaginal septum 351 Table 2 Association between defects of the rectovaginal septum (RVS) as visualized on three-dimensional transvaginal ultrasound (3D TVS) and clinical posterior compartment descent, sonographic rectocele on two-dimensional translabial ultrasound (2D TLS) and symptoms of obstructed defecation Significant clinical posterior compartment descent Rectocele on 2D TLS Symptoms of obstructed defecation 3D TVS parameter Yes No Yes No Yes No Mean RVS thickness (mm) Mean RVS extent cranially (mm) Mean RVS extent caudally (mm) Gaps in RVS Present (n = 10) 1 9* Absent (n = 36) *P = (chi-square test). high or low, transverse or longitudinal, medial and/or paramedian defects may have to be repaired to cure rectocele, while imaging supports exclusively the concept of high transverse defects. Such high transverse defects of the RVS fully explain the appearance of a rectocele on radiological or ultrasound imaging as a diverticulum of the rectal ampulla into the vagina, defined by a clear lower margin that is formed by a transverse ridge at the upper margin of the perineal body. However, demonstrating the RVS in the operating theater requires careful dissection of the posterior vaginal wall, preferably with the help of hydrodissection, in order to avoid cutting through the septum by leaving it attached to the vaginal skin. This often occurs during posterior colporrhaphy, the traditional approach to vaginal rectocele repair 16,andasa result it is not surprising that many gynecological surgeons have never seen this structure. It would be highly desirable to identify the RVS preoperatively by imaging, but so far no attempts to do so have been reported. In addition, there are now several other techniques for posterior compartment repair, such as mesh implantation 17 and stapled transanal resection 18, which ignore the RVS altogether. Defects of the RVS (not the septum itself) are identified on translabial ultrasound or defecation proctography as sacculations or diverticulum-like pockets, extending from the rectal ampulla into the vagina. They are associated with symptoms of prolapse and obstructed defecation 19,20, although such associations vary depending on the diagnostic technique used. All symptoms of obstructed defecation have other potential (anatomical or functional) causes that usually are not sought by gynecologists once a rectocele is identified, and stool quality seems to be at least as strong a predictor of such symptoms 21. Not surprisingly, the effect of surgical rectocele repair on symptoms varies greatly 20, and there has been a trend away from traditional posterior colporrhaphy due to its perceived lack of efficacy, the fact that rectocele is often asymptomatic 22 and the risk of dyspareunia 23. Rectoceles are sometimes seen in young, nulliparous women 24, but the prevalence increases after childbirth 25, even though parity does not seem to be a major etiological factor in women seen later in life 7. In this small observational series high-resolution intravaginal 3D ultrasound was used in an attempt to identify the RVS itself, rather than just the herniation through a presumed defect in the RVS, which is identified as a rectocele on dynamic translabial ultrasound 7. Unfortunately, static 3D ultrasound of the posterior vaginal wall did not seem to yield any discrete findings associated with posterior compartment prolapse or sonographic rectocele formation. This may have been due to limited reproducibility of the method or suboptimal image quality, or to defects lateral to the midline. Another potential explanation may be that the structure visualized in this study and by others was not in fact the RVS. In my opinion the most likely explanation is that transvaginal 3D imaging is necessarily undertaken with the patient at rest, as the presence of the probe would impede rectocele development on Valsalva. This may stop a defect in the RVS from opening up sufficiently to become visible since rectoceles are usually only apparent on Valsalva maneuver. It is also possible that actual defects of the RVS may not always result in a visible rectocele on translabial imaging due to the compressive effects of prolapse in other compartments. There are a number of methodological weaknesses of this study that must be taken into consideration. It was a small series, and, since all subjects were seen for symptoms of pelvic floor dysfunction, there were no normal, i.e. asymptomatic, young and nulliparous controls. Patients were examined while in the supine position only, and on Valsalva, which may limit the degree to which results can be compared to the results of defecation proctography, the gold standard method for diagnosing rectocele. The bowel was not prepared and no contrast medium was used in either vagina or rectum, because this seems to be unnecessary 7,9,26 since stool in the rectal ampulla usually provides for excellent contrast. However, it is conceivable that vaginal and/or intrarectal gel might have improved visibility. Furthermore, this study did not provide validation of the imaging technique by other imaging modalities or surgical dissection, which would strengthen any conclusions substantially. Further studies using such validation methods are clearly necessary. Finally, the limited field of vision of the linear 3D transducer used in this

5 352 Dietz study could have influenced results, since the length of the array (6.5 cm) may not be sufficient to image the entire posterior vaginal wall in some women. In conclusion, static transvaginal 3D ultrasound imaging does not seem to yield any findings that correlate with clinical or 2D translabial ultrasound findings of posterior vaginal wall prolapse. Further studies with larger populations, including an asymptomatic, nulliparous control group, may be necessary to define the role of intracavitary imaging of the RVS. DISCLOSURE H.P. Dietz has acted as a consultant for AMS and CCS, has received speaker s honoraria from GE and Astellas, and has received equipment loans from GE, Toshiba and B&K. REFERENCES 1. Aigner F, Zbar A, Ludwikowski B, Kreczy A, Kovacs P, Fritsch H. The rectogenital septum: morphology, function, and clinical relevance. Dis Colon Rectum 2004; 47: Stecco C, Macchi V, Porzionato A, Tiengo C, Parenti A, Gardi M, Artibani W, De Caro R. Histotopographic study of the rectovaginal septum. Ital J Anat Embryol 2005; 110: Shull BL, Bachofen C. Enterocele and rectocele. In Urogynecology and Reconstructive Pelvic Surgery, Walters MD, Karram MM (eds). Mosby: St Louis: Richardson AC. The rectovaginal septum revisited: its relationship to rectocele and its importance in rectocele repair. Clin Obstet Gynecol 1993; 36: Leffler KS, Thompson JR, Cundiff GW, Buller JL, Burrows LJ, Schon Ybarra MA. Attachment of the rectovaginal septum to the pelvic sidewall. Am J Obstet Gynecol 2001; 185: Halligan S, McGee S, Bartram CI. Quantification of evacuation proctography. Dis Colon Rectum 1994; 37: Dietz HP, Steensma AB. Posterior compartment prolapse on two-dimensional and three-dimensional pelvic floor ultrasound: the distinction between true rectocele, perineal hypermobility and enterocele. Ultrasound Obstet Gynecol 2005; 26: Bignardi T, Condous G. Sonorectovaginography: a new sonographic technique for imaging of the posterior compartment of the pelvis. J Ultrasound Med 2008; 27: Dietz HP. Ultrasound imaging of the pelvic floor. Part I: twodimensional aspects. [Review]. Ultrasound Obstet Gynecol 2004; 23: DeLancey J. Structural anatomy of the posterior pelvic compartment as it relates to rectocele. Am J Obstet Gynecol 1999; 180: Cundiff GW, Weidner AC, Visco AG, Addison WA, Bump RC. An anatomic and functional assessment of the discrete defect rectocele repair. Am J Obstet Gynecol 1998; 179: Abramov Y, Gandhi S, Goldberg RP, Botros SM, Kwon C, Sand PK. Site-specific rectocele repair compared with standard posterior colporrhaphy. Obstet Gynecol 2005; 105: Miklos JR, Kohli N, Lucente V, Saye WB. Site-specific fascial defects in the diagnosis and surgical management of enterocele. Am J Obstet Gynecol 1998; 179: ; Discussion Smith ARB. Role of connective tissue and muscle in pelvic floor dysfunction. Curr Opin Obstet Gynecol 1994; 6: Shull BL, Capen CV, Riggs MW, Kuehl TJ. Preoperative and postoperative analysis of site-specific pelvic support defects in 81 women treated with sacrospinous ligament suspension and pelvic reconstruction. Am J Obstet Gynecol 1992; 166: ; Discussion Nichols DH, Randall CL. Posterior colporrhaphy and perineorrhaphy. In Vaginal Surgery, Nichols DH, Randall CL (eds). Williams and Wilkins: Baltimore, 1996; Barry C, Dietz H, Lim Y, Rane A. A short-term independent audit of mesh repair for the treatment of rectocele in women, using 3-dimensional volume ultrasound: a pilot study. Aust N Z Continence J 2006; 12: Boccasanta P, Venturi M, Salamina G, Cesana B, Bernasconi F, Roviaro G. New trends in the surgical treatment of outlet obstruction: clinical and functional results of two novel transanal stapled techniques from a randomised controlled trial. Int J Colorectal Dis 2005; 19: Dietz HP, Korda A. Which bowel symptoms are most strongly associated with a true rectocele? Aust N Z J Obstet Gynaecol 2005; 45: Brubaker L. Rectocele. Curr Opin Obstet Gynecol 1996; 8: Dietz H. Rectocele or stool quality: what matters more for symptoms of obstructed defecation? Tech Coloproctol 2009; 13: Karram M, Porter R. Pathophysiology, diagnosis and management of rectoceles. In Female Urology and Urogynaecology, Cardozo L, Staskin D (eds). Isis Medical Media: London, 2001; Crafoord K, Sydsjo A, Nilsson K, Kjolhede P. Primary surgery of genital prolapse: a shift in treatment tradition. Acta Obstet Gynecol Scand 2006; 85: Dietz HP, Clarke B. Prevalence of rectocele in young nulliparous women. Aust N Z J Obstet Gynaecol 2005; 45: Dietz HP, Steensma AB. The role of childbirth in the aetiology of rectocele. BJOG 2006; 113: Perniola G, Shek K, Chong C, Chew S, Cartmill J, Dietz H. Defecation proctography and translabial ultrasound in the investigation of defecatory disorders. Ultrasound Obstet Gynecol 2008; 31: