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

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.