The reliability of puborectalis muscle measurements with 3-dimensional ultrasound imaging

Objective

Our aims were to: (1) recognize the anatomic landmarks for measurement of puborectalis muscle on 3-dimensional ultrasound images, (2) assess intra- and interobserver reliability of puborectalis muscle measurements, (3) determine whether there is measurable puborectalis muscle shortening with pelvic floor squeeze, and (4) assess pelvic hiatus symmetry.

Study design

Twenty-seven nulliparous asymptomatic women were imaged with 3-dimensional ultrasound at rest and squeeze. Three-dimensional ultrasound volumes were rotated by using a standardized technique and analyzed by 2 observers.

Results

Anatomic landmarks (lower end of pubic bone and apex of anorectal angle) were recognized consistently. There is significant shortening of puborectalis muscle and pelvic floor hiatus dimensions with squeeze. Inter- and intraobserver correlations demonstrate reproducibility of measurements. Both halves of pelvic floor hiatus are mirror images of each other.

Conclusion

Three-dimensional ultrasound imaging allows localization of anatomic landmark and yields reliable measurements of the puborectalis muscle and pelvic floor hiatus.