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.