Validating New Ultrasound Parameters for Quantifying Pelvic Floor Muscle Contraction

Objective. To determine the reliability and validity of new ultrasound parameters, measured in the polar coordinate system, as a representation of pelvic floor muscle action.
Methods. From January 2005 to December 2007, a survey was conducted in 209 women who had urodynamic stress incontinence to validate new ultrasound parameters for quantifying pelvic floor muscle contraction. The survey included intravaginal digital palpation of voluntary pelvic floor muscle contractility and an ultrasound assessment of the positions of the bladder neck and anorectal junction at rest and during pelvic floor muscle contraction. The positions of the bladder neck and anorectal junction were expressed by bladder neck angle and bladder neck distance and levator hiatal angle and sagittal hiatal diameter, respectively. The vector lengths of the motion of bladder neck and anorectal junction during pelvic floor muscle contraction were calculated from the positions at rest and during pelvic floor muscle contraction by mathematical formula.
Results. The ultrasound parameters measured in this study demonstrated good inter- and intra-rater reliability. During pelvic floor muscle contraction, elevated bladder neck distance and shortened sagittal hiatal diameter were two valid parameters representing stronger pelvic floor muscle contractility with shortened sagittal hiatal diameter having the best correlation (r = -0.348, P < 0.001).
Conclusion. Overall, the methods used in this study are reliable tools for quantifying pelvic floor muscle contractility with sagittal hiatal diameter proving to be a superior measure.