On-screen vector-based ultrasound assessment of vesical neck movement

Objective: We sought to develop a vector-based assessment to determine the magnitude and direction of bladder neck movements, as well as to assess whether probe movement relative to the pubis needs to be taken into account. Study Design: Ten nulliparous continent, 10 primiparous continent, and 10 primiparous stress-incontinent women were recruited. Perineal ultrasound scanning was performed in standing women while they were resting, performing the Valsalva maneuver, coughing, and performing Kegel exercises. A direct on-screen assessment of bladder neck displacement from rest to the peak of dynamic activity relative to the pubic axis was made. Transducer movement was assessed by measuring the displacement of the pubic bone. Results: The method was feasible because measurements were possible in all 30 subjects. Vesical neck and pubic point movement in millimeters (± SD) and the percentage error if pubic point movement is not accounted for are as follow: strain, vesical neck 16.9 ± 6.1 and pubic point 4.8 ± 3.9, 28%; cough, vesical neck 10.2 ± 5.4, pubic point 2.9 ± 3.4, 33%; Kegel exercise, vesical neck 7.0 ± 3.6 and pubic point 0.7 ± 1.4, 37%. Similar discrepancies in angle were found and are presented. Uncorrected direction of vesical neck and pubic point movement in degrees and the percentage error if pubic point movement is not accounted for are as follow: strain, vesical neck 169.4 ± 18.5 and pubic point 214.0 ± 56.7, 18%; cough, vesical neck 162.0 ± 12.8, pubic point 238.4 ± 27.4, 22%; Kegel exercise, vesical neck –0.9 ± 12.7 and pubic point –4.8 ± 20.6, 87%. Test-retest reliability correlations were more than an r value of 0.7 in all measures and 86% of the measurements greater than 0.8. Conclusion: The vector-based system provides a simple method for quantifying distance and direction of vesical neck motion, as well as localizing the resting vesical neck position. (Am J Obstet Gynecol 2001;185:65-70.)