Normative pelvic floor parameters in children assessed by transabdominal ultrasound

Purpose: Successful management of dysfunctional voiding in children hinges on retraining inappropriate pelvic floor muscle recruitment. Recently dynamic pelvic floor muscle activity was visualized in adults using transabdominal ultrasound. We evaluated transabdominal ultrasound for visualizing and measuring pelvic floor muscle activity in normative children. Materials and Methods: A total of 21 volunteers, including 10 boys and 11 girls 7 to 16 years old (mean age 11.6) who were free of bladder disorders consented to participate in the study. Subjects were screened and demonstrated normative bladder emptying before being imaged while supine and standing using a sagittal curved linear array 2 to 5 MHz transducer over the suprapubic region. After pelvic floor muscle contraction was explained 4 parameters were measured 3 times each, including the direction of movement/displacement from freeze-frame ultrasound images, and endurance and coordination from ultrasound movie loops. The methodology for digitizing movie data were developed, tested and found to be reliable. New variables of endurance as a percent of maximum coordination amplitude and coordination as the amplitude between maximum and minimum effort were created. Results: Overall 66% and 71% of subjects demonstrated anterior displacement of the pelvic floor during voluntary contraction while lying and standing, respectively, with no significant difference in lying vs standing. However, coordination displacement was greater while lying than standing. During 20-second contractions pelvic floor muscle activity attained peak amplitude at 5.5 seconds, followed by a marked decay with 1 or more cycles of muscular re-recruitment. It was observed that fatigue led to repeat recruitment of the rectus and oblique abdominal muscles. Conclusions: In children free of voiding dysfunction pelvic floor displacement and coordination are highly variable. Noninvasive ultrasound of the pelvic floor provided visual assessment of muscular activity, a biofeedback component for the patient and measurement potential for the therapist.