Dynamic urethral pressure profilometry pressure transmission ratio: what do the numbers really mean?

Sixty-three women with genuine stress urinary incontinence were evaluated urodynamically both before and after modified Burch colposuspension to determine the association between pressure transmission ratio and leakage of urine during dynamic urethral pressure profile and the effect of surgery on pressure transmission ratio. Preoperatively, there was no difference in pressure transmission ratios between urethral pressure profiles associated with leakage of urine and those without urine leakage. Postoperatively, there were differences in pressure transmission ratios between leak and nonleak profiles in the sitting full and supine positions (P less than .001). We could not determine a threshold pressure transmission ratio that was more characteristically associated with leakage of urine. Finally, preoperative pressure transmission ratios were not associated with surgical success, but the higher the postoperative pressure transmission ratio, the more likely the surgery was to be successful (P = .023). In addition, the greater the difference between preoperative and postoperative pressure transmission ratios, the more likely was a cure (P = .011). The pressure transmission ratio may not be helpful in discriminating leak from nonleak dynamic urethral pressure profiles, and there may not be a threshold pressure transmission ratio below which patients characteristically leak urine. However, comparison of preoperative and postoperative pressure transmission ratios is helpful in determining the adequacy of surgical correction of the anatomical defect associated with genuine stress incontinence.