Compliance of the bladder neck supporting structures:: Importance of activity pattern of levator ani muscle and content of elastic fibers of endopelvic fascia

Aims: Firm bladder neck support during cough, suggested to be needed for effective abdominal pressure transmission to the urethra, might depend on activity of the levator ani muscle and elasticity of endopelvic fascia. Methods: The study group of 32 patients with stress urinary incontinence and hypermobile bladder neck, but without genitourinary prolapse, were compared with the control group of 28 continent women with stable bladder neck. The height of the bladder neck (HBN) and compliance of the bladder neck support (C) were assessed, the latter by the quotient of the bladder neck mobility during cough and the change in abdominal pressure. By using wire electrodes, the integrated full-wave rectified electromyographic (EMGave) signal of the levator ani muscle was recorded simultaneously with urethral and bladder pressures. The pressure transmission ratio (PTR), time interval between the onset of muscle activation and bladder pressure increment (AT), and area under the EMGave curve during cough (EMGcough) were calculated. From bioptic samples of endopelvic fascia connecting the vaginal wall and levator ani muscle, elastic fiber content was assessed by point counting method. Mann-Whitney test was used to compare all the variables. Correlations between the parameters were evaluated by using the Spearman correlation coefficient. Results: In the study group, HBN was significantly lower (P < 0.001), C was significantly greater (P < 0.001), and PTR was significantly lower (P < 0.001). In the study group, the muscular activation started later (median, Delta T-1, -0.147 second; Delta T-r, -0.150 second), and in the control group, it preceded (Delta T-1, 0.025 second; P < 0.001; DeltaT(r), 0.050 second; P < 0.001) the bladder pressure increment. EMG-cough on the left side was significantly greater in the study group (P < 0.046). Elastic fiber content showed no difference between the groups. The analysis of all patients revealed negative correlations between C and PTR (r = -0.546; P < 0.001) and between C and Delta T-1 (r = -0.316; P < 0.018). Conclusions: Firm bladder neck support enables effective pressure transmission. Timely activation of the levator ani seems to be an important feature.