How accurate are we in urethral mobility assessment? Comparison of subjective and objective assessment

Summary

Objective: The knowledge of the mobility of urethra plays important role in patients with stress urinary incontinence and its assessment is a part of standard urogynecological examination. It has been assumed that increased mobility is associated with higher likelihood of successful treatment. There is arbitrary defined cut-off for hypermobile urethra – descend of more than 15 mm or 30-degree resp. 50-degree rotation or more during Valsalva manoeuvre. Clinically we routinely categorize mobility of the urethra as high mobile or hypermobile urethras, low mobile urethra and the situation in-between as mobile urethras. But how accurate are we with such a subjective assessment? We have provided retrospective analysis of mobility of the urethra assessed during the clinical examination by transperineal ultrasound (US) with subjective scoring of the mobility (low, norm, hyper) and compared this assessment with detailed measurement of descent and rotation of the urethra.

Design: Retrospective cohort study.

Setting: Ob/Gyn department First Faculty of Medicine, Charles University and General University Hospital, Prague.

Methods: This is a retrospective analysis of urethral mobility of women diagnosed with urodynamic stress incontinence (USI) and treated with tension free vaginal slings during the period 01/2009 – 10/2016. For each patient, there was available description of mobility at the time of preoperative assessment (low-, norm- or hyper-mobile) and we compared this assessment with measured parameters of bladder neck mobility analysed later from stored 4D US volumes. We have measured dorsocaudal movement of the bladder neck (BN) (H-distance). This is the distance of the BN from the horizontal line at the level of lower margin of the symphysis and we compared the position at rest and at Valsalva. Secondly, we measured rotation of the urethra using the gama angle – angle between the line connecting BN to lower margin of symphysis and axis of symphysis at rest and during the Valsalva manoeuvre. Mobility of the BN is the difference between the rest and Valsalva position. We compared the objective parameters of mobility with subjective assessment. We have provided correlation of both objective parameters.

Results: 427 patients were treated during the analysed period, 393 had available stored 4D US volume for analysis. Mean age 56.5 years (min 29, max 87, SD 7.9), mean BMI 27.4 (min 18.3, max 39.6, SD 7.9), mean parity 2.14. Mean descent of the bladder neck was 11.8 mm (min -1, max 37; SD 6.9) Mean rotation of the bladder neck was 38.8 degree (min -5, max 118, SD 20.0). When we subjectively assessed the mobility as low the mean mobility was 23.9 ° resp. 7.3 mm, for normal 34.8 ° resp. 10.4 mm and 48.6 ° resp. 15 mm for hypermobile uretras. We have found good correlation of both parameters – H-distance, gama angle – r = 0.693.

Conclusion: Subjective assessment of mobility of the urethra seems to be reasonably accurate for distinguishing between low and hypermobile uretra.

Keywords: stress urinary incontinence, urethral mobility, bladder neck mobility, ultrasound bladder neck mobility assessment