The relationship between urethral mobility and parity

Objective Urethral mobility is associated with stress urinary incontinence (SUI) and urodynamic stress incontinence, and this is particularly true for mid-urethral mobility. The purpose of this study was to determine whether there is a significant relationship between segmental urethral mobility and vaginal parity in women undergoing urodynamic testing for prolapse or lower urinary tract symptoms. Design Retrospective study. Setting Tertiary referral service for multichannel urodynamic testing. Population Women undergoing urodynamic testing for lower urinary tract symptoms or pelvic organ prolapse. Methods The stored 3D translabial ultrasound volume data sets of 648 women were assessed. Measurements were performed using post-processing software in volumes obtained at rest and on maximal Valsalva manoeuvre. Analysis was based on a co-ordinate system using the dorsocaudal margin of the pubic symphysis. The urethral length was traced and divided into five equal segments. Mobility vectors are determined by the formula √[(y_V - y_R)² + (x _V - x_R)²], where V indicates Valsalva and R indicates rest, with 'x' as the vertical distance and 'y' as the horizontal distance from the dorsocaudal margin of the pubic symphysis. Main outcome measures Mobility vector lengths. Results The distal urethra is consistently the least mobile part of the organ, regardless of parity. Vaginal childbirth seems to increase urethral mobility by about 20% for all urethral segments (all P ≤ 0.009). The first vaginal delivery showed the greatest effect, particularly on mid-urethral mobility. Conclusions There is a significant association between urethral mobility and vaginal delivery in women seen for symptoms of pelvic floor dysfunction, affecting all segments of the urethra equally. Most of this effect seems to result from the first vaginal birth.