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117 - SONOGRAPHIC EVIDENCE OF INCREASED OUTFLOW RESISTANCE AFTER SLING SURGERY

117

SONOGRAPHIC EVIDENCE OF INCREASEDOUTFLOW RESISTANCE AFTER SLING SURGERY

L. WEN 1, K. SHEK2,N. SUBRAMANIAM 1, T. FRIEDMAN 1, H. DIETZ 1;
1Sydney Med. Sch. Nepean, Sydney, Australia, 2WesternSydney Univ., Sydney, Australia.

Introduction: Suburethral slings(SUS) work by dynamic urethral compression. Excessive compression maybe identified via high voiding pressures on pressure- flow orpotentially on ultrasound imaging.
Objective: To study anyassociation between sonographic appearances and voiding function onurodynamic testing after suburethral sling surgery.
Methods:This is a retrospective study on 141 patients seen for urodynamictesting and translabial 4D ultrasound after SUS surgery between 2006and 2016. Fifteen cases were excluded because of prior incontinenceprocedures, abnormal sling placement, missing urodynamic data orinadequate volume data acquisition, leaving 126 complete data setsfor analysis. All urodynamic studies were performed using amultichannel fluid-filled system. Ultrasound volumes were acquired aspreviously described (1). Postprocessing of ultrasound volumes forsling pubis gap (SPG) (2) and urethral motion profile (UMP) (3) wasperformed on a later date using proprietary software on a desktop PC,blinded to all clinical data (Figure 1). Urethral mobility wasassessed using a semi-automated Excel® program to determine x and ycoordinates of 6 equidistant points along the length of urethra frombladder neck (point 1) to external urethral meatus (point 6), againstthe dorsocaudal margin of the symphysis pubis (3), both at rest andon Valsalva. Mobility vectors were calculated using the formula, SQRT[(xval _ xrest)2 + ( yval _ yrest)2]. The correlation between UMP andSPG and between these ultrasound measures and urodynamic parametersof voiding function were determined using Spearman’s rankcorrelation. A p <0.05 was considered statistically significant.


Figure 1: Determination of urethralmotion profile by plotting the urethra at rest (A) and on Valsalva(B). Six equidistant points from the bladder neck (point 1) to theexternal urethral meatus (Point 6) are shown. The suburethral slingis indicated by a white arrow in A. BL, bladder, P: pubic symphysis,V: vagina, R: rectum, SPG: sling-pubis gap (double headed arrow inB).
Results: Mean age was 64.3 years, mean follow-upinterval was 4.1 years (range 0.3-18.0). Forty-six (36.5%) women hada retropubic sling and 80 (63.5%) a transobturator sling. On freeflowmetry, the median maximum flow rate centile according to theLiverpool nomogram was 30 (IQR 15 - 50) and the median postvoidresidual (PVR1) was 20 (IQR 5 - 50) ml. On voiding cystometry, themedian maximum flow rate (Qmax) was 14 (IQR 8 - 23) ml/s, mediandetrusor pressure at maximum flow (Pdet Qmax) was 25 (IQR19 - 37) mmH2O and the median postvoid residual (PVR 2)was 50 (IQR 10 - 130.5) ml. Four patients had voiding pressures of 60cm H2O or higher. On imaging the mean SPG was 11.5 ±3.4(range 3.5-24.2) mm. Mean mobility vectors of Point 1 to Point 6in cm were 2.20 ± 0.96, 2.12 ± 0.83, 1.92 ± 0.68, 1.78 ± 0.64,1.92 ± 0.69 and 2.07 ± 0.72 respectively. A significant correlationwas found between SPG and midurethral mobility of point 3, 4 and 5 (P= 0.019, 0.002, 0.016). Significant associations were found betweenSPG and Pdet Qmax, as well as midurethral mobility vectors with Qmaxand PdetQmax (Table 1).

Table1.Correlations between SPG, UMP and voiding function on urodynamictesting (N = 126).


FRC

PVR1

Qmax

PdetQmax

PVR2

r

p

r

p

r

p

r

p

r

p

SPG

0.027

NS

-0.056

NS

0.034

NS

-0.019

0.037

-0.112

NS

Urethralmobility vector

Point1

0.137

NS

0.020

NS

0.178

NS

-0.032

NS

0.045

NS

Point2

0.151

NS

-0.045

NS

0.218

0.020

-0.080

NS

-0.028

NS

Point3

0.098

NS

-0.116

NS

0.198

0.035

-0.119

NS

-0.074

NS

Point4

0.159

NS

-0.152

NS

0.267

0.004

-0.257

0.004

-0.135

NS

Point5

0.129

NS

-0.162

NS

0.238

0.011

-0.237

0.009

-0.101

NS

Point6

0.095

NS

-0.150

NS

0.197

0.036

-0.196

0.031

-0.085

NS


Conclusions: There was asignificant correlation between sling 'tightness' as quantified bythe sling- pubis gap and midurethral mobility on the one hand andobjective voiding function on the other hand. The smaller the gapbetween sling and symphysis pubis and the less midurethral mobilityon Valsalva, the higher were voiding pressures on multichannelurodynamic testing.
References: 1. Ultrasound ObstetGynecol. 2004;23:80-92.
2. Aust NZ J Obstet Gynaecol.2012;18:70-78.
3. Aust NZ J Obstet Gynaecol. 2008;48:337-42.