Aims:
Tension
free Vaginal Tape (TVT)
is believed to correct
stress incontinence (SI)
by mid-urethral support(1,2)
and the colposuspension
(Colpo) by bladder neck
elevation. We have already
shown that TVT produces
some bladder neck elevation
at 1month but less than
Colpo (3). This paper
aims to compare urodynamic
and outcome measures to
gain insight into mechanisms
of continence in the two
procedures and assess
whether the tape tightens
with time.
Methods:
Thirty-six
women undergoing primary
stress incontinence surgery
were prospectively studied
and non-randomised to
TVT(n=20) or Colp(n=16).
All had urodynamically proven SI without significant prolapse or
detrusor instability (DI).
Transperineal ultrasound
(3.5MHz linear array probe)
and microtip Urethral
Pressure Profiles (UPP's)
were performed pre-operatively
then at 1 and 6months
post-operatively.
Subtraction cystometry
(CMG) was performed pre-
and 6months post-operatively. Scanning technique, calculations of bladder
neck angles, movement
on valsalva and post-operative
elevation of the resting
bladder neck position
are described previously
(3). The Mann-Whitney test was used for analysis between TVT and Colpo
groups and Wilcoxon Matched
Pair’s test for analysis
between pre and post-operative
values. Correlation between
bladder neck elevation
(BNE) and other parameters
was assessed by Pearson
Correlation and Linear
Regression.
Results:
The average age and weight were 51years(SD10.7) and 73Kg(SD19.1); median
parity 2(range 0-11),
with no difference between
TVT and Colpo groups(p>
0.44). The objective SI cure rate (CMG and 1hour pad test) at 6months for TVT was
74% with 26% improvement;
and for Colpo was 88%
cure with 12% improvement.
Overall the post-op urge
incontinence (UI) rate
was 10.5% for TVT &
12.5% for Colpo.
Sixty% had pre-op
UI; 73% improved post
TVT and 60% post Colpo.
In each group, 2 patients
needed to double void
but none required long
term catheters. There
were no differences between
groups for any pre-operative
parameter (p>0.111).
There
was a significant decrease
in bladder neck movement
and angles for both TVT
and Colpo at 1and 6months
compared with pre-op,
except for resting angle
at 6months for TVT.
At both 1 and 6months
post-operatively, movement
and angles were significantly
less for Colpo than TVT
(p=0.00) and BNE significantly
greater for Colpo than
TVT (p<.02) i.e. elevation
of 4.7mm(SD6.69) for TVT
vs. 17.5mm (SD17.41) for
Colpo at 1month and 2.1mm(SD4.92)
for TVT vs 11.5mm(SD5.27)
for Colpo at 6months.
Elevation significantly decreased between 1 and 6months post-op (p<
0.037); the amount decreased
was similar for both groups
(p=0.197).
The following table compares pre-op and 6months post-op UPP and CMG values.
Analyses were performed
between pre- and post-operative
values for each group
and the post-op changes
between groups.
|
|
FULcough(SD)
|
MUCPcough(SD)
|
PTRquad1(SD)
|
PTRquad2(SD)
|
PeakFlowRate(SD)
|
|
TVT pre-op
|
15.1mm (6.63)
|
38.9cm(41.00)
|
105.7%(29.32)
|
93.6%(20.53)
|
32.8ml/s(17.35)
|
|
TVT post-op
|
19.2mm(4.48)
|
54.3cm(35.26)
|
106.7%(13.53)
|
118.6%(27.75)
|
23.5ml/s(10.82)
|
|
p(post vs. pre)
|
0.052
|
0.214
|
0.623
|
* 0.020
|
*0.035
|
|
Colpo pre-op
|
11.5mm(7.09)
|
35.5cm(34.05)
|
101.1%(7.63)
|
102.1%(18.56)
|
27.6ml/s(14.95)
|
|
Colpo post-op
|
19.9mm(8.43)
|
63.9cm(34.81)
|
111.2%(11.24)
|
122.1%(12.29)
|
24.3ml/s(11.91)
|
|
p(post vs. pre)
|
* 0.008
|
* 0.009
|
0.068
|
*0.020
|
0.187
|
|
p(TVT vs Colpo)
|
NS
|
NS
|
NS
|
NS
|
NS
|
FUL=functional urethral length,
MUCP =maximal urethral
closure pressure, PTR=pressure
transmission ratio.
There
was a similar significant
improvement in PTRquad-3
as for PTRquad-2 but no
improvement in PTRquad-4
for either group.
Maximal void pressure
did not change. There
was a statistically but
not clinically significant
increase in urinary residual
in both groups (25-31mls).
The only UPP parameter
that decreased over time
between 1 and 6months
post-op was FULcough,
by 4.1cm water
(SD 6.27), p=0.028. The level of bladder neck elevation correlated
with improvement of MUCPrest
at 6months for TVT (regression
coefficient:1.70; 95%CI=
0.32-3.07 p=0.028) and
showed a trend toward
correlation with improvement
PTR quad-1 for Colpo (regression
coeff:1.94; 95%CI= 0.09-3.78
p=0.064).
Conclusions:
Bladder
neck elevation is greater
with the Colpo than the
TVT, and both decrease
equally by 6months so
there is no indication
that the TVT is tightening
over this time. The TVT
produces a mid-urethral
increase in pressure transmission
(quad2&3); the site
of continence for the
TVT is likely to be mid-urethral.
The Colpo produces a tendency
toward an increased pressure
transmission at the bladder
neck (quad1) and an increase
at the mid-urethra; the
site of continence for
the Colpo is likely to
be the bladder neck but
mid-urethral pressure
changes may also play
a part . The TVT decreases
peak flow rate. Urge incontinence and voiding difficulties
may not avoided
by the TVT despite its
mid-urethral site of action. Longer and larger studies are required to fully
assess TVT's mechanism
of action and impact on
bladder function.
References:
(1)Br
Journ Obstet Gynaecol
1999; 106:345-350
(2)Int Urogynecol
J 1996: 7:81-86
(3)Neurourol & Urodyn
1999; 18(4):370-371
