Keywords pelvic organ prolapse - magnetic resonance imaging - cross-sectional studies
Palavras-chave prolapso dos órgãos pélvicos - ressonância magnética - estudos transversais
Introduction
Pelvic organ prolapse (POP) is a major health issue worldwide, and treatment is often
surgical. However, reoperation rates may vary from 5% to 40%; up to 30% of the patients
undergo more than 1 surgery throughout their lives.[1 ] The symptoms of POP are not always associated with physical examination findings,
and the role of magnetic resonance imaging (MRI) in cases of POP has been investigated
in recent years.[2 ]
[3 ]
[4 ]
Many lines of reference and different protocols are used for the evaluation, and the
most frequently used is the pubococcygeal line (PCL).[5 ] This line appears to have the best interobserver correlation and accordance with
POP quantification systems (such as the Pelvic Organ Prolapse Quantification System,
POP-Q), especially in the vaginal anterior wall.[4 ] In 2017, the European Society of Urogenital Radiology (ESUR) and the European Society
of Gastrointestinal and Abdominal Radiology (ESGAR) released a joint recommendation
guideline for MRI in POP, also recommending the PCL as the line of reference.[6 ]
The role of the levator ani muscle (LAM) complex in pelvic support has been thoroughly
described in the literature, as LAM alterations occur in women with POP, and are described
on both ultrasound and MRI.[7 ] Rodrigues Junior et al.[8 ] have recently described the estimated levator ani subtended volume (eLASV) through
MRI, and have showed significant posterior enlargement in patients with surgical failure
following reconstructive prolapse surgery.[8 ]
[9 ]
Apical defects (uterine prolapse, vault prolapse) are usually corrected by abdominal
sacrocolpopexy (ASC) or vaginal sacrospinous fixation (VSF). In a previous study (Juliato
et al.[10 ]), our group showed that using an anterior mesh (VSF-AM) in the anterior compartment,
the vaginal axis is deviated in both surgeries, however with no difference between
them.[10 ] Nonetheless, we still have little data about the behavior of the MRI lines of reference
for patients operated for POP and their association with physical examination findings
and subjective cure using standardized questionnaires. Thus, we aimed to study these
postoperative findings. Moreover, a receiver operating characteristic (ROC) curve
was built for eLASV to look for a cutoff point as a failure of the surgical treatment.
Methods
Study Design
A secondary analysis of a prospective, randomized, single-blinded, two-arm, parallel
study was performed from 2016 to 2017 in the Pelvic Floor Dysfunction Division, Department
of Obstetrics and Gynecology, Faculdade de Ciências Médicas, Universidade Estadual
de Campinas (FCM/UNICAMP). The present study was approved by the institutional Review
Board (CAAE 64652217.0.0000.5404), and this trial was registered at the Clinical Trials
Registry (http://www.ensaiosclinicos.gov.br , code RBR-7t6rg2). The present study followed the Consolidated Standards of Reporting
Trials (CONSORT) guidelines.
Inclusion Criteria
The randomized controlled trial (RCT) included postmenopausal women aged 55 to 75
years with advanced POP (stage 3 or 4 according to the POP-Q) with no current hormone
replacement therapy, and no previous gynecological surgery or malignancy.[11 ] These women were randomized by a computer-generated sequence. The attending physicians
in the postoperative period were blinded to the surgery performed. All surgeries were
performed from 2014 to 2016 in the Women's Hospital at UNICAMP, and all women were
revaluated at least one year postoperatively.
Exclusion Criteria
The exclusion criteria were the use of metallic implants (intrauterine devices, cardiac
valves or stents, aneurism clips, orthopedic implants, or piercings), use of electronic
implants (cardiac pacemakers, cochlear implants), claustrophobia, or recent tattoos.
Interventions
The women were randomized into two groups ([Fig. 1 ]). The first group underwent surgery with hysterectomy and bilateral vaginal sacrospinous
fixation with an anterior mesh (VSF-AM group). To correct the anterior vaginal wall,
a polyvinylidene fluoride mesh (DynaMesh, FEG Textiltechnik, Aachen, North Rhine-Westphalia,
Germany) was used in this group. The second group underwent abdominal supracervical
hysterectomy with abdominal sacralcolpopexy (ASC group). Details of both intervention
arms were published elsewhere.[11 ] If the patients presented concomitant stress urinary incontinence, they did not
receive treatment for incontinence.
Fig. 1 Flowchart depicting the recruitment process of the patients.
After at least one year of follow-up, the women underwent a physical examination performed
by only one trained urogynecologist with at least five years of experience with the
POP-Q who was blinded to the surgery performed.[12 ] During this visit, all women were instructed to answer a questionnaire regarding
vaginal symptoms (International Consultation on Incontinence Questionnaire-Vaginal
Symptoms, ICIQ-VS).[13 ] The MRI was scheduled no more than two weeks after the physical examination.
MRI Protocol
Thei MRI was performed postoperatively. The women were instructed to empty their bladder
within 2 hours before the MRI, and were taught the Valsalva maneuver for at least
20 seconds by a senior urogynecologist. Images were acquired in the supine position
at rest and at maximum Valsalva using a 1.5-Tesla Philips Achieva Scanner v3.2 (Philips
Medical Systems, Best, The Netherlands) with a 4-channel phased-array coil. At rest,
T1-weighted sequences were obtained in the sagittal, coronal, and axial planes for
the estimation of the pelvic anatomical structure and image planning. After vaginal
introduction of 30 mL of ultrasound gel for better evaluation of the contours, T2-weighted
single-shot fast spin-echo dynamic rest and Valsalva images were obtained through
the midsagittal and parasagittal pelvic planes using the following parameters: repetition
time, 1,300 milliseconds; echo time, 60 milliseconds; slice thickness, 6 mm; field
of view, 36 cm; matrix size, 256 × 160. The description of this technique did not
include one step of the ESUR/ESGAR guidelines with regard to the use of ultrasound
gel in the rectal canal; we have had limitations regarding the use of this material
in the steps to analyze rectal function (rest, straining, squeezing and evacuation).
The images were interpreted with the aid of the MicroDicom software (Medical Imaging
& Technology Alliance, Arlington, VA, US), using the PCL as references.[6 ] All images were analyzed independently by two professionals: a radiologist (SSD)
with 18 years of experience in pelvic floor imaging, and a urogynecologist (LCSJ)
with 5 years of experience in pelvic imaging. Both physicians were blinded to the
surgery performed in each patient.
Outcomes
The primary endpoint was the postoperative mid- and long-term MRI findings for both
surgical techniques. The anatomical MRI references followed the ESUR/ESGAR recommendations
([Fig. 2 ]).[6 ]
Fig. 2 MRI in sagittal view depicting anatomical points and lines of reference (static and
dynamic). Upper left (static); abbreviations: ARJ, anorectal junction; BB, bladder
base; PCL, pubococcygeal line; VV, vaginal vault. Upper right (dynamic): rectocele
pouch measure. Bottom left (static); red: H-line; light blue: M-line; yellow: pubococcygeal
line. Bottom right (static); abbreviations: PCL, pubococcygeal line; PICS, pelvic
inclination correction system line; SCIPP, sacrococcygeal inferior pubic point line.
The staging of the POP followed the ESUR/ESGAR recommendations. Regarding the PCL,
the “rule of three” was used for the anterior and apical walls, and the POP was considered
pathological starting at grade 2.[14 ] The anorectal junction (ARJ) has a different staging system; an ARJ descent > 5 cm
is defined as grade II.[15 ] Measurement of the rectocele followed the “rule of two,” with grade II (> 4 cm)
considered pathological.[7 ]
[16 ]
Failure of the MRI was defined as bladder base stage ≥ 2, vaginal vault stage ≥ 2,
or rectocele pouch stage ≥ 2.[6 ] Objective failure was defined as any point of prolapse beyond the hymen in the POP-Q
(Points Ba [point B in the anterior vaginal wall, in centimeters]; Bp [point B in
the posterior wall, in centimeters]; or C [point C in the apical wall] > 0).[17 ] Subjective cure was considered when ICIQ-VS questions 5a and 6a were equal to zero.
The H line (anteroposterior width of the levator hiatus), M-line (represent distance
of its descent) and the width of the levator hiatus were also measured in millimeters
in static MRI to calculate the eLASV: eLASV in mm3 = −72.838 + 0.598 (H-line) + 1.217 (M-line) + 1.136 (width of levator hiatus).[9 ]
The variables of the physical examination were basically defined by POP-Q measurements.[12 ] Sociodemographic characteristics were also recorded.
Statistical Analysis
Objective measures, subjective measures, and cure rates are expressed as means or
percentages, and the groups were compared using the Chi-squared test and the Fisher
exact test. The Fisher exact test was used to compare the objective cure rate by physical
examination, subjective cure rate, and MRI-based cure. The MRI and POP-Q were compared
using the PCL as a line of reference. We also calculated the eLASV for each patient
and compared it with surgical failure. A ROC curve was calculated to look for a cut-off
point so that the eLASV could predict worse surgical outcomes. Correlations between
the different methods (MRI versus POP-Q) were calculated using the Spearman correlation
index. Values of p < 0.05 were considered statistically significant. The data were analyzed using the
Statistical Analysis System (SAS, SAS Institute, Cary, NC, US) software for Windows,
version 9.2.
Results
MRI and Physical Examination Results
[Fig. 1 ] shows the flowchart of the studied patients, and [Table 1 ] displays their sociodemographic characteristics. Out of 71 women from the original
RCT who were screened for the present study, 12 could not be reached (lost to follow-up),
and another 19 patients dropped out because of: refusal to participate (n = 3), moved to other states (n = 3), health restrictions (n = 2), MRI restrictions (cardiac pacemaker; n = 1), and absence from 2 scheduled MRI examinations (n = 10) ([Fig. 1 ]). The final sample comprised 40 women. The mean follow-up was of 27 months. [Table 1 ] shows the baseline characteristics and both groups are similar, except for a higher
mean age of menopause for the ASC group (p = 0.009).
Table 1
Sample demographics and preoperative status
Variables
ASC (n = 20)
VSF-AM (n = 20)
p -value
Age (years) – mean (±SD)
67.9 (4.9)
67.1 (4.82)
0.75
< 60 years
1
2
60–69 years
12
10
> 70 years
7
8
Pregnancies – mean (±SD)
4.85 (3.7)
5.4 (3)
0.28
Vaginal delivery – mean (±SD)
4.15 (3.39)
4.35 (3.08)
0.74
Body mass index (kg/m2 ) – mean (±SD)
27.06 (3.72)
25.79 (4.84)
0.26
Tobacco use (current or previous)
3
4
0.66
Menopause (years of age) – mean (±SD)
51.85 (3.67)
48.4 (4.25)
0.009
Preoperative POP-Q
Anterior
1.0
stages → 2
1
0
3
10
10
4
9
10
Apical
0.75
stages → 3
11
10
4
9
10
Posterior
0.79
stages → 0
1
2
1
31
2
2
6
3
3
3
3
4
9
10
GH – mean, in centimeters (±SD)
3.5 (1.08)
3.37 (1.72)
0.06
PB – mean, in centimeters (±SD)
2.15 (0.72)
2.05 (0.77)
0.77
Abbreviations: ASC, abdominal sacrocolpopexy; GH, genital hiatus; PB, perineal body;
POP, Pelvic Organ Prolapse; POP-Q, Pelvic Organ Prolapse Quantification System; SD,
standard deviation; VSF-AM, vaginal sacrospinous fixation with an anterior mesh.
Regarding the MRI results, the mean kappa coefficient between the two professionals
presented good reliability (0.7). The measurements of the vaginal vault were larger
for the VSF-AM group than for the ASC group (−0.08 ± 1.84 cm versus −1.43 ± 1.07 cm
respectively; p = 0.007). The mean rectocele pouch was significantly larger in the ASC than in the
VSF-AM group (3.91 ± 0.98 cm versus 3.38 ± 0.66 cm respectively; p = 0.033). The MRI staging showed no significant difference between the groups with
regard to the anterior wall (p = 0.73), the apical segment (p = 1.0), or the posterior wall (ARJ) (p = 1.0); however, the rectocele staging revealed significantly more stage-2 diagnoses
in the ASC group (p = 0.013) ([Table 2 ]).
Table 2
MRI and POP-Q measurements of the operated patients
Variables
VSF-M (n = 20)
ASC (n = 20)
p -value
Objective cure
13
15
0.49
Subjective cure
17
17
1.0
MRI measures
Bladder base – mean (±SD)
1.6 (1.8)
1.1 (1.6)
0.51
Vaginal vault – mean (±SD)
-0.08 (1.8)
-1.4 (1.0)
0.007
Anorectal junction – mean (±SD)
2.4 (0.9)
2.5 (1.0)
0.93
Rectocele – mean (±SD)
3.3 (0.6)
3.9 (0.9)
0.033
Bladder base MRI stage
Stages 0 and 1
13
14
0.73
Stage ≥2
7
6
0.73
Vaginal vault MRI stage
Stages 0 and 1
16
17
1.0
Stage ≥2
4
3
1.0
Anorectal junction MRI stage
Stage 0
14
14
1.0
Stage 1 or 2
6
6
1.0
Rectocele MRI stage
Stage 0 or 1
18
11
Stage 2
2
9
0.0013
MRI cure
12
9
0.52
Apical POP-Q
stage 0
12
14
0.74
stage 1
7
6
stage 2
1
0
Anterior (bladder)
stage 0
7
8
0.27
stage 1
2
2
stage 2
7
10
stage 3
4
0
Posterior (rectal)
stage 0
19
11
0.013
stage 1
0
4
stage 2
1
4
stage 3
0
1
Abbreviations: ASC, abdominal sacrocolpopexy; MRI, Magnetic resonance imaging; POP-Q,
pelvic organ prolapse quantification; SD, standard deviation; VSF-AM, vaginal sacrospinous
fixation with an anterior mesh.
When the physical examination using the POP-Q was performed, more patients in the
ASC group had stage 2 and 3 posterior prolapses than those in the VSF-AM group (5
versus 1 respectively; p = 0.013). The rate of objective cure was of 65% (n = 13) and 75% (n = 15) in the VSF-AM and ASC groups respectively (p = 0.49) ([Table 2 ]). The rate of subjective cure did not present any difference between the groups;
in total 85% of the women were cured according the ICIQ-VS (p = 1.0) ([Table 2 ]).
MRI versus Physical Examination – POP-Q
When comparing failure rates between both methods (MRI and physical examination),
there was a significant correlation with anterior wall failure: 13 patients had MRI-based
failures, and 11 had POP-Q failures (p = 0.002) and general failures (p = 0.007). The MRI detected more apical failures than physical examination (7 versus
0). In the posterior segment, there were only 2 POP-Q failures versus 12 MRI-based
failures with regard to the ARJ (p = 0.08), and 11 failures after rectocele pouch MRI-staging (p = 0.47). Using subjective failure as a reference, we found no association between
the POP-Q findings and the rate of subjective cure (p = 0.55); we have also found no association between POP-Q measurements and MRI-based
cure in general (p = 0.6), in the anterior wall (bladder base; p = 1.0), in the apical wall (vaginal vault; p = 1.0), or in the posterior wall (rectocele; p = 0.12) ([Table 3 ]).
Table 3
Comparison among MRI, physical examination (POP-Q) and subjective cure rates
Vaginal wall - n (%)
MRI failure
POP-Q Failure
p -value
Subjective failure
p -value
General
19 (47.5)
12 (30)
0.007[a ]
6 (15)
0.6[e ]
0.055[f ]
Anterior
13 (32.5)
11 (27.5)
0.02[b ]
6 (15)
0.31[g ]
1.0[h ]
Apical
7 (17.5)
0
[* ]
6 (15)
[* ]
Posterior
ARJ
12 (30)
2 (5)
0.08[c ]
6 (15)
0.6[i ]
Rectocele
11 (2.5)
2 (5)
0.47[d ]
0.12[j ]
Abbreviations: ARJ, anorectal junction; MRI, magnetic resonance imaging; POP-Q, Pelvic
Organ Prolapse Quantification System.
Notes:
a MRI general failure versus POP-Q general failure (Fisher exact test).
b Bladder base to PCL in the MRI (grade ≥ 2) versus POP-Q Ba > 0 (Fisher exact test).
c Anorectal junction to PCL in the MRI (grade ≥ 1) versus POP-Q Bp > 0.
d Rectocele measure in the MRI (grade ≥ 2) versus POP-Q Bp > 0.
e Subjective cure in the ICIQ-VS versus general MRI cure.
f Subjective cure in the ICIQ-VS versus POP-Q general failure.
g Subjective cure in the ICIQ-VS versus POP-Q Ba > 0 (grade ≥ 2).
h Subjective cure in the ICIQ-VS versus BB to PCL in the MRI.
i Subjective cure in the ICIQ-VS versus ARJ to PCL in the MRI (grade ≥ 1).
j Subjective cure in the ICIQ-VS versus rectocele pouch stage in the MRI (grade ≥ 2).
* Vaginal vault to PCL in the MRI (stage ≥ 2) versus POP-Q C > 0 and subjective cure
(ICIQ-VS questions 5a and 6a equal to zero) – homogenous sample, no test was made.
Abbreviations: ARJ, anorectal juntion; Ba, point B in the anterior vaginal wall, in
centimeters;BB, bladder base; Bp, point B in the posterior wall, in centimeters; C,
point C in the apical wall, in centimeters; ICIQ-VS, international consultation on
incontinence questionnaire - vaginal symptoms; MRI, Magnetic resonance imaging; PCL,
pubococcygeal line; POP-Q, pelvic organ prolapse quantification.
Levator Ani Subtended Volume (LASV)
The width of the levator hiatus and the length of the H- and M-lines were measured
in static MRI for eLASV calculation, and the numbers were compared by dividing the
sample according to POP-Q success. The H- and M-lines were significantly longer among
the patients who presented POP-Q failure than among those who achieved objective success
(69.6 ± 5.6 mm versus 62.2 ± 7.8 mm respectively; p = 0.004; and 23.5 ± 7.8 mm versus 16.7 ± 6.9 mm respectively; p = 0.004). The width of the levator hiatus was similar: 38.5 ± 8.1 mm for the patients
with failure versus 34.6 ± 5.5 mm for those with success (p = 0.08).
The eLASV was calculated for each patient, and it was larger among those with failure
than among those with success (41.1 ± 16.5 mm3 versus 24.1 ± 13.6 mm3 respectively; p = 0.002). The area under the ROC curve was of 0.813 (p = 0.002; confidence interval [CI] = 0.672–0.953), and the optimal cutoff was of 33.5 mm3 , with specificity of 89.2% (70.6% to 97.1%), sensitivity of 66.6% (35.4% to 88.7%),
and accuracy of 83.5% (66.4% to 92.1%). Among the patients who experienced surgical
failure, 66.6% had an eLASV of ≥ 33.5 mm3 versus 10.7% among those who experienced surgical success (p < 0.001) ([Fig. 3 ]).
Fig. 3 eLASV measurement (ROC curve). Area under the curve: 0.813; p = 0.002; 95%CI: 0.672–0.953; cutoff point: eLASV ≥ 33.5 mm3.
Discussion
The present study showed good results for both vaginal and abdominal surgeries, especially
regarding subjective outcomes at the mean 27-month follow-up. The MRI staging showed
greater failures compared with the POP-Q, and neither correlated well with the symptomatology.
In their nonrandomized study, Ginath et al.[18 ] compared two surgical approaches (ASC versus Prolift vaginal mesh) and showed equally
good postoperative results for both techniques in the POP-Q, but not in the MRI, which
revealed no difference between the preoperative and postoperative anatomical positions
and angles relative to the PCL. Van der Weiden et al.[19 ] evaluated 43 women at 6 months after laparoscopic ASC, and found great improvement
in prolapse measures for all compartments, but only for the apex in the MRI assessment,
resulting in a poor correlation with the POP-Q.[19 ] Conversely, Brocker et al.[20 ] studied 69 patients who underwent vaginal mesh repair for POP; during the one-year
follow-up, both the dynamic MRI and the clinical examination showed good results,
but the MRI showed more prolapse.
The correlation between the POP-Q and the symptoms is frequently poor because the
symptoms do not necessarily correlate with the severity of the POP.[21 ] The MRI assessment seems to be even more dissociated from the symptomatology – MRI
scans often describe a great number of prolapses in asymptomatic women.[22 ] We also found no significant correlation between subjective cure or quality of life
questionnaire scores and MRI-based prolapse staging and failure definitions.
Several studies[4 ]
[23 ] have compared physical examination findings with different lines of reference and
points of anatomical interest in the MRI, mainly with poor results. The anterior wall
seems to show good accordance.[2 ] Our results were also better for the anterior compartment in terms of a significant
association between MRI-based pathological POP and a Ba point > 0 in the POP-Q. We
found a rate of 70% of objective cure, a rate of 85% of subjective cure, and a rate
of 52.5% of MRI-based cure for the whole sample, without a significant association
among symptomatology, POP-Q, and MRI. The MRI staging system showed a greater number
of pathological prolapses than the POP-Q and the symptoms in our sample.
The MRI has become an important asset in the evaluation of pelvic-floor dysfunction.[24 ] The most commonly used line of reference, the PCL, is also the one with the greatest
interobserver correlation indexes.[7 ] This line unites the pubic bone and coccyx, but precise definitions vary among studies.
We used the PCL as described by El Sayed et al.[6 ] in 2017,; that is, a line from the inferior tip of the pubic bone to the anterior
aspect of the last visible coccygeal joint.
Another important contribution of the MRI is the proper evaluation of the eLASV and
its role in pelvic support. We intended to do a study similar to the research by Wyman
et al.[9 ]; they found a cutoff in the eLASV that correlated with surgical failure: they retrospectively
analyzed a cohort of 66 women who underwent laparoscopic uterosacral ligament suspension,
and found a significant association between the eLASV and surgical failure at the
one-year follow-up, with a cutoff value of 38.5 mm3 . In our study, an eLASV ≥ 33.5 mm3 was associated with surgical failure, with good accuracy. However, as this parameter
was analyzed postoperatively, we cannot say that this would be a predictor of surgical
failure, but as a diagnosis and/or audit of the surgery performed. Our sample might
have comprised women with worse preoperative prolapses, and a smaller eLASV could
be associated with failure, given that other important factors such as age or parity
also play important roles in surgical outcomes. Apart from that, we evaluated a different
surgical modality.
Our study has many strengths. We studied a homogeneous group of women without previous
surgical treatment who were randomized according to two surgical POP correction techniques
for a mean follow-up > 2 years. We have followed the latest recommendations regarding
MRIs for prolapse. Our limitations are: we did not use rectal gel or perform MRI defecography,
and this might have impaired our evaluation of the posterior wall. Additionally, almost
all operations were performed for advanced cases of prolapse, which affected the preoperative
MRI examinations of these patients for purposes of comparison. The assessment of the
eLASV by postoperative MRI could have produced some bias, and the fact that the ARJ
was not adequately visualized may have impaired the measurement of the H-line; this
can alter the eLASV assessment as well. However, we do not believe that our surgical
techniques directly affected the measurements used for this calculation (that is,
the length of the H- and M-lines and the width of the levator hiatus). Finally, we
included a limited number of patients, and further studies with larger samples are
necessary.
Conclusion
The MRI and POP-Q cure rates were associated, but only in the anterior wall. The MRI
staging showed greater failures compared with the POP-Q, and neither correlated well
with the symptomatology. Both surgical techniques for advanced prolapse were similar
in terms of the objective POP-Q and MRI cure rates. The objective results were poorer
in the posterior compartment in the ASC group. The eLASV was larger among the patients
whho experienced surgical failure, and when this value was ≥ 33.5 mm3 , there was a significant increase in the chance of postoperative failure, but with
the limitation that it was only analyzed postoperatively.
