Key words
uterine prolapse - sonography - urinary incontinence
Schlüsselwörter
Uterusprolaps - Ultraschall - Harninkontinenz
Introduction
Urogynecological complaints such as urinary incontinence, overactive bladder/urge
or pelvic organ prolapse are increasingly common, particularly in countries with higher
life expectancy [1], [2]. The risk of requiring surgery for urinary incontinence or pelvic organ prolapse
is reported to be between 11.8–20 % [3], [4], [5].
The pelvic floor musculature is the most important functional anatomy of the female
pelvis. A detailed urogynecological examination includes careful assessment of pelvic
floor muscle strength [6]. Targeted pelvic floor training plays an important role in the conservative management
of urinary and fecal incontinence [7].
Use of palpation to determine the presence of muscular defects of the levator ani
complex after vaginal birth was first described in the 1940s [8]. Several decades later, modern imaging techniques such as magnetic resonance imaging
[9], [10] and 3D sonography of the pelvis [11] have resulted in a renewed focus on pelvic floor musculature. These more recent
techniques have provided evidence for the impact of vaginal birth, particularly forceps
birth, on pelvic floor musculature and highlighted vaginal birth as a major cause
of defects of the pelvic musculature [10], [11], [12]. In addition to the palpatory evaluation of the pelvic floor musculature [6], [13], imaging methods such as urogenital sonography or magnetic resonance imaging are
becoming increasingly important in urogynecological examinations [9], [14], [15], [16], [17], [18], [19], [20]. In recent years, sonography has become an indispensable part of standard urogynecological
diagnostics as it is widely available, requires only a limited number of staff and
is comparatively inexpensive [19], [21]. The urogenital hiatus and the levator ani complex can be displayed using modern
3D and 4D techniques [21].
Defects of the levator ani complex appear to be the pathophysiological link between
vaginal birth and the emergence of urogynecological symptoms many years later [11], [22]. Several studies have demonstrated the connection between levator avulsion and pelvic
organ prolapse [22]. Levator ani defects also appear to be a significant risk factor for recurrence
after pelvic floor surgery [23], [24].
The aim of this study was to investigate the prevalence of levator ani defects using
3D sonography and palpation in a cohort of urogynecological patients. Moreover, the
study also aimed to investigate the relationship between levator ani muscle defects
and clinical symptoms such as stress incontinence, overactive bladder and prolapse.
Material and Methods
Patient population
Retrospective analysis was done of the data of 319 patients who presented to our urogynecological
clinic between March 2011 and June 2013 on an outpatient basis. Only women who had
3D or 4D sonography of the pelvic floor were included in the study. Women who had
previously undergone surgery for incontinence or prolapse were excluded from the study.
Approach
After taking a detailed medical history including a careful description of symptoms,
the patient was examined clinically with palpatory assessment of the levator ani muscle,
followed by 3D or 4D perineal ultrasound.
During the medical history, the patient was asked about bladder symptoms, using the German Pelvic Floor Questionnaire
[25], to determine whether the patient had urge symptoms or stress urinary incontinence.
Objective prolapse findings were used rather than subjective symptoms of proplapse.
Findings were based on speculum examination, with pelvic organ prolapse defined according to standard recommendations as prolapse
of the anterior, middle or posterior compartment lower than − 1 cm above the hymenal
plane (equivalent to POP-Q [Pelvic Organ Prolapse Quantification System] stage ≥ 2)
on maximum Valsalva maneuver [26], [27].
During clinical palpation, the index finger followed the distal muscular part of the levator ani muscle, the
puborectalis muscle, from dorsal to its point of insertion on the inferior pubic ramus.
The presence of muscle tissue at the inferior pubic ramus bilaterally was assessed
during pelvic floor contraction or at rest in women with acontractile pelvic floor
muscles [28].
Ultrasound examination
Ultrasound examination was done with the patient in the lithotomy position after palpation
and spontaneous voiding of the bladder. Ultrasound was done using a GE Voluson e®
system and a 3D abdominal probe (curved array probe, RAB 4-8-RS, 4–8.5 MHz). The probe
was positioned along the longitudinal axis of the patient perpendicular to the introitus
for mid-sagittal imaging of the pelvic floor. This is the standard plane used in 2D
ultrasound and shows the symphysis on the right and the anechoic urethra, the bladder,
the anterior vaginal wall and the anorectum, in accordance with the recently revised
S2k guidelines of the German, Austrian and Swiss medical association [20]. The hyperechoic puborectalis muscle of the levator ani complex is dorsal to the
anorectal junction ([Fig. 1]).
Fig. 1 Standard mid-sagittal plane on 2D sonography. Image orientation done according to
the recommendations of the German, Austrian and Swiss medical association shows the
symphysis (oval) on the right and the puborectal sling of the levator ani (circle)
dorsal to the anorectum on the left. Caudal structures are depicted in the lower half
of the image. The levator hiatus, which is the standard plane in 3D sonography, is
orthogonal to the mid-sagittal plane at the level of the shortest distance between
the symphysis and the puborectal sling (dotted line).
The patient was requested to contract her pelvic floor, relax it again and then do
a maximum Valsalva maneuver. The 3D ultrasound volume sequences were stored electronically
as 3D or 4D images for later processing.
Sonographic assessment of levator ani status based on stored ultrasound images was subsequently done offline by the same investigator
using image processing software (4D View, GE Healthcare) with standardization performed
in plane C.
In the mid-sagittal plane the orthogonal plane of minimal hiatal dimensions according
to Dietz defines the shortest distance between the puborectalis muscle and the symphysis
[29]. A levator ani defect was defined as discontinuity in the rendered volume of the
hyperechoic puborectalis muscle of the levator ani complex at the inferior pubic ramus
at maximum contraction of the pelvic floor or at rest if the pelvic floor was acontractile
([Figs. 2 a] to [c]) [30].
Fig. 2 a to c “Rendered volume” of the “hiatal plane”: the “rendered volume” is given as a semitransparent
depiction of all pixels (or voxels) of a defined volume sequence at the level of the
levator hiatus. Image orientation was from caudal to cranial. a Intact levator ani: image shows the hyperechoic puborectal sling with bilateral ventral
muscle attachments on the inferior pubic ramus (above) at the anorectum (below). b Left-sided levator ani defect: intact point of insertion on the right side and missing
muscle attachment on the left (marked with a *). c Bilateral levator ani defect: no point of insertion of the hyperechoic puborectal
sling bilaterally on the inferior pubic ramus (marked with a *).
Statistical analysis
Patient age was given as mean, standard deviation, minimum and maximum. For statistical
analysis, categorical data were described using relative and absolute frequencies.
This included the prevalence of a levator ani defect. Bar graphs were used for the
graphical representation of data. The exact 95 % confidence intervals (CI) are given
for individual prevalences.
Univariate logistic regression analysis was carried out to assess the impact of different
influencing variables (stress incontinence [SI], prolapse and urge) on the target
variables “levator ani defect on ultrasound” or “levator ani defect on palpation”.
Odds ratio (OR), the 95 % CI and the respective p-values were calculated. Bonferroni
correction was used because of multiple testing, and overall significance was set
to 5 %; this means that a p-value < 0.05/6 = 0.008 was considered significant.
Results
Patient population
The data of 319 patients were retrospectively analyzed. Average age of the patients
was 64.9 years (29–94 years, standard deviation 2.12). Mean parity was 2.1 (0–7);
4.7 % of patients were nulliparous ([Table 1]).
Table 1 Characteristics of the cohort of urogynecological patients.
|
Study population
|
319
|
100 %
|
|
Mean age (range)
|
64.9 years
|
29–94 years
|
|
Postmenopausal patients
|
271
|
85.0 %
|
|
Nulliparous
|
15
|
4.7 %
|
|
Primiparous
|
84
|
26.3 %
|
|
Para 2
|
125
|
39.2 %
|
|
Para 3
|
67
|
21.0 %
|
|
Para 4
|
16
|
5.0 %
|
|
> Para 4
|
12
|
3.8 %
|
We divided the patients into groups based on the three main symptoms: prolapse, stress
incontinence and urge symptoms ([Fig. 3]). A total 135 patients (42.3 %; 95 % CI: 36.83–47.95) had prolapse of the pelvic
organs, 162 women (50.8 %; 95 % CI: 45.16–56.40) complained of stress incontinence,
and 221 patients had urge symptoms (69.3 %; 95 % CI: 63.90–74.30).
Fig. 3 Prevalence of the three main symptoms: prolapse (42.3 %), stress incontinence (50.8 %)
and urge (69.3 %).
Prevalence of levator ani defects on ultrasound and palpation
On sonography, a levator ani defect was found in 76 patients (23.8 %; 95 % CI: 19.26–28.89);
in 29 patients (9.1 %; 95 % CI 6.17–12.79) this defect was bilateral.
On palpation, a defect of the levator ani muscle was found in 64 cases of the patient
population (20.0 %; 95 % CI 15.81–24.88); in 31 of these women (9.7 %; 95 % CI: 6.70–13.51)
the defect was bilateral.
Prevalence of levator ani defects correlated to symptoms
In the group of patients with urge symptoms, 43 patients (19.5 %; 95 % CI: 14.45–25.30)
were found to have a levator ani defect on palpation and 50 (22.6 %; 95 % CI: 17.28–28.72)
had a levator ani defect on ultrasound.
In the group of patients with stress incontinence symptoms, 26 patients (16.0 %; 95 %
CI: 10.76–22.63) had a levator ani defect detected on palpation, and 33 patients (20.4 %;
95 % CI: 14.46–27.40) had a levator ani defect on ultrasound.
In the group of patients with prolapse, 36 women (26.7 %; 95 % CI: 19.43–34.96) had
a levator ani defect which was detected on palpation, and 44 women (32.6 %; 95 % CI:
24.78–41.19) had a levator ani defect detected on ultrasound ([Fig. 4]).
Fig. 4 In the group of patients with prolapse, a levator ani defect was detected on palpation
in 26.7 % of patients and a levator ani defect was found on ultrasound in 32.6 % of
patients.
Univariate logistic regression analysis only found a statistically significant impact
on the target variable “levator ani defect on ultrasound” for the symptom “prolapse”
(OR 2.3; 95 % CI: 1.36–3.88, p = 0.002) but not for the symptoms “stress incontinence”
or “urge” ([Table 2]).
Table 2 A statistically significant impact on the target variable “levator ani defect on
ultrasound” was only found for prolapse.
|
Dependent variable
|
Independent variables
|
OR
|
95 % CI
|
p-value
|
|
OR: odds ratio; CI: confidence interval
|
|
Levator ani defect on ultrasound
|
Stress incontinence yes vs. no
|
0.68
|
0.40–1.14
|
0.142
|
|
Prolapse yes vs. no
|
2.28
|
1.36–3.88
|
0.002
|
|
Urge yes vs. no
|
0.81
|
0.47–1.40
|
0.450
|
|
Levator ani defect on palpation
|
Stress incontinence yes vs. no
|
0.60
|
0.34–1.04
|
0.071
|
|
Prolapse yes vs. no
|
2.03
|
1.16–3.53
|
0.013
|
|
Urge yes vs. no
|
0.89
|
0.49–1.59
|
0.685
|
Univariate logistic regression analysis only showed a noticable value for the target
variable “levator ani defect on palpation” in patients with prolapse (OR 2.0; 95 %
CI: 1.16–3.53, p = 0.013); however, after Bonferroni correction this did not reach
statistical significance.
Discussion
In our urogynecological patient population, a levator ani muscle defect was found
in 23.8 % of patients using 3D sonography and in 20.0 % of patients using palpation.
A higher prevalence of detected levator ani muscle defects was found in the group
with prolapse, both on ultrasound and on palpation (32.6 and 26.7 %, respectively),
while the prevalence was similarly low, both in the group with stress incontinence
(20.4 and 16.0 %, respectively) and in the group with urge symptoms (22.6 and 19.5 %,
respectively).
The prevalence of urogynecological symptoms in patients visiting a pelvic floor center
was comparable with the figures published by Dietz et al. [22], although the percentage of patients whom we diagnosed with stress incontinence
was somewhat lower (50.8 % compared to 76 %) and the percentage of patients whom we
diagnosed with prolapse was slightly higher (42.3 % compared to 38 %). The mean age
of our patients was slightly higher with 64.9 years, but mean parity was the same
(2.1). The differences in the prevalence of symptoms could be due to the different
ethnicity of the investigated patients, the higher mean age of our patients or the
difference in how health services are structured in Australia and Germany.
Although pelvic floor training is an important and effective strategy in the conservative
management of urge symptoms and stress incontinence [7], we found no statistical correlation with levator ani defects for those two groups
in our patient population [31]. “Levator ani defects” or “levator avulsion” are defects of the puborectalis muscle,
i.e. of the distal part of the levator ani complex and not necessarily of the entire
levator ani complex. In contrast to the more proximal muscles, this muscle segment
is subjected to the greatest muscle stretch during vaginal delivery [10], [32].
The connection between levator ani defects and prolapse has been confirmed in other
studies [22], [31]. Mechanically, the muscular limitation of the genital hiatus makes it the “largest
hernial portal of the human body” [33] through which the pelvic organs can prolapse. Any structural weakness of this muscular
limitation can lead to excessive widening of the genital hiatus, also referred to
as “hiatal ballooning”, which is known to be correlated with levator ani defects [34]. Along with levator ani defects, this is considered an independent parameter for
prolapse [35].
The inferiority of clinical palpation compared to 3D ultrasound has been previously
described in the literature [28], although correct palpatory assessment of levator ani status appears to depend on
the experience of the investigator [36].
Acontractile pelvic floor musculature makes the manual assessment of levator ani integrity
more difficult. The compensatory contraction of superficial muscle layers such as
the bulbospongiosus muscle or of deeper muscle layers such as the pubococcygeus muscle
can potentially lead to misinterpretation. Although, in contrast to ultrasound diagnosis
in prolapse patients, the clinical palpation of levator ani defects did not reach
statistical significance, a statistical trend was discernable, which could potentially
reach statistical significance if the number of study participants were larger.
As only urogynecological patients who have had 3D or 4D ultrasound were included in
this analysis, it is not possible to exclude inclusion bias.
A further limitation of our analysis is that both clinical palpation and ultrasound
diagnosis were both carried out by the same investigator.
Conclusion
The prevalence of levator ani defects in our population of urogynecological patients
was 23.8 %. Patients with prolapse had statistically significantly more muscular defects
of the pelvic floor. In contrast, the prevalence of levator ani defects did not differ
between women with stress incontinence and women with urge symptoms.
Levator ani defects are found more frequently with 3D ultrasound compared to palpation
alone. Nevertheless, although ultrasound appears to be superior to palpation alone
for the detection of levator ani defects, our own clinical experience has shown that
urogynecological diagnosis requires that ultrasound be done in combination with palpatory
assessment of the pelvic floor musculature.
The fact that the risk of recurrence after prolapse surgery is significantly higher
in patients with levator ani defects is of particular clinical importance [23], [24], [37]. Presurgical determination of levator ani defects could help ensure that groups
at special risk of recurrence are identified preoperatively. In future, this could
justify the targeted use of alloplastic mesh implants in a primary setting in patients
with levator ani defects.
