Pelvic floor ultrasound evaluation in the diagnosis of exposure of synthetic implanted materials in the lower urinary tract

To evaluate the diagnostic performance of pelvic floor ultrasound (PFUS) to recognize prosthetics exposure in the bladder and/or urethra in women with lower urinary tract symptoms (LUTS).


| INTRODUC TI ON
Pelvic floor disorders encompass several conditions such as urinary incontinence, pelvic organ prolapse, defecatory dysfunction, and sexual dysfunction.They represent a worldwide public health issue, and prevalence is going to rise along with the aging of the population.Symptoms related to pelvic floor disorders involve alterations in the bladder, bowel, and sexual functions. 1Pelvic floor disorder management includes both conservative and surgical treatment according to the specific condition, symptoms, and patient's general health and will. 2 However, surgical repair remains the mainstay of some of the most frequent conditions, such as pelvic organ prolapse and stress urinary incontinence.In an attempt to ameliorate surgical therapy outcomes, the implantation of synthetic materials such as mesh and tapes has become popular to treat conditions.4][5][6][7] In particular, mesh extrusion inside the urinary tract is considered uncommon and has been mainly related to incorrect suburethral tape positioning (bladder/urethra perforation or submucosal placement).Chronic contact of a foreign body with urine can lead to concretion and calculus, which can bring recurrent urinary tract infections, urgency, dysuria, and bladder pain.Consequently, in the case of irritative bladder symptoms in patients with previous implantation of genital prosthetics, a lower urinary tract mesh exposure should be suspected and ruled out.Cystoscopy is considered the reference standard for diagnosis, but X-ray imaging, magnetic resonance imaging or ultrasound can also be useful. 8However, symptoms are non-specific, and the proposed diagnostic examinations are either expensive or invasive.In particular, routine use of diagnostic cystoscopy is an issue, owing to costs, increased operative time, lack of proper training, and risk of trauma. 9Consequently, the risks while managing these patients can be either underestimating symptoms or overexposing patients to invasive and expensive examinations.Pelvic floor ultrasound (PFUS) allows evaluation of the lower urinary tract anatomy and visualization of pubocervical fascia and the prosthetics implanted in the anterior compartment, such as anterior mesh or midurethral slings. 8,10,11Specific advantages of ultrasonography include non-invasiveness, widespread diffusion, low costs, and lack of ionizing radiation.One pilot study, which has retrospectively reviewed data charts of patients with sling-related complications, has proposed interesting diagnostic performances of translabial ultrasound (TLUS) in identifying urinary tract exposure. 12wever, to date there are no high-quality data on the diagnostic performance of PFUS in identifying lower urinary tract implant exposure in symptomatic patients.
As a consequence, with the present cross-sectional study, we aimed to compare PFUS diagnostic performance-including both translabial and transvaginal approaches-with reference standard cystoscopy in terms of sensitivity, specificity, positive predictive value, and negative predictive value.

| MATERIAL S AND ME THODS
This was a cross-sectional study.We analyzed 100 consecutive patients with synthetic materials implanted in the anterior compartment who developed lower urinary tract symptoms (LUTS).Inclusion criteria were age 18 years or older and at least 6 months from mesh surgery.The preliminary evaluation involved clinical history collection to assess the presence of LUTS and gynecologic examinations to exclude vaginal mesh exposure, infections, or other conditions that could explain the symptoms.At the time of the study, our standard approach to these patients included a routine diagnostic cystoscopy to exclude the presence of prosthetic material exposure in the lower urinary tract.In case there was the indication to perform diagnostic cystoscopy, patients underwent preliminary PFUS.This was performed using a combined translabial and transvaginal approach.
All sonographic examinations were performed by a dedicated and trained urogynecologist with significant experience with PFUS examinations (MF), with full access to patients clinical data, but before cystoscopy evaluation.All PFUS were performed with the patient in a supine position and the bladder partially filled (≥100 mL).All scans were acquired using the Flex Focus 400 ultrasound system (BK Medical, Herlev, Denmark).TLUS is performed with a convex transducer (Type 8802; 4.3-6 MHz; BK Medical) placed longitudinally over the perineum/vulva without excess pressure to simultaneously visualize the pubic symphysis, urethra, bladder, vagina, rectum, and anal canal (Figure 1) in sagittal/parasagittal views.
Transvaginal ultrasound (TVUS) is performed with an endovaginal biplanar probe (Type 8848; BK Medical).The linear longitudinal transducer of 65 × 5.5 mm is used to obtain sagittal/parasagittal scans of the anterior compartment (Figure 2).On gray-scale scans, synthetic implants can be easily seen as highly echogenic bands in the aspects of the anterior vaginal wall.Specifically, midurethral slings appear as a hyperechoic band aligned parallel to the posterior wall of the urethra, whereas anterior transvaginal mesh may appear as either flat or folded hyperechoic tissue lying behind the posterior bladder wall (Figure 3).Moreover, the bladder lumen can be easily recognized by its anechoic content, while the center of the urethral longitudinal smooth muscle, which is hypoechoic, indicates the urethral lumen.This involves an adequate gray-mode contrast between mesh and bladder/urethral lumen and allows the proper measure of the distance between implant and bladder/urethral lumen.We measured the distance between prosthetics and both urethral and bladder lumen at their nearest point, with TLUS and TVUS.A distance of 1 mm or less was considered highly suspect for mesh exposure (PFUS positive), otherwise it was considered reassuring (PFUS negative).All diagnostic cystoscopies were performed after PFUS, by a different operator, with adequate bladder filling.The visualization of synthetic material exposed in the urethra/bladder lumen was diagnostic for mesh exposure (cystoscopy positive), otherwise, F I G U R E 1 Translabial ultrasound performed with a convex transducer placed longitudinally over the perineum/vulva without excess pressure to simultaneously visualize the pubic symphysis (PS), urethra (U), bladder (B), vagina (V), rectum (R), anal canal (A), and puborectalis muscle (PR) in sagittal/parasagittal views.On gray-scale scans, synthetic implants can be easily seen as highly echogenic bands in the aspects of the anterior vaginal wall.
the examination was considered negative (cystoscopy negative).
Specifically, for the aim of the study, the visualization of mesh in the bladder or urethral wall, without direct exposure, was noted but considered negative.

| RE SULTS
A total of 100 consecutive women were analyzed.Population characteristics are shown in Table 1.Data on prosthetic materials implanted during the index surgery are reported in Table 2. LUTS in the considered population are shown in Table 3. Notably, the most frequent LUTS leading to prosthetics material investigation was overactive bladder (67.0%); chronic bladder pain and hematuria were less frequent (2.0%).The median follow-up time from index surgery  Distances between mesh/tapes and bladder/urethra lumen by PFUS are reported in Table 4.We found a significant association between PFUS (both TLUS and TVUS) and reference standard cystoscopy for both diagnoses of mesh exposure in the bladder or urethra (Table 5).Specifically, TLUS resulted in a 100% (1/1) sensitivity and 98.0% (97/99) specificity for urethral prosthetics exposure, with positive and negative predictive values of 33.3% (1/3) and 100% (97/97), respectively, with estimated accuracy of 98%

| DISCUSS ION
In the last decades, pelvic floor surgery has greatly changed by the introduction of prosthetic materials.In SUI surgery, midurethral slings have become the reference standard because of their efficacy.In surgery for pelvic organ prolapse, mesh implantation has been introduced to augment prolapse repairs in an attempt to reduce recurrence rates and has become popular through the introduction of user-friendly commercial mesh kits.After the 2011 US Food and Drug Administration (FDA) warning on mesh use for pelvic organ prolapse surgery, many products have been discontinued, and vaginal mesh implantation has greatly reduced.
Specifically, the FDA warning has raised awareness about meshrelated complications.Specifically, mesh erosion in the urinary tract following pelvic floor surgery is considered a rare event but may occur in up to 8.1% of patients, as a consequence of either unrecognized intraoperative trocar perforation or gradual erosion of the polypropylene material into the bladder and urethra over time. 13This complication represents a concern, as the effect on the quality of life may be devastating, the management challenging, and the diagnostic delay considerable.Urethrocystoscopy represents the reference standard because a careful inspection is able to identify and locate exposed mesh material.However, routine use of cystoscopy may be problematic because of costs, lack of proper training, and risk of lower urinary tract trauma and infections. 9A possible strategy may be to perform selective cystoscopy only in patients with "high suspicion", but a risk-stratification strategy based on symptoms may be ineffective and lead to missed diagnosis because of their lack of specificity.
Recently, ultrasound has been proposed as a possible diagnostic tool to preliminarily assess urethral or bladder wall extrusion, but there are limited data for comparison with cystoscopy-which remains the reference standard. 12,14To the best of our knowledge, there is only one study available about the diagnostic performance of PFUS for lower urinary tract mesh exposure.In this study, Viragh et al., 12   exposure comparable to ours, they found a sensitivity and specificity for exposure of 93% and 72%, respectively for TLUS.However, according to the authors, the TLUS approach can be technically challenging, and results may reflect the expertise of the center, and be less robust in routine clinical practice with less experienced physicians.The authors conclude that TLUS performed by experienced sonographers in a referral center is a good imaging tool for the detection and localization of mesh products and has a complementary role to cystourethroscopy, but a prospective validation is necessary. 12The present cross-sectional study demonstrated-for the first time-that PFUS has very high sensitivity and specificity for both bladder and urethral prosthetics exposure.Moreover, negative predictive values for mesh exposure with both TLUS and TVUS approaches were 100%-meaning that PFUS may work as an excellent, non-invasive, and low-cost screening examination to reduce the use of diagnostic cystoscopy in patients at risk for lower urinary tract mesh exposure.
In our series, mesh/tape identification was achieved in all patients, confirming that polypropylene implants (both slings and prolapse mesh) have optimal sonographic characteristics to allow detection and localization in the context of surrounding tissue and lower urinary tract lumen.TVUS resulted in better performance compared with TLUS in the diagnosis of urethral exposure.In our opinion, this can be explained by enhanced visualization of the urethral lumen by TVUS, in which the probe is placed close and parallel to the area of interest, leading to fewer false positives.
Consequently, TVUS is likely to be a more effective and userfriendly approach compared with TLUS and might facilitate ultrasound evaluation adoption in centers with less experience with PFUS, which represented one of the limitations accounted for by Viragh et al. 12 To the best of our knowledge, this is the first non-retrospective study evaluating the diagnostic performance of PFUS in identifying prosthetics exposure in the lower urinary tract in women with LUTS after anterior compartment synthetic material implantation.Other strengths of our study include the blinded cross-sectional design, the bimodal PFUS evaluation with both TLUS and TVUS, and the large population considered.Moreover, our analysis included both midurethral slings and mesh for anterior compartment prolapse repair, thus making our results more generalizable.A limitation is the relatively low number of "positive" events, which anyway reflect the low prevalence of the condition evaluated and are consistent with those previously reported. 12 conclusion, our study demonstrated that PFUS, both by TLUS scans with standard convex probe and TVUS scans with the dedicated biplanar probe, represents an effective and reliable non-invasive screening test to exclude prosthetics exposure in the bladder and/or urethra in women with LUTS.As a result of the low prevalence of this condition, this may allow a large reduction in the use of endoscopy-up to 94% of cases-with a reduction in costs and discomfort for the patients.However, in case of high suspicion, diagnostic cystoscopy is mandatory to confirm and evaluate mesh exposure.
The study was approved by the Institutional Review Board of San Gerardo Hospital in Monza, Italy.Informed consent was acquired before the start of the study from all the patients.Data were entered into a dedicated database by one author and double-checked by one other author.Descriptive statistics were calculated as absolute numbers with percentages for categorical variables and as median (interquartile range) for continuous ones.The diagnostic performance of PFUS compared with the reference standard endoscopy was expressed in terms of sensitivity, specificity, and positive and negative predictive values.Statistical analysis was performed with JMP 7.0 (SAS, Cary, NC, USA).A P-value less than 0.05 was considered significant.

aa
to evaluation was 7 years (range 3-11 years).According to the reference standard cystoscopy, the rate of tape exposure in the lower urinary tract was 3% (2% of bladder exposure and 1% of urethral exposure).F I G U R E 2 Sagittal/parasagittal view of the anterior compartment obtained with transvaginal ultrasound performed with an endovaginal biplanar probe.Mesh is indicated by arrows.F I G U R E 3 Midurethral slings (arrow) appear as a hyperechoic band aligned parallel to the posterior wall of the urethra, while anterior transvaginal mesh may appear as either flat or folded hyperechoic tissue lying behind the posterior bladder wall.TA B L E 1 Population characteristics.Continuous data are presented as median (interquartile range) and non-continuous data as absolute frequency (relative frequency).b Body mass index is calculated as weight in kilograms divided by the square of height in meters.TA B L E 2 Prosthetics material implanted.a Data are presented as absolute frequency (relative frequency).
in a population of women who underwent surgical treatment for sling-related complications, performed a retrospective revision of preoperative TLUS findings in terms of specificity, sensitivity, and predictive values.Using a definition of sonographic TA B L E 4 Ultrasound findings characteristics.