Magnetic resonance imaging of pelvic floor dysfunction - joint recommendations of the ESUR and ESGAR Pelvic Floor Working Group
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Abstract
Objective
To develop recommendations that can be used as guidance for standardized approach regarding indications, patient preparation, sequences acquisition, interpretation and reporting of magnetic resonance imaging (MRI) for diagnosis and grading of pelvic floor dysfunction (PFD).
Methods
The technique included critical literature between 1993 and 2013 and expert consensus about MRI protocols by the pelvic floor-imaging working group of the European Society of Urogenital Radiology (ESUR) and the European Society of Gastrointestinal and Abdominal Radiology (ESGAR) from one Egyptian and seven European institutions. Data collection and analysis were achieved in 5 consecutive steps. Eighty-two items were scored to be eligible for further analysis and scaling. Agreement of at least 80 % was defined as consensus finding.
Results
Consensus was reached for 88 % of 82 items. Recommended reporting template should include two main sections for measurements and grading. The pubococcygeal line (PCL) is recommended as the reference line to measure pelvic organ prolapse. The recommended grading scheme is the “Rule of three” for Pelvic Organ Prolapse (POP), while a rectocele and ARJ descent each has its specific grading system.
Conclusion
This literature review and expert consensus recommendations can be used as guidance for MR imaging and reporting of PFD.
Key points
• These recommendations highlight the most important prerequisites to obtain a diagnostic PFD-MRI.
• Static, dynamic and evacuation sequences should be generally performed for PFD evaluation.
• The recommendations were constructed through consensus among 13 radiologists from 8 institutions.
Keywords
MRI pelvic floor MR defecography Recommendations ESUR ESGARIntroduction
Imaging of the female pelvic floor is of rising interest due to an ageing population, harboring an increasing incidence of pelvic floor disorders (PFD) and the rising need for comprehensive diagnosis and treatment. The Population Reference Bureau reported the percentage of the population aged 65 and older to be 13 % of the total population in the U.S. in 2010 with an expected increase to 20 % in 2050, whereas in Europe, the percentage was reported around 18 % in 2010 with an expected increase to 28 % in 2050 [1]. Women that are affected by PFD, often complain most about the impairment of their quality of life and ask for sufficient therapy, which is commonly surgical repair [2, 3]. Thus, imaging techniques have been constantly developed in recent years to support therapy planning and management. Magnetic resonance imaging (MRI) of the female pelvic floor, particularly, combines high-resolution images with an excellent soft tissue contrast and provides the possibility to assess noninvasively and more objectively a spectrum of possible disorders affecting the pelvic floor in one examination [4, 5, 6, 7]. There is general agreement that MRI of the pelvic floor should encompass static and dynamic MR images, whereas dynamic means imaging under maximum stress to the pelvic floor and MR defecography. Static MR images visualize pelvic floor anatomy and defects of the supporting structures, while dynamic MR images visualize pelvic organ mobility, pelvic floor weakness, pelvic organ prolapse (POP) and associated compartment defects [5, 8, 9, 10, 11]. Additionally, MRI may diagnose unexpected underlying masked functional abnormalities, which might be discrepant from the dominant symptom and may influence the choice of the surgical technique in around 42 % of patients with different spectra of PFD [12, 13].
Several studies and detailed reviews are published about MRI of the pelvic floor and different acronyms have been used for this examination including static and dynamic MR of the pelvic floor, MR defecography or MR proctography [4, 12, 14, 15, 16]. However, to date, there is neither consensus on a standardized imaging protocol nor on a systematic reporting scheme for MR-imaging of PFD. This may be due to the complexity of the anatomy and the functional interaction of the organs with the supporting structures resulting in a broad spectrum of PFD. Another important factor that contributes to this lack of consensus is the fact that PFD is treated by urologists, urogynecologists or proctologists. Consequently, each clinician may manage the patients’ condition from a different perspective. Therefore, MR-imaging acquisition varies according to the referring specialty and their rudiments for proper management and treatment decision. The wide range of different available MR protocols and a lack of standardization additionally increase variation between different centers. There is, therefore a necessity for recommendations from an expert panel that clearly defines the minimum prerequisites to obtain a state-of-the-art MR examination of the pelvic floor. This paper reports the recommendations of a panel of expert radiologists in pelvic floor imaging, which are joined in the pelvic floor-working group, which is under the umbrella of the European Society of Urogenital Radiology (ESUR) and the European Society of Gastrointestinal and Abdominal Radiology (ESGAR).
Materials and methods
Flow chart of the five basic steps of the study
- Step 1
Member recruitment and data sheet creation
- Step 2
Review of imaging protocols of the participating institutions and data sheet creation for literature review
- Step 3
Literature search, data collection and analysis
Literature search was conducted in the Medline database for articles published between 1993 and 2013 using the following keywords: “MRI AND Pelvic Floor“, “MRI defecography“, “MRI pelvic organ prolapse“, “MRI anal incontinence“, “MRI stress urinary incontinence“, “MRI AND defecography“, “Pelvic obstruction syndrome and MRI“, “Pelvic outlet obstruction and MRI“, “MRI and fecal incontinence“, “Pelvic floor and MRI“, “MRI and urinary incontinence“ and “Pelvic organ prolapse and MRI“.
Inclusion criteria were original data with full information about the parameters and the protocol of the examination that matched with our final data collection sheet for literature review.
Articles that were not written in English, did not deal with a human study population or lack of information about the performance of the examination were excluded.
- Step 4
Creation and analysis of a questionnaire
- Step 5
Discussion and voting for the final consensus recommendations
The second face-to-face meeting took place during ECR congress in 2015. For those questions that did not reach consensus at the first round of the questionnaire analysis, wording was modified to obtain better-defined statements subjected for voting by the experts in a face-to-face meeting. During that meeting the panelists discussed those items and were asked to vote. However, there were items that did not reach consensus but were reported by number of panelist to be important and warrants being included in the recommendations. These items were re-analyzed, and those that were found to be supported by case control or cohort studies from the literature, in particular level of evidence 2 according to the sign criteria, whereas expert opinion is level of evidence 4 (www.sign.ac.uk), were also included in the final recommendation.
Results
Consensus was reached for 88 % of 82 items and the recommendations regarding indication, patient preparation, imaging protocol, criteria for MRI assessment and reporting were constructed from these.
Indications for MR imaging of pelvic floor dysfunction
Most common indications for MR-imaging of pelvic floor dysfunction*
Indications | Score of agreement achieved** |
|---|---|
Anterior compartment | |
Stress urinary incontinence | 7/13 |
Recurrence after surgical POP repair | 7/13 |
Middle compartment | |
Recurrence after surgical POP repair | 11/13 |
Enterocele / Peritoneocele | 11/13 |
POP | 7/13 |
Posterior compartment | |
Outlet obstruction | 12/13 |
Rectocele | 12/13 |
Anismus | 11/13 |
Fecal incontinence | 10/13 |
Recurrence after surgical POP repair | 9/13 |
Rectal intussusception | 8/13 |
Non-specific compartment | |
Pelvic pain / perineal pain | 7/13 |
Descending perineal syndrome | 7/13 |
Patients’ preparation and hardware requirements
Full patients’ history of pelvic floor disorder should be taken prior to scanning (consensus 100 %). The patient should be examined at least in a 1.5 T MRI unit with a phased array coil, as this is the most agreed-upon field strength (consensus 100 %). The patient is examined in the supine position with the knees elevated (e.g. on a pillow with firm consistency) as this was found to facilitate straining and evacuation (consensus 100 %). The coil should be centered low on the pelvis to ensure complete visualization of prolapsed organs [4, 15]. The bladder should be moderately filled, therefore voiding 2 hours before the examination is recommended (consensus 100 %).
Prior to the examination the patient should be trained on how to correctly perform the dynamic phases of the examination and the evacuation phase (consensus 100 %). The patient is instructed to squeeze as if trying to prevent the escape of urine or feces and hold this position for the duration of the sequence. For maximum straining, the patient is instructed to bear down as much as she/he could, as though she/he is constipated and is trying to defecate [15]. For the evacuation phase, the patient should be instructed to repeat the evacuation process until the rectum is emptied.
To decrease possible patient’s discomfort, a protective pad or a diaper pant should be offered to the patient, which helps to increase patients’ compliance during dynamic and evacuation phases (consensus 100 %). No oral or intravenous contrast is necessary [15].
The rectum should be distended in order to visualize the anorectal junction (ARJ), rectoceles and intussusceptions, and to evaluate the efficacy of rectal evacuation (consensus 100 %). Ultrasound gel is the recommended medium to distend the rectum, however, the amount varies between 120 to 250 cc (consensus 100 %). For rectal distension a large amount of gel (180-200 cc) likely improves the capacity of the patient to defecate. A checklist for the recommended patients’ preparation is listed in (Table 2).
Checklist for the recommended patients’ preparation and MR-Imaging protocols
MR-imaging protocol
Recommended MR-imaging protocols
Plane | Sequence | Technique | TE (ms) | TR (ms) | ST (mm) | FOV (mm) | Matrix | Angulation | Number of slices | Level of evidence* | |
|---|---|---|---|---|---|---|---|---|---|---|---|
Static MRI sequences 2D MRI | |||||||||||
Sagittal | T2WI | Turbo/fast spin echo | 77-132 | 500-4210 | 4 | 200-300 | 256-448 | Midsagittal | 23 | 2 | |
Transverse | T2WI | Turbo/fast spin echo | 88-132 | 500-7265 | 4 | 200-300 | 256-512 | Perpendicular to the urethra | 25 | 2 | |
Coronal | T2WI | Turbo/fast spin echo | 80-132 | 500-7265 | 4 | 200-260 | 256-512 | parallel to the urethra | 26 | 2 | |
Dynamic MR sequences | |||||||||||
Squeezing | |||||||||||
Sagittal | T2WI | GE, FFE | 1.27-1.88 | 3.3-397.4 | 8 | 250-310 | 126-280 | Midsagittal | 1 or 3 | 2 | |
Straining | |||||||||||
Sagittal | T2WI | GE, FFE | 1.27-1.88 | 3.3-397.4 | 8 | 250-310 | 126-280 | Midsagittal | 1 or 3 | 2 | |
optionala | Transverse | T2WI | GE, FFE | 1.6-80 | 5.0-1200 | 5 or 6 | 250-310 | 126-280 | Perpendicular to the urethra | 5 | 2 |
optionalb | Coronal | T2WI | GE, FFE | 1.6 | 5 | 5 or 6 | 300 | 256 | Parallel to the urethra | 5 | 2 |
MR-Defecography | |||||||||||
sagittal | T2w | GE, FFE | 1.27-1.88 | 3.3-397.4 | 8 | 250-310 | 168-280 | Midsagittal | 1 or 3 | 2 | |
optionalc | coronal | T2w | GE, FFE | 1.27-1.6 | 5-397 | 4 or 8 | 257-350 | 154-256 | Parallel to anorectum | 5 | 2 |
Schedule of the recommended imaging sequences, the instruction given to the patient and the time duration per sequence
Since the performance of adequate pelvic stress during the dynamic sequences is important in order to assess the full extent of PFD, quality control of the study is essential. The study can only be considered diagnostic if a clear movement of the abdominal wall is seen during squeezing and straining. If no evacuation of rectal content at all or a delayed evacuation time (more than 30 seconds to evacuate 2/3 of the rectal content) is present, anismus should be considered (consensus 88 %) [23].
Image analysis, measurements, grading and MRI report
Image analysis
Basic measurements. a. Dynamic Balanced Fast Field Echo (BFFE) sequence in the midsagittal plane at rest shows how to plot the basic measurements of pelvic organ prolapse. The pubococcygeal line (PCL), drawn on sagittal plane from the inferior aspect of the pubic symphysis (PS) to the last coccygeal joint. After defining the PCL, the distance from each reference point is measured perpendicularly to the PCL at rest and at maximum straining. B; bladder base, C; cervix, P; pouch of Douglas, ARJ; Anorectal junction. Measured values above the reference line have a minus sign, values below a plus sign. b. Dynamic BFFE during maximum straining shows the movement of the organs compared to their location at rest. It is recommend to give the difference of the values at rest and during straining for each organ-specific reference point (pelvic organ mobility). R; Rectocele, ARJ; Ano-Rectal Junction. c. MRI defecography (BFFE) in the mid sagittal plane during evacuation of the intra-rectal gel. Dynamic MR imaging during evacuation is mandatory, because certain abnormalities and the full extent of POP are only visible during evacuation. In this case compared to the maximum staining phase it is obvious that there is increase of the degree of the pelvic organ descent and development of new pathology including the loss of urine and the detection of masked intussusception, which was detected only during excavation (white arrow)
Checklist for the recommended MRI reporting scheme
Specialty-based MRI reporting scheme
Urologic patients |
Report of pathologies if present |
During dynamic sequences |
Loss of urine through the urethra at maximum straining |
Hypermobility of the urethra |
Kinking of the vesicourethral junction |
Uretherocele |
Cystocele; type (distension or displacement), size (cm), grade |
On static images |
Damage of the supporting urethral ligaments |
Avulsion or defect of the puborectal muscle |
Measurements |
Pelvic organ mobility |
Pelvic floor relaxation |
Iliococcygeus angle |
Hiatal dimensions |
Further evaluation |
Additional findings regarding the pelvic organs* |
Coexistent middle and posterior compartment disorders |
(Uro)gynecologic patients |
Report of pathologies, if present: |
During dynamic sequences |
Cystocele; type (distension or displacement), size (cm), grade |
Uterine prolapse: partial or total |
Enterocele: type (content of the peritoneal sac), size (cm), grade |
On static images |
Avulsion or defect of the puborectal muscle |
Measurements |
Pelvic organ mobility |
Pelvic floor relaxation |
Iliococcygeus angle |
Hiatal dimensions |
Further evaluation |
Additional findings regarding the pelvic organs* |
Coexistent anterior and posterior compartment disorders |
Proctologic patients |
Report of pathologies, if present: |
During dynamic sequences |
Rectocele: type (anterior or rarely posterior) size (cm), grade |
Rectal mucosal invagination or prolapse: differentiation, extent, grade |
Rectal descent: distance to PCL (cm), grade |
Enterocele: type (content of the peritoneal sac), size (cm), grade |
Lack of changes of ARA |
Insufficient opening of the anal canal with inadequate rectal emptying during evacuation |
Rectal intussusception |
Measurements |
Rectocele |
Rectal decent |
ARA |
Pelvic organ mobility |
Pelvic floor relaxation |
Further evaluation |
Additional findings regarding the pelvic organs* |
Coexistent anterior and middle compartment disorders |
Measurements
The pubococcygeal line (PCL), drawn on sagittal plane from the inferior aspect of the pubic symphysis to the last coccygeal joint, is recommended as reference line to measure POP (consensus 100 %). It shows the highest inter- and intraobserver reliability of MRI measurements in women with POP of the anterior and middle compartment compared to all proposed reference lines in the literature with an intercorrelation coefficient (ICC) between 0.70-0.99 (Fig. 3a) [14, 37, 38].
After defining the PCL, the distance from each reference point is measured perpendicularly to the PCL at rest and at maximum strain (consensus 100 %) [26, 29]. In the anterior compartment, the organ-specific reference point is the most inferior aspect of the bladder base (B), in the middle compartment, the organ-specific reference point is the anterior cervical lip (most distal edge of the cervix)(C), or the vaginal vault in case of previous hysterectomy (V), and in the posterior compartment, the organ-specific reference point is the anorectal junction (ARJ) (consensus 100 %) (Fig. 3a) [15, 16, 20, 25, 29, 39]. Measured values above the reference line have a minus sign, values below a plus sign (consensus 100 %) [25].
Reporting of the movement of the organs compared to their location at rest is stated to give more valuable information for the referrer than a grading system alone [8, 25]. We therefore recommend giving the difference of the values at rest and during straining for each organ-specific reference point (pelvic organ mobility)(consensus 100 %) (Fig 3a, b).
Pelvic floor relaxation and posterior compartment measurements. a,b,c Dynamic Balanced Fast Field Echo (BFFE) sequence in the midsagittal plane at rest (a) , mild (b), and maximum straining (c). (a) shows how to quantify the pelvic floor laxity. The H-line extends from the inferior aspect of the pubic symphysis to the anorectal junction, the M-line is dropped as a perpendicular line from the pubococcygeal line (PCL) to the posterior aspect of the H-line. (b) Demonstrates the anorectal angle (ARA) drawn along the posterior border of the rectum and a line along the central axis of the anal canal on sagittal plane. ARJ; Ano-Rectal Junction. (c) Shows how to measure and diagnose a pathological rectocele: a line drawn through the anterior wall of the anal canal is extended upward, and a rectal bulge of greater than 2 cm anterior to this line is described as a rectocele (R). The levator plate angle (LPA) is enclosed between the levator plate and the PCL. d,e. Dynamic Balanced Fast Field Echo (BFFE) sequence in axial (d) and coronal (e) plane at rest and during maximum straining. In the axial plane the width of the levator hiatus is enclosed between the puborectalis muscle slings. On the coronal plane, the iliococcygeus angle is measured between the iliococcygeus muscle and the transverse plane of the pelvis in posterior coronal images at the level of the anal canal
Overview of the published reference values for quantitative MR-measurements of the pelvic floor
Parameters | Reference value ± standard deviation | Reference |
|---|---|---|
Anterior compartment | ||
Bladder base position (according to PCL) at rest | −2.3 ± 0.46 cm | [39] |
Bladder base position (according to PCL) during straining | 0.81 ± 1.11 cm | [39] |
Middle compartment | ||
Anterior cervical lip position (according to PCL) at rest | 4.31 ± 0.78 cm | [39] |
Anterior cervical lip position (according to PCL) during straining | −0.79 ± 1.65 cm | [39] |
Posterior compartment | ||
Anterior bulge of the rectal wall during straining (rectocele) | 2.6 ± 0.6 cm | [39] |
Ano rectal junction (ARJ) at rest | ≤3 cm below the PCL 0.53 ± 0.99 cm | |
ARJ during squeezing | Elevation of ARJ | [36] |
ARJ during straining | 2.99 ± 1.03 cm | [39] |
Anorectal angle (ARA) at rest | 85-95° 93° ± 4.8° | |
ARA during squeezing | 71° sharpening of 10-15° | |
ARA during straining or defecation | 103° 15-25° more obtuse 108° ± 14.7° | |
Measurements for quantification of the pelvic floor laxity | ||
H-line (hiatus) during straining | 5.8 ± 0.5 cm | [15] |
M-line (descent of H-line to PCL) during straining | 1.3 ± 0.5 cm | [15] |
Levator plate angle during straining | 11.7 ± 4.8° | [15] |
Iliococcygeus angle at rest | 20.9 ± 3.5° | [15] |
Iliococcygeus angle during straining | 33.4 ± 8.2° | [15] |
Transverse diameter of levator hiatus at rest | 3.3 ± 0.4 | [15] |
Transverse diameter of levator hiatus during straining | 4.5 ± 0.7 cm | [15] |
Grading
The “Rule of three’ is the recommended grading system in the anterior and middle compartment starting at 1 cm below the PCL (Table 4) [15, 16, 32, 34, 40]. This is based on the fact that the pelvic floor may descend and widen up to 2 cm during abdominal pressure. Consequently, the pelvic organs follow the movement of the pelvic floor inferiorly but without protrusion through their respective hiatuses [4]. The bladder base, particularly, may descend up to 1 cm below the PCL during straining in continent women and should not be stated as a cystocele (consensus 100 %) [24, 34].
The “Rule of two” is recommended for grading the anterior rectal wall bulge in rectoceles (consensus 100 %) (Table 4) [16; 23; 25; 26; 31]. It should be reported as pathological from grade °II, as a grade °I rectocele can be observed in nearly 78-99 % of parous women, while rarely in men [20, 28, 41].
Anorectal junction descent (ARJD) is graded (grade °I) between 3 and 5 cm below the PCL, and (grade °II) with at least 5 cm (consensus 100 %) [36].
Small intussusceptions of the rectal wall are considered to be normal findings during defecation, observed in nearly 80 % of healthy subjects [41].
Reporting other functional abnormalities and structural defects
Functional abnormalities on dynamic MR images
Loss of urine through the urethra during maximum straining records urinary incontinence (UI) and should be reported if present (consensus 88 %)[15]. Urethral hypermobility as a predictor for UI should be reported if present (consensus 88 %) [29]. If a cystocele is present, the differentiation of a distention or a displacement cystocele can be made, which is helpful for therapy planning, however it reached no consensus for general reporting [42].
If an enterocele is present, the report should include the content of the peritoneal sac, as clinical examination alone may have shortcomings in identifying the content (consensus 100 %) [5, 20, 22, 31, 43].
The end of evacuation phase is important to identify intussuception (Fig. 3c) [30].
The change of the ARA during dynamic and evacuation sequence compared to the ARA at rest expresses the functioning of the puborectal muscle. In particular, the ARA should sharpen during squeezing and should become more obtuse during straining and evacuation [16, 27, 39]. We recommend to report the individual function, as the literature presents with a widespread of normal reference values (consensus 100 %).
Structural defects on static MR images
Functional three -part pelvic supporting system. a,b. Static T2W Turbo-Spin Echo (TSE) MR images in sagittal and axial plane. (a) Sagittal MR image illustrating the levels of the endopelvic fascia (paracolpium) that attaches the upper vagina to the pelvic walls, it is divided into three levels. Level I (suspension); the portion of the vagina adjacent to the cervix (the cephalic 2–3 cm of the vagina) functionally it provides the upper vaginal support. Level II (attachment); located in the mid portion of the vagina, it stretches the vagina transversely between bladder and rectum. The anterior vaginal wall provides urinary bladder support. The posterior vaginal wall and the endopelvic fascia (rectovaginal) form a restraining layer that prevents the rectum from protruding forward. (b) Axial T2W image shows detachment of the puborectalis muscle from its origin identified by discontinuity of its attachment to the pubic bone on the right side (dotted black arrow) (white arrow, normal bony attachment), (** loss of H-shaped vagina on the right side), (*; normal lateral vaginal attachment on the left side)
Limitations of the study
The study has few limitations. Four panelists who participated in Step 1 and 2 of the study were from the same institution. Therefore, only 1 out of their 4 completed questionnaire was included in the final analysis to avoid biased results. Nevertheless, since all 8 panelists who have completed the questionnaire were from different institutions these recommendations can be considered to represent the entire spectrum of expert opinions in the field of pelvic floor MRI. Second, the recommendations given in this study with regard to technical aspects of MRI of the pelvic floor relate to conventional closed-configuration magnets for MR imaging allowing patient positioning in lying body position only. However, this is the most agreed upon scanner, in addition several studies have shown that patient positioning does not significantly influence diagnostic performance of MR imaging of the pelvic floor [17, 19, 47, 48].
Conclusion
Based on an extensive literature review and analysis and of expert consensus, these proposed recommendations can be used as guidance for standardized MR imaging and reporting of PFD. Nevertheless, our joint ESUR-ESGAR pelvic floor-working group is aware about the complexity of the topic and that further studies are mandatory to achieve additional refinements of guidelines for MR imaging, diagnosing and reporting of PFD.
Copyright information
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