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ECR 2019 / C-2282
Cum Laude
Imaging evaluation of pelvic floor: Pictorial review of the most recent recommendations
Congress: ECR 2019
Poster No.: C-2282
Type: Educational Exhibit
Keywords: Imaging sequences, MR-Functional imaging, MR, Urinary Tract / Bladder, Pelvis, Genital / Reproductive system female, Pelvic floor dysfunction
Authors: P. M. Costa1, D. Monteiro2, A. Silva1, C. A. R. A. Silva3, M. Ribeiro1, J. A. Machado2; 1Matosinhos/PT, 2Porto/PT, 3Guimarães/PT
DOI:10.26044/ecr2019/C-2282

Findings and procedure details

                      Recommended MRI Imaging Protocols

 

Static and dynamic sequences should be acquired; T2-weighted images (T2WI) are recommended for both, due to its greater anatomic detail. ( Fig. 1 ). [3]

T1WI should complement the examination, whenever a pelvic lesion is detected.

 

  • Static images → Detection and classification of structural abnormalities

          → Pelvic floor anatomy

          → Defects of the supporting structures

          → Anal sphincter complex

 

  • Dynamic images (during squeezing, straining and defecation) → functional abnormalities that are assessed by metric measurements of the three compartments

          → Pelvic organ mobility

          → Pelvic floor relaxation

          → Pelvic organ prolapse (POP)

          → Associated compartment defects

 

No oral or intravenous contrast is necessary. [3]

 

 

                                     Anatomy brief review

 

 

Pelvic compartments 

 

Pelvic floor is one functional unity commonly divided into three different compartments ( Fig. 2 ):

 

  • Anterior Compartment (AC) - Bladder and Urethra

         - Cystocele

         - Urethral Hypermobility

 

  • Middle Compartment (MC) - Uterus, Cervix and Vagina

         - Uterine/Vaginal prolapse

 

  • Posterior Compartment (PC) - Anus, Anal Canal, Rectum, Sigmoid colon

         - Pelvic Floor Relaxation

         - Rectocele

         - Intussusception

 

The cul-de-sac is often considered a "virtual" compartment, where pathological processes also occur:

 

         - Enterocele

         - Peritoneocele

         - Sigmoidocele

 

   

◊ Supporting Structures

 

Endopelvic Fascia - located immediately beneath the peritoneum; it has various thickenings or condensations in specific areas. [5]

 

⇒ Most of Endopelvic Fascia ( Fig. 3 ) is not directly visualized in MRI → Defects are inferred based on secondary signs! [6]

 

° Level I (suspension) - Cephalic 2–3 cm of the vagina and above

     - Provides the upper vaginal support (Parametrium and Paracolpium) [6,7]

 

° Level II (attachment) - Mid-portion of the vagina (between level I and III)

     - Transverse support of the vagina (Paracolpium)

     -  Urinary bladder support (through the anterior vaginal wall)

     - Prevents the anterior protrusion of the rectal wall (through the posterior vaginal wall and rectovaginal fascia)

     - Prevents the bowel from herniating inferiorly (rectovaginal fascia) [4]

 

° Level III - At the level of the hymen ring and the 2–3 cm above it → directly attached to the surrounding structures (urethra, perineal body, levator ani muscles)     

     - Urethral support [4,5,7]

                                                   

                                                   ⇓

                       Static images in normal patients show ( Fig. 4 ):

 

  1. Symmetrical urethral ligaments on an axial scan (no distortion or defect)
  2. Bladder neck positioned close to the pubis symphysis
  3. Vaginal lumen with a widened H-appearance in axial sequences and the lateral vaginal walls are close to the puborectalis muscle [3,4]

 

 

Pelvic Diaphragm -  The levator ani (pubococcygeus, puborectalis and iliococcygeus muscles) and ischiococcygeus muscles. [4,5,7] ( Fig. 5 )

 

 - Iliococcygeus forms, posteriorly, a firm midline raphe ⇒ Levator plate

 - Puborectalis ⇒ U-shaped sling - elevates the bladder neck and compress it against the pubic symphysis [4,5,7]

 

Urogenital Diaphragm -  Connective tissue and the deep transverse muscle of the perineum (anterior to the anorectum) [4,8]

 

 

                    Pelvic organ prolapse vs pelvic floor relaxation

 

Different entities, but frequently coexistent in pelvic floor weakness

 

Pelvic organ prolapse - abnormal descent of a pelvic organ through the hiatus beneath it [3]:

- bladder (cystocele)

- vagina (vaginal prolapse)

- uterus (uterine prolapse)

- mesenteric fat (peritoneocele)

- small intestine (enterocele)

- sigmoid colon (sigmoidocele)

 

Pelvic floor relaxation - excessive descent and widening of the entire pelvic

floor during rest and/or evacuation, regardless of whether prolapse is present. [3]

 

 

                                How to look at the MRI?

 

 ◊ Dynamic Images - Identifying and grading the abnormality(ies)

 

1 - Maximum straining - Is there:

  • Loss of urine through the urethra?
  • Urethral hypermobility? ( Fig. 6 )
  • Kinking of the urethrovesical junction?
  • An enterocele? Which is the content of the peritoneal sac?
  • Loss of rectal gel during straining? ( Fig. 7 )

2 - Rest, squeezing and defectation - Trace the Anorectal Angle (ARA) ( Fig. 8 ) - expresses the functioning of the Puborectal muscle

 

     - At rest – 93º

     - During squeezing - sharpening of 10-15°

     - During straining or defecation - 15-25° more obtuse [3]

 

 

ARA should close with squeezing and open with defecation ⇒ The change of ARA with dynamic sequences is more important than the absolute values. [3]

 

 

3 - Rest, maximum straining and defecation - Trace the pubococcygeal line (PCL) ( Fig. 9 )

 

   3.1 - Measure the perpendicular distance between the PCL and each reference point (values above the reference line have a minus sign, values below a plus sign): [3,4,6]

 

  • Anterior compartment → the most inferior aspect of the bladder base
  • Middle compartment → the most distal edge of the cervix or the vaginal vault in case of previous hysterectomy
  • Posterior compartment → the anorectal junction

 

⇒ Cystocele and POP are graded accordingly to the “rule-of-three", starting at 1 cm below the PCL [3]:

 

      - Grade I - 1–3 cm

      - Grade II - 3–6 cm

      - Grade III - > 6 cm 

 

Refer cystocele and POP as pathological just when grade II or III. [3]

 

⇒ Anorectal Junction descent (ARJ) is graded starting at 3 cm below the PCL [3]:

      - Grade I - 3 - 5 cm below the PCL

      - Grade II - > 5 cm below the PCL

 

 

〉 The difference between rest and maximum straining should be noted - Pelvic Organ Mobility.

 

〉 The full extent of POP is only visible during evacuation! [3]

 

 

4 - End of evacuation phase

 

   4.1 -Is there a rectocele? (Measure the distance between the anterior rectal wall and a vertical line that goes through the anterior wall of the anal canal) ( Fig. 10 )

 

⇒ Grade rectoceles using the “rule-of-two” - pathological starting from II [3]

      - Grade I - < 2 cm

      - Grade II - 2–4 cm

      - Grade III - > 4 cm 

 

   4.2 - Is there any mucosal invagination/rectal prolapse? ( Fig. 11 )

 

   4.3 -Was rectal emptying adequate? Was it delayed?

   

   → In the presence of incomplete evacuation or delayed evacuation time (more than 30 seconds to evacuate 2/3 of the rectal content), anismus should be considered. [3,6]

 

___________________________________________________________

 

Δ Routinely measuring pelvic floor relaxation reached no consensus! [2]

  • H-line (hiatus length)
  • M-line (descent of the levator plate)
  • Levator plate angle

                    ⇓

     Measured in the sagittal plane ( Fig. 12 )

         

        Normal values [6]:

        - H-line during straining 5.8 ± 0.5 cm

        - M-line during straining 1.3 ± 0.5 cm

        - Levator plate angle during straining 11.7 ± 4.8° [9]

 

 

  • Transverse width of the levator hiatus (axial plane)
  • Iliococcygeus angle (coronal plane)

                    ⇓

    Measured in the axial and coronal planes - Optional sequences [3]

 

___________________________________________________________

 

 ◊ Static Images - Finding the underlying structural defect responsible for the previously identified abnormalities.

 

   - Urethral support system - maintains urinary continence

  • Level III endopelvic fascial defects

          → Widening of the retropubic space - Moustache sign ( Fig. 4Fig. 18Fig. 19 ) [3,4,7]

  • Puborectalis muscle detachment, disruption, atrophy or avulsion ( Fig. 13 ) [3,4,7]

   - Vaginal support system - prevents prolapse

  • Level I and II paravaginal fascial defects

          → Loss of the H-shape of the vagina

          → Sagging of the posterior bladder wall → "Saddlebag" sign ( Fig. 14 ) [3,4,7]

  • Iliococcygeus diffuse or focal muscle abnormality

   - Anal sphincter complex - maintains anal continence [3,4,6]

  • Mucosa/Submucosa
  • Internal anal sphincter
  • External anal sphincter
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