dynamic magnetic resonance imaging of the pelvic floor · ing the female reproductive organs...

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Dynamic Magnetic Resonance Imagingof the Pelvic FloorSindhura Alapati, MD,* and Kedar Jambhekar, MD

http://dx.doi.or0887-2171/& 2

ment of Radiolk, AR.reprint requ4301 West Matisindhu27@g

Downloade

Pelvic floor dysfunction is a widespread condition affecting up to 50% of elderly women. Itmarkedly compromises the quality of life owing to various disabling symptoms such as pelvicpain, pelvic organ prolapse, and urinary and fecal incontinence. Although age and female sexare the main risk factors, others include multiparity, obesity, and connective tissue disorders.Pelvic floor dysfunction is frequently multicompartmental, and failure to diagnose it accuratelyoften leads to treatment failure. Dynamic pelvic floor magnetic resonance imaging is a robusttool that enables simultaneous visualization of the 3 pelvic floor compartments and isindispensable for precise preoperative evaluation.Semin Ultrasound CT MRI 38:188-199 C 2017 Elsevier Inc. All rights reserved.

Introduction

P elvic floor dysfunction is an umbrella term for a spectrumof functional disorders affecting the 3 compartments of

the pelvic floor, caused by impairment of the supportligaments, fasciae, and muscles. It is a prevalent disorderaffecting up to 50% of women older than 50 years of age.1 Itaffects 23.7% of women in the United States with a prevalenceof 9.7%-49.7%, that increases with age.2,3 Pelvic floor dys-function is a debilitating disorder that can substantiallyjeopardize a women 's quality of life by causing symptomssuch as generalized pelvic pain, urinary incontinence, dyspar-eunia, fecal incontinence, obstructed defecation, and organprolapse. Increasing age and female sex are considered to bethe greatest risk factors. Pregnancy itself leads to decreasedstrength of the perineal musculature secondary to mechanicaland hormonal elements. Genital tract trauma from perinealtears and episiotomy is associated with greater risk of floordysfunction. Other contributing factors include obesity, men-opause, connective tissue disorders, smoking, chronic obstruc-tive pulmonary disease, and any condition that causes chronicincrease in intra-abdominal pressure.Pelvic organ prolapse and pelvic floor weakness often

coexist but are 2 separate entities that need to be differ-entiated.1 Pelvic organ prolapse is defined as abnormal descent

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ogy, University of Arkansas for Medical Sciences, Little

ests to Sindhura Alapati, c/o Kedar Jambhekar,arkham, Slot 556, Little Rock, AR 72205. E-mail:mail.com

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of one or more pelvic organs through the hiatus secondary toineffective support structures. This disorder can manifest asprolapse of any of the following anatomical structures either inisolation or in combination with one another: urethra(urethrocele), urinary bladder (cystocele) or both (cystoureth-rocele), vaginal vault and cervix (vaginal prolapse), uterus(uterine prolapse), rectum (anterior or posterior rectocele),small bowel (enterocele), and peritoneum (peritoneocele). Onthe contrary, pelvic floor weakness is due to ineffective pelvicsling structures (active and passive supporting structures of thepelvic floor) resulting in pelvic floor dysfunction at rest andduring activities that increase intra-abdominal pressure(coughing, sneezing, urination, or defecation).1,4

The development of pelvic floor disorders is complex andmultifactorial, with the dysfunction often being multicom-partmental. Failure to accurately diagnose this abnormalitycan lead to therapeutic failure and recurrence. Hence,women with pelvic floor problems require a comprehensiveevaluation, which includes thorough clinical history, phys-ical examination, physiologic testing, and imaging. Althoughclinical examination is the first step in the diagnosticalgorithm, it frequently underestimates the degree of pro-lapse or misdiagnoses the site of prolapse.1 In addition,peritoneocele, which requires abdominal rather than vaginalsurgery, is not detected clinically. Physiological testing(urodynamics and anorectal manometry) is invaluable forassessment of the pathophysiology of pelvic floor disorders.However, it does not depict the anatomical problem.3

Therefore, preoperative imaging is an important componentof the diagnostic chain and is extremely helpful for selectingsurgical candidates and determining surgical strategy.

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Figure 1 Line diagram showing the 3 compartments of the pelvis andtheir contents.

Dynamic MR imaging of pelvic floor 189

Dynamic magnetic resonance imaging (MRI) has emerged asa reliable tool for evaluating pelvic floor weakness, especiallywhen multicompartment involvement is suspected, as itallows visualization of all 3 compartments simultaneously. Inour institution, dynamic pelvic floor MRI is used as asupplement to physical examination and physiologicaltesting.The article will review the anatomy of the pelvic floor and

will discuss MRI technique and indications. A stepwiseapproach for interpretation of pathologies involving eachpelvic compartment will be provided. Treatment options willalso be discussed.

AnatomyUnderstanding the complex anatomy of the pelvic floor isfundamental for image interpretation and evaluation of pelvicfloor dysfunction. The female pelvis is divided into thefollowing 3 compartments: anterior compartment composedof urinary bladder and urethra, middle compartment contain-ing the female reproductive organs (vagina, uterus, andadnexae), and the posterior compartment consisting of anusand rectum (Fig. 1). The main supporting structures of thepelvic organs are divided into active and passive supports. Themuscles of the pelvic floor, particularly the levator ani, provideactive support, whereas the fascia and ligaments provide passivesupport. From cranial to caudal, the pelvic floor supports areorganized into the following 3 layers: endopelvic fascia andligaments, pelvic diaphragm, andurogenital diaphragm (Table).

Endopelvic Fascia and LigamentsEndopelvic fascia is the superior layer of the pelvic floor and iscomposed of connective tissue (Figs. 2 and 3). It attaches tothe bony pelvis and covers the pelvic viscera and levator animusculature in a continuous sheet. The component ofendopelvic fascia between the urinary bladder and the vaginais termed pubocervical fascia, which in conjunction withperiurethral, paraurethral, and pubourethral ligaments pro-vides support to the urinary bladder, bladder neck, and theurethra. Extension of fascia from the uterus and cervix to thepelvic sidewall is called parametrium, the condensations ofwhich form cardinal and uterosacral ligaments. In a similar

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manner, fascia extending from the vagina to the pelvicsidewall is called paracolpium. Portion of endopelvic fasciabetween the rectum and the vagina is referred to as rectova-ginal fascia. Laterally, condensations of all fascia unite toform the arcus tendineus that provides anchor to the levatorani muscles and in turn supports the pelvic organs. Inaddition to lateral extension to the arcus tendineus, therectovaginal fascia extends inferiorly to the perineal body(located in the anovaginal septum) and to the uterosacralligaments superiorly.

Pelvic DiaphragmThe pelvic diaphragm is composed of 4 muscles: puborectalis,pubococcygeus, iliococcygeus, and the ischiococcygeus(Figs. 4 and 5). Of these, the puborectalis, pubococcygeus,and iliococcygeus together constitute the levator ani (Fig. 4).These muscles contract continuously providing tone to thepelvic floor in addition to maintaining the pelvic organs incorrect position. The ischiococcygeus is posterior to the levatorani and extends from the ischial spines to the lateral margins ofthe sacrum and coccyx. The 2 most important components ofthe levator ani are the iliococcygeus and puborectalis. Thepuborectalis is a “U” shaped muscle that has a horizontalorientation and arises from the pubic bones anteriorly andforms a sling around the rectum (Fig. 5). The iliococcygeusmuscle is also a horizontally oriented muscle that arises fromthe external anal sphincter and fans out laterally toward thearcus tendineus. Posterior and midline condensation of theiliococcygeus results in a raphe anterior to the coccyx referredto as the levator plate. Pubococcygeus, the third muscle of thelevator ani, arises from the superior ramus of the pubicsymphysis and inserts on the arcus tendineus and coccyx.This muscle also has attachments to the vagina and perinealbody (Table).

Urogenital DiaphragmUrogenital diaphragm is located caudal to the pelvic dia-phragm and anterior to the anorectum. The urogenitaldiaphragm has the following 2 main components: connectivetissue and muscles (Figs. 4B and 5). The connective tissueencloses the muscular contents and forms the superior and theinferior boundaries of the urogenital diaphragm known as thesuperficial and the deep perineal fascia, respectively. The latteris also referred to as the perineal membrane. The musclesinclude the sphincter urethrae and the transverse perinealmuscle (Table).Perineal body, also known as the central tendon of the

perineum, is another important pelvic support. It is the site ofattachment for many structures including endopelvic fascia,external anal sphincter, urogenital diaphragm, bulbocaverno-sus muscle, and puborectalis muscle.

Indications for ImagingPelvic floor MRI is indicated before surgical repair in thefollowing 2 types of patients: (1) patients with clinical


Table Summarizing the Female Pelvic Floor Supports, Structure, and Function

Female Pelvic Floor Supports

Structure Contents Anatomy Function

Endopelvic fascia Pubocervical fascia Extends between the urinary bladder and the vagina Provides support to the pelvic organsRectovaginal fascia Extends between the vagina and the rectumArcus tendineus Fascial condensations which help to anchor the

levator ani to the pelvic sidewalls

Levator ani complex Puborectalis Arises from the pubic bone and forms asling around the rectum

Keeps bladder neck compressedagainst the pubic symphysis

Iliococcygeus Horizontal sheet-like muscle that extends acrossthe pelvic floor to the coccyx

Forms a midline raphe called levator platewhich is an important posterior compartment support

Pubococcygeus Extends across the pelvic floor from the pubic boneto coccyx

Reinforces the levator plate at its insertion to the coccyx

Urogenital diaphragm Superficial perineal fascia Encloses the urogenital diaphragm Fills in the gap between the pubic arches anteriorlyand provides support to the anterior and middlecompartment pelvic organs

Sphincter urethrae Arises from both pubic arches and traverses mediallyto encircle the urethra

Superficial and deep transverseperineal muscle

Superficial: horizontally between the inner bordersof the ischial rami to the perineal body andexternal anal sphincter

Deep: from the inferior rami of the ischium to themedian plane, where it interlaces with thecontralateral muscle

Deep perineal fascia Also called perineal membrane and forms the inferiorboundary of the urogenital diaphragm

Perineal body – Common point of insertion of muscles of the pelvicfloor that separates the vagina from the rectum

Prevents widening of the urogenital hiatuswhich is an opening in the levator animuscle through which the urethra,vagina, and rectum course

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Figure 2 Diagrammatic representation of the endopelvic fascia (bluedotted line) that extends as pubocervical fascia between the urinarybladder and the uterus, and rectovaginal fascia between the rectumand the vagina. B, urinary bladder; U, uterus; R, rectum; PR,puborectalis sling. (Color version of figure is available online.)

Figure 3 The line diagram is a representation of the support ligamentsof the pelvic organs as seen from above. Note that the cardinalligaments extend laterally and attach onto the tendinous arch oflevator ani, also called arcus tendineus. U, urinary bladder; C, cervix;R, rectum. (Color version of figure is available online.)


manifestations of multicompartmental weakness and (2)patients who underwent prior surgical repair.

MRI TechniqueDynamic pelvic floor MRI is performed in a 1.5 or 3 T magnetwith the patient in supine position. Alternatively, dynamicimaging can also be performed in a sitting position in an openMRI. However, in the detection of clinically relevant pelvicfloor abnormalities, there is no substantial difference inimaging patients in a sitting or in a supine position.5 The scanis performed with rectal contrast. Approximately 180 mL ofwarm ultrasound gel is instilled into the rectum via a smallflexible catheter at our institution. It is vital to discuss thedynamic MRI scan with the patient before the start of theexamination and explain the importance of rectal distensionincluding patient acceptance and understanding of the steps ofthe dynamic examination including the pelvic squeeze, bearingdown, and evacuation of the gel for optimal results. Owing tothe high soft tissue resolution of MRI, opacification of thebowel loops, urinary bladder, and vagina is not performed.Coronal T2 single-shot fast spin echo (HASTE), high-resolution axial T2, wide field of view axial T1 and T2 arethe initial sequences obtained at our institution. Thesesequences are performed without rectal contrast injection.Preliminary cine sagittal T2 single-shot fast spin echo is alsoperformed before distension of the rectum. This sequence issolely for patients ' practice so that they get used to perform thevarious maneuvers of the dynamic examination. Sagittal T2single-shot fast spin echo or balanced steady-state sequenceacquired as “cine loop” after the rectal distension forms theworkhorse of dynamic pelvic floor MRI. The “cine loop” isacquired while the patient performs maneuvers such as


squeezing, straining, and defecation in the supine position.As the study is performed in the supine position (nonphysio-logical), explanation of themaneuvers to the patient and givingappropriate instructions are indispensable to ensure theiractive participation. At least 2 acquisitions of approximately40-60 seconds each are necessary to ascertain adequate cover-age of slow or difficult evacuation, though in our experience, atleast 3 acquisitions should be performed to get the best results.The entire study is completed in 15-20 minutes.

MRI Interpretation—StepwiseApproachInterpretation of pelvic floor MRI requires a standardizedapproach. The first and foremost step is to draw pubococcy-geal line (PCL) that extends from the inferior border of thepubic symphysis to the last coccygeal joint in the midsagittalplane.1,3-7 The PCL represents the level of the pelvic floor andis the landmark for measuring organ prolapse. This line isreproducible and includes the pubic bone and the coccyx thatare attachments of the pelvic floor (Fig. 6).5 The levator plateis parallel to the PCL in normal population. The referencepoint of the anterior compartment is the most posterior andinferior aspect of the base of the urinary bladder. In a similarfashion, reference point of the middle compartment is themost anterior and inferior aspect of the cervix (or poster-osuperior vaginal apex in women who are status posthysterectomy). Lastly, the posterior aspect of the anorectaljunction forms the reference point of the posterior compart-ment. Distances from the PCL to the aforementionedreference points aremeasured in neutral, contraction (squeez-ing), and straining (defecation) phases. In healthy women,there is minimal descent of the pelvic organs, even duringmaximal pelvic strain (defecation). Prolapse severity can beeasily graded according to the “rule of three”: prolapse of anorgan below the PCL by 3 cm or less is mild, between 3 and6 cm is moderate, and more than 6 cm is severe.1,5

Subsequently, H andM lines are measured in the analysis ofpelvic floor dysfunction. H line is drawn from the inferior


A B

Figure 4 (A) Coronal T2-weighted MR image with superimposed line diagram shows the 3 layers of the pelvic floorsupports. The superior layer is the endopelvic fascia, middle layer is pelvic diaphragmwhich ismainly composed of levatorani, and inferior-most layer is the urogenital diaphragm. U, uterus; B, urinary bladder; LA, levator ani, EPF, endopelvicfascia; and UGD, urogenital diaphragm. (B) Line diagram showing the pelvic floor as viewed from the top. It demonstratesthe middle (pelvic diaphragm or levator ani) and inferior layer (urogenital diaphragm) in one plane. Pelvic diaphragmconstituted by levator ani (pubococcyges, iliococcygeus, and ischiococcygeus) spans through all 3 pelvic compartments.Urogenital diaphragm is restricted to the anterior and themiddle compartments of the pelvis as the name implies. PS, pubicsymphysis; C, coccyx; IT, ischial tuberosity; U, urethra; V, vagina; R, rectum; MR, magnetic resonance. (Color version offigure is available online.)

S. Alapati and K. Jambhekar192

border of the pubic symphysis to the posterior wall of therectum at the anorectal junction and corresponds to theanteroposterior width of the levator hiatus (Fig. 6).5 M line isa vertical line drawn perpendicularly from the PCL to themostposterior aspect of the H line and represents the verticaldescent of the levator hiatus (Fig. 6).5 Normally, H andM linesshould not exceed 5 cm and 2 cm, respectively.5 Both theselines become elongated during the straining phase in patientswith pelvic floor laxity. H line measuring greater than 5 cm

U

V

PERINEAL BODY

PUBRECTALIS

Figure 5 Schematic diagram of inferior view of the pelvic floor isshown. The puborectalis is a U-shaped, which forms a sling aroundthe rectum. The perineal body also called central tendon of theperineum is located between the middle and the posterior compart-ments. PB, pubic bone; IT, ischial tuberosity; C, Coccyx; U, urethra; V,vagina; R, rectum. (Color version of figure is available online.)


represents levator hiatuswidening, whereasM line greater than2 cm is consistent with descent of the levator plate, both ofwhich are suggestive of pelvic floor dysfunction.Finally, the anorectal angle is drawn between the longitu-

dinal axis of the anal canal and the posterior rectal wall (Fig. 7).Normal measurement of the anorectal angle is 901-1101 inneutral phase.3 In healthy patients, the anorectal anglebecomes more acute during squeezing raising the anorectaljunction by 1-2 cm from the resting (neutral) position.The anorectal angle becomes more obtuse during straining(defecation), thus allowing evacuation of the contents.5

A less commonly employed reference line for evaluation ofpelvic floor dysfunction is the mid pubic line (MPL)1 (1)(Fig. 8). This line corresponds to the level of the vaginal hymen(landmark for physical examination) and is drawn caudally,bisecting the long axis of the pubic symphysis. The points ofreference of the 3 compartments are the same as mentionedearlier (1). Perpendicular lines drawn from the reference pointsto the MPL portray the degree of pelvic organ descent orprolapse (Fig. 8). A total of 5 stages from “0” to “4” have beendescribed. A measurement of greater than or equal to 3 cmabove the MPL is stage 0. Distance between 1 and 3 cm abovethe MPL is stage 1, less than or equal to 1 cm above or belowtheMPL is stage 2, greater than 1 cm below theMPL is stage 3,and complete organ eversion is stage 4.1,8

Normal Appearance of the PelvicFloorMinimal descent of the pelvic organs is demonstrated inhealthy women. The bladder neck, cervix (vaginal apex), andanorectal junction all remain at or above the PCL. During


Figure 6 Sagittal T2-weighted image through the midline demonstrat-ing the normal lines for evaluating the pelvic floor. Solid long whiteline—pubococcygeal line (PCL) extending from the inferiormargin ofthe pubic symphysis to the last coccygeal joint, dashed white line—Hline extending from the inferior margin of the pubic symphysis to theanorectal junction, solid short white line – M line is a perpendiculardrawn from the PCL to the anorectal junction. U, uterus; R, rectum;A, anus; B, urinary bladder.

Figure 8 Sagittal T2 HASTE MR image through the midline pelvis atrest shows mid pubic line (solid white line) that bisects the pubicsymphysis. Dotted white lines represent perpendicular lines drawnfrom the anterior (posterior- and inferior-most aspect of the base of theurinary bladder), middle (most anterior and inferior aspect of thecervix), and posterior (posterior aspect of the anorectal junction)reference points. B, urinary bladder; U, uterus; R, rectum; A, anus;MR, magnetic resonance.


increased intrapelvic pressure, for example while straining, theurethra should maintain its normal vertical orientation to thebladder base. The H line should measure 5 cm or less, and theM line measures 2 cm or less in normal women. Anorectalangle measures 901-1101 during the neutral phase andbecomes acute during squeezing and more obtuse during thestraining phase. On high-resolution axial T2 images, the entirelevator sling is of uniform thickness and homogenous lowsignal intensity. Artifactual thinning of the puborectalis musclemay be encountered on either side owing to chemical shiftartifact and based on the direction of the frequency encodinggradient (Fig. 9). On coronal T2 image, the iliococcygeus isconvex in an upward direction (Fig. 10). In older women, thelevator ani muscle may appear thin; however, no tears should

A B

Figure 7 (A) Line diagram demonstrating normal orientation ofanorectal angle (green angle) that ranges between 901 and 1101than 901 during squeezing as indicated above. (C) In strainievacuation of the rectal contents. (Color version of figure is ava


be identified. The vagina should have a normal “H” or“butterfly” shaped configuration with close apposition of thelateral vaginal walls to the puborectalis (Fig. 11). This can bedistorted in women who have undergone multiple surgeries.

Pelvic Floor PathologyAnterior CompartmentCystocele, cystourethrocele, and urethral hypermobility.

CystoceleThe most common presenting symptom of cystocele is stressincontinence. Cystocele is defined as greater than 1 cmdescent

C

the rectum at rest (in neutral position) and thus normal. (B) The anorectal angle becomes more acute, that is lessng phase, the anorectal angle becomes obtuse allowingilable online.)


Figure 9 Axial T1-weighted MR image through the perineum demon-strates thinning of the right aspect of the puborectalis compared to theleft side owing to chemical shift artifact. R, rectum; curved whitearrows, puborectalis sling around the rectum.MR,magnetic resonance.

Figure 11 Axial T2-weighted fat-saturatedMR image shows normal “H”or “butterfly” shaped vagina (solid arrow). MR, magnetic resonance.


of the bladder neck (base of the urinary bladder) below thePCL. When the descent of the bladder base below the PCL isless than 3 cm the cystocele is termed mild, while 3-6 cm istermed moderate, and greater than 6 cm is severe (Fig. 12).This abnormality is secondary to stretching or tearing of thepubocervical fascia and is usually seen in postmenopausalwomen with low estrogen levels.5 In large cystoceles, thebladder base occupies the majority of the levator hiatusresulting in posterior and inferior displacement of the uterusand anorectal junction. This eventually results in elongation ofthe H andM lines to greater than 5 cm and 2 cm, respectively.Another consequence of a large cystocele is bowing of theanterior vaginal wall, which can ultimately lead to eversion ofthe vaginal mucosa.5

Treatment. Retropubic urethropexy is the surgery of choicefor repair of cystoceles, of which Burch and Marshall-Marchetti-Krantz are the 2 main types. These surgeries can

Figure 10 Coronal T1-weighted image through thepelvis demonstratesnormal upward convexity of bilateral iliococcygeus muscles (curvedwhite arrows).


be performed via open or laparoscopic transabdominalapproach. In Burch procedure, the periurethral tissue issuspended from the iliopectineal (Cooper 's) ligament withsutures, thus lifting the urethra. In Marshall-Marchetti-Krantzprocedure, similar results are produced by suspending theperiurethral tissue from the periosteum of the pubic bone(Fig. 13).

Urethral HypermobilityIn healthywomen, the urethramaintains vertical orientation inthe event of increase in intra-abdominal pressure duringstraining, coughing, sneezing, etc (Fig. 14A). However, inwomen with loss of urethral sphincter and fascial support(mainly from distortion of periurethral and paraurethralligaments), there is anterior and superior rotation of theurethral axis into horizontal direction, described as urethral

Figure 12 Sagittal T2-weighted image through the midline pelvisduring straining phase demonstrates a large cystocele (dotted line).U, urethra; B, urinary bladder; solid line, pubococcygeal line.


A B

Figure 13 Line diagram demonstrating the 2 surgical procedures for treating cystoceles. Burch procedure (A), where thePVC sling (green) courses posterior to themid urethra and suspends it to the iliopectineal ligament on both sides.Marshall-Marchett-Krantz (B) procedure,where the PVC sling (green) is sutureddirectly to the pubic bone instead of the iliopectinealligament. PB, pubic bone; B, urinary bladder; U, uterus. (Color version of figure is available online.)


hypermobility (Fig. 14B). Consequently, the urethra is kinkedwith loss of intrinsic urethral sphincter integrity. This canmasksymptoms of stress incontinence and paradoxically causeurinary retention. The most common causative factors con-tributing to urethral hypermobility include aging, vaginaldelivery, pregnancy, and obesity.

Treatment. Diagnosis of urethral hypermobility withdynamic pelvic floor MRI is essential to determine surgicalapproach, as pubocervical (pubovaginal) sling is necessary foradequate repair of this abnormality.5,9

Middle CompartmentUterine or vaginal vault prolapse is the single most importantmiddle-compartment pathology.

B

V

A B

Figure 14 Sagittal T2-weightedMR image through themidline pe(solid white arrow). V, vagina; B, urinary bladder. (B) Sagittal T2in the straining phase shows horizontal orientation of the urethrathere is descent of the urinary bladder below the PCL (dotted wV, vagina; R, rectum; PCL, pubococcygeal line.


Uterine or Vaginal Vault ProlapseThe uterus, cervix, and vagina have circumferential supports.The parametrium andparacolpium suspend the uterus and thevagina, respectively, from the presacral fascia. Laterally, thepubocervical fascia anchors the vagina to the pelvic sidewall,and posteriorly the rectovaginal fascia attaches the posteriorportion of the vagina to the perineal body. Uterine or vaginalvault prolapse is measured perpendicularly from the PCL tothe anteroinferior portion of the cervix. In patients who haveundergone hysterectomy, posterosuperior vaginal apex repla-ces the cervix as the point of reference. Grading of the severityof prolapse is similar to cystocele (o3 cm, mild; 3-6 cm,moderate; and46 cm, severe) (Fig. 15). In cases of completeuterine prolapse or procidentia, the vaginal walls are everted,and the uterus is visible as a bulging mass outside the externalgenitalia. The H and M lines are elongated suggesting levator

lvis demonstrates normal vertical orientation of the urethra-weightedMR Image through the midline pelvis obtainedwhich is described as urethral hypermobility. In addition,hite line) termed cystocele. B, urinary bladder; U, urethra;


Figure 16 Sagittal MRI HASTE image showing descent of the pouch ofDouglas with peritoneal fat (curved white arrow). This is termedperitoneocele and is secondary to a defect in the rectovaginal fascia.B, urinary bladder; R, rectum.

B

U

B

U

A B

Figure 15 (A) Sagittalmidline T2-weightedMR image at rest shows normal position of the pelvic organs above the PCL. Alsonote normal convex orientation of the vaginal wall. (B) On straining, there is a cystocele (solid white arrow) in conjunctionwith descent of the cervix below the PCL (solid short white line). The dotted white line indicates bowing of the anteriorvaginal wall due to mass effect from the cystocele. B, urinary bladder; U, uterus; PCL, pubococcygeal line.


hiatus widening and levator plate descent, respectively. Thevagina loses its normal “H” shaped configuration on axialimages and vertical oblique orientation on sagittal images. Inextreme cases, the puborectalismusclemay be avulsed from itsinsertion on the pubic ramus. On coronal magnetic resonanceimage, the iliococcygeus muscle is flat or convex in a down-ward direction.

Treatment. Uterine or vaginal vault prolapse are corrected byuterosacral suspension. Sacral colpopexy with mesh repair ischosen for severe cases.7

PeritoneoceleThe pouch of Douglas (rectovaginal pouch) is a normalextension of the peritoneum between the middle and theposterior compartments of the pelvis. If this peritoneal sacprojects beyond the proximal (apical) one-third of the vagina,separating the vagina from the rectum, it is described asperitoneocele (if it only contains peritoneal fat) or enterocele(if it contains small bowel loops in addition to peritoneal fat), orsigmoidocele (contains a portion of the sigmoid colon)(Fig. 16). These defects can be collectively termed “cul-de-sachernia.” Simple cul-de-sac defects have no associated vaginalvault prolapse. In contrast, complex defects occur in con-junction with anterior or posterior vaginal vault prolapse.Weakening of the supporting ligaments, rectovaginal fascia,and iliococcygeusmuscle are the causative factors, and patientswho have undergone hysterectomy are at increased risk.Clinical manifestations include dyspareunia and vaginal pres-sure due to bulging into the posterior vaginal wall as well as


incomplete evacuation and obstructed defecation secondary tomass effect on the rectum. On dynamic MRI, peritoneocelemanifests at the end of the evacuation phase after emptying ofthe bladder and rectum.

Treatment. The treatment of choice is culdoplasty, which isdescribed as obliteration of the cul-de-sac with sutures. Thiscan be performed at the time of hysterectomy to preventperitoneoceles. Presence of an enterocele precludestransvaginal surgical approach.



Posterior CompartmentRectocele, intussusception, and rectal prolapse are the 3common posterior compartment abnormalities.

Figure 18 Sagittal T2-weighted MR image during straining demon-strates in-folding of the anterior wall of the rectum into the anal canal(short solid white arrow), consistent with full-thickness intra-analintussusception. Once this extends beyond the anal canal, it is termedrectal prolapse.

RectoceleRectocele is defined as outpouching of the rectal wall beyondits normal confines. Anterior rectocele is common and ismeasured as the depth of wall protrusion beyond the expectedmargin of the normal anorectal wall (Fig. 17). Small rectocelemeasures less than 2 cm, while moderate is 2-4 cm, and severeis 4 cm or more. Anterior rectoceles of less than or equal to3 cm are commonly seen, and these are considered clinicallysignificant only when symptoms develop. Posterior rectocelesare rare and when seen the same fundamentals apply. Ananterior rectocele is due to a defect in the rectovaginal fascia,while a less-common posterior rectocele is due to a defect inthe anococcygeal ligament. Clinically, patients with anteriorrectocele present with vaginal pressure due to bulging into theposterior vaginal wall or incomplete emptying due to trappedrectal contents in the rectocele that ultimately leads toobstructed defecation. Such patients often report a need fordigital assistance for defecation. Rectoceles are coexistent withother compartment abnormalities, and therefore easily missedwith physical examination alone. Dynamic pelvic floor MRIenables visualization of subtle rectoceles in association withother pelvic floor abnormalities. Many patients are unable toevacuate rectal contrast on dynamic MRI as the entire contrastgets entrapped into the rectocele. These patients reportsymptoms of incomplete evacuation, hence confirming thediagnosis.

Figure 17 Sagittal T2-weighted MR image in straining phase demon-strates levator hiatus widening and descent of the levator platesuggested by increased measurements of the H (8 cm—dashed whiteline) and M (6 cm—dotted white line) lines, respectively. Outpouch-ing of the anterior rectal wall is denoted by the short solid line, and thisis termed “anterior rectocele.” B, urinary bladder; U, uterus; R, rectum;PCL, pubococcygeal line. MR, magnetic resonance.


Treatment. Surgical repair involves repair of the rectovaginalfascia or posterior fixation of the rectumwith possible sigmoidor rectal resection.9

Rectal Intussussception and ProlapseRectal intussusception and prolapse represent a continuum ofposterior compartment abnormalities. Rectal intussusceptionis characterized by invagination of the rectal wall into the rectallumen anteriorly, posteriorly, or circumferentially. Low-gradeintussusception is defined as in-folding of the rectal mucosaalone, whereas high-grade intussusception is full-thicknessinvagination of the rectal wall (mucosa and muscularis)(Fig. 18). Rectal intussusceptions are further classified asintrarectal (if they remain in the rectum) or intra-anal (whenthey extend into the anal canal). Full-thickness rectal wallinvagination projecting beyond the anal sphincter (extra-analintussusception) is termed “rectal prolapse.” Low-grade intus-susception can be an incidental finding in asymptomaticpatients. Patientswith high-grade intussusception in intrarectal

Figure 19 Line diagram shows the rectum (R) being suspended to thesacrum (yellow) using a mesh (green). This procedure is calledrectopexy. (Color version of figure is available online.)


B R

A B

Figure 20 (A) Sagittal T2-weightedMR image at rest demonstrates a normal anorectal angle of 103.81. (B) Sagittal T2HASTEMR image during straining showsmore acute anorectal angle of 71.81. This is due to failure of relaxation of the puborectalismuscle. There is resultant anterior rectocele (solid white arrow). MR, magnetic resonance.


or intra-anal location develop symptoms of incomplete defe-cation due to outlet obstruction. Common symptoms of rectalprolapse include ulceration and bleeding in addition toincomplete evacuation. The main advantage of pelvic floorMRI is its high soft resolution, which distinguishes mucosalfrom full-thickness intussusception. This information is criticalfor surgical planning.10

Treatment. Simple mucosal prolapse is treated with transanalexcision of the prolapsing mucosa, whereas full-thicknessrectal invagination requires rectopexy. In rectopexy, therectum is mobilized and fixated either to the iliopectinealligament (Cooper 's ligament) anteriorly or to the sacrumposteriorly (Fig. 19). A mesh can be used variably foradditional support and to prevent recurrence. In resectionrectopexy procedure, portion of the sigmoid colon is resectedand colorectal anastomosis is performed in addition torectopexy.11-13

Figure 21 Sagittal T2-weighted MR image obtained at rest demon-strates widening of the levator hiatus (elongation of the H line) anddescent of the levator plate (elongation of the M line). This conditionof generalized pelvic floor weakness at rest is described as “descendingperineal syndrome.” B, urinary bladder; PCL, pubococcygeal line.MR,magnetic resonance.

Spastic Pelvic Floor SyndromeSpastic pelvic floor syndrome is also called anismus or solitaryrectal ulcer syndrome. It is a result of paradoxical contractionand failure of relaxation of the puborectalis muscle duringdefecation. Patients suffer from incomplete evacuation andobstructed defecation. The etiology of this condition is unclearand can include both abnormal muscle activity and psycho-logical or cognitive factors. Lack of descent of the pelvic floorduring defecation (straining phase), prominent puborectalisimpression, and failure of the anorectal angle to open (becomemore obtuse) during defecation are suggestive of this diagnosison dynamic MRI (Fig. 20). There is resultant prolonged andincomplete evacuation of the rectal gel and a long intervalbetween opening of the anal canal and start of defecation.Anterior rectocele is frequently associated with spastic pelvicfloor syndrome. The puborectalis muscle may also appearhypertrophied.


Treatment. The mainstay of treatment is biofeedback andnonsurgical.

Descending Perineal SyndromeGeneralized pelvic floor muscular weakness with resultantexcessive descent of the pelvic contents (typically all 3compartments) at rest or during evacuation is termed“descending perineal syndrome” (Fig. 21).1 The level of theanorectal junction at rest is a global indicator of the musculartone and elasticity of the pelvic floor. On resting MRI, therectum is located at an inferior position compared to normal,and the level of the anorectal junction is below the PCL, whichis highly suggestive of this diagnosis. Decreased rising of the



rectum during maximum contraction is an additional featurethat can be seen in this condition. The syndrome is initiallycharacterized by constipation and perineal pain, but over timefecal and urinary incontinence dominate the clinical picture.

Treatment. Conservative management with physiotherapyand biofeedback has been reported to be effective.

LimitationsDrawbacks of dynamic pelvic floor MRI include (1) incon-venience from rectal contrast injection, (2) embarrassmentand discomfort owing to performance of maneuvers in non-physiological position (supine rather than sitting), and (3)claustrophobia. The quality of the study is highly patientdependent, and without adequate patient participation it canunderestimate the degree of abnormality andmight be entirelynondiagnostic.

ConclusionIn summary, magnetic resonance defecography (dynamicpelvic floor imaging) has emerged as a robust tool forappropriate and accurate preoperative evaluation of pelvicfloor dysfunction. It serves as a one stop shop for detection ofsingle- or multicompartmental pelvic floor abnormalities andthus reduces the risk of unnecessary surgeries, surgical failure,and recurrence of symptoms.


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