Pelvic Floor Disorders: Surgical Approach

4. Imaging of Pelvic Floor Disorders

Valeria Fiaschetti, Valentina Funel  and Giovanni Simonetti

(1)

Department of Diagnostic and Molecular Imaging, Interventional Radiology and Radiation Therapy, Tor Vergata University, Rome, Italy

Valentina Funel

Email: valefunel@hotmail.it

Abstract

Evacuation disorders, frequently found in elderly patients, are often caused by morphologic and functional abnormalities that are unlikely to be identified with static imaging techniques. The most common indications for “functional” imaging are constipation, incomplete evacuation or incontinence (often associated with rectal bleeding), mucous discharge, and perineal pain or discomfort [1].

4.1 Introduction

Evacuation disorders, frequently found in elderly patients, are often caused by morphologic and functional abnormalities that are unlikely to be identified with static imaging techniques. The most common indications for “functional” imaging are constipation, incomplete evacuation or incontinence (often associated with rectal bleeding), mucous discharge, and perineal pain or discomfort [1].

Conventional defecography (CD) represents the gold standard examination for the identification and staging of morphological and functional disorders of the recto-anal region and pelvic floor in evacuation dysfunctions. Defecography evaluates in real time the morphology of rectum and anal canal in correlation with pelvic bone components both statically and dynamically, and it has assumed an important role in the diagnosis and management of these disorders [2].

Due to the recognition of the association of defecatory disorders with pelvic organ prolapse in women, the need to evaluate the pelvic floor as a unit has arisen. To meet this need, defecography has been extended to include not only evaluation of defecation disorders but also the rest of the pelvic floor by opacifying the small bowel, vagina, and the urinary bladder. The term dynamic cystocolpoenteroproctography (DCP) has been appropriately applied to this examination. Colpocystodefecography (CCD) combines vaginal opacification, voiding cystography, and defecography. Rectal emptying performed with DCP provides the maximum stress to the pelvic floor resulting in complete levator ani relaxation.

In addition to diagnosing defecatory disorders, this method of examination demonstrates maximum pelvic organ descent and provides organ-specific quantification of organ prolapse, information that is only inferred by means of physical examination. It has been found to be of clinical value in patients with defecation disorders and the diagnosis of associated prolapse in other compartments, which are frequently unrecognized by taking history and because of the limitations of physical examination. The technique is also important for follow-up of patients who have undergone surgery of the pelvic region.

Other imaging techniques, such as anal manometry and electromyography, provide complementary functional information. Recently, magnetic resonance defecography (MRD) has been of increasing interest because of its accuracy in morphologic and functional assessment, as well as avoiding radiation exposure for the patient. Open-configuration magnetic resonance (MR) systems are required to perform the study with the patient sitting (providing natural conditions). Unfortunately, open-configuration MR systems are expensive and scarce. However, defecography can be performed in any hospital with a fluoroscopic room; a relatively short training time is required for the radiologist [3].

Fluoroscopic CCD has been proven to be better than physical examination in the detection and characterization of functional abnormalities of the anorectum and surrounding pelvic structures. Similarly MRD, performed either with an open-configuration or with a closed-configuration unit, appears to be an accurate imaging technique to assess clinically relevant pelvic floor abnormalities. Moreover, MRD negates the need to expose the patient to harmful ionizing radiation and allows excellent depiction of the surrounding soft tissues and support structures of the pelvic organs [4].

4.2 Cystocolpoenteroproctography Technique

4.2.1 Preparation

The patient fasts, beginning the evening before the procedure, and performs a rectal cleaning enema at home a few hours before going to the hospital. In the hospital, the patient receives 400 ml of an oral barium solution to obtain opacification of the pelvic loops of the small bowel at the time of examination (about 45 min later). It is important to obtain a complete clinical history of the patient. Defecography can be an embarrassing experience for the patient, and the radiologist must provide a clear explanation of the procedure in order to obtain complete collaboration.

4.2.2 Procedure

At the beginning of examination the patient is positioned on the left side, and about 300 mL of thick barium paste is injected into the rectum by means of a plastic syringe. When the subject reaches the stimulus to evacuate, the anal bulb is completely filled and injection can be interrupted. Barium paste is obtained by using barium sulfate powder for rectal use (enema) mixed with warm water or by mixing equal proportions of potato starch and barium solution with water. In both cases it is important that the barium paste has the consistency of normal stool or be a little more fluid to permit ease of injection into the rectum. These characteristics avoid the alteration of the diagnostic results.

Finally, in female patients, the vagina is opacified with either a commercially available barium sulfate paste for oral use or an echographic gel mixed with iodinated contrast medium. The opacification of the bladder is obtained with diluted uroangiographic contrast medium introduced by means of a bladder catheter that is removed immediately after filling.

The patient is seated on a radiolucent commode, which is upright on the end of a vertically oriented X-ray table. Deliberate efforts are made to ensure privacy. The patient is then asked to sit on the commode in right lateral projection. The examination is performed by filming the 3dynamics of defecation and urination step by step with short radioscopic sequences (1–3 images per second) and radiographs, the latter taken at rest, during squeezing and Valsalva effort. The patient must be instructed to empty the rectum and the bladder completely and without interruption: this process takes less than 30 s in physiologic conditions [2].

4.2.3 Parameters

The image analysis is aimed at the evaluation of the morphology of the pelvic organs and their position relative to the pelvic floor during the various dynamic phases.

The anorectal angle (ARA) represents the activity of the puborectalis muscle. Fibers of the puborectal muscle insert into the symphysis pubis and form a V-shaped sling around the posterior wall of the anorectal junction (ARJ). The ARA is measured from the longitudinal axis of the anal canal to a line along the posterior wall of the rectum or parallel to the longitudinal axis of the rectum.

At rest, the anal canal is almost completely closed, and the ARA is about 95–96° (physiological range, 65–100°), without noticeable differences between men and women. During maximal contraction, the angle becomes 15–20° sharper than at rest, while during straining and defecation it becomes 15–20° more obtuse.

The second important parameter to evaluate is the movement of the ARJ. The line drawn between the ischial tuberosities is called the bis-ischiatic line and can be used as a fixed bony landmark. Another fixed reference point is represented by the tip of the coccyx or recently by the pubococcygeal line (PCL), defining the pelvic floor base. The PCL is drawn from the inferior border of pubic symphisis to the last visible coccygeal joint.

The craniocaudal migration of the ARJ indirectly represents the elevation and descent of the pelvic floor. The reproducibility and reliability of these parameters as usually measured have been confirmed, but their clinical significance is still controversial [5].

The posterior urethrovescical angle, measured between the inferoposterior wall of the bladder and the posterior wall of the urethra, is about 90–120°. An increase may indicate incontinence.

4.2.4 Normal Findings

In the resting phase, the anal canal is almost completely closed and the impression of puborectal sling is visible on the posterior wall of caudal rectum. In this condition, the angle between the anal canal and the rectum is 95–96° (Fig. 4.1).

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Fig. 4.1

Colpocystodefecography in the resting phase. The anorectal junction, the vaginal fornices, and the bladder neck lie over the pubococcygeal line (dashed line). The anorectal angle measures 93°

During voluntary contraction of the pelvic floor, the ARA decreases to about 75°, and the ARJ migrates cranially. The puborectal impression becomes more evident because of the contraction of the levator ani, pulling the ARJ toward its insertion at the symphysis pubis.

When the patient is asked to strain, the converse is seen: the ARA increases with partial to complete loss of puborectal impression, and the pelvic floor descends. The degree of caudal migration, as measured in relation to the bony landmarks, is considered normal when it is less than 3.5 cm relative to the resting position.

During evacuation, the anal canal and the rectum migrate caudally. The ARA increases in relation to the relaxation of external and internal sphincters and puborectal muscle, respectively. Puborectalis sling impression on the rectum posterior wall disappears almost completely, and the anal canal reaches the widest diameter (it should open to a mean anteroposterior diameter of 1.5 cm).

During the late phases of evacuation, the rectal bulb funnels and its walls progressively collapse. A small amount of infolding of redundant anterior and posterior rectal walls is considered normal. The entire process lasts less than 30 s in physiologic conditions.

At the end of evacuation, the resting condition is reached when the anal sphincters close and levator ani restores its tone, pulling the ARJ cranially. The rectum is completely empty, and only minimal barium dye can be found [2].

4.3 Magnetic Resonance Defecography Technique

Pelvic floor anatomy is complex and DCP does not show the anatomical details that pelvic magnetic resonance imaging (MRI) provides. Technical advances, allowing acquisition of dynamic rapid MRI sequences, have been applied to pelvic floor imaging [6]. MRD, although still an experimental technique, may be a useful tool in preoperative planning of these disorders and may lead to a change in surgical therapy, reducing postoperative relapses especially in patients with multicompartmental disorders [79].

Concerns about the risks related to radiation, especially in women of childbearing age, and the spreading of pelvic floor MRI in addition to questions relating to the clinical significance of DCP findings have added to these controversies. Furthermore MRD allows the detection of incidental pathologic conditions, such as urethral and bladder diverticula, endometrial polyps, malignant lesions, fibroids, and adnexal lesions [1012].

A potential disadvantage of MRD is its less physiologic nature if performed with the patient in the supine position, but sitting dedicated systems have been developed [1314]. In some studies, MRD has been performed in the orthostatic position also [15].

4.3.1 Preparation

The patient performs a rectal cleaning enema at home. The MRI protocol requires no oral or intravenous contrast agents, since the small bowel is inherently delineated. In some protocols, contrast material is not used to opacify the bladder and patients are requested not to void for 1–2 h prior to their examination.

4.3.2 Technique

Protocols vary by institution, with MRI studies performed with the patient in both supine and upright positions, either with closed or open magnets. Studies have been performed without contrast material, with vaginal and rectal markers, and with rectal, vaginal, urethral, and bladder contrast material.

In the majority of cases, a 1.5 T system is used and T2-weighted turbo spin echo and balanced fast field echo sequences are acquired, with the patient in the supine position. Pelvic or torso phased-array coils are centered low on pelvis to ensure visualization of prolapsed organs.

At the beginning of examination, the patient is positioned on the left side with flexed knees and the rectum is filled with 200 mL echographic gel; the vagina is also filled with an echographic gel suspension of 100 mL. Finally, the bladder is filled with 180 mL physiological solution via a 16 F double-way Foley catheter, which is removed soon after filling; otherwise the patient is asked not to void for 1–2 h before the examination.

With the patient at rest, static images of the entire pelvis are acquired in the axial, sagittal, and coronal planes using rapid half-Fourier T2-weighted sequences (HASTE, half-Fourier acquisition single-shot turbo spin echo) (recommended parameters: TR 3,000 ms; TE 90 ms; flip angle 90°; slice thickness 5 mm; FOV 250 × 250, matrix 448 × 345).

After the midline between the pubic symphysis and the coccyx is localized, dynamic images are acquired with a balanced sequence in the sagittal plane; a single stack of images is acquired continuously at rest, and during maximal contraction, straining, and defecation (recommended parameters: TR 2.7 ms; TE 1.35 ms; flip angle 45°; slice thickness 10 mm; FOV 300 × 300, matrix 160 × 160; dynamic scan time 0.432 s, dynamic images 100).

At our institution, MRD is also performed on a permanent open magnet with changeable position and static 0.25 T field. The magnet table is provided with a tilting mechanism going from 0° to 90° and pitched at 80° to allow a semi-orthostatic acquisition [15].

A surface lumbar spine DPA coil is used as the receiving coil, composed of a stiff base and a flexible anterior band with variable dimensions.

Before the examination, the rectum is filled with 200 mL mashed potato mixed with 1 mL paramagnetic contrast medium. The bladder is also filled with 180 mL physiological solution mixed with 3 mL contrast medium via a catheter, left in place during the entire study. Finally vagina is filled with an echographic gel suspension mixed with 0.5 mL paramagnetic contrast medium.

The three orthogonal image planes are acquired at rest using three-dimensional HYCE (hybrid contrast enhanced), a type of gradient echo (GE) balanced sequence (TR 10 ms; TE 5 ms; flip angle 90°; sections 20; section thickness 2.5 mm; FOV 280 × 280, matrix 200 ×160).

Static images are acquired in the sagittal plane at rest, during sphincter contraction and straining using a GE T1-weighted sequence (TR 35 ms; TE 10 ms; flip angle 90°; section 1; section thickness 5.5 mm; FOV 300 × 300, matrix 192×128).

Finally, the dynamic phase is performed during defecation using a GE T1-weighted sequence in the midsagittal plane (TR 30 ms; TE 6 ms; flip angle 90°; section 1; section thickness 5.5 mm; FOV 300 × 300, matrix 192×128; acquisition time 3 s/image).

The urinary study is performed after removing the bladder catheter.

4.3.3 Parameters

The interpretation of the images should begin in the sagittal plane by drawing the PCL, defining pelvic floor base, extending from the inferior border of pubic symphysis to the last visible coccygeal joint [13]. The distance between the PCL and the lowest recognizable part of pelvic organs (the bladder neck, vaginal fornices, and ARJ) should be measured at rest, during maximal sphyncterial contraction, and during straining and evacuation (Fig. 4.2).

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Fig. 4.2

Magnetic resonance defecography performed on a 1.5 T magnet. T2-weighted turbo spin echo sequence acquired at rest in the sagittal plane. The anorectal junction, the vaginal fornices, and the bladder neck are located above the pubococcygeal line (dashed line). The anorectal angle measures 90°

Two other lines should be measured according to the HMO system: the H line, which represents the anteroposterior width of the levator hiatus and is drawn from the inferior aspect of the pubic symphysis to the ARJ; the M line, representing the vertical descent of the levator hiatus and is drawn perpendicular from the PCL to the ARJ; and the O component, which represents the organ prolapse [8].

The ARA and the posterior urethrovescical angle are measured similarly to conventional defecography examinations.

On the axial and coronal images, the puborectal and iliococcygeal muscles should be examined for thinning and tears. The pelvic sling appears relatively symmetric and is hypointense on T2-weighted images. Paravaginal fascial tears can be inferred from posterior displacement of the vaginal fornix. Lateral pubovesical ligaments can also be seen.

4.3.4 Normal Findings

In the upright position, the support to pelvic organs is primarily provided by the bony pelvis, while the pelvic floor muscles and the endopelvic fascia counteract intermittent increases in abdominal pressure. On axial images, the entire the levator ani should be of similar thickness and homogeneous low signal intensity. No tears should be identified. On coronal images, the iliococcygeal muscle should be intact and upwardly convex.

On axial images, the urethral cuff is located anteriorly with a bull’s eye configuration; the vagina should have an H-shaped configuration, which indicates adequate lateral fascial support; the perineum is a diamond-shape structure, with the anorectum lying behind the transverse perineum (Fig. 4.3).

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Fig. 4.3

Magnetic resonance defecography performed on a 1.5 T magnet. T2-weighted turbo spin echo sequence acquired at rest in the axial plane. The pelvic sling appears symmetric and hypointense

In healthy, continent patients, even with maximal downward pelvic strain, MR images demonstrate minimal descent of the pelvic organs (M line < 2 cm).

The ARA and the posterior urethrovescical angle can be measured in the saggital plane; normal values are similar to those cited for conventional defecography (see Section 4.2.4).

4.4 Pathological Findings

4.4.1 Intussusception and Rectal Prolapse

Rectal prolapse can be categorized as intrarectal, rectoanal, or external, depending on extension inside the viscus; and as simple or complete, depending on the involved wall layers.

The pathological condition called simple prolapse or procidentia occurs when the mucosal layer protrudes into the lumen. Complete prolapse or intussusception can be observed when all layers of the wall are involved and there is an invagination of the rectal wall into the rectal lumen or the anal canal.

Clinical manifestations frequently associated with rectal prolapse are outlet obstruction and persistent desire to defecate by blocking the rectal ampulla during evacuation, tenesmus, hematochezia, and incontinence. Symptoms are caused by the obstructive effect of the prolapsed wall on the propulsion of rectal contents and on sphincter irritation or weakness. This condition is frequently found in association with solitary ulcer syndrome [16].

4.4.1.1 Conventional Defecography

At the end of defecation, small infoldings of less than 3 mm thickness can be frequently observed without any clinical significance. Larger protrusions have also been observed in asymptomatic patients. Intussusception usually originates 6–8 cm above the anal canal at the level of the main rectal fold and can be either anterior, circumferential, or posterior in location.

Simple intrarectal prolapse is identified as a wall protrusion inside the rectal lumen more evident during straining and evacuation. Mucosal protrusions are almost exclusively found on the anterior rectal wall with a thickness less than 1 cm because of their simple mucosal composition.

In complete prolapse, all layers of the wall are involved. Dilation of the anal canal is evident during evacuation, and a circular infolding of the rectal wall invaginates into the lumen (Fig. 4.4). Descent can be so dramatic as to pass through the anus and prolapse externally, with associated incontinence.

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Fig. 4.4

Conventional proctography in the voiding phase. Circular infoldings of the rectal wall (arrows) can be seen in the middle part of the rectum. In addition, moderate anterior and posterior rectoceles are present

The intussuscepting rectum pulls down the anterior peritoneal covering and can determine an enterocele, meaning a deep pouch anterior to the rectum that contains small bowel.

Evacuation can be blocked by the intrarectal prolapsed wall, which creates a plug obstructing the stool transit, causing barium paste to stagnate inside the viscus.

4.4.1.2 Magnetic Resonance Defecography

Intussusceptions can be difficult to detect on MRI: the sensitivity has been reported to be 70% relative to CD. However the soft tissue resolution may allow better differentiation between simple and complete prolapse. Diagnostic criteria are similar to CD.

An invagination of the rectal wall can be seen on the midsagittal plane (Fig. 4.5) as well as on the transaxial plane (“target sign”).

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Fig. 4.5

Magnetic resonance defecography performed on a 1.5 T magnet. T2-weighted balanced fast field echo sequence acquired in the voiding phase. A complete internal rectal prolapse is visible (arrow), involving all the layers of the wall

Depending on the location, the intussusception is classified as intra-rectal (grade I), intra-anal (grade II), or external rectal prolapse (grade III).

4.4.2 Descending Perineum Syndrome

This syndrome represents a condition of pelvic floor muscle hypotonia and presents with difficult evacuation, incomplete emptying of the rectum, and/or incontinence. This condition is usually found in elderly women; risk factors are chronic constipation, neurologic dysfunction, perineal trauma, multiparity, and surgical procedures.

Abnormalities of the perineal body and levator ani musculature cause perineal descent, which is quantified by measuring the descent of the ARJ (the M line). Descent of the perineal body is measured by the width of the levator hiatus (the H line).

Caudal migration of the ARJ indirectly represents the perineal descent because this is caused by increased intra-abdominal pressure during straining associated with relaxation of the puborectalis and pelvic muscles. In this pathological condition, muscles of the perineum are hypotonic and overwhelmed by the caudal migration of abdominal organs, so that the descent of ARJ is abnormally pronounced.

This repeated stretching of pelvic floor chronically causes damage to the nervous structures, most notably the pudendal nerve, and determines dysfunction of continence and pain. Incontinence is frequently associated with this syndrome. If this process is chronic, a vicious cycle is established in which intense and prolonged strain is necessary to evacuate, leading to further stretching and weakening of the pelvic muscles. Descending perineum syndrome can be conservatively treated by means of suppositories to reduce straining during evacuation.

4.4.2.1 Conventional Defecography

The main radiographic feature is the caudal migration of the more than 3.5 cm during straining. The degree of descent is calculated from the resting position to the most caudal position during straining or evacuation in relation to the bony landmark. Similarly, the ARA is more than 130° at rest and increases to more than 155° during straining.

Recently, the PCL has become the main bony landmark and rectal descent is calculated perpendicular from that line to the ARJ. In normal conditions, the ARJ lies within 1 cm of the PCL. The rectal prolapse is considered mild if the ARJ lies between 1 and 3 cm under the PCL, moderate if it lies between 3 and 6 cm under the PCL, and severe if the ARJ descends more than 6 cm under the PCL (Fig. 4.6).

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Fig. 4.6

Colpocystodefecography during straining. A caudal migration of the bladder, the vagina, and the rectum can be appreciated as a descent of bladder neck, vaginal fornices, and anorectal junction below the pubococcygeal line (dashed line). The anorectal angle measures 137°

4.4.2.2 Magnetic Resonance Defecography

The descent of the ARJ is measured as in CD, and the ARA is also measured (Fig. 4.7).

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Fig. 4.7

Magnetic resonance defecography performed on a 1.5 T magnet. T2-weighted balanced fast field echo sequence acquired in the voiding phase. The bladder neck and the anorectal junction are located below the pubococcygeal line (dashed line). The anorectal angle measures 143°. A moderate anterior rectocele is also present

The MRI can provide additional information about the components of the levator ani muscle, i.e., the iliococcygeus muscle and the puborectalis muscle (Fig. 4.8). The normal thickness ranges from 3 mm (iliococcygeus) to 5–6 mm (puborectalis); little asymmetry is considered normal. In the absence of prolapse, the levator plate parallels the PCL.

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Fig. 4.8

Magnetic resonance defecography performed on a 1.5 T magnet. T2-weighted turbo spin echo sequence acquired at rest in the axial plane. The pelvic sling appears enlarged and it shows heterogeneous signal intensity

4.4.3 Multicompartmental Syndrome

Classification of pelvic floor abnormalities has been topographic but distinctions are artificial in most cases. In fact abnormalities of the levator sling can determine defects in one or more compartment and they affect one other.

Evaluation of patients with pelvic floor complaints begins with a thorough history and physical examination, but the degree and the presence of pelvic organ defects are not always apparent on clinical examination.

A cystocele can be present, as a well as a vaginal vault prolapse or descending perineum syndrome. If two or three of these defects are associated, it is a case of bicompartmental or tricompartmental syndrome.

4.4.3.1 Conventional Defecography and Magnetic Resonance Defecography

Descent of pelvic organs is evaluated as described for descending perineum syndrome.

A comprehensive evaluation is considered essential in the preoperative setting in order to establish correct surgical planning and to avoid relapses due to unrecognized defects. MRI has the advantage of being able to evaluate all the compartments simultaneously, and it is achieving a primary role in the assessment of patients with pelvic floor weakness.

4.4.4 Rectocele

Rectocele is the most common cause of obstructed evacuation treated by surgery. It consists of an anterior bulge of the rectal wall. This condition is most commonly found in females because of laxity of the rectovaginal septum (congenital or caused by obstetric traumas or surgical procedures).

Pouches smaller than 2 cm are frequently found in asymptomatic females; these protrusions have no clinical significance and are not considered pathological. Pouches larger than 2 cm are significantly associated with evacuation disorders.

Excessive straining may also cause posterior bulges of the rectum because of hernias of the levator ani on posterolateral pelvic floor. Clinical manifestations are caused by incomplete emptying of the rectum; some patients apply digital rectal or vaginal maneuvers to complete evacuation.

4.4.4.1 Conventional Defecography

On defecography, an outpouching of the anterior or posterior rectal wall bulges and dislocates the opacified vaginal lumen during straining and evacuation. It is evaluated drawing a line parallel to the anterior or posterior wall of the anal canal and measuring the distance between this line and the widest point of the bulging.

There are three degrees of rectocele: a mild degree is < 2 cm in anteroposterior diameter (not clinically significant); a moderate degree is between 2 and 4 cm; and a severe degree is > 4 cm. A certain amount of radiopaque paste can be retained inside the pouch and persist at the end of defecation.

4.4.4.2 Magnetic Resonance Defecography

The measurement of the rectocele is obtained as described for CD (Fig. 4.9).

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Fig. 4.9

Magnetic resonance defecography performed on a 1.5 T magnet. T2-weighted balanced fast field echo sequence acquired in the voiding phase. A severe anterior rectocele is present (arrow)

4.4.5 Dyskinetic Puborectalis Muscle Syndrome

Also known as spastic pelvic floor syndrome or anismus, this condition is caused by inappropriate contraction of the puborectalis muscle during evacuation instead of physiologic relaxation. Most cases are idiopathic, although focal pathological alterations such as fistulas, solitary ulcers, and thrombotic hemorrhoids can be associated with this syndrome. The etiology is unclear and includes abnormal muscle activity and physiological or cognitive factors.

Patients experience evacuation failure associated with incomplete emptying; evacuation time longer than 30 s is highly predictive of dyskinetic puborectalis muscle syndrome.

4.4.5.1 Conventional Defecography and Magnetic Resonance Defecography

This syndrome is characterized by a lack of pelvic floor descent during straining and evacuation and paradoxical contraction of the levator ani: the levator plate bulges convexly when the patient is asked to strain.

Another less specific feature is an aberrantly deep impression of the puborectalis sling on the posterior rectal wall at rest; this is even more evident during squeezing. This sign is caused by the presence of a hypertrophic levator ani muscle, but its specificity is low; it can be also observed in asymptomatic subjects.

Measurement of the ARA changes shows no significant difference between symptomatic subjects and asymptomatic controls, and it is not a reliable parameter of this syndrome.

4.4.6 Enteroceles and Sigmoidoceles

Herniation of a peritoneal sac into the pouch of Douglas containing ileal loops or part of the sigmoid are respectively called enterocele and sigmoidocele. They are almost exclusively found in female subjects; pelvic surgical procedures are risk factors for this condition, especially gynecological procedures such as hysterectomy or urethropexy. Patients describe a sensation of pelvic oppression during evacuation and incomplete emptying of the rectum. These symptoms are usually not associated with obstructed defecation, and rectum emptying is complete at defecography.

Enterocele may be simple or complex, depending on the absence or presence of an associated vaginal vault prolapsed.

4.4.6.1 Conventional Defecography

Good opacification of ileal loops is essential for identification of intestinal herniation into the rectovaginal space. Descent of barium-filled ileal loops is evident during evacuation in the space between the rectum and vagina that is widened.

Widening of this space is also an indirect sign of enterocele when opacification of ileal loops is not achieved. The presence of air between the rectum and opacified vaginal lumen can confirm this suspicion. These signs are evident during straining or evacuation (increased abdominal pressure). Occasionally enterocele becomes evident only when the rectum has been completely emptied and sufficient space is left for the small bowel loops to herniate. Protrusion of herniated viscera on the anterior rectal wall frequently causes an associated rectal prolapse.

4.4.6.2 Magnetic Resonance Defecography

The main limitations of defecography are related to the conventional technique: low-contrast resolution and bidimensional imaging. MRI has been shown to be superior to CCD, which fails to demonstrate up to 20% of enteroceles.

Descent of small bowel loops or sigmoid colon more than 2 cm into the rectovaginal space indicates tearing of the rectovaginal fascia. On axial images, loops of sigmoid or small bowel can be seen insinuated between the rectum and vagina. These findings may be seen on images obtained with the patient at rest, with a larger enterocele evident during straining (Fig. 4.10).

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Fig. 4.10

Magnetic resonance defecography performed on a 0.25 T magnet. T1-weighted gradient echo sequence acquired at rest in the sagittal plane. Ileal loops are visible in the rectovaginal space (arrow)

References

1.

Nygaard I, Barber MD, Burgio KL et al (2008) Prevalence of symptomatic pelvic floor disorders in US women. JAMA 300:1311–1316PubMedCrossRef

2.

Karasick S, Karasick D, Karasick SR (1993) Functional disorders of the anus and rectum: findings on defecography. AJR Am J Roentgenol 160:777–782PubMedCrossRef

3.

Pannu HK, Scatarige JC, Eng J (2009) Comparison of supine magnetic resonance imaging with and without rectal contrast to fluoroscopic cystocolpoproctography for the diagnosis of pelvic organ prolapse. J Comput Assist Tomogr 33:125–130PubMedCrossRef

4.

Kelvin FM, Maglinte DD, Hale DS (2000) Female pelvic organ prolapse: a comparison of triphasic dynamic MR imaging and triphasic fluoroscopic cystocolpoproctography. AJR Am J Roentgenol 174:81–88PubMedCrossRef

5.

Jorge JM, Habr-Gama A (2001) Clinical applications and techniques of cinedefecography. Am J Surg 182:93–101PubMedCrossRef

6.

El Sayed RF, El Mashed S, Farag A (2008) Pelvic floor dysfunction: assessment with combined analysis of static and dynamic MR imaging findings. Radiology 248:518–530PubMedCrossRef

7.

Bove A, Ciamarra P (2007) The corner of the coloproctologist: What to ask to radiologist. Eur J Radiol 61:449–453PubMedCrossRef

8.

Boyadzhyan L, Raman SS, Raz S (2008) Role of static and dynamic MR imaging in surgical pelvic floor dysfunction. Radiographics 28:949–967PubMedCrossRef

9.

Woodfield CA, Krishnamoorthy S, Hampton BS, Brody JM (2010) Imaging pelvic floor disorders: trend toward comprehensive MRI. AJR Am J Roentgenol 194:1640–1649PubMedCrossRef

10.

Bertschinger KM, Hetzer FH, Roos JE et al (2002) Dynamic MR imaging of the pelvic floor performed with patient sitting in an open-magnet unit versus with patient supine in a closedmagnet unit. Radiology 223:501–508PubMedCrossRef

11.

Fielding JR (2002) Practical MR imaging of female pelvic floor weakness. Radiographics 22:295–304PubMedCrossRef

12.

Seynaeve R, Billiet I, Vossaert P et al (2006) MR imaging of the pelvic floor. JBR-BTR 89:182–189PubMed

13.

Roos JE, Weishaupt D, Wildermuth S et al (2002) Experience of 4 years with open MR defecography: pictorial review of anorectal anatomy and disease. Radiographics 22:817–832PubMedCrossRef

14.

Schoenenberger AW, Debatin JF, Guldenschuh I et al (1998) Dynamic MR defecography with a superconducting, open-configuration MR system. Radiology 206:641–646PubMed

15.

Fiaschetti V, Squillaci E, Pastorelli D (2011) Dynamic MR defecography with an open-configuration, low-field, tilting MR system in patients with pelvic floor disorders. Radiol Med 116:620–633PubMedCrossRef

16.

Hausammann R, Steffen T, Weishaupt D et al (2009) Rectocele and intussusception: is there any coherence in symptoms or additional pelvic floor disorders? Tech Coloproctol 13:17–25PubMedCrossRef