(Radiographics. 2002;22:817-832.)
© RSNA, 2002
Experience of 4 Years with Open MR Defecography: Pictorial Review of Anorectal Anatomy and Disease1
Justus E. Roos, MD,
Dominik Weishaupt, MD,
Simon Wildermuth, MD,
Jürgen K. Willmann, MD,
Borut Marincek, MD and
Paul R. Hilfiker, MD
1 From the Institute of Diagnostic Radiology, University Hospital Zurich, Switzerland. Recipient of a Certificate of Merit award for an education exhibit at the 2000 RSNA scientific assembly. Received November 9, 2001; revision requested December 13 and received February 27, 2002; accepted March 5. Address correspondence to P.R.H., MR Institute, Private Hospital Bethanien, Toblerstrasse 51, CH-8044 Zurich, Switzerland (e-mail: hilfiker@mri-roentgen.ch).
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Abstract
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Functional disorders of the pelvic floor are a common clinical problem. Diagnosis and treatment of these disorders, which frequently manifest with nonspecific symptoms such as constipation or incontinence, remain difficult. Fluoroscopic x-ray defecography has been shown to aid in detection of functional and morphologic abnormalities of the anorectal region. With the advent of open-configuration magnetic resonance (MR) imaging systems, MR defecography with the patient in a vertical position became possible. MR defecography permits analysis of the anorectal angle, the opening of the anal canal, the function of the puborectal muscle, and the descent of the pelvic floor during defecation. Good demonstration of the rectal wall permits visualization of intussusceptions and rectoceles. Excellent demonstration of the perirectal soft tissues allows assessment of spastic pelvic floor syndrome and descending perineum syndrome and visualization of enteroceles. MR defecography with an open-configuration magnet allows accurate assessment of anorectal morphology and function in relation to surrounding structures without exposing the patient to harmful ionizing radiation.
© RSNA, 2002
Index Terms: Defecography, 757.12143, 757.12144, 757.1288 • Rectum, 757.92 • Rectum, abnormalities, 757.159, 757.73 • Rectum, MR, 757.12143, 757.12144, 757.1288
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LEARNING OBJECTIVES
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After reading this article and taking the test, the reader will be able to:
- Describe the normal anatomy and landmarks of the pelvic floor and especially the anorectal region.
- Discuss the technique and advantages of dynamic open MR defecography.
- Identify the different pathologic conditions of the anorectal region according to the findings at open MR defecography.
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Introduction
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Disorders of anorectal function represent a common clinical problem and have a significant impact on quality of life. It is estimated that between 10% and 20% of patients seeking medical care in gastrointestinal clinics have anorectal dysfunction (1). Diagnosis remains difficult in many cases, and findings at physical examination are frequently equivocal. Patients often present with nonspecific symptoms such as constipation, incontinence, or pain. Incontinence, descensus, and organ prolapse occur in varying combinations. To arrive at a final diagnosis, an additional imaging modality is imperative. During the past decades, fluoroscopic x-ray defecography, which was described in 1952 (2), played a central role in diagnosis of functional and morphologic abnormalities of the anorectal region. Defecography provides insight into rectal function and structure. In addition, it permits assessment of the anosphincteric, puborectal, and levator muscles (3). However, the technique is limited by its projectional nature and its inability to depict the perirectal soft tissues. To overcome these limitations, some authors have proposed, besides rectal administration of a contrast material enema, the simultaneous administration of contrast agent into the urethra, bladder, vagina, small intestine, or peritoneum (4–6).
Magnetic resonance (MR) imaging is already used in the evaluation of anorectal disease. It has been shown to be capable of demonstrating congenital anomalies (7), helping stage neoplasms, as well as enabling detection of inflammatory processes (8), pelvic floor descent, rectoceles, and intussusceptions (9,10). To date, MR imaging of defecation has been hampered by the closed architecture of conventional MR systems, limiting the patient position to the horizontal plane. With the advent of open-configuration MR systems, which enable image acquisition in a vertical patient position, MR defecography with the patient in the sitting position has become possible (Fig 1) (11). Beyond the lack of ionizing radiation—fluoroscopic x-ray defecography produces a mean effective dose of up to 4.9 mSv (12,13)—multiplanar imaging capability, unsurpassed soft-tissue contrast, and reasonable temporal resolution add to the attractiveness of MR defecography.
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Figure 1a. Technical preparation and planning of dynamic MR defecography performed with a superconducting open-magnet system. (a) Photograph shows a superconducting open-configuration MR system (0.5 T), which is normally used for research and interventional purposes. (b) Photograph shows a removable wooden chair, which functions as a toilet and fits exactly into the gap between the two vertical magnets. The MR signal is transmitted and received with a flexible radio-frequency coil strapped around the pelvis. (c) Photograph obtained through the side hole of the magnet shows a volunteer in the sitting position on the wooden chair with the radio-frequency coil strapped around the pelvis. This arrangement allows a vertical (physiologic) position of the patient during imaging with the anorectal region right in the center of the image volume. (d) Axial MR image (spoiled gradient-echo sequence; repetition time msec/echo time msec = 150/7.7; 60° flip angle; bandwidth = 12.5 kHz; field of view = 30 x 30 cm; section thickness = 10 mm). Such images are used as localizers for planning MR defecography, which is performed in the midsagittal plane (white line). (e) Midsagittal 15-mm-thick multiphase T1-weighted spoiled gradient-echo MR section shows a cross section of the rectal canal.
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Figure 1b. Technical preparation and planning of dynamic MR defecography performed with a superconducting open-magnet system. (a) Photograph shows a superconducting open-configuration MR system (0.5 T), which is normally used for research and interventional purposes. (b) Photograph shows a removable wooden chair, which functions as a toilet and fits exactly into the gap between the two vertical magnets. The MR signal is transmitted and received with a flexible radio-frequency coil strapped around the pelvis. (c) Photograph obtained through the side hole of the magnet shows a volunteer in the sitting position on the wooden chair with the radio-frequency coil strapped around the pelvis. This arrangement allows a vertical (physiologic) position of the patient during imaging with the anorectal region right in the center of the image volume. (d) Axial MR image (spoiled gradient-echo sequence; repetition time msec/echo time msec = 150/7.7; 60° flip angle; bandwidth = 12.5 kHz; field of view = 30 x 30 cm; section thickness = 10 mm). Such images are used as localizers for planning MR defecography, which is performed in the midsagittal plane (white line). (e) Midsagittal 15-mm-thick multiphase T1-weighted spoiled gradient-echo MR section shows a cross section of the rectal canal.
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Figure 1c. Technical preparation and planning of dynamic MR defecography performed with a superconducting open-magnet system. (a) Photograph shows a superconducting open-configuration MR system (0.5 T), which is normally used for research and interventional purposes. (b) Photograph shows a removable wooden chair, which functions as a toilet and fits exactly into the gap between the two vertical magnets. The MR signal is transmitted and received with a flexible radio-frequency coil strapped around the pelvis. (c) Photograph obtained through the side hole of the magnet shows a volunteer in the sitting position on the wooden chair with the radio-frequency coil strapped around the pelvis. This arrangement allows a vertical (physiologic) position of the patient during imaging with the anorectal region right in the center of the image volume. (d) Axial MR image (spoiled gradient-echo sequence; repetition time msec/echo time msec = 150/7.7; 60° flip angle; bandwidth = 12.5 kHz; field of view = 30 x 30 cm; section thickness = 10 mm). Such images are used as localizers for planning MR defecography, which is performed in the midsagittal plane (white line). (e) Midsagittal 15-mm-thick multiphase T1-weighted spoiled gradient-echo MR section shows a cross section of the rectal canal.
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Figure 1d. Technical preparation and planning of dynamic MR defecography performed with a superconducting open-magnet system. (a) Photograph shows a superconducting open-configuration MR system (0.5 T), which is normally used for research and interventional purposes. (b) Photograph shows a removable wooden chair, which functions as a toilet and fits exactly into the gap between the two vertical magnets. The MR signal is transmitted and received with a flexible radio-frequency coil strapped around the pelvis. (c) Photograph obtained through the side hole of the magnet shows a volunteer in the sitting position on the wooden chair with the radio-frequency coil strapped around the pelvis. This arrangement allows a vertical (physiologic) position of the patient during imaging with the anorectal region right in the center of the image volume. (d) Axial MR image (spoiled gradient-echo sequence; repetition time msec/echo time msec = 150/7.7; 60° flip angle; bandwidth = 12.5 kHz; field of view = 30 x 30 cm; section thickness = 10 mm). Such images are used as localizers for planning MR defecography, which is performed in the midsagittal plane (white line). (e) Midsagittal 15-mm-thick multiphase T1-weighted spoiled gradient-echo MR section shows a cross section of the rectal canal.
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Figure 1e. Technical preparation and planning of dynamic MR defecography performed with a superconducting open-magnet system. (a) Photograph shows a superconducting open-configuration MR system (0.5 T), which is normally used for research and interventional purposes. (b) Photograph shows a removable wooden chair, which functions as a toilet and fits exactly into the gap between the two vertical magnets. The MR signal is transmitted and received with a flexible radio-frequency coil strapped around the pelvis. (c) Photograph obtained through the side hole of the magnet shows a volunteer in the sitting position on the wooden chair with the radio-frequency coil strapped around the pelvis. This arrangement allows a vertical (physiologic) position of the patient during imaging with the anorectal region right in the center of the image volume. (d) Axial MR image (spoiled gradient-echo sequence; repetition time msec/echo time msec = 150/7.7; 60° flip angle; bandwidth = 12.5 kHz; field of view = 30 x 30 cm; section thickness = 10 mm). Such images are used as localizers for planning MR defecography, which is performed in the midsagittal plane (white line). (e) Midsagittal 15-mm-thick multiphase T1-weighted spoiled gradient-echo MR section shows a cross section of the rectal canal.
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In the literature, a considerable variation regarding the optimal method of performing MR defecography exists. Several studies have been performed with the patient in the supine position in closed-magnet MR systems (14–17); owing to the limited availability of vertically open-configuration systems, fewer studies have been performed with the patient in the sitting position (11,18,19). The administration of contrast agent also varies, from use of no contrast agent to filling of the rectum, vagina, urethra, and bladder with contrast agent; placement of markers in the vagina or rectum; or placement of urethral catheters (14,15,20). For MR defecography, ultrasound gel or mashed potatoes doped with gadopentetate dimeglumine are frequently used for rectal filling (15,18,19,21). A similar variety among the different groups of investigators has been reported regarding the imaging plane and the maneuvers during MR imaging (11,14,21).
In this article, we describe our experience of over 4 years performing open MR defecography in a clinical setting, describe the technique of MR imaging with the patient in a sitting position, review the anatomic structures that provide rectal function, and discuss and illustrate imaging findings in patients with anorectal dysfunctions.
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Patients and MR Imaging Technique
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Use of open MR defecography as a standardized clinical examination started in August 1997 at our institution. Over 250 patients (mean age, 56 years; range, 15–90 years) have been referred for open MR defecography. Whereas most patients in 1997 were referred by staff at our hospital (surgeons, gastroenterologists), most patients currently referred for MR defecography (61%) are outpatients from other hospitals or are referred by clinicians in private practice. Eighty-six percent of the patients have been female, and 65% had undergone pelvic surgery. The clinical indications for MR defecography were constipation (33%), a feeling of incomplete evacuation (29%), pain (10%), incontinence (10%), organ prolapse (8%), and other indications (10%). In January 1998, open MR defecography completely replaced conventional fluoroscopic x-ray defecography at our institution.
MR imaging is performed with a 0.5-T superconducting, open-configuration MR system (Signa SP; GE Medical Systems, Milwaukee, Wis). A wooden chair, which fits into the open space between the two magnet rings, allows imaging in the sitting position (Fig 1). Before the subject is placed on the seat, the rectum is filled with 300 mL of a contrast agent solution, which consists of a suspending agent (mashed potatoes) doped with 1.5 mL of gadopentetate dimeglumine (377 mg/mL) (Magnevist; Schering, Berlin, Germany). With a gadolinium concentration of 2.5 mmol/L, this regimen provides sufficient T1 shortening to permit visualization of the rectal lumen on T1-weighted gradient-echo images. No other particular preparation of the patients (eg, voiding) is necessary. After contrast agent administration, the subject is placed on the seat in the upright position. A flexible transmit/receive radio-frequency coil is strapped around the pelvis (Fig 1).
On the basis of axial localizing images, a multiphase, 15-mm-thick, T1-weighted spoiled gradient-echo acquisition is planned, which traverses the rectal canal in the midsagittal plane (Fig 1). The imaging parameters are as follows: 23.9/11.3; 90° flip angle; bandwidth = 12.5 kHz; and one signal acquired. A field of view of 32 cm and a matrix of 256 x 128 produce an in-plane resolution of 1.25 x 2.5 mm. An image update is provided every 2 seconds. Images are obtained with the patient at rest, at maximal sphincter contraction, during straining, and during defecation in the midsagittal plane. When necessary, additional axial or coronal gradient-echo images are obtained (eg, for imaging of intussusceptions or lateral rectoceles, respectively). Images are analyzed on an attached workstation in the cine loop mode and videotaped.
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Normal Anatomy
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The normal pelvic floor "suspension" is provided by an interaction of bony structures, muscles, and ligaments. Many structures such as the pelvic diaphragm, urogenital diaphragm, and endopelvic fascia support the pelvic floor and its organs. The anatomic complexity is furthermore underlined by the fact that the pelvic floor—which is vertically traversed by the urethra, vagina, and rectum—must allow an opening to accommodate excretion and parturition (22,23). Therefore, an understanding of the relationships of the pelvic floor organs is without a doubt crucial for accurate radiologic demonstration of pelvic floor dysfunction.
The pelvic floor is divided into three compartments, which correspond to typical clinical symptoms or presentations of pathologic conditions: the anterior compartment (lower urinary tract symptoms, cystocele, urinary incontinence); the middle compartment (vaginal vault or uterine prolapse); and the posterior compartment (constipation, fecal incontinence, rectal prolapse) (24). With MR defecography, assessment of adjacent structures and spaces is possible without the additional application of contrast agent into the vagina, small intestine, or peritoneum. The high contrast resolution of soft tissue that is inherent to MR imaging permits differentiation of surrounding structures like the prostate, vagina, bladder, small intestine, or puborectal muscle from the contrast agent–filled rectum (Figs 2, 3).
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Figure 2. Drawing of defecographic landmarks and measurements (female patient). The inferior pubococcygeal line (PCL) is defined as the line joining the inferior border of the symphysis pubis to the last coccygeal joint. The anorectal angle (ARA) is defined as the angle between the posterior border of the distal part of the rectum and the central axis of the anal canal. The anorectal junction (ARJ) (black point at the intersection of the two lines defining the ARA) is defined as the point of taper of the distal part of the rectum as it meets the anal canal. The wall protrusion of anterior rectoceles (R) is determined by measurement of the depth beyond the margin of the expected normal anterior rectal wall (dotted line). U = uterus, UB = urinary bladder.
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Figure 3a. Dynamic MR defecograms of a 60-year-old woman (a, b) and a 73-year-old man (c, d) with normal pelvic floor motion obtained at rest (a, c) and during maximal contraction of the anal sphincter (b, d). The contrast agent-filled rectum is clearly distinguished from the levator ani muscle (black arrowhead), bladder (single white arrowhead), uterus (arrow in a), and enlarged prostate (arrow in c). In general, no additional administration of contrast agent into the vagina, bladder, small intestine, or peritoneum is needed for assessment of structures adjacent to the anorectum. The relative positions of the pelvic floor compartments—the bladder, vaginal vault, and rectum (ARJ [double white arrowhead])—are measurable (vertical lines) with respect to the inferior PCL (horizontal line). The degree of pelvic floor lift during maximal contraction of the anal sphincter is well demonstrated.
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Figure 3b. Dynamic MR defecograms of a 60-year-old woman (a, b) and a 73-year-old man (c, d) with normal pelvic floor motion obtained at rest (a, c) and during maximal contraction of the anal sphincter (b, d). The contrast agent-filled rectum is clearly distinguished from the levator ani muscle (black arrowhead), bladder (single white arrowhead), uterus (arrow in a), and enlarged prostate (arrow in c). In general, no additional administration of contrast agent into the vagina, bladder, small intestine, or peritoneum is needed for assessment of structures adjacent to the anorectum. The relative positions of the pelvic floor compartments—the bladder, vaginal vault, and rectum (ARJ [double white arrowhead])—are measurable (vertical lines) with respect to the inferior PCL (horizontal line). The degree of pelvic floor lift during maximal contraction of the anal sphincter is well demonstrated.
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Figure 3c. Dynamic MR defecograms of a 60-year-old woman (a, b) and a 73-year-old man (c, d) with normal pelvic floor motion obtained at rest (a, c) and during maximal contraction of the anal sphincter (b, d). The contrast agent-filled rectum is clearly distinguished from the levator ani muscle (black arrowhead), bladder (single white arrowhead), uterus (arrow in a), and enlarged prostate (arrow in c). In general, no additional administration of contrast agent into the vagina, bladder, small intestine, or peritoneum is needed for assessment of structures adjacent to the anorectum. The relative positions of the pelvic floor compartments—the bladder, vaginal vault, and rectum (ARJ [double white arrowhead])—are measurable (vertical lines) with respect to the inferior PCL (horizontal line). The degree of pelvic floor lift during maximal contraction of the anal sphincter is well demonstrated.
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Figure 3d. Dynamic MR defecograms of a 60-year-old woman (a, b) and a 73-year-old man (c, d) with normal pelvic floor motion obtained at rest (a, c) and during maximal contraction of the anal sphincter (b, d). The contrast agent-filled rectum is clearly distinguished from the levator ani muscle (black arrowhead), bladder (single white arrowhead), uterus (arrow in a), and enlarged prostate (arrow in c). In general, no additional administration of contrast agent into the vagina, bladder, small intestine, or peritoneum is needed for assessment of structures adjacent to the anorectum. The relative positions of the pelvic floor compartments—the bladder, vaginal vault, and rectum (ARJ [double white arrowhead])—are measurable (vertical lines) with respect to the inferior PCL (horizontal line). The degree of pelvic floor lift during maximal contraction of the anal sphincter is well demonstrated.
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The dynamic process of defecography is demonstrated by using multiphase sagittal gradient-echo images. Analyses during straining or defecation show an increase in the ARA, widening and opening of the anal canal, functioning of the puborectal muscle, as well as positioning of the pelvic floor and descent of the perineum (Figs 3, 4). In addition, the anterior and posterior rectal walls are well depicted. The spatial resolution appears adequate to demonstrate the relevant surrounding morphology. The temporal resolution, with one image update every 2 seconds, is sufficient for the depiction of defecational dynamics.
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Figure 4a. Measurement of the ARA (white lines) with dynamic fluoroscopic defecography (a-c) and open MR defecography (d-f) with the patient at rest (a, d), during maximal contraction of the anal sphincter (b, e), and during straining (c, f). There is good correlation between the ARA measurements obtained with fluoroscopic defecography and those obtained with MR defecography. The ARA decreases during maximal contraction of the anal sphincter and increases during straining, followed by descent of the ARJ.
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Figure 4b. Measurement of the ARA (white lines) with dynamic fluoroscopic defecography (a-c) and open MR defecography (d-f) with the patient at rest (a, d), during maximal contraction of the anal sphincter (b, e), and during straining (c, f). There is good correlation between the ARA measurements obtained with fluoroscopic defecography and those obtained with MR defecography. The ARA decreases during maximal contraction of the anal sphincter and increases during straining, followed by descent of the ARJ.
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Figure 4c. Measurement of the ARA (white lines) with dynamic fluoroscopic defecography (a-c) and open MR defecography (d-f) with the patient at rest (a, d), during maximal contraction of the anal sphincter (b, e), and during straining (c, f). There is good correlation between the ARA measurements obtained with fluoroscopic defecography and those obtained with MR defecography. The ARA decreases during maximal contraction of the anal sphincter and increases during straining, followed by descent of the ARJ.
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Figure 4d. Measurement of the ARA (white lines) with dynamic fluoroscopic defecography (a-c) and open MR defecography (d-f) with the patient at rest (a, d), during maximal contraction of the anal sphincter (b, e), and during straining (c, f). There is good correlation between the ARA measurements obtained with fluoroscopic defecography and those obtained with MR defecography. The ARA decreases during maximal contraction of the anal sphincter and increases during straining, followed by descent of the ARJ.
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Figure 4e. Measurement of the ARA (white lines) with dynamic fluoroscopic defecography (a-c) and open MR defecography (d-f) with the patient at rest (a, d), during maximal contraction of the anal sphincter (b, e), and during straining (c, f). There is good correlation between the ARA measurements obtained with fluoroscopic defecography and those obtained with MR defecography. The ARA decreases during maximal contraction of the anal sphincter and increases during straining, followed by descent of the ARJ.
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Figure 4f. Measurement of the ARA (white lines) with dynamic fluoroscopic defecography (a-c) and open MR defecography (d-f) with the patient at rest (a, d), during maximal contraction of the anal sphincter (b, e), and during straining (c, f). There is good correlation between the ARA measurements obtained with fluoroscopic defecography and those obtained with MR defecography. The ARA decreases during maximal contraction of the anal sphincter and increases during straining, followed by descent of the ARJ.
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The ARA is defined—in accordance with conventional defecography (25)—as the angle between two lines that intersect at the ARJ; these lines are formed along the posterior border of the distal part of the rectum and along the central axis of the anal canal (23). Measurements of the ARA based on MR and x-ray fluoroscopic images obtained with the patient at rest, during maximal contraction of the anal sphincter, and during straining correlate well (Figs 2, 4) (11,23,26).
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Pathologic Conditions
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MR defecography permits detection and characterization of various anorectal abnormalities with a diagnostic impact often superior to that of fluoroscopic defecography (11,27). We have developed a standardized classification system for evaluation of anorectal and pelvic floor abnormalities with dynamic MR defecography. This classification system is slightly different from that of Comiter et al (21), who suggest a global grading and classification system for pelvic floor prolapse and dysfunction. We measure rectal descent, bladder descent, and vaginal vault descent with respect to the inferior PCL and grade the abnormalities at our institution as small, moderate, and large on the basis of specific, defined measurements (Table) (28). The PCL is defined as the line joining the inferior border of the symphysis pubis to the last coccygeal joint (Figs 2, 3).
In the following paragraphs, we describe various pathologic conditions depicted with MR defecography performed with an open-configuration, superconducting magnet system.
Enterocele
An enterocele is a herniation of a peritoneal sac downward and along the ventral rectal wall into the cul-de-sac or pouch of Douglas. At fluoroscopic defecography, separation of the opacified vagina and the upper rectum during straining or defecation suggests an enterocele (4,25). This enlarged rectogenital fossa may contain small intestine, omental fat, or sigmoid colon; it is difficult to distinguish these contents from each other with conventional defecography without additional opacification of the intestine or intraperitoneal cavity. In contrast, MR defecography plays a useful role in detection and characterization of enteroceles (Fig 5). Most enteroceles lie posterior in the superior portion of the rectovaginal or rectovesical space (Fig 6).
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Figure 5a. Enterocele and rectal prolapse in a 30-year-old mentally handicapped man with incontinence. (a, b) MR defecograms obtained at the beginning of defecation show rectal prolapse (arrowhead). (c, d) MR defecograms obtained during defecation show a huge enterocele that protrudes downward. The enterocele consists of sigmoid colon (arrow), omental and mesenteric fat, and small intestine (arrowheads).
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Figure 5b. Enterocele and rectal prolapse in a 30-year-old mentally handicapped man with incontinence. (a, b) MR defecograms obtained at the beginning of defecation show rectal prolapse (arrowhead). (c, d) MR defecograms obtained during defecation show a huge enterocele that protrudes downward. The enterocele consists of sigmoid colon (arrow), omental and mesenteric fat, and small intestine (arrowheads).
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Figure 5c. Enterocele and rectal prolapse in a 30-year-old mentally handicapped man with incontinence. (a, b) MR defecograms obtained at the beginning of defecation show rectal prolapse (arrowhead). (c, d) MR defecograms obtained during defecation show a huge enterocele that protrudes downward. The enterocele consists of sigmoid colon (arrow), omental and mesenteric fat, and small intestine (arrowheads).
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Figure 5d. Enterocele and rectal prolapse in a 30-year-old mentally handicapped man with incontinence. (a, b) MR defecograms obtained at the beginning of defecation show rectal prolapse (arrowhead). (c, d) MR defecograms obtained during defecation show a huge enterocele that protrudes downward. The enterocele consists of sigmoid colon (arrow), omental and mesenteric fat, and small intestine (arrowheads).
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Figure 6a. Enterocele in a 23-year-old man with chronic constipation and rectal prolapse for 3 years. (a) MR defecogram obtained with the patient at rest shows normal muscular function of the pelvic floor. (b) MR defecogram obtained during early defecation shows the clinically known rectal prolapse (single arrowheads) and a small rectocele (double arrowhead). (c) MR defecogram obtained during the middle and end of defecation shows simultaneous voiding and formation of a moderate enterocele extending to the pelvic floor (arrow). (d) MR defecogram obtained after defecation shows spontaneous repositioning of the enterocele and rectal prolapse.
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Figure 6b. Enterocele in a 23-year-old man with chronic constipation and rectal prolapse for 3 years. (a) MR defecogram obtained with the patient at rest shows normal muscular function of the pelvic floor. (b) MR defecogram obtained during early defecation shows the clinically known rectal prolapse (single arrowheads) and a small rectocele (double arrowhead). (c) MR defecogram obtained during the middle and end of defecation shows simultaneous voiding and formation of a moderate enterocele extending to the pelvic floor (arrow). (d) MR defecogram obtained after defecation shows spontaneous repositioning of the enterocele and rectal prolapse.
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Figure 6c. Enterocele in a 23-year-old man with chronic constipation and rectal prolapse for 3 years. (a) MR defecogram obtained with the patient at rest shows normal muscular function of the pelvic floor. (b) MR defecogram obtained during early defecation shows the clinically known rectal prolapse (single arrowheads) and a small rectocele (double arrowhead). (c) MR defecogram obtained during the middle and end of defecation shows simultaneous voiding and formation of a moderate enterocele extending to the pelvic floor (arrow). (d) MR defecogram obtained after defecation shows spontaneous repositioning of the enterocele and rectal prolapse.
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Figure 6d. Enterocele in a 23-year-old man with chronic constipation and rectal prolapse for 3 years. (a) MR defecogram obtained with the patient at rest shows normal muscular function of the pelvic floor. (b) MR defecogram obtained during early defecation shows the clinically known rectal prolapse (single arrowheads) and a small rectocele (double arrowhead). (c) MR defecogram obtained during the middle and end of defecation shows simultaneous voiding and formation of a moderate enterocele extending to the pelvic floor (arrow). (d) MR defecogram obtained after defecation shows spontaneous repositioning of the enterocele and rectal prolapse.
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After surgery in the pelvic region, an undetected enterocele may result in progressive symptoms and the need for repeat surgery (Fig 7) (29). The range of symptoms is usually very broad; for example, the enterocele may follow the sacral curve and result in compression of the distal part of the anorectum. These patients frequently experience incomplete evacuation due to the resulting outlet obstruction.
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Figure 7a. Enterocele in a 60-year-old woman 2 years after perimenopausal hysterectomy and ampullopexy. (a) MR defecogram obtained with the patient at rest shows an enterocele (arrow) that protrudes toward the anterior compartment and bulges into the vagina. The ARA is pathologic (150°). (b) MR defecogram obtained during squeezing shows that the ARA is almost normalized (106°) and the enterocele is repositioned. (c) MR defecogram obtained during defecation shows the enterocele (arrow) protruding clearly distal to the PCL; the enterocele consists mainly of fat. In addition, a small anterior rectocele is evident (arrowhead).
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Figure 7b. Enterocele in a 60-year-old woman 2 years after perimenopausal hysterectomy and ampullopexy. (a) MR defecogram obtained with the patient at rest shows an enterocele (arrow) that protrudes toward the anterior compartment and bulges into the vagina. The ARA is pathologic (150°). (b) MR defecogram obtained during squeezing shows that the ARA is almost normalized (106°) and the enterocele is repositioned. (c) MR defecogram obtained during defecation shows the enterocele (arrow) protruding clearly distal to the PCL; the enterocele consists mainly of fat. In addition, a small anterior rectocele is evident (arrowhead).
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Figure 7c. Enterocele in a 60-year-old woman 2 years after perimenopausal hysterectomy and ampullopexy. (a) MR defecogram obtained with the patient at rest shows an enterocele (arrow) that protrudes toward the anterior compartment and bulges into the vagina. The ARA is pathologic (150°). (b) MR defecogram obtained during squeezing shows that the ARA is almost normalized (106°) and the enterocele is repositioned. (c) MR defecogram obtained during defecation shows the enterocele (arrow) protruding clearly distal to the PCL; the enterocele consists mainly of fat. In addition, a small anterior rectocele is evident (arrowhead).
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Rectocele
A rectocele is a bulge of varying size of the anterior wall of the rectum or less frequently the posterior or lateral wall due to inadequate support and laxity of the endopelvic fascia above the anal canal. Rectoceles are more frequently found in women, usually as a result of obstetric injury. Different approaches to quantifying the extent of rectoceles have been described. For an anterior rectocele, we measure the depth of wall protrusion beyond the expected margin of the normal anterior rectal wall (Figs 2, 8). Other authors draw the reference line upward through the anterior wall of the anal canal (9,15). At our institution, the extent of the rectocele is reported to the clinicians according to our grading system (Table). Rectoceles smaller than 2 cm are frequently found inasymptomatic individuals (30). The clinical significance of a rectocele depends on fulfillment of the following criteria: size exceeding 2 cm, retention of contrast media, reproducibility of the symptoms, and need for evacuatory assistance (eg, digital pressure on the posterior vaginal wall for complete defecation) (Figs 8–10) (31). MR defecography provides objective information about the size of the rectocele, the dynamics of its emptying, and coexistent enteroceles or sigmoidoceles, many of which are missed at physical examination.
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Figure 8a. Anterior rectocele in a 50-year-old woman. The rectocele was diagnosed at physical examination. (a) MR defecogram obtained with the patient at rest shows a moderate rectocele. (b) MR defecogram obtained during straining and defecation shows that the rectocele (arrow) enlarges and becomes severe. Dotted line = expected normal rectal wall. (c) MR defecogram shows the patient evacuating the rectocele by pressing on the posterior vaginal wall with her fingers (arrowhead). This case includes all of the clinically significant criteria for a rectocele: size larger than 2 cm, retention of contrast medium, reproducibility of the symptoms, and need for evacuatory assistance.
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Figure 8b. Anterior rectocele in a 50-year-old woman. The rectocele was diagnosed at physical examination. (a) MR defecogram obtained with the patient at rest shows a moderate rectocele. (b) MR defecogram obtained during straining and defecation shows that the rectocele (arrow) enlarges and becomes severe. Dotted line = expected normal rectal wall. (c) MR defecogram shows the patient evacuating the rectocele by pressing on the posterior vaginal wall with her fingers (arrowhead). This case includes all of the clinically significant criteria for a rectocele: size larger than 2 cm, retention of contrast medium, reproducibility of the symptoms, and need for evacuatory assistance.
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Figure 8c. Anterior rectocele in a 50-year-old woman. The rectocele was diagnosed at physical examination. (a) MR defecogram obtained with the patient at rest shows a moderate rectocele. (b) MR defecogram obtained during straining and defecation shows that the rectocele (arrow) enlarges and becomes severe. Dotted line = expected normal rectal wall. (c) MR defecogram shows the patient evacuating the rectocele by pressing on the posterior vaginal wall with her fingers (arrowhead). This case includes all of the clinically significant criteria for a rectocele: size larger than 2 cm, retention of contrast medium, reproducibility of the symptoms, and need for evacuatory assistance.
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Figure 9a. Intussusception in a 54-year-old man with painful defecation. (a) MR defecogram obtained during middefecation shows a mural intussusception (arrow) protruding into the anal canal and a small rectocele (arrowhead). (b) Axial localizing MR image obtained after defecation shows the invagination, which is reproducible with maximal pressure and appears as a double lumen (arrow).
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Figure 9b. Intussusception in a 54-year-old man with painful defecation. (a) MR defecogram obtained during middefecation shows a mural intussusception (arrow) protruding into the anal canal and a small rectocele (arrowhead). (b) Axial localizing MR image obtained after defecation shows the invagination, which is reproducible with maximal pressure and appears as a double lumen (arrow).
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Figure 10a. Intussusception and anterior rectocele in a 35-year-old woman with pain and perineal discomfort after defecation. (a) MR defecogram obtained during straining and the start of defecation. (b) MR defecogram obtained during defecation shows a circumferential mural intussusception (arrowheads) that extends into the rectal ampulla. An anterior rectocele is also evident (arrow).
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Figure 10b. Intussusception and anterior rectocele in a 35-year-old woman with pain and perineal discomfort after defecation. (a) MR defecogram obtained during straining and the start of defecation. (b) MR defecogram obtained during defecation shows a circumferential mural intussusception (arrowheads) that extends into the rectal ampulla. An anterior rectocele is also evident (arrow).
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Intussusception and Rectal Prolapse
Invaginations of the rectal wall that descend toward the anal canal are called rectal intussusceptions. The involved rectal wall differs in thickness, and the invagination includes mucosal or mural components. The location can be anterior or posterior or even affect the rectum circumferentially. The intussusception may remain internal (intrarectal) (Fig 10), extend into the anal canal (intraanal) (Fig 9), or even pass the anal sphincter, resulting in an external rectal prolapse (extrarectal or extraanal) (Fig 11). Therefore, the widely used clinical term rectal prolapse corresponds anatomically to an extrarectal intussusception (Figs 5, 6). With descent of the rectal wall, an opening pouch anterior to the rectum is formed, which can contain an additional enterocele (Figs 5, 12). Similarly to rectoceles, invagination of parts of the rectal wall into the ARJ (intrarectal) is a relatively common finding in asymptomatic patients (30). If the intussusception reaches the anal canal (intraanal), patients may experience incomplete defecation due to severe outlet obstruction. Most patients with external rectal prolapse (extraanal) have associated incontinence (Fig 5).
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Figure 11a. Intussusception and mucosal prolapse in an 18-year-old patient with clinical findings of rectal hemorrhoids. (a) MR defecogram obtained with the patient at rest shows that the perineum bulges downward. However, its position normalized during maximal contraction of the anal sphincter. (b) MR defecogram obtained during midevacuation shows that the anorectal mucosa protrudes downward (arrow) to the anal canal and comes to rest right in the anal canal. (c) MR defecogram shows that the muscular part of the rectum does not shift. Therefore, this case represents an exquisite mucosal intraanal intussusception or so-called mucosal anal prolapse.
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Figure 11b. Intussusception and mucosal prolapse in an 18-year-old patient with clinical findings of rectal hemorrhoids. (a) MR defecogram obtained with the patient at rest shows that the perineum bulges downward. However, its position normalized during maximal contraction of the anal sphincter. (b) MR defecogram obtained during midevacuation shows that the anorectal mucosa protrudes downward (arrow) to the anal canal and comes to rest right in the anal canal. (c) MR defecogram shows that the muscular part of the rectum does not shift. Therefore, this case represents an exquisite mucosal intraanal intussusception or so-called mucosal anal prolapse.
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Figure 11c. Intussusception and mucosal prolapse in an 18-year-old patient with clinical findings of rectal hemorrhoids. (a) MR defecogram obtained with the patient at rest shows that the perineum bulges downward. However, its position normalized during maximal contraction of the anal sphincter. (b) MR defecogram obtained during midevacuation shows that the anorectal mucosa protrudes downward (arrow) to the anal canal and comes to rest right in the anal canal. (c) MR defecogram shows that the muscular part of the rectum does not shift. Therefore, this case represents an exquisite mucosal intraanal intussusception or so-called mucosal anal prolapse.
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Figure 12a. Rectal prolapse and sigmoidocele in a 50-year-old man. (a) MR defecogram obtained with the patient at rest shows no abnormalities. (b, c) Dynamic MR defecograms obtained during straining show rectal prolapse (arrows) as well as a sigmoidocele (arrowhead).
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Figure 12b. Rectal prolapse and sigmoidocele in a 50-year-old man. (a) MR defecogram obtained with the patient at rest shows no abnormalities. (b, c) Dynamic MR defecograms obtained during straining show rectal prolapse (arrows) as well as a sigmoidocele (arrowhead).
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Figure 12c. Rectal prolapse and sigmoidocele in a 50-year-old man. (a) MR defecogram obtained with the patient at rest shows no abnormalities. (b, c) Dynamic MR defecograms obtained during straining show rectal prolapse (arrows) as well as a sigmoidocele (arrowhead).
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Descending Perineal Syndrome
In the descending perineal syndrome, the muscle tone of the pelvic floor is pathologically decreased mainly due to pudendal nerve damage. However, the relation of this syndrome to age, gender, incontinence, or constipation is not absolutely convincing. The diagnosis is based on the results of clinical examination, electrophysiologic tests, and imaging. Although pelvic floor descent can occur at rest, it typically occurs during straining or defecation. Typically, bulging of the whole perineum is seen (Fig 13). It may involve only one compartment or all three compartments (Figs 14, 15). There are many grading systems in the literature. Along with others, we prefer to measure descent of the rectum, bladder, and vaginal vault as the main structures of the three compartments with respect to the inferior PCL (28). Open MR defecography is a straightforward and reproducible method of grading cases as small, moderate, and large (Table). In cases of descending perineal syndrome, decreased raising of the pelvic floor at maximal contraction is usually observed (Figs 13, 14). The syndrome is often associated with perineal discomfort and pain and a feeling of incomplete evacuation, leading to increased straining during defecation. The latter represents an additional neuropathic injury of the external anal sphincter, resulting in incontinence.
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Figure 13a. Descending pelvic floor syndrome with an enterocele and anterior rectocele in a 56-year-old multiparous woman with diffuse perineal pressure and pain after hysterectomy. There was no incontinence, but the patient had a sensation of incomplete defecation. (a) MR defecogram obtained with the patient at rest shows obvious bulging of the whole peritoneum under the PCL (white line). (b) MR defecogram obtained during maximal contraction of the anal sphincter shows reduced raising of the pelvic floor, thus confirming the presence of pelvic floor weakness. (c) MR defecogram obtained during defecation shows protrusion of a large enterocele into the extended, convex perineum (arrow) as well as an anterior rectocele (arrowhead). (d) MR defecogram obtained after defecation shows that the rectocele and the main part of the enterocele are unchanged.
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Figure 13b. Descending pelvic floor syndrome with an enterocele and anterior rectocele in a 56-year-old multiparous woman with diffuse perineal pressure and pain after hysterectomy. There was no incontinence, but the patient had a sensation of incomplete defecation. (a) MR defecogram obtained with the patient at rest shows obvious bulging of the whole peritoneum under the PCL (white line). (b) MR defecogram obtained during maximal contraction of the anal sphincter shows reduced raising of the pelvic floor, thus confirming the presence of pelvic floor weakness. (c) MR defecogram obtained during defecation shows protrusion of a large enterocele into the extended, convex perineum (arrow) as well as an anterior rectocele (arrowhead). (d) MR defecogram obtained after defecation shows that the rectocele and the main part of the enterocele are unchanged.
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Figure 13c. Descending pelvic floor syndrome with an enterocele and anterior rectocele in a 56-year-old multiparous woman with diffuse perineal pressure and pain after hysterectomy. There was no incontinence, but the patient had a sensation of incomplete defecation. (a) MR defecogram obtained with the patient at rest shows obvious bulging of the whole peritoneum under the PCL (white line). (b) MR defecogram obtained during maximal contraction of the anal sphincter shows reduced raising of the pelvic floor, thus confirming the presence of pelvic floor weakness. (c) MR defecogram obtained during defecation shows protrusion of a large enterocele into the extended, convex perineum (arrow) as well as an anterior rectocele (arrowhead). (d) MR defecogram obtained after defecation shows that the rectocele and the main part of the enterocele are unchanged.
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Abstract
LEARNING OBJECTIVES
