DOI:10.2214/AJR.05.0508
AJR 2006; 187:W275-W284
© American Roentgen Ray Society
MRI of Rectal Disorders
Christine C. Hoeffel1,
Louisa Azizi1,
Najat Mourra2,
Maïté Lewin1,
Lionel Arrivé1 and
Jean-Michel Tubiana1
1 Department of Radiology, Université Paris-Descartes Faculté de
Medecine Cochin Port-Royal, Hôpital Saint-Antoine, 184 Rue du Faubourg,
Saint-Antoine 75571, Paris cedex 12, France.
2 Department of Pathology, Hôpital Saint-Antoine, Saint-Antoine 75571,
Paris cedex 12, France.
Received March 23, 2005;
accepted after revision June 7, 2005.
Address correspondence to C. C. Hoeffel
(christine.hoeffel{at}sat.ap-hop-paris.fr).
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Abstract
OBJECTIVE. The objective of this pictorial essay is to provide a
review of the diseases involving the rectal wall with an emphasis on the key
clinical and radiologic differentiating features.
CONCLUSION. A wide spectrum of disease processes can involve the
rectum in adults. MRI is the technique of choice in the definitive diagnosis
of these disease conditions, mainly because of its superior tissue contrast
differentiation.
Keywords: colon • gastrointestinal radiology • MRI
Introduction
The rectum is the part of the gastrointestinal tract in which MRI studies
are the most successful. The superb soft-tissue contrast and multiplanar
imaging capability of this technique helps in characterizing rectal disorders
and permits visualizing the perirectal area. MRI has primarily been used to
study rectal carcinoma and to assess involvement from tumors of pelvic origin.
But MRI has an important role to play in a number of nonneoplastic rectal
diseases in adults, including congenital and developmental diseases,
inflammatory and infectious diseases, vascular diseases, and lesions of
endometriosis. Accurate diagnosis of these conditions is crucial because it
can significantly alter clinical management. The aim of this pictorial essay
is to review the diseases involving the rectal wall, highlighting the main
clinical or radiologic differentiating features.
Congenital and Developmental Lesions
Developmental Cysts
Developmental cysts mostly occur in middle-aged women. They are
asymptomatic in 50% of cases, but patients may present with symptoms resulting
from local mass effect or with complications such as infection, bleeding, or
malignant degeneration. Enteric cysts, defined as cysts partially or
completely lined with intestinal mucosa (tailgut cysts and rectal
duplication), are the most frequent. They may impinge on the rectum or be
intimately attached to the rectal wall. Cystic rectal duplication is rare,
representing 5% of all developmental cysts, but is the only cystic lesion
defined by continuity or contiguity with the rectum. An enteric cyst typically
appears as a well-defined, unilocular or multilocular, thin-walled,
homogeneous lesion that is hypointense on T1-weighted images and hyperintense
on T2-weighted images and nonenhancing. High signal intensity on T1-weighted
images is likely to result from mucoid content in a tailgut cyst. The cyst may
be thick-walled with surrounding inflammatory changes
[1] (Figs.
1A,
1B, and
1C).
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Fig. 1A —Retrorectal tailgut cyst in 25-year-old woman. Sagittal
T2-weighted (A) and axial fat-suppressed contrast-enhanced T1-weighted
(B) MR images show lesion adherent to rectum (arrow, B)
extending from behind anal canal upward into retrorectal space. Lesion
consists of group of cystic lesions surrounded by unenhanced,
low-signal-intensity, fibrous thick wall (arrowheads). Note that main
cystic lesion displays slightly heterogeneous high signal intensity on
T1-weighted image due to mucoid content.
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Fig. 1B —Retrorectal tailgut cyst in 25-year-old woman. Sagittal
T2-weighted (A) and axial fat-suppressed contrast-enhanced T1-weighted
(B) MR images show lesion adherent to rectum (arrow, B)
extending from behind anal canal upward into retrorectal space. Lesion
consists of group of cystic lesions surrounded by unenhanced,
low-signal-intensity, fibrous thick wall (arrowheads). Note that main
cystic lesion displays slightly heterogeneous high signal intensity on
T1-weighted image due to mucoid content.
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Fig. 1C —Retrorectal tailgut cyst in 25-year-old woman. Photograph of
gross specimen of resected mass shows main cystic component (C) with mucoid
content as well as fibrous wall (F) interspersed with cysts (arrow).
Lesion was found to be adherent to rectal wall, dissociating its muscular
fibers.
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Diffuse Cavernous Hemangioma
This rare, benign vascular malformation consists of an extensive network of
vascular lakes involving the entire intestinal wall, which may infiltrate into
the surrounding connective tissue. Clinical and radiologic clues include a
history of chronic rectal bleeding in young adults, a moderately high
T2-weighted signal intensity, a markedly thickened rectosigmoid wall, and
high-signal-intensity heterogeneous perirectal fatty tissue with enhancing
serpiginous structures—small vessels supplying the malformation
[2] (Figs.
2A,
2B, and
2C). Diffuse cavernous
hemangioma may extend to perirectal tissue, including pelvic musculature.
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Fig. 2A —Rectal cavernous hemangioma in 21-year-old woman. Sagittal
T2-weighted (A) and axial fat-suppressed contrast-enhanced T1-weighted
(B) MR images show T2-weighted high-signal-intensity concentric rectal
wall thickening. Mesorectal fat is heterogeneous (arrow, A).
Note enhancing rectal wall as well as small enhancing serpiginous structures
in mesorectum (arrowhead, B).
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Fig. 2B —Rectal cavernous hemangioma in 21-year-old woman. Sagittal
T2-weighted (A) and axial fat-suppressed contrast-enhanced T1-weighted
(B) MR images show T2-weighted high-signal-intensity concentric rectal
wall thickening. Mesorectal fat is heterogeneous (arrow, A).
Note enhancing rectal wall as well as small enhancing serpiginous structures
in mesorectum (arrowhead, B).
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Inflammatory and Infectious Conditions
Idiopathic inflammatory bowel disease accounts for the majority of
inflammatory and infectious cases. The findings may often be nonspecific, and
ancillary clinical information usually leads to the most probable diagnosis.
When the diagnosis has been established, MRI will be useful to assess the
extent and severity of the disease and to identify complications.
Ulcerative Colitis and Crohn's Disease
MRI alone will not easily differentiate ulcerative colitis from Crohn's
disease. Findings include rectal wall thickening with marked contrast-material
enhancement, mural stratification, hyperintensity of the rectal wall on
T2-weighted images, sinus tract fistulas and abscesses, luminal narrowing, and
lymph node enlargement. Perianal and perineal disorders are key features of
Crohn's disease. Ulcerative colitis usually springs from the rectum and
extends proximally in a contiguous fashion, displaying rectal wall thickening
that is typically less pronounced and more symmetric than in Crohn's disease.
Fibrofatty proliferation and the presence of skip lesions suggest the
diagnosis of Crohn's disease rather than ulcerative colitis. (Figs.
3,
4,
5A, and
5B).
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Fig. 4 —Rectocolic Crohn's disease in 43-year-old woman with acute
symptoms. Coronal T2-weighted MR image shows concentric thickening of rectal
wall. Note rectal lumen stenosis (arrowhead) and submucosal edema
(arrow).
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Fig. 5A —Ulcerative colitis in 45-year-old woman with acute symptoms
of proctitis and history of surgical treatment by ileorectal anastomosis.
Axial unenhanced (A) and fat-suppressed contrast-enhanced (B)
T1-weighted MR images show mildly thickened enhancing upper rectal wall
(arrows) compared with normal ileal wall (arrowheads). Note
multiple small lymph nodes.
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Fig. 5B —Ulcerative colitis in 45-year-old woman with acute symptoms
of proctitis and history of surgical treatment by ileorectal anastomosis.
Axial unenhanced (A) and fat-suppressed contrast-enhanced (B)
T1-weighted MR images show mildly thickened enhancing upper rectal wall
(arrows) compared with normal ileal wall (arrowheads). Note
multiple small lymph nodes.
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Radiation Therapy
The earliest change than can stem from radiation therapy is increased
signal intensity in the submucosa on T2-weighted images; the outer wall
remains of low signal intensity. Strong enhancement of the rectal wall is seen
at this stage. With progressive injury, the wall becomes thicker, and the
outer muscle layer shows high signal intensity on T2-weighted images
[3]
(Fig. 6).
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Fig. 6 —60-year-old woman with history of radiation therapy for tumor
of anal canal 1 year earlier. Axial T2-weighted MR image shows regularly
thickened rectal wall with increased signal intensity of both submucosa and
outer layer (arrows).
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Infection
The most common source of infection involving the rectum is anorectal
inflammatory disease, but the infection may also be due to rectal perforation,
a surgical procedure, spread from an adjacent infection (pelvic inflammatory
disease), or trauma. Abnormalities include inflammatory edema, cellulitis, and
abscess (Fig. 7). MRI is
useful for distinguishing between supralevator and infralevator abscesses:
supralevator abscesses displace the levator ani laterally and may require a
transvaginal, endorectal, or transgluteal approach or a laparotomy, whereas
infralevator collections displace the levator ani medially and can be drained
through the perineum.
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Fig. 7 —Rectal sinus tracts and abscesses in 40-year-old man who had
been treating his headaches with antiinflammatory suppositories for at least
10 years. Axial T2-weighted MR image reveals partial destruction of internal
sphincter (arrow), which is replaced by complex fistulas and sinus
tracts (arrowheads).
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Deeply Infiltrating Endometriosis
The most frequent location of intestinal involvement is the rectosigmoid
junction. Rectal involvement is suggested by an irregular thickening of the
anterior rectal wall, forming an obtuse angle with the normal wall and
displaying a signal intensity close to that of pelvic muscle on all sequences
and sometimes containing high-signal-intensity foci on T1-weighted,
T2-weighted, or fat-suppressed images
[4]. Associated findings
include anterior attraction of the rectum toward the torus uterinus and
involvement of the latter and of the uterosacral ligaments (Figs.
8 and
9).
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Fig. 8 —Rectal endometriosis in 35-year-old woman. Axial T1-weighted
MR image shows discrete nodule of anterior rectal wall (arrow)
displaying isointensity with respect to pelvic muscle and containing small
foci of high signal intensity.
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Fig. 9 —Rectal endometriosis in 40-year-old woman. Axial T1-weighted
image shows that rectal wall is irregularly thickened anteriorly
(arrowhead) and attracted forward to torus uterinus (arrow).
Note involvement of uterosacral ligaments.
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Neoplasms
Rectal Adenocarcinoma
MRI is a valuable tool for the preoperative workup and follow-up of
patients with rectal adenocarcinoma. Careful staging is required for
therapeutic selection. Depth of cancer invasion (T stage) and presence of
lymph node involvement, particularly of those located outside the mesorectal
fascia, have to be assessed. Moreover, in patients considered suitable for
mesorectal excision, it is crucial to evaluate the spread of the tumor to the
mesorectal fascia. A T3 tumor is typically seen as a broad-based bulge or
nodular projection of intermediate signal intensity (higher signal than the
outer rectal muscle and lower signal than the submucosa on T2-weighted images)
projecting beyond the outer muscle layer. A desmoplastic reaction may be seen.
A T4 tumor is characterized by abnormal signal extension into the adjacent
organ or through the peritoneal reflection
(Fig. 10).
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Fig. 10 —66-year-old man with stage pT3 rectal carcinoma. Axial
T2-weighted MR image shows tumor (T) displaying lower signal than that of
submucosa but higher than that of proper muscle layer. Tumor is seen invading
muscularis propria (arrowhead). Note presence of mesorectal lymph
nodes.
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Fig. 11A —28-year-old man with mucinous rectal adenocarcinoma. Coronal
T2-weighted MR image shows large ill-circumscribed mass involving rectum and
extending downward into anal canal (arrowhead), laterally to left
levator ani muscle (arrow), and into mesorectum and supralevator
space. No extension is visible in ischiorectal fossa. Lesion is brighter than
fat.
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Fig. 11B —28-year-old man with mucinous rectal adenocarcinoma. Axial
fat-suppressed contrast-enhanced T1-weighted image shows poor enhancement of
mass apart from central part around rectal lumen, with extension to seminal
vesicles and to right inferior hypogastric nerve plexuses
(arrow).
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Mucinous adenocarcinomas are histologic subtypes of rectal adenocarcinomas
and are known to be highly infiltrative lesions. They typically display a
markedly high signal intensity on T2-weighted MR images, higher than that of
the submucosa in parts of the mucous lakes
[5] (Figs.
11A,
11B, and
11C).
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Fig. 12A —Large villous tumor in 70-year-old man. Axial fat-suppressed
contrast-enhanced T1-weighted MR image reveals poorly enhancing large mass
filling rectal lumen and displaying frondlike projections in lumen
(arrow).
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Villous Adenomas
Villous adenomas occur mainly in patients over 60 years old and half of the
cases include carcinoma foci. They generally are large and bulky, resulting in
constipation, occasional bleeding, and rectal prolapse. On imaging, a villous
adenoma appears as a large mass filling the rectal lumen and displaying
frondlike projections without perirectal or pelvic lymphadenopathy
[6] (Figs.
12A and
12B).
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Fig. 13A —Stromal rectal tumor fistula forming in subperitoneal rectum
in 54-year-old woman. Coronal (A) and axial (B) T2-weighted MR
images show large heterogeneous rectal mass containing signal voids expanding
right side of rectal wall (arrowheads) related to presence of air due
to fistula within digestive tract. Right levator ani muscle is not visible,
whereas left one is normal (arrow, A). No lymph node
enlargement is seen.
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Fig. 13B —Stromal rectal tumor fistula forming in subperitoneal rectum
in 54-year-old woman. Coronal (A) and axial (B) T2-weighted MR
images show large heterogeneous rectal mass containing signal voids expanding
right side of rectal wall (arrowheads) related to presence of air due
to fistula within digestive tract. Right levator ani muscle is not visible,
whereas left one is normal (arrow, A). No lymph node
enlargement is seen.
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Fig. 14A —Rectal lymphoma in 21-year-old woman. Sagittal T2-weighted
(A) and fat-suppressed axial contrast-enhanced T1-weighted (B)
MR images show huge homogeneous rectal mural mass that is isointense with
respect to muscle on A and moderately enhancing. Rectal lumen is still
visible (arrow, B) and there is no bowel distension.
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Fig. 14B —Rectal lymphoma in 21-year-old woman. Sagittal T2-weighted
(A) and fat-suppressed axial contrast-enhanced T1-weighted (B)
MR images show huge homogeneous rectal mural mass that is isointense with
respect to muscle on A and moderately enhancing. Rectal lumen is still
visible (arrow, B) and there is no bowel distension.
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Fig. 16A —Prostate adenocarcinoma with metastatic involvement of rectum
in 76-year-old man. Axial fat-suppressed contrast-enhanced T1-weighted MR
image shows hypointense prostatic tumor extending to anterior part of rectal
wall (arrow).
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Fig. 16B —Prostate adenocarcinoma with metastatic involvement of rectum
in 76-year-old man. Axial fat-suppressed contrast-enhanced T1-weighted MR
image obtained at higher level than A shows abnormal concentric
heterogeneous irregular thickening of rectal wall.
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Rectal Stromal Tumors
Rectal stromal tumors [7]
are mesenchymal tumors typically arising in the muscularis propria of the
rectal wall. They are characterized by the expression of the so-called c-kit
receptor (CD117, tyrosine growth factor receptor). Kit immunoreactivity not
only singles out these tumors as unique from other mesenchymal neoplasms, but
it also identifies the tumors as targets for kit-inhibitor therapy.
Presentation and symptoms vary depending on tumor size. The diagnosis of
rectal stromal tumor should be suggested in a patient who has a large,
well-marginated rectal mass that expands the rectal wall; has a smooth, broad
pushing border; contains evidence of hemorrhage or necrosis; and lacks
perirectal adenopathy. Rectal stromal tumors often have a large exophytic
component. Lesions with extensive hemorrhage or necrosis may form cavities
that communicate with the digestive lumen and contain air (Figs.
13A and
13B).
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Fig. 16C —Prostate adenocarcinoma with metastatic involvement of rectum
in 76-year-old man. Photograph of gross surgical resection (abdominoperineal
resection and prostatectomy), confirms diffuse involvement of rectal wall seen
as white thickening of wall layers (arrowhead) compared with normal
wall (arrow). Difference between normal rectal mucosa and abnormal
mucosa caudad is also well visualized. P = prostatectomy, M = normal rectal
mucosa.
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Rectal Lymphoma
Rectal lymphoma is a rare condition; however, the incidence has recently
been increasing among the HIV-positive population. Typical MRI appearances are
those of a homogeneous mural mass or marked concentric wall thickening
engulfing the rectum with luminal restriction but minor obstruction
(aneurysmal dilatation of the rectum), fistula formation, thickening of the
adjacent levator ani muscles, and adenopathy (Figs.
14A and
14B).
Rectal Carcinoid Tumor
Rectal carcinoid tumors are quite rare and may present as solitary, smooth,
round protrusions with a broad base in the rectum
(Fig. 15).
Rectal Melanoma
Rectal melanoma is a rare disease in which preoperative diagnosis is
difficult. Although melanin shows high signal intensity on T1-weighted images,
its distribution is heterogeneous and thus difficult to differentiate from
hemorrhage within the tumor.
Secondary Neoplastic Involvement
The most common pathway to rectal involvement is direct invasion caused by
a tumor originating in the adjacent organs such as prostate, urinary bladder,
uterus, or vagina or in the ischiorectal fossa.
Prostatic carcinoma rarely involves the rectum because Denonvilliers'
fascia is very firm. MRI may help in assessing rectal extension, either for
signs of extracapsular extension (asymmetry of periprostatic planes, blurring
of the seminal vesicle angles, or soft-tissue masses extending from the
prostate into the rectum) associated with irregular thickening of the anterior
rectal wall or for circumferential, asymmetric thickening of the rectum (Figs.
16A,
16B, and
16C). Accurate diagnosis may
be difficult, and an elevated level of serum acid phosphatase may aid in the
diagnosis.
Linitis plastica of the rectum usually results from stomach, prostate, or
breast primary disease. It causes circumferential thickening of the rectal
wall over a long segment and may display a concentric ring pattern on
T2-weighted images [8].
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Abstract
Introduction
