AJR 2000; 175:353-358
© American Roentgen Ray Society
Pelvic Endometriosis
Various Manifestations and MR Imaging Findings
Christina A. Gougoutas1,
Evan S. Siegelman1,
Jennifer Hunt2 and
Eric K. Outwater3
1
Department of Radiology, University of Pennsylvania Medical Center, 3400
Spruce St., 1st Floor Silverstein, Philadelphia, PA 19104-4283.
2
Department of Pathology, University of Pennsylvania Medical Center, 6th Floor
Founders, Philadelphia, PA 19104-4283.
3
Department of Radiology, University of Arizona Medical Center, 1501 N.
Campbell Ave., Rm. 1361, Tucson, AZ 85724-5067.
Received November 15, 1999;
accepted after revision January 24, 2000.
Address correspondence to E. S. Siegelman.
Introduction
Endometriosis is defined as the presence of endometrial glands in locations
outside the uterus. The ectopic endometrium responds to hormonal stimulation
with various degrees of cyclic hemorrhage that result in suggestive symptoms
and appearances. Recent awareness of the increasing incidence of endometriosis
in asymptomatic women has led to the hypothesis that endometrial implants are
in fact physiologic and do not in themselves indicate a disease process until
recurrent bleeding occurs in these implants, causing symptoms and progressive
disease [1].
The three hallmarks of endometriosis are peritoneal endometrial implants,
endometriomas (endometriotic cysts), and adhesions. The most common peritoneal
sites of involvement (in decreasing order of frequency) are the ovaries,
uterine ligaments, cul-de-sac, and pelvic peritoneum reflected over the
uterus, fallopian tubes, rectosigmoid, and bladder. Rare extraperitoneal sites
include the lungs and the central nervous system.
Because sonography is usually the first technique performed for evaluation
of pelvic disease during the reproductive years, it can aid diagnosis and
treatment of endometriosis. Sonography may not differentiate some
endometriomas from hemorrhagic cysts or other ovarian neoplasms and is
insensitive in the detection of peritoneal implants. Because of these
limitations, laparoscopy has remained the standard of reference for diagnosis
and staging of pelvic endometriosis. Laparoscopy does not visualize well
"atypical" nonpigmented extraperitoneal sites of involvement and,
particularly, regions obscured by pelvic adhesions. MR imaging may be an
alternative for evaluation of endometriosis before surgery. MR imaging has
shown a sensitivity and specificity of greater than 90% in the detection of
endometriomas, with its main limitation being the detection of small (<3
mm) peritoneal implants. The addition of fat-saturated T1-weighted imaging has
improved diagnostic accuracy in the evaluation of both endometriomas and
peritoneal disease by narrowing the dynamic range, increasing lesion
conspicuity [2], and
differentiating lipid-containing ovarian masses from those containing blood
[3] (Fig.
1A,1B,1C).
This pictorial essay shows the imaging spectrum of endometriosis with emphasis
on unusual pelvic manifestations.
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Fig. 1A. —38-year-old woman with left-sided ovarian dermoid cyst,
endometrioma, and right-sided ovarian corpus luteum. Axial T1-weighted MR
image (TR/TE, 550/14) shows two high-signal-intensity masses (arrows)
in left ovary.
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Fig. 1B. —38-year-old woman with left-sided ovarian dermoid cyst,
endometrioma, and right-sided ovarian corpus luteum. Axial T2-weighted fast
spin-echo MR image (4000/120) shows left-sided masses (arrows) to be
heterogeneous in signal intensity. Note involuting corpus luteum
(arrowhead) in right ovary.
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Fig. 1C. —38-year-old woman with left-sided ovarian dermoid cyst,
endometrioma, and right-sided ovarian corpus luteum. T1-weighted fat-saturated
MR image (270/1.8) shows anterior mass (open arrow) to be
predominantly fatty and posterior mass to be hemorrhagic (solid
arrow). Left-sided ovarian dermoid cyst and endometrioma were proven at
surgery.
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Endometrial Implants
The peritoneal implant represents the presence of endometrial surface
epithelium and stroma embedded in serosal tissues in the peritoneal cavity.
The ectopic location of endometrium in the peritoneal cavity causes reactive
proliferation of the stromal vessels that leads to recurrent hemorrhage. The
implant has a varied appearance depending on the age of associated blood
products. Pathologically, the implants begin as red highly vascular lesions,
typically 2-3 mm. Recurrent bleeding and inflammation cause fibrosis and
hemosiderin deposition, leading to a raised nodular "powder burn"
lesion. Lack of detection of these small foci of peritoneal involvement has
been a major limiting factor in the acceptance of MR imaging as a staging tool
for pelvic endometriosis.
Endometriomas
Endometriomas ("chocolate cysts") of the ovary contain dark
gelatinous material surrounded by a fibrous wall of variable thickness.
Endometriomas are usually multiple and bilateral. They are characteristically
homogeneously hyperintense on T1-weighted sequences with relatively low signal
intensity on T2-weighted sequences (Fig.
2A,2B,2C,2D).
This loss of signal intensity on the T2-weighted sequences is caused by high
concentrations of intracystic methemoglobin and other protein or iron products
[4]. Some lesions are
heterogeneous in signal intensity because the blood products are in various
stages of degradation from multiple episodes of bleeding. As free water in the
cyst is resorbed, the concentration of iron increases along with the viscosity
of the cyst contents. Takahashi et al.
[5] have shown the density
(chronicity) of cyst contents to be directly proportional to the iron
concentration, with a corresponding decrease in the T2 relaxation time as the
concentration of iron and the viscosity of cyst fluid increase. Iizuka et al.
[6] have also shown that the
concentration of iron in an ovarian cyst helps in differentiating
endometriomas from serous cystadenocarcinomas, which do not contain a high
concentration of iron.
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Fig. 2A. —42-year-old woman with right-sided endometrioma and cul-de-sac
endometrial implants. T1-weighted spin-echo MR image (TR/TE, 450/16) shows
high-signal-intensity mass (E) representing endometrioma. Anterior rectal wall
thickening is present (arrow).
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Fig. 2B. —42-year-old woman with right-sided endometrioma and cul-de-sac
endometrial implants. T2-weighted fast spin-echo MR sequence (4650/126) shows
endometrioma (solid arrow) with low signal intensity. Fibrotic
cul-de-sac implant (open arrow) infiltrates perirectal fat. A =
adenomyosis.
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Fig. 2C. —42-year-old woman with right-sided endometrioma and cul-de-sac
endometrial implants. T1-weighted fat-saturated gradient-echo MR image
(250/2.9) after administration of IV gadopentetate dimeglumine shows layered
appearance of endometrial wall (solid arrow) with
low-signal-intensity layer. Fibrotic cul-de-sac implant shows enhancement
(open arrow).
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Fig. 2D. —42-year-old woman with right-sided endometrioma and cul-de-sac
endometrial implants. Photomicrograph of histopathologic specimen shows
endometrial wall with fibrosis (F) and hemosiderin deposition (large
arrows). Inset shows endometrial glands (small arrows) along
another part of cyst wall. (H and E, x40)
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Endometriotic cysts may contain a peripheral rim of low signal intensity
representing hemosiderin or fibrous capsule (Fig.
2A,2B,2C,2D).
Enhancement of the periovarian peritoneal surfaces after contrast material
administration may occur [7]
(Fig.
2A,2B,2C,2D).
Large endometriomas may contain multiple thin septations and frequently show
hematocrit levels.
Endometriomas may predispose the ovary to twist less often than other
ovarian masses, possibly because of surrounding adhesions. The diagnosis of
ovarian torsion may be established with MR imaging by showing an endometrioma
in an enlarged poorly enhancing ovary with peripherally located follicles
(Fig.
3A,3B,3C).
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Fig. 3A. —33-year-old woman with endometrioma of left ovary and ovarian
torsion. T1-weighted spin-echo MR image (TR/TE, 450/8) shows
high-signal-intensity cystic structures (arrows) surrounded by
intermediate-signal-intensity tissue.
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Fig. 3B. —33-year-old woman with endometrioma of left ovary and ovarian
torsion. T1-weighted fat-saturated gradient-echo MR image after administration
of IV gadopentetate dimeglumine shows low-signal-intensity poorly enhancing
ovarian stroma (arrows) around endometriomas (B). Soft tissue around
central endometrioma shows high-signal-intensity ovarian stroma with cortex
displaced peripherally.
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Fig. 3C. —33-year-old woman with endometrioma of left ovary and ovarian
torsion. Sagittal T2-weighted fast spin-echo MR image (6000/140) shows
displaced follicles (arrowheads) at periphery of markedly enlarged
torsed ovary (arrows).
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Hydrosalpinx
Approximately 30% of women with endometriosis have associated tubal
abnormalities present at laparoscopy
[8]. Hydrosalpinges have a
tubular, often folded, configuration and can be differentiated from other
adnexal masses on MR imaging by the use of multiple imaging planes. Dilated
fallopian tubes with high signal intensity on T1-weighted sequences are
associated with endometriosis. These fallopian tubes do not always show T2
shortening typical of endometrial cysts. In addition, debris can be present
within the dependent portions of the tube (Fig.
4A,4B,4C).
A complicated hydrosalpinx may be the only imaging finding indicating
endometriosis (Fig.
5A,5B).
Although the presence of complicated hydrosalpinges may not influence patient
treatment, it does increase the specificity for pelvic endometriosis.
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Fig. 4A. —42-year-old woman with endometriomas, hematosalpinx, and corpus
luteum. Axial T1-weighted MR image (A) (TR/TE, 500/8) reveals two
high-signal-intensity foci in left ovary that lose signal intensity on
T2-weighted MR image (B) (5800/100), representing endometriomas
(open arrow). Adjacent corpus luteum (arrowhead) shows
heterogeneous signal intensity and higher signal intensity on T2-weighted
image than endometriomas showed. Note presence of simple ovarian cyst
(asterisk). Solid arrow indicates hematosalpinx.
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Fig. 4B. —42-year-old woman with endometriomas, hematosalpinx, and corpus
luteum. Axial T1-weighted MR image (A) (TR/TE, 500/8) reveals two
high-signal-intensity foci in left ovary that lose signal intensity on
T2-weighted MR image (B) (5800/100), representing endometriomas
(open arrow). Adjacent corpus luteum (arrowhead) shows
heterogeneous signal intensity and higher signal intensity on T2-weighted
image than endometriomas showed. Note presence of simple ovarian cyst
(asterisk). Solid arrow indicates hematosalpinx.
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Fig. 4C. —42-year-old woman with endometriomas, hematosalpinx, and corpus
luteum. Sagittal T2-weighted MR image (3550/140) shows oval structure adjacent
to cul-de-sac to represent hematosalpinx (solid arrow). Open arrow
indicates endometriomas. Asterisk indicates ovarian cyst.
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Fig. 5A. —43-year-old woman with endometriosis of left fallopian tube.
T1-weighted spin-echo MR image (TR/TE, 500/8) shows dilated left fallopian
tube with high signal intensity (arrow), consistent with
hematosalpinx.
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Fig. 5B. —43-year-old woman with endometriosis of left fallopian tube.
Photomicrograph of histopathologic specimen of tubal wall shows abundant
interstitial hemorrhage (H) and endometrial glands (arrowhead).
L=tubal lumen. (H and E, x100)
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Solid Endometriosis
Deep nodular (solid) endometriosis is typically found in the rectovaginal
septum and in other fibromuscular pelvic structures such as the uterine
ligaments and the muscular wall of pelvic organs. The endometrial glands and
stroma infiltrate the adjacent fibromuscular tissue and elicit smooth muscle
proliferation and fibrous reaction, resulting in solid nodule formation.
MR imaging characteristics of these solid masses have been described as low
to intermediate in signal intensity with punctate regions of high signal
intensity on T1-weighted images, uniform low signal intensity on T2-weighted
images, and enhancement corresponding to the abundant fibrous tissue seen in
these lesions at histologic examination
(Fig. 6). The punctate foci of
high signal intensity represent regions of hemorrhage surrounded by solid
fibrotic tissue. These solid masses of endometriosis may simulate metastatic
peritoneal implants from intraperitoneal malignancies such as ovarian
carcinoma. These disease processes can be differentiated by the low signal
intensity on T2-weighted sequences of solid endometriosis, often in
combination with the presence of endometrial cysts. Solid endometriosis can
also develop in cesarian section scars involving Pfannenstiel's incision after
cesarian section (Fig.
7A,7B).
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Fig. 6. —26-year-old woman with ovarian and rectal endometriosis. T1-weighted
spin-echo image (TR/TE, 700/16) shows single right-sided ovarian endometrioma
(open arrow) and spiculated fibrotic mass of endometriosis with
punctate high-signal-intensity foci (solid arrow). T2-weighted MR
images showed mass to be low signal intensity (not shown), reflecting fibrous
content.
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Fig. 7A. —26-year-old woman with solid endometriosis in cesarean section scar.
Sagittal T2-weighted MR image (TR/TE, 4816/135) shows low-signal-intensity
spiculated mass (arrow) in surgical incision extending to and
contiguous with uterus. This mass showed high signal intensity on T1-weighted
sequences and avid enhancement after gadopentetate dimeglumine administration
(not shown).
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Fig. 7B. —26-year-old woman with solid endometriosis in cesarean section scar.
Photomicrograph of histopathologic specimen shows abundant fibrous tissue (F)
surrounding scattered endometrial glands (G). Scar endometriosis is likely
caused by direct implantation of endometrial glands as opposed to more common
cause of retrograde menstruation. (H and E, x100)
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Some masses of endometriosis are composed of a large proportion of
glandular material with little fibrotic reaction that results in high signal
intensity on T2-weighted images. This solid glandular material will enhance
with contrast material administration, thus distinguishing it from necrosis or
intratumoral hemorrhage (Fig.
8A,8B,8C,8D).
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Fig. 8A. —Solid glandular endometriosis in 37-year-old woman. Axial
T2-weighted MR image (TR/TE, 4700/105) shows mass in cul-de-sac
(arrow) to be high signal intensity, atypical for solid
endometriosis.
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Visceral Endometriosis
Solid endometriosis can involve the alimentary and urinary tracts. Bladder
involvement has been described, and similarly the ureter may be involved.
Urinary tract disease may present as hydronephrosis caused by ureteral
obstruction (Fig.
9A,9B,9C)
or as a submucosal lesion within the bladder or ureter (Fig.
10A,10B,10C).
The rectosigmoid is the most common segment of bowel involved. The implants
adhere to the serosal surface of the bowel and may invade the muscle layers,
eliciting marked smooth muscle proliferation. Stricture formation and
obstruction may result.
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Fig. 9A. —Ureteral endometriosis in 68-year-old woman. Coronal T2-weighted
single-shot fast spin-echo MR image (TR/TE, infinite/99) shows left ureteral
obstruction (arrow) causing hydronephrosis.
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Fig. 9B. —Ureteral endometriosis in 68-year-old woman. Sagittal T2-weighted
fast spin-echo MR image (4000/140) shows solid low-signal-intensity
endometriosis (arrow) obstructing left ureter (arrowheads)
at pelvic inlet.
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Fig. 10B. —42-year-old woman with right-sided ureteral endometriosis causing
obstruction. T1-weighted gradient-echo MR images (350/2.9) before (B)
and after (C) administration of IV gadopentetate dimeglumine show
enhancement of polypoid structure in right ureter (white arrow).
Right ureteroscopy and biopsy showed endometrial glands and stroma. Right
ovarian endometrioma is present (black arrow, B).
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Fig. 10C. —42-year-old woman with right-sided ureteral endometriosis causing
obstruction. T1-weighted gradient-echo MR images (350/2.9) before (B)
and after (C) administration of IV gadopentetate dimeglumine show
enhancement of polypoid structure in right ureter (white arrow).
Right ureteroscopy and biopsy showed endometrial glands and stroma. Right
ovarian endometrioma is present (black arrow, B).
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Malignant Transformation of Endometriosis
Malignant transformation is a rare complication of endometriosis, the exact
incidence and prevalence of which is unknown. Criteria for diagnosis include
adjacent benign and malignant endometrial tissues without findings to suggest
metastatic disease from another primary site. The histologic patterns reflect
an endometrial origin and include endometrioid adenocarcinoma and clear cell
carcinoma from glandular elements and endometrial stromal sarcoma from stromal
tissues (Fig.
11A,11B).
Endometriomas with solid components and intermediate or high signal intensity
on T2-weighted images or papillary projections are suggestive of
malignancy.
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Fig. 11A. —50-year-old woman with endometrial stromal sarcoma arising in
endometriosis. T1-weighted spin-echo MR image (TR/TE, 500/16) shows mass
(solid arrow) adjacent to hemorrhagic fluid collection (open
arrow).
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Fig. 11B. —50-year-old woman with endometrial stromal sarcoma arising in
endometriosis. T2-weighted fast spin-echo MR image (4000/126) shows solid mass
(solid arrow) behind hemorrhagic collection (open arrow).
Mass was excised and shown to be low-grade endometrial stromal sarcoma arising
in endometriosis.
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Summary
MR imaging has become an increasingly accepted technique in the diagnosis
and characterization of endometriosis. Limitations remain regarding detection
of small peritoneal implants and atypical implants, identifying adhesions, and
accurate staging of the disease. However, as illustrated in this pictorial
essay, the common and less typical manifestations of endometriosis have
suggestive findings on MR imaging because of the underlying proteinaceous,
hemorrhagic, or fibrous content of these lesions.
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Top
Introduction
Endometrial Implants
