Dr. Wolfman is an Assistant Professor at Uniformed Services
University of the Health Sciences, Walter Reed National Military
Medical Center, Bethesda, MD; Dr. Allison is an Associated Professor and Director of Ultrasound, and Dr. Ascher
is a Professor and Co-Director of Abdominal Imaging, in the Department
of Radiology, Georgetown University Hospital, Washington, D.C.
patients with gynecologic disease, including women with abnormal
uterine bleeding, imaging is an essential tool in every stage of
management. Ultrasound (US) is the accepted primary modality for the
evaluation of abnormal uterine bleeding. Sonohysterogram (SonoHSG) and
magnetic resonance imaging (MRI) are useful for problem solving and when
US is indeterminate. The most common benign etiologies for abnormal
uterine bleeding diagnosed on imaging include leiomyomas, adenomyosis,
endometrial hyperplasia, and endometrial polyps. This article will review
the imaging findings on US, sonoHSG, and MRI of the most common benign
etiologies of abnormal uterine bleeding.
also referred to as fibroids, are the most common pelvic tumors,
occurring in up to 25% of women over the age of 35.Leiomyomas are
composed of smooth muscle cells arranged in a whorl-like pattern with
variable amounts of intervening collagen, extracellular matrix, and
fibrous tissue. Leiomyomas are classified according to their location:
Intramural, submucosal, subserosal, and pedunculated (Figure 1).
Leiomyomas can also occur, although less commonly, in the cervix, broad
ligament, or completely unrelated to the female genital tract. As
fibroids grow, they can outgrow their blood supply and degenerate. Five
types of degeneration have been described: hemorrhagic or carneous,
hyaline, fatty, cystic, and sarcomatous. Sarcomatous degeneration is
much less likely, occurring in < 2% of cases.
ultrasound (TVS) is the initial imaging study of choice. However, TVS
can be limited by its restrictive field of view, the patient’s body
habitus, and/or distorted anatomy secondary to large and/or multiple
fibroids.1-4 Although the ability to detect small
leiomyomasis increased with TVS, their precise location in relation to
the uterine cavity is uncertain at times.5 Performing a
transabdominal US, in addition to TVS, is helpful in evaluating for
leiomyomas that extend beyond the field of view on TVS (Figure 2). MR is
useful in cases whereTVS is equivocal or nondiagnostic for the above
reasons. SonoHSG can be useful to distinguish submucosal leiomyoma from
On US, leiomyomas may appear as single or
multiple masses. Alternatively, they may present as part of an enlarged
uterus with an irregular contour. In some cases, the sole clue to the
presence of leiomyoma on US is an irregularly enlarged uterus with
distortion or obscuration of the endometrial stripe.6
seen as discrete lesions, leiomyomas may appear hyperechoic or
hypoechoic, homogeneous, or heterogeneous. Regardless of their
echogenicity or echotexture, shadowing and attenuation are the hallmarks
of leiomyoma on ultrasound (Figure 3). The composition, ie, the
relative amount of smooth muscle and areas of necrosis and/or
degeneration,7 dictates their sonographic appearance. When
the muscular component predominates, leiomyomas appear as hypoechoic
solid masses with poor sound through transmission. With fibrous
degeneration, echogenicity increases because of the presence of tiny
cystic areas that permit improvement through transmission. Cystic or
hemorrhagic degeneration results in an anechoic mass with posterior
acoustic enhancement. Dystrophic calcifications, usually seen in older
patients, present as echogenic foci with posterior shadowing. Varying
degrees of vascularity may be seen with leiomyomas on color Doppler US.
Typically, leiomyomas have marked peripheral blood flow with decreased
central flow or an avascular core (Figure 4).8
sonoHSG, submucosal leiomyomas are seen to have an overlying layer of
echogenic endometrium and may distort the endometrial-myometrial
interface (Figure 5).9 SonoHSG is more sensitive than TVS for detecting the presence, exact location, and number of submucosal leiomyomas.10,11
These features are important to document when evaluating leiomyomas
because their location in relation to the uterinecavity is a more
relevant factor than size in determining whether bleeding and
infertility are clinical problems.11
leiomyomas are well-circumscribed masses that have low T2 signals
relative to the myometrium, with lesions as small as 0.5cm routinely
imaged.12 A high-signal intensity, T2 rim is often present and represents dilated lymphatics and/or veins and/or edema.13
Leiomyomas have an extremely variable appearance after gadolinium
contrast administration; they may appear as hypo-, iso- or
hyperenhancing compared to the adjacent myometrium (Figure 6).14
On T1-weighted images, nonhemorrhagic leiomyomas are not visible except
for the distortion of the uterine contour that may occur.
Leiomyomas over 3 to 5 cm often have a heterogeneous T2 signal secondary to degeneration.15
Hemorrhagic degeneration appears as high-T1 signal without gadolinium
contrast enhancement (Figure 7). Advanced hyaline degeneration can
sometimes include fatty degeneration. However, if macroscopic fat is
detected in a uterine mass, a benign mixed Müllerian tumor or
lipoadenofibroma should be considered.12,16 The MR imaging
appearance of leiomyosarcomas is limited. In one study of 12 cases,
masses with 50% high T2-weighted signal,tiny high T1-weighted signal
foci, and well-demarcated nonenhancing regions raise the suspicion of
sarcoma.17 Other characteristics that suggest possible
sarcomatous degeneration include a suddenly enlarging leiomyoma,
especially after menopause, and/or indistinct borders and/or invasion
into adjacent structures.
Adenomyosis is a condition in which ectopic endometrial glands and stroma are embedded in the myometrium.
is seen in 19% to 62% of hysterectomy specimens, often presenting
symptomatically in the reproductive years and within the perimenopausal
years.18 Both diffuse and focal forms of adenomyomas exist.18,19
Although US has been shown in the past to be imprecise in diagnosing adenomyosis,20 newer studies have demonstrated a high degree of accuracy, sensitivity and specificity. 21
Reinhold and colleagues reported from the literature a sensitivity of
80% to 86%, specificity of 50% to 96%, and overall accuracy of 68% to
86% in diagnosing diffuse adenomyosis.21,22 However, it can
still be difficult to diagnose adenomyosis on TVS if there are
co-existent fibroids and/or there is focal adenomyosis. The advantages
of MR imaging of adenomyosis include being able to reliably diagnose
adenomyosis, including adenomyoma, diagnosing coexistent leiomyomas and
the reproducibility of MR, which allows for accurate treatment
Sonographic features of adenomyosis are
best appreciated using higher-frequency transvaginal transducers and
during real-time scanning as opposed to static images. 22 In most patients,adenomyosis appears as myometrial heterogeneity that may be focal or diffuse (Figure 8).21,24
Myometrial heterogeneity results from a combination of echogenic foci,
representing heterotopic endometrial tissue, and hypoechoic foci
representing smooth muscle hyperplasia.25,26 Diffuse
adenomyosis often results in asymmetric myometrial thickness and/or
globular enlargement of the uterus. Other findings in adenomyosis
include small myometrial cysts representing dilated cystic glands and
echogenic nodules and/or linear striations extending from the
endometrium into the myometrium representing ectopic endometrial tissue.
Focal adenomyosis or adenomyoma can be mistaken for a leiomyoma on US.26 Lack
of a uterine contour abnormality or mass effect, elliptical shape,
increased echogenicity and ill-defined margins favor the diagnosis of
adenomyoma over leiomyoma.10 Color Doppler US may also aid in
distinguishing adenomyoma from leiomyoma on US. Color Doppler US of
adenomyosis may demonstrate scattered penetrating vessels,27 versus the peripheral draping vascular pattern seen with leiomyoma (Figure 9).26-29
sequences are the key to diagnosing adenomyosis with MR since these
sequences highlight the uterine zonal anatomy. Diagnostic criteria
include focal or diffuse widening of the low-T2-signal intensity
junctional zone or an ill-defined low-T2-signal intensity myometrial
mass.30-32 The low-signal intensity on T2-weighted images is
secondary to densely packed smooth muscle hyperplasia that
pathologically resembles the inner portion of the myometrium (the
histopathological correlate to the junctional zone).31
zone width on MR is an important criterion used to diagnose
adenomyosis. If the junctional-zone width is ≤8 mm, then adenomyosis is
excluded. If the junctional-zone width is ≥12 mm, then the diagnosis of
adenomyosis can be made with confidence. 33 However, if the
junctional-zone width is between 9 to 11 mm, then the presence of
ancillary findings may help to establish the diagnosis of adenomyosis
Ancillary findings in adenomyosis include: poorly
defined margins, high-signal foci on T1- or T2-weighted sequences and
linear striations of high T2-signal radiating from the endometrial zona
basale into the myometrium. The high T1- or T2-weighted signal-intensity
foci may represent ectopic endometrium, cystically dilated endometrial
glands, and/or hemorrhage.18-19, 30-31 High signal-intensity striations may cause pseudo widening of the endometrium.
is usually occult on T1-weighted sequences with the exception of
occasional high-signal foci that represent hemorrhage.18,31 Gadolinium contrast enhancement does not aid in the diagnosis of adenomyosis.14,19 Early
phase images may show perfusion abnormalities and a “swiss cheese”
appearance. This “swiss cheese” appearance is secondary to
cross-sectional imaging of dilated endometrial glands within the
proliferation of the endometrial glands is termed endometrial
hyperplasia. The endometrial gland-to-stroma ratio is increased and the
glands can be cystically dilated. This condition may be focal or
diffuse. Endometrial hyperplasia is most often seen secondary to
unopposed estrogen stimulation. Two categories are described: with or
without cellular atypia. In patients with cellular atypia, 25% have foci
of endometrial carcinoma or will develop it at some point in the
future, which compares to 2% in patients without cellular atypia.
Endometrial hyperplasia is the underlying cause in 8% of cases of
TVS and sonoHSG are the
studies of choice for the characterization of endometrial hyperplasia.
MR is useful when these modalities are nondiagnostic or when sampling of
the endometrium would be difficult.
On US and sonoHSG,
endometrial hyperplasia usually appears as a diffusely thickened,
echogenic endometrium (Figure 11). However, focal, asymmetric thickening
may also be seen. Small cysts may be seen in endometrial hyperplasia
representing dilated cystic glands at histology.35 The US and
sonoHSG appearance of endometrial hyperplasia is nonspecific and
endometrial hyperplasia cannot be differentiated from endometrial
carcinoma based on imaging alone.
On MR, endometrial hyperplasia
usually appears as diffuse widening of the endometrium on T2-weighted
images. Hyperplastic endometrium is iso- to hypointense on T2 sequences
relative to normal endometrium. Small foci of increased-T2 signal may be
seen embedded in hyperplastic endometrium. These foci of increased-T2
signal represent cystically dilated glands. After
contrast, hyperplastic endometrium enhances less than the adjacent
normal myometrium. If there are cystically dilated glands, they do not
enhance after contrast administration (Figure 12).36 Similar
to TVS and sonoHSG, the MR-imaging characteristics of endometrial
hyperplasia are nonspecific and stage 1A endometrial cancer cannot be
distinguished from endometrial hyperplasia based on imaging alone.
polyps are focal excrescences of endometrial hyperplasia covered by
endometrium. Three types of endometrial polyps exist:hyperplastic,
atrophic, and functional. Hyperplastic polyps resemble glandular
endometrial hyperplasia; atrophic polyps are composed of cystically
dilated-atrophic glands and functional polyps undergo cyclical changes.
Endometrial polyps can be sessile or pedunculated and can protrude into
the endometrial canal. The most common locations are the uterine fundus
and cornua. Endometrial polyps occur in 10% of women and are multiple
20% of the time. Malignancy is seen in 0.5% of endometrial polyps.
Tamoxifen use increases the relative risk of having endometrial polyps.
TVS and sonoHSG are the studies of choice for the initial detection and characterization of endometrial polyps.37 MRI
is helpful in equivocal cases or when TVS is nondiagnostic. MRI is also
helpful in cases where sampling may be difficult (eg, cervical
stenosis, large-body habitus).
On US, endometrial polyps appear as
nonspecific, echogenic endometrial thickening or as a focal, echogenic
endometrial mass. Anechoic regions within the polyps may be seen and
correspond histologically to dilated glands.35 Color Doppler
imaging demonstrates a single feeding vessel. At sonoHSG, endometrial
polyps are smooth margined, echogenic masses protruding into the
endometrial canal(Figure 13).
The MR appearance of endometrial polyps is variable, especially on T2-weighted sequences.38
Most commonly, the MR appearance on T2-weighted sequences is a slightly
decreased signal compared to endometrium. Endometrial polyps may also
be isointense to endometrium on T2-weighted sequences, appearing as
focal or diffuse thickening of the endometrium; heterogeneous with both
cystic and solid areas; and/or have a low T2-signal intensity fibrous
core or stalk (Figure 14). On T1-weighted images, endometrial polyps are
isointense to endometrium. Polyps enhance with gadolinium contrast,
usually less than normal endometrium but more than normal myometrium.
The contrast-enhancement pattern is not specific. The MR imaging
features of endometrial polyp are nonspecific and endometrial
hyperplasia and endometrial cancer may appear similarly.
is the primary imaging modality for the evaluation of women with
abnormal uterine bleeding. MR and sonoHSG are helpful for problem
solving and/or when TVS is equivocal. New techniques, such as
3-dimensional TVS, 3-dimensional sonoHSG, and MR diffusion-weighted
imaging, are emerging. Three-dimensional TVS has already been shown to
improve the evaluation of uterine shape and the endometrial cavity.39-41 Initial studies in the use of 3-dimensional sonoHSG have been mixed, but more data is needed before a conclusion can be made.42-43
Very little data exist on the use of MR diffusion-weighted imaging in
the evaluation of abnormal uterine bleeding, but preliminary results are
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