is an Assistant Professor of Diagnostic Radiology in the
Departments of Radiology and Obstetrics & Gynecology at the
Medical College of Wisconsin in Milwaukee, WI.
he technique of hysterosonography (HSG) was introduced in 1987, and
became used clinically in the early 1990s. Hysterosonography is the
technique whereby sterile saline is instilled into the uterine
cavity, thus allowing improved transvaginal ultrasound (TVUS)
imaging of the uterus and endometrium. The clinical applications of
HSG are for the evaluation of postmenopausal bleeding, further
evaluation of an abnormal endometrial interface seen on
transvaginal sonography, and to assess possible causes of
Traditionally, in patients requiring evaluation of the uterine
cavity, there had been two mainstay methods. It could be evaluated
indirectly by hysterosalpingography with the use of radiographic
contrast and x-rays, or by direct visualization with
In the late 1980s, transvaginal sonography began to be used
clinically in addition to traditional transabdominal sonography in
the evaluation of the female pelvis. The use of TVUS significantly
improved the ability to examine the structures of the female
pelvis. Transvaginal ultrasound became the imaging method of choice
for evaluating endometrial abnormalities, particularly in patients
with abnormal vaginal bleeding. It is a highly sensitive technique
for detecting small uterine masses and endometrial abnormalities,
but it is nonspecific.
The disadvantage of TVUS, however, is that it cannot reliably
distinguish between lesions of myometrial origin located centrally
in the uterus and those of endometrial origin. Endometrial polyps
are more evident during the proliferative phase of the menstrual
cycle by transvaginal sonography because of the inherent
physiologic changes of the endometrium that can be seen on
ultrasound, but can be easily shown by HSG at any stage of the
Initially a brief patient history is obtained, regarding
symptoms, duration of symptoms, and any history suggesting active
pelvic infection. Also, it is important to inquire if the patient
has had a recent endometrial biopsy. If the patient is
premenopausal, she should also have a negative pregnancy test.
A baseline transvaginal ultrasound is performed to assess the
uterus/endometrium and adnexal structures. Using aseptic technique,
a sterile speculum is placed in the vagina with direct
visualization of the cervix. The cervix is cleansed with betadine.
The sterile 5-French hysterosonography catheter (Lyco HSG Catheter;
Model 06-105F) is then placed into the uterine cavity by direct
visualization of the external cervical os. The speculum is removed
carefully, leaving the catheter in place, and the 5-7 MHz
multifrequency transvaginal ultrasound transducer is inserted into
the vagina. Under ultrasound visualization, the balloon of the
catheter is inflated with saline. The balloon is then drawn gently
toward the internal os to anchor it in place and also to avoid the
instilled saline from draining out through the cervix during the
exam. Sterile saline is then instilled through the catheter to
distend the uterine cavity during TVUS imaging. Approximately 10 cc
of saline is usually sufficient to achieve adequate uterine
distention. Sagittal and coronal imaging of the uterus is
performed. It is common to see fluid in the cul-de-sac after the
procedure. This infers patency of at least one fallopian tube.
In the normal exam, the uterine cavity is distended
symmetrically. The endo-metrium appears symmetric and uniformly
thick. On conventional TVUS, a uniform endometrial thickness of the
two coapted layers of <5 mm is considered normal in the
The measurement of the endometrial thickness on HSG is obtained by
adding the thickness of the opposite endometrial linings. Note that
the total added thickness should not exceed 5 mm. No masses distort
the uterine cavity or are present within the uterine cavity (figure
Several abnormalities can be detected by HSG; the most commonly
found include adhesions, polyps, leiomyomas, endometrial tumors,
and tamoxifen-related changes.
--By conventional TVUS, the endometrial lining may appear normal.
Adhesions can be one of the etiologies of infertility. On HSG,
bridging bands of tissue can be seen which distort the uterine
cavity. Thick, broad bands may make it difficult to distend the
uterine cavity (figures 2 and 3).
Patients with uterine polyps can present with unexplained
infertility and abnormal vaginal bleeding. On conventional TVUS, a
thickened endometrium can often be seen. On HSG, an intracavitary
polyp outlined by the anechoic saline can be demonstrated (figure
4). The endometrial lining is normal. Often the point of
attachment, as well as the thickness of the stalk, can be
identified on HSG. Color Doppler can be useful in helping to
identify the stalk of the polyp. Usually, polyps are seen as
homogenous, smooth hyperechoic masses with well-defined margins.
They may be sessile or pedunculated, solitary or multiple.
Occasionally, small cystic spaces are visible within the polyps.
Polyps are associated with a three-fold increase in endometrial
--Leiomyomas are common gynecological abnormalities. They can be
clinically silent, or can present with abnormal vaginal bleeding,
pain, or unexplained infertility. Conventional TVUS can be used to
identify the leiomyoma, its relationship with the endometrial
interface, and any distortion of the myometrial/endometrial
interface. HSG can be helpful for further localization of the
leiomyoma, whether it is submucosal or intramural (figure 5). This
information can affect the patient's management and also help to
differentiate if the fibroid is the etiology of the abnormal
Intramural leiomyomas are located within the myometrium and do
not distort the endometrial cavity. Submucosal leiomyomas often
distort the endometrial cavity and have little or no intervening
myometrium between the fibroid and endometrium. There is a normal
layer of endometrium present over the fibroid (figure 6).
--Basically, endometrial abnormalities can occur in two groups of
patients, perimenopausal and postmenopausal women with bleeding.
The major concern with the perimenopausal patient with unexplained
vaginal bleeding is endometrial carcinoma; however, the most common
etiology is atrophic endometrium. Therefore, demonstrating an
endometrial stripe by ultrasound of <5 mm would be very
important in differentiating these two groups of patients and their
The majority of postmenopausal women with bleeding will have
benign etiologies for the bleeding. Exogenous estrogen is a cause
in 30% of patients; atrophic endometritis/vaginitis in 30%;
endometrial hyperplasia in 10%; endometrial polyps in 10%;
submucosal fibromyomas in 10%; and endometrial carcinoma in
approximately 10% of these patients.
Approximately 75% of all cases of endometrial carcinoma occur in
Because this cancer often presents with abnormal vaginal bleeding,
most cases are detected at an early stage when they are highly
curable. Early detection can offer a 5-year survival rate of 83%.
These cancers also tend to be early-stage, low-grade, minimally
invasive lesions that have a favorable prognosis.
Patients who are taking unopposed estrogen therapy have a four- to
eight-fold increase in risk of developing endometrial carcinoma.
This risk can be nearly eliminated by combining progesterone with
On HSG, endometrial carcinoma can appear as an irregularly
thickened endometrium with variable echogenicity, with an
endometrial-myometrial junction that may or may not be intact.
An endometrial thickness >5 mm in a postmenopausal woman should
be further evaluated for the possibility of endometrial
--Tamoxifen is widely used as part of the treatment of breast
cancer. It has an antiestrogenic effect on the breast and a weak
estrogenic effect on the uterus. An increase in endometrial cancer
has been reported with the use of tamoxifen as a finding of the
National Surgical Adjuvant Breast and Bowel Project (NSABP) B-14
The final conclusion with regard to this patient population was
that the benefit of tamoxifen treatment for breast cancer outweighs
the potential increase in endometrial cancer.
Other findings that can be seen in the endometrium of patients
taking tamoxifen include polypoid lesions (figure 7), endometrial
hyperplasia, and subendometrial cystic lesions.
These microcystic changes are located in the proximal myometrium
while the endo-metrium remains thin and atrophic. These changes are
thought to represent reactivation of foci of adenomyosis due to the
estrogen effects of tamoxifen.
Endometrial biopsy vs. HSG in the postmenopausal
Hysteroscopy is an accurate method for the diagnosis and
treatment of endometrial abnormalities. However, not every patient
with postmenopausal bleeding will require such an invasive and
high-cost intervention for diagnosis and treatment. The cost of
performing and interpreting the results of a blind endometrial
biopsy is comparable to the cost incurred for performing a TVUS.
Based on the findings of the TVUS and the finding of thickened
endometrial lining, the additional cost of performing a
hysterosonogram justifies the added information it provides and
thus results in decreased total patient care cost.
According to a prospective double-blind study of 47
postmenopausal women comparing HSG with hysteroscopy, it was found
that HSG was 86% sensitive and 100% specific in the diagnosis of
An endometrial thickness >5 mm is a sensitive finding on TVUS
for the presence of endometrial abnormalities. Sensitivities as
high as 97% have been reported in detecting endometrial cancer in
patients with endometrial thicknesses >5 mm.
Variable results in sensitivity for detecting endometrial tumors
with blind endometrial biopsies range from 33% to 85%.
Endometrial biopsy samples only a small portion of the endometrium,
and the endometrial lesion may be easily missed when performed
blindly. Therefore, endometrial biopsy alone is not sufficient to
evaluate the postmenopausal patient with bleeding. The added
information attained with TVUS increases the sensitivity of
detection of endometrial abnormalities. Which, if found, could be
further evaluated with HSG and then be used as a guide for biopsy
Clinical indications for HSG
Hysterosonography can be useful in several clinical situations.
It is effective in the postmenopausal woman with vaginal bleeding
who is found to have an abnormal endometrial thickness. It can be
used as a screening tool to evaluate for endometrial changes
related to tamoxifen. Uterine malformations as a possible etiology
of infertility can be easily evaluated with HSG. The uterine cavity
can also be assessed after myomectomy, metroplasty, and lysis of
synechiae with HSG.
Absolute contraindications to performing HSG are pregnancy,
stenotic endocervix, active pelvic inflammatory disease, and recent
pelvic surgery and/or biopsy. The major risks are infection and
perforation. There also are a few limitations of HSG. If the
patient has cervical stenosis and the cervix can not be cannulated,
the procedure can not be performed. Inadequate distention of the
uterine cavity can occur under several conditions. Primarily, this
occurs in patients with a patulous cervix, but can also occur if
fluid easily leaks out of the fallopian tubes. Bilateral tubal
occlusion may result in difficult and painful distension of the
endometrial cavity. DeVore also described the theoretical risk of
spread of infection and dissemination of endometrial carcinoma by
However, this is unlikely as such a small amount of fluid is
instilled and it is instilled under low pressure.
Finally, it is sometimes difficult to visualize abnormalities just
above the internal os. The balloon of the catheter may obscure
these lesions. To help with visualization of this region, saline is
instilled through the catheter while watching with ultrasound as
the catheter is being withdrawn.
Hysterosonography is well tolerated by patients. It does not
require anesthesia or analgesia. It can be performed in an
outpatient setting and does not incur the expense of the operating
room. It allows improved depiction of the endometrial cavity
without the use of ionizing radiation or iodinated contrast. It
allows differentiation of intracavitary, endometrial, and
submucosal abnormalities with a greater degree of confidence.
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