Sonographic Evaluation of the Uterus. Text Version

This unit will cover:

  • Ultrasound Evaluation of and Anatomic Locations of Leiomyomas  
  • Ultrasound Evaluation of Endometrial Abnormalities

Ultrasound Evaluation of and Anatomic Locations of Leiomyomas

Uterine leiomyomas are also termed fibroids or myomas. Myomas arise from an overgrowth of connective tissue and smooth muscle, occurring frequently in 50 to 77% of all women. Myomas are the most common solid benign neoplasms of the uterus and are present predominantly in reproductive-age women. Myomas are, therefore rare in puberty and decline in size in the postmenopausal years. Being estrogen-dependent, myomas may increase in size during pregnancy and may undergo painful degeneration. Myomas undergo malignant transformation to leiomyosarcomas in less than 1% of cases. 

Clinical Presentations

Risk factors and common clinical presentations for myomas are listed in the following charts.  

Imaging Considerations


Ultrasound is the major imaging modality for the evaluation of uterine myomas. Either transabdominal or transvaginal ultrasound may be employed and each method has advantages and disadvantages. While transvaginal ultrasound may be superior for small near-field myomas, the depth of field may limit its use for larger myomas. The following tables illustrate these concepts.

Anatomic Location of Leiomyoma

In 2011, the International Federation of Gynecology and Obstetrics (FIGO) proposed a classification of uterine fibroids.  The classification defines a number of uterine and extra-uterine anatomic sites for the presence of uterine fibroids and while some deficiencies are reported.  The classification represents a method to define a common language for defining the location of uterine fibroids.

Above. The FIGO classification system. Image 1.

Schematic drawing of various types of uterine fibroids Image 2.


Above. A small intramural uterine fibroid. Image 3.

Above. A very large (9 cm) probable submucous fibroid of the uterus. Image 4.

Above. A relatively large submucosal leiomyoma; it fills out the major part of the endometrial cavity. Image 5.

Above. 5 cm. subserosal fibroid. Note the relationship to the urinary bladder and to the body of the uterus. Image 6.

Above. Abdominal radiograph of partially calcified myomas.

Above left. Note large subserosal myoma and clearly defined uterine body. Above right. Same patient. Large subserosal myoma.

Above. Color flow peripheral to the fibroid. Note uterine body separately. Image 7.

Ultrasound Evaluation of Endometrial Abnormalities

Endometrial abnormalities represent a wide spectrum of findings. Ultrasound is the usual imaging modality but MRI. CT scans, sonohysterography, and hysterosalpingography may be used to correlate with ultrasound findings. The ultrasound assessment of the endometrium poses a challenge since the endometrium changes during the menstrual cycle and is affected by age and pregnancy status. In addition, the administration of exogenous hormones such as tamoxifen may engender endometrial changes.

The following chart represents some of the potential endometrial abnormalities.

Assessment of the Endometrium

Transvaginal ultrasound is the preferred imaging method to assess the endometrium but transabdominal ultrasound may be useful in the presence of large uterine myomas, a globally enlarged uterus, or adnexal masses impinging upon the uterus. The endometrium changes during the menstrual cycle and becomes atrophic in postmenopausal women. During menstruation, the endometrium appears as a thin, echogenic line 1–4 mm in thickness; during the proliferative phase, the endometrium becomes thicker (5–7 mm) and more echogenic, while the endometrium typically reaches a maximum thickness during the mid-secretory phase of the menstrual cycle.

Quantitative Assessment of Endometrial Thickness

The following is a summary of the quantitative assessment of endometrial thickness*.

  • Endometrial thickness: maximum measurement in the sagittal plane, includes both endometrial layers
  • Uterus: midsagittal plane, the whole endometrial stripe needs to be seen from the fundus to the endocervix
  • The calipers should be placed at the level of the two opposite endometrial-myometrial interfaces. should be reported in millimeters, and rounded up to one decimal point.
  • When intracavitary fluid is present, the thickness of both single layers is measured in the sagittal plane
  • Intracavitary fluid should be defined by its largest measurement in the sagittal plane.
  • If the endometrium is thickened asymmetrically, the anterior and posterior endometrial thicknesses should also be reported separately
  • When the endometrium cannot be adequately visualized in its entirety, report as not measurable and incompletely visualized

Endometrial Changes during the Normal Menstrual Cycle


Above. Normal premenopausal endometrium in week 1 of the menstrual cycle. Note relatively thin, hypoechoic endometrium. Image 8.

Above. Normal premenopausal endometrium in weeks 2 and 3. Late proliferative endometrium with the trilaminar appearance. Image 9.


The secretory phase is manifest by a loss of the trilaminar appearance of the proliferative phase and then reaches a maximum of 15 mm. in thickness. The endometrium becomes echogenic compared to the surrounding myometrium. Image 10.

Postmenopausal Endometrium

Above. Postmenopausal endometrium with fluid. Sagittal ultrasound shows a normal thin, echogenic endometrium separated by fluid. The endometrial thickness on each side of the fluid pocket is measured and added together.

Endometrial Polyps


Among gynecological polyps, endometrial polyps occur in 7.8 to 50% of women in the 20 to 74-year-old age group.


Endometrial polyps are considered hyperplastic growths of the endometrial stroma and glands, which are typically benign but rarely can be malignant.

Clinical Presentation

The most common clinical presentation is abnormal uterine bleeding, while many women will be asymptomatic in the presence of an endometrial polyp.

Risk factors

The following are apparent risk factors for the development of endometrial polyps.

Imaging Considerations

Transvaginal ultrasound has increased the number of patients diagnosed with endometrial polyps.

Ultrasound imaging is recommended to be performed on day 10 of the menstrual cycle since a thin endometrial background yields a more favorable environment for imaging purposes and reduces the false positives or false-negative results.   Confirmation of the diagnosis can be obtained with contrast saline infusion sonography (SIS), gel instillation sonography (HyCoSy), or hysteroscopy.

Most endometrial polyps are hyperechoic and most commonly arise in the uterine cornual area or fundus and rarely can prolapse through the cervix. Color Doppler imaging can be helpful by demonstrating the vascular pedicle, seen in just under 50% of polyps.


Above. Echogenic endometrial polyp. Image 11.

Above. Endometrial polyp with feeding vessel. The anechoic area near the polyp is fluid. Image 12.

Above. Hysterosalpingogram demonstrating a pedunculated filling defect representing an endometrial polyp. Image 13.

Above. Saline infusion demonstrating endometrial polyps in a premenopausal woman. Image 14.

Submucosal Fibroids

See above for a discussion of uterine myomas or fibroids. Submucosal myomas are the less common of the uterine myomas but tend to produce the greater symptoms due to their encroachment and projection into the uterine cavity. Submucosal myomas can produce either pain and/or bleeding.


Above.  Sagittal sonohysterography image. There is an intracavitary extension of a submucosal myoma. Image15.

Above. Hysterosalpingogram demonstrates smooth filling defects distorting the uterine cavity and representing submucosal fibroids. Image 16.

Endometrial Hyperplasia

The abnormal proliferation of endometrial stroma and glands result in endometrial hyperplasia which represents a range of changes from atypia to neoplasia.  Endometrial hyperplasia may be an antecedent event to endometrial cancer in up to 1/3 of cases.  Ultrasound is not able to distinguish between endometrial hyperplasia and endometrial cancer and biopsy is the final arbiter. Greater than 10 mm. in endometrial thickness defines endometrial hyperplasia, especially in postmenopausal women.

The following are ultrasound appearances that might mimic endometrial hyperplasia.

Above. Sagittal view transvaginal ultrasound. Endometrial thickness measures 19 mm. meeting the criteria for endometrial hyperplasia. Image 17.

Above. After saline infusion into the endometrial cavity, measurement of endometrial thickness confirms endometrial hyperplasia. Image 18.

Above. Endometrial hyperplasia with fluid collection within the endometrial cavity. A biopsy is required to rule out endometrial cancer.  Image 19.

Endometrial Adenocarcinoma

Endometrial adenocarcinoma is the most common invasive neoplasm of the uterus. As noted above the ultrasound findings for endometrial adenocarcinoma are non-specific and suspicious findings always require biopsy.

Imaging Considerations

Some findings warrant close attention and these include irregular thickening and the presence of polypoid tumors on ultrasound.  Irregularity of the interface between the endometrium and myometrium may suggest invasive disease and any collection of fluid within the endometrium should lead to a biopsy.


Transvaginal ultrasound in a postmenopausal woman. Note anechoic endometrial fluid. The image would be highly suspicious for endometrial cancer and the patient would require further investigation. Image 20.

Above. Transvaginal ultrasound sagittal view. Thickened, asymmetric, and lobulated endometrium. The endometrium measures 5.64 cm. and fluid and/or blood occupy the cavity. Biopsy confirmed endometrial cancer. Image 21.

Above. Transvaginal ultrasound sagittal view with thickened endometrium. Note arrows showing the interface between the myometrium and the thickened endometrium. Biopsy confirmed endometrial cancer. Image 22.

Tamoxifen-associated Changes

Tamoxifen is a pro-estrogen medication that is used to treat breast cancer.

Tamoxifen Effects

The effects on the endometrium are listed in the following table.

Within 6 to 36 months almost 50% of patients treated with tamoxifen for breast cancer are at risk for the development of an endometrial abnormality.  If a patient develops bleeding while on this therapy, further evaluation should be undertaken.

Imaging Considerations

Ultrasound observations:

The endometrium is thickened, irregular, and cystic.

Punctate cystic spaces may be secondary to reactivation of adenomyosis and may represent small sub endometrial sonolucencies in the proximal myometrium.

The degree of thickening of the endometrium corresponds to the length of tamoxifen use and about 48% of patients will show an endometrial thickness of 8 mm. or greater.

MRI imaging may be useful in the evaluation of those patients on tamoxifen therapy.


Tamoxifen-associated endometrial changes. A transvaginal ultrasound image in a patient receiving tamoxifen for breast cancer shows endometrial thickening with cystic changes. Image 23

Above. Endometrial thickening is associated with tamoxifen therapy. The image reveals marked endometrial thickening (arrowheads) associated with sub endometrial cysts (arrows) resulting from tamoxifen therapy. Image 24.

Endometrial Adhesions

Posttraumatic or postsurgical injury to the endometrial lining can result in endometrial adhesions. The result may be infertility, recurrent pregnancy loss, and lack of menses. The diagnosis is often difficult to make with ultrasound and distention of the endometrial cavity with sonohysterography or hysterosalpingography may be necessary to define the adhesions.


Above. Adhesions. Note Strands of tissue, crossing the endometrial cavity, adjoining the opposing uterine walls, and entrapping fluid. Image 25.

Endometrial adhesions. Hysterosalpingogram reveals irregular filling defects in the endometrium (arrows) representing adhesions. Image 26.

Intrauterine fluid collections

Any significant fluid collection is abnormal and father evaluation is necessary due to a wide range of potential disorders.

Clinical Conditions Associated with Intrauterine Fluid Collections

In postmenopausal women, a small amount of fluid within the endometrial cavity on transvaginal ultrasound may be normal. However, if the peripheral endometrium in the presence of fluid is thicker than 3 mm. sampling of the endometrium is mandatory.

Other causes of fluid accumulation within the endometrial cavity include an obstructing tumor or cervical stenosis.

In premenopausal and prepubertal patients, the following possibilities exist for fluid accumulation.

  • Menstruation
  • Early intrauterine pregnancy
  • Pseudogestational sac in an ectopic pregnancy
  • Hematometrocolpos in prepubertal patients

Imaging Considerations.

The fluid may range in appearance from hypoechoic to hyperechoic depending on whether it is composed of serum, mucin, or blood.


Above. Transvaginal ultrasound. Sagittal view. Intrauterine fluid collection in a postmenopausal patient. Note the thin endometrial lining. Image 27.

Above. Transvaginal ultrasound in a postmenopausal woman. Note anechoic endometrial fluid. The image would be highly suspicious for endometrial cancer and the patient would require further investigation. Image 28.

Above. Transvaginal ultrasound in a premenopausal woman, The anechoic area suggests fluid accumulation.

Gestational Trophoblastic Disease

Gestational trophoblastic neoplasia (GTN) terminology includes complete hydatidiform mole (CHM), partial hydatidiform mole (PHM), invasive mole, choriocarcinoma, and placental site trophoblastic tumor. These neoplastic changes in placental trophoblastic tissue are typically associated with increased hCG production and may have other clinical manifestations such as early-onset preeclampsia, hyperemesis, and bleeding. Among the GTN subtypes, HM is the most common occurring at a frequency of 1 in 750 pregnancies.

Imaging Considerations

In CHM, there is generalized trophoblastic hyperplasia and swelling of the chorionic villi in the absence of an embryo or fetus, while in PHM, there is focal trophoblastic hyperplasia and focal swelling of villous tissue in the presence of fetal or embryonic tissue.


Above. Complete hydatidiform mole. Note echogenic tissue with multiple cystic spaces. Image 29.

Above. Color Doppler of the above image shows the mass to be highly vascular. Image 30.

Intrauterine Contraceptive Devices

Intrauterine contraceptive devices (IUD) are highly echogenic and most often detected with either transabdominal or transvaginal ultrasound. Transvaginal ultrasound is indicated if there is confusion between the endometrial stripe and the IUD. If there is concern relative to uterine perforation, a CT scan may determine whether the IUD is within the peritoneal cavity.


Above. Transvaginal ultrasonography showing an IUD with copper as a hyperechoic (rendered as bright) line at right, 3 centimeters away from the uterus at left. The IUD is surrounded by a hypoechoic (dark) foreign-body granuloma. The urinary bladder is seen beneath it, close to the circular tip of the ultrasound probe at the bottom. The patient was a 29-year-old woman who had a painful IUD insertion 2 months earlier. Image 31.