Category: 5. Uterine Ultrasound Pathology

Measurement of the endometrium can be used to help assess for pathologies such as hyperplasia or neoplasm that may expedite referral to gynecology for further evaluation or biopsy. The table below outlines the normal values for endometrial thickness which generally decreases after menopause (Nalaboff et al., 2001; Ozcan & DeCherney, 2019). (Values may be slightly elevated in postmenopausal patients undergoing hormone replacement or tamoxifen therapy.)

	Normal Endometrial Measurement
Premenopausal	<15 mm
Postmenopausal	<5 mm

Endometrial Hyperplasia and Neoplasm

Endometrial hyperplasia is characterized by a high endometrial gland-to-stroma ratio. Hyperplasia is concerning because it can develop into endometrial neoplasm. Ultrasound assessment of the endometrium can enhance the detection of hyperplasia that may need referral to gynecology for definitive diagnostic biopsy to rule out neoplasm.

Presentation:

• Postmenopausal uterine bleeding
• History of high estrogen states like obesity, pregnancy, estrogen-secreting tumors, polycystic ovarian syndrome, etc.
• Enlarging pelvic mass (neoplasm, especially if rapidly growing in postmenopausal women)
• Pelvic pain

Assess for endometrial hyperplasia on pelvic ultrasound by measuring the endometrial lining.

Concern for endometrial hyperplasia and neoplasm may be raised by the following ultrasound findings:

• Diffuse thickening of the endometrium (Nalaboff et al., 2001):
  > 15 mm in premenopausal women
  > 5 mm in postmenopausal women
• Focal thickening or heterogenous echogenicity of the endometrium (abnormal even if below threshold levels).
• Obscured endometrium-myometrium border in the case of neoplasm (Lobo et al., 2016).

Endometriosis

Endometriosis is defined as the presence of endometrial tissue (stroma or glands) outside the uterus. While several theories on the pathogenesis of endometriosis exist, most expand on Sampson’s theory which attributes endometriosis to retrograde transplantation of menstrual tissue (Nap et al., 2004; Sampson, 1927).

These ectopic lesions may infiltrate several areas of the pelvis including the ovaries, pouch of Douglas, bladder, and rectum. Given the various locations, sizes, and appearance of endometriosis on ultrasound, this pathology is not easily visualized by ultrasound and usually requires laparoscopic diagnosis.

Endometritis

Endometritis is acute or chronic infection of the endometrium due to a handful of causes including pelvic inflammatory disease, retained products of conception after miscarriage or delivery, and IUD placement.

Presentation:

• Fever
• Abnormal uterine bleeding
• Pelvic pain
• Infertility

While ultrasound imaging can be normal in early stages of infection, the following findings can be visualized as the infection progresses.

• Thickened endometrium
• Free fluid in the pelvis
• Increased vascularity (visualize with Doppler)

Bicornuate Uterus

Congenital uterine abnormalities such as a Bicornuate Uterus may be seen on pelvic ultrasound as a uterus with two conjoined cavities. The biggest risks of having a Bicornuate Uterus are preterm labor and cervical insufficiency.

An Intrauterine Device (IUD) is a birth control device identifiable on ultrasound as a hyperechoic structure exhibiting posterior shadowing and located within the uterine/endometrial cavity. Ultrasound can be used to confirm the proper placement of an Intrauterine Device (IUD) as well as to detect complications such as perforation, expulsion, or migration of the contraceptive device after insertion.

Fibroids are the most common type of benign uterine neoplasm. These estrogen-dependent tumors can arise in a variety of locations within the smooth muscle layer of the uterus and therefore produce a spectrum of symptoms depending on the size and location of the mass.

Most patients with fibroids are asymptomatic but may experience abnormal uterine bleeding or infertility. Association of fibroids with severe pain or uterine bleeding warrants referral to gynecology.

The different types of fibroids you may encounter on pelvic ultrasound are illustrated below:

Ultrasound findings of Fibroids (Leiomyomas)

On ultrasound imaging, the presence of fibroids can usually be detected by heterogeneous enlargement of the uterus due to the presence of well-demarcated, hypoechoic masses within the myometrium. However, Fibroids may also appear isoechoic or hyperechoic.

Remember to examine all parts of the uterus because fibroids can extend beyond the normal contours of the uterus and may be found outside the myometrium alone.

Submucosal Fibroids

Submucosal fibroids are the most common subclass of fibroids and are located just beneath the endometrium. They may also be attached to the uterus by a small piece of tissue called a pedicle, in which case they are classified as pedunculated submucosal fibroids. Patients with submucosal fibroids may present with infertility and uterine bleeding as these tumors grow into the uterine cavity.

Subserosal Fibroids

Subserosal fibroids grow off the surface of the uterus and can extend to impinge on surrounding pelvic structures. Pedunculated subserosal fibroids are also possible.

Intramural Fibroids

Intramural fibroids are another common subclass of leiomyomas but are rarely symptomatic because they grow entirely within the myometrium of the uterus.

Uterine abnormalities are a common cause of pelvic complaints that can be detected well using Point-of-Care Ultrasound. You may especially want to assess for uterine pathologies if uterine measurements are larger than the normals indicated in the chart below.

	Normal (nulliparous)	Normal (parous)
Length (cm)	6-8.5	8-10.5
Depth (cm)	2-4	4-6
Width (cm)	3-5	4-6

Normal Uterine Measurements