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|
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.
- 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 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 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.
- Abnormal uterine bleeding
- Pelvic pain
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)
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.