The endometrium is the innermost layer of the uterus. The endometrium lines the uterine cavity. Endometrial thickness is a standard measurement in ultrasounds of the pelvis. There is a range of thickness depending on whether the women is premenopausal or post menopausal.
The normal thickness in women who undergo menstruation depends on the phase of the menstrual cycle. The endometrium is thickest during the secretory phase of the cycle and thinnest during menstruation. The normal thickness of the endometrium can range up to 15 mm. This is measured with the uterus in profile or longitudinal dimension on a transvaginal scan.
Endometrial hyperplasia is a more common cause of abnormal thickening of the endometrium on ultrasound before menopause. This is an abnormal proliferation of the endometrial glands. This can occur in women of all ages and present with vaginal bleeding. The major concern is transformation to cancer. Unopposed estrogen is thought to be the major cause. Thickness of greater than 15 mm will be abnormal. Lesser degrees of thickening may be abnormal depending on the phase of the menstrual cycle. It may not be possible to distinguish hyperplasia from cancer just based on the imaging.
Endometrial cancer is the major concern with an abnormally thickened endometrium. Most cases occur in women past menopause. Many cases present with vaginal bleeding. Often a thickened endometrium or mass will be found. Abnormal thickening of the endometrium in women before menopause depends on the phase of the menstrual cycle. Tissue sampling is needed for diagnosis.
Other causes of endometrial thickening on Ultrasound in women before menopause depend on the clinical history. For example, women who taken tamoxifen for breast cancer can have a thickened endometrium. There are multiple pregnancy related causes of thickened endometrium, including early pregnancy and ectopic pregnancy.
Endometritis is infection or inflammation of the endometrium. This can occur after a procedure or as a result of pelvic inflammatory disease. This can complicate vaginal deliveries or after miscarriage. This often presents with pelvic pain and fever. The diagnosis is often clinical but ultrasound will show a thickened endometrium. There is often fluid in the endometrium and blood flow is increased.
Thickening of the endometrium on ultrasound in women before menopause can have many reasons. One of the most important being endometrial cancer. This is however more common in women after menopause. Tissue sampling of the endometrium may be needed to exclude cancer. The imaging appearance of thickened endometrium is often non specific for a single diagnosis.