Author | Dr. Wang
Source｜Medical World Obstetrics and Gynecology Channel
Many women experience thickened endometrium on gynecological ultrasound during routine checkups, but without any clinical symptoms. Other patients experience irregular vaginal bleeding or abnormal uterine bleeding, with the ultrasound also indicating thickened endometrium. So, what should you consider when you see such an ultrasound report?
01
Endometrial changes are cyclical
Under normal physiological conditions, the thickness of the uterine lining changes with the menstrual cycle.
The menstrual cycle can be divided into the menstrual phase, proliferative phase, and secretory phase based on the histological changes of the endometrium. During menstruation, the functional layer of the endometrium sheds, and the endometrium is at its thinnest. During the proliferative phase, the endometrium undergoes proliferative changes under the influence of estrogen, reaching a thickness of 3-5 mm in the late proliferative phase. During the secretory phase, the endometrium further thickens under the combined influence of estrogen and progesterone, exhibiting secretory changes, reaching a thickness of up to 10 mm in the late secretory phase.
Causes of endometrial thickening include endometrial polyps, submucosal uterine fibroids, endometrial hyperplasia (simple hyperplasia, complex hyperplasia, atypical hyperplasia), and endometrial cancer. It can also be seen in patients using exogenous estrogen medications.
02
Color Doppler ultrasound is the primary diagnostic tool for detecting endometrial thickening.
Transvaginal color Doppler ultrasound is of high value in the differential diagnosis of endometrial thickening.
Under ultrasound, endometrial polyps may present as localized thickening and bulging of the endometrium, disappearance or deformation of the uterine cavity line, narrow base, and clear boundary between the echo and myometrium.
Submucosal fibroids may present with heterogeneous and swirling echoes, or be spherical in shape, with a clear boundary between the echoes and the muscle layer.
Endometrial proliferation can manifest as uniform thickening of the endometrium, uneven and stronger echogenicity, and a clear boundary between the echogenicity and the myometrium.
Endometrial cancer can present as endometrial thickening, heterogeneous echogenicity, and diverse lesions. Strong echoes may appear as clumps or punctate areas within hypoechoic regions, with unclear boundaries between the endometrium and myometrium. Distant metastasis and myometrial infiltration may occur. If the patient has cervical obstruction, uterine fluid or blood accumulation may occur, presenting as anechoic areas.
However, ultrasound examination can only be used as a screening tool to check for abnormalities in the endometrium; it cannot indicate the pathological type.
03
Hysteroscopy is the primary method for diagnosing endometrial lesions.
Hysteroscopy allows direct visualization of lesions within the uterine cavity, enabling observation of local characteristics, preliminary assessment of benign or malignant nature, and simultaneous fractional curettage to obtain endometrial tissue for pathological examination and definitive diagnosis. This significantly improves the detection rate of malignant transformation of endometrial polyps and endometrial cancer, overcoming the limitations of simple diagnostic curettage. Furthermore, hysteroscopic surgery can be performed simultaneously for endometrial polyps and submucosal fibroids.
04
Age is an important factor in the treatment of patients with endometrial thickening.
Endometrial thickening can occur in women of reproductive age and postmenopausal women. Patients may experience menstrual abnormalities, irregular vaginal bleeding, abnormal uterine bleeding, or vaginal discharge, or they may be asymptomatic.
Women of childbearing age
For women of childbearing age, if an ultrasound shows thickened endometrium but there are no clinical symptoms, a follow-up gynecological ultrasound can be performed within 3 days after the next menstrual period ends.
However, if the endometrium is still thick during a follow-up examination, caution is advised. The presence of symptoms such as irregular vaginal bleeding should raise even greater concern. If necessary, a hysteroscopy with fractional curettage may be required to confirm the diagnosis.
Studies have found that the occurrence of endometrial lesions in women of reproductive age is related to abnormal ovarian function and anovulation leading to elevated estrogen levels alone. Therefore, for women of reproductive age whose ultrasound indicates endometrial thickening, ovulation can be monitored to identify potential warning signs of endometrial abnormalities.
Postmenopausal women
In postmenopausal women, the endometrium atrophies. Currently, it is generally accepted that the endometrial thickness in postmenopausal women should not exceed 5 mm. However, there is still no consensus on the cutoff value for endometrial thickness during hysteroscopy.
In postmenopausal women, ultrasound findings of endometrial thickening accompanied by abnormal uterine bleeding or vaginal discharge warrant hysteroscopy and endometrial tissue biopsy for pathological examination to confirm the diagnosis. Studies have found that endometrial thickness is an independent risk factor for predicting endometrial cancer. In patients with thickened endometrium and vaginal bleeding, the sensitivity of excluding endometrial cancer gradually increases with cutoff values of 5 mm, 4 mm, and 3 mm. However, smaller cutoff values lead to a large number of women without endometrial lesions undergoing invasive examinations, increasing patient discomfort, wasting medical resources, and creating a cost-effectiveness problem.
Therefore, in order to reduce medical waste, minimize invasive examinations for women, and rule out most endometrial lesions as much as possible, the 4-5 mm value recommended by the Society of Obstetrics and Gynecology of Canada (SOGC) guidelines is currently widely adopted. Furthermore, women with thickened endometrium accompanied by vaginal bleeding, especially older women and those with a long postmenopausal period, should be closely monitored and undergo regular checkups even if pathology shows no precancerous lesions or cancer.
For asymptomatic postmenopausal patients with endometrial thickening, the cutoff value for endometrial thickness for hysteroscopy and biopsy remains controversial. Currently, there are several cutoff values for endometrial thickness for biopsy, including 10 mm, 11 mm, and 15 mm, with 11 mm being the most commonly used. For patients with an endometrial thickness of 4–11 mm, if the endometrium continues to thicken, vaginal bleeding occurs, or high-risk factors for endometrial cancer are present, including hypertension and obesity, a biopsy should be performed to rule out malignancy.
Endometrial thickening is common in postmenopausal women, and its occurrence is related to the sustained growth of the endometrium caused by estrogen stimulation and the decrease in progesterone levels. In terms of treatment, medroxyprogesterone acetate tablets, a progesterone derivative, can inhibit the secretion of pituitary gonadotropins, thereby reducing luteinizing hormone and follicle-stimulating hormone levels. Currently, there is research into the use of progestins to treat endometrial thickening.
Studies have found that low-dose medroxyprogesterone acetate tablets are effective in treating postmenopausal endometrial thickening, effectively reducing endometrial thickness without serious adverse reactions, making it safe and effective. However, hysteroscopy and endometrial biopsy should be performed to confirm the diagnosis before using this medication.
Therefore, in clinical practice, different treatments should be given to patients with endometrial thickening based on their age, clinical manifestations, and endometrial thickness.
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