Normal Endometrial Wall Thickness
Normal endometrial thickness varies by menopausal status, with postmenopausal women having a threshold of ≤4 mm considered normal, while premenopausal women have variable thickness depending on menstrual cycle phase, typically ranging from 3-13 mm. 1
Postmenopausal Women
Normal Range
- ≤4 mm is considered normal in postmenopausal women 1
- Endometrial thickness ≤4 mm in a postmenopausal woman conveys a negative predictive value for endometrial cancer of nearly 100% 1
- The average thickness of endometrium for postmenopausal women without bleeding is 1.4 ± 0.7 mm (range 1-5 mm) 2
Clinical Implications
- Endometrial thickness ≥5 mm in postmenopausal women generally prompts evaluation by endometrial tissue sampling 1
- For asymptomatic postmenopausal women, endometrial biopsy is strongly recommended if thickness is ≥11 mm 3, 4
- In postmenopausal women with vaginal bleeding, the risk of cancer is approximately 7.3% if endometrium is >5 mm and <0.07% if ≤5 mm 4
Premenopausal Women
Normal Range by Menstrual Cycle Phase
- Follicular phase: 7.8 ± 2.1 mm (range 3-13 mm) 2
- Around ovulation: 10.4 ± 1.9 mm (range 8-13 mm) 2
- Luteal phase: 10.4 ± 2.3 mm (range 8-19 mm) 2
Clinical Implications
- There is no validated absolute upper limit cutoff for endometrial thickness in premenopausal women 1
- Normal endometrial thickness varies with the phase of the menstrual cycle 1
- Endometrial thickness alone is not a reliable indicator of endometrial pathology in premenopausal women 1
- Even if thickness is <5 mm, endometrial polyps or other pathology may be present 1
Abnormal Findings and Pathology Correlation
Postmenopausal Women with Bleeding
- Atrophic endometrium: 2.2 ± 2.0 mm 2
- Hydrohystera: 14.5 ± 6.1 mm 2
- Endometrial hyperplasia: 17.4 ± 6.7 mm 2
- Endometrial polyps: 16.7 ± 7.7 mm 2
- Endometrial carcinoma: 24.4 ± 11.9 mm 2
Imaging Considerations
- Transvaginal ultrasound (TVUS) is considered the first-line screening test for endometrial cancer in the setting of postmenopausal bleeding 1
- A combined transabdominal and transvaginal approach is typically recommended for complete assessment of pelvic structures 1
- For both postmenopausal and premenopausal women, abnormal echogenicity and texture of the endometrium correlates with significant underlying uterine pathology 1
- In women without abnormal uterine bleeding, TVUS measurement of endometrial thickness is effective in excluding focal intrauterine pathology, especially in postmenopausal women 5
Common Pitfalls to Avoid
Misinterpreting premenopausal measurements: Do not apply postmenopausal thickness thresholds to premenopausal women, as thickness normally varies throughout the menstrual cycle.
Relying solely on thickness in premenopausal women: Many studies have shown that endometrial thickness in premenopausal women is not a reliable indicator of endometrial pathology 1.
Ignoring endometrial texture and echogenicity: Abnormal appearance can indicate pathology even when thickness is within normal range 1.
Failing to consider endometrial fluid: The presence of endometrial fluid with thickness >4 mm may indicate pathology in postmenopausal women 6.
Not accounting for hormone therapy: Women on tamoxifen or hormone therapy may have increased endometrial thickness without pathology 7.