Pelvic Ultrasound Can Accurately Measure Endometrial Thickness
Yes, transvaginal ultrasound combined with transabdominal ultrasound is the recommended first-line imaging modality for measuring endometrial thickness in both premenopausal and postmenopausal women with abnormal uterine bleeding. 1, 2, 3
Measurement Technique
The proper technique requires specific positioning and measurement standards:
- Position the transvaginal probe to obtain a longitudinal (sagittal) view of the uterus, identifying the endometrium as the echogenic lining of the endometrial cavity 3
- Measure the double-layer thickness at the thickest portion, perpendicular to the endometrial-myometrial interface, including both anterior and posterior layers 3
- The American College of Radiology recommends performing combined transabdominal and transvaginal approaches whenever possible for complete pelvic assessment 2, 3
Common Measurement Errors to Avoid
Several technical pitfalls can compromise accuracy:
- Measuring in an oblique plane rather than true sagittal plane falsely increases thickness 3
- Including adjacent myometrium in the measurement or measuring only a single layer are frequent errors 3
- Failing to identify the true endometrial-myometrial interface or not measuring at the thickest portion compromises diagnostic accuracy 3
Clinical Thresholds and Interpretation
Postmenopausal Women
The evidence strongly supports specific cutoff values:
- Endometrial thickness ≤4 mm has a negative predictive value for endometrial cancer of nearly 100% 2, 3, 4
- Thickness ≥5 mm generally requires endometrial tissue sampling 2, 3
- The European Society for Medical Oncology uses a slightly more conservative cutoff of ≤3 mm 2
- Transvaginal ultrasound is at least as sensitive as endometrial biopsy for detecting endometrial cancer 4
Premenopausal Women
Interpretation is more complex due to physiologic variation:
- There is no validated absolute upper limit cutoff for endometrial thickness as it varies with menstrual cycle phase 3
- Thickness exceeding 11 mm in asymptomatic premenopausal women warrants tissue sampling to rule out hyperplasia or malignancy 1
- Abnormal echogenicity and texture correlate with significant pathology even when thickness appears normal 2, 3
Diagnostic Limitations and When Additional Testing Is Needed
While ultrasound effectively measures thickness, it has important limitations:
- Ultrasound is sensitive for evaluating endometrial thickness but cannot reliably determine the etiology of endometrial thickening 2
- Sonohysterography should be performed when initial ultrasound demonstrates focal endometrial abnormalities, with sensitivity of 96-100% for assessing endometrial pathology 1, 4
- Color Doppler evaluation of endometrial vascularity helps identify abnormal vascular patterns suggestive of polyps or cancer 1, 3
Critical Clinical Pitfalls
- Do not rely solely on endometrial thickness measurement without tissue sampling when thickness exceeds 11 mm in premenopausal women or 4-5 mm in postmenopausal women with bleeding 1, 2
- In asymptomatic postmenopausal women, the conventional 4-5 mm threshold used for women with bleeding is not directly transferable for excluding focal intrauterine pathology 5
- Office endometrial biopsies have a false-negative rate of approximately 10% in postmenopausal women, necessitating hysteroscopy if clinical suspicion remains high despite negative biopsy 2
- When ultrasound and endometrial biopsy results do not agree, hysteroscopy with direct visualization and targeted biopsy is essential 6
Enhanced Diagnostic Features Using IETA Terminology
Specific ultrasound features help stratify cancer risk: