Synopsis
Select transabdominal ultrasound, transvaginal ultrasound, hysteroscopy or endometrial sampling from the clinical question, interpret endometrial measurements in context, and prevent a reassuring scan from delaying cancer assessment.
- Name the imaging question before ordering: pregnancy location, endometrium, fibroid mapping, adenomyosis, ovarian mass, torsion, abscess or device position require different timing and interpretation.
- Transvaginal ultrasound usually provides higher-resolution views of endometrium and adnexa; seek specific consent, offer a chaperone and provide a transabdominal or deferred alternative when declined.
- Transabdominal ultrasound gives a wider pelvic overview and can help with large masses or when transvaginal scanning is unsuitable, but a full bladder and lower resolution can limit detail.
- For heavy menstrual bleeding with suspected submucosal fibroid, polyp or endometrial pathology, NICE recommends outpatient hysteroscopy as first-line investigation rather than ultrasound alone.
- For heavy bleeding with a palpable uterus, suspected pelvic mass or difficult examination, NICE recommends pelvic ultrasound as first-line investigation; transvaginal ultrasound is preferred when adenomyosis is suspected.
- In premenopausal patients, endometrial thickness changes across the cycle and no single cut-off excludes hyperplasia or cancer; symptoms, risk factors, focal appearance and histology determine next steps.
- For postmenopausal bleeding, transvaginal endometrial measurement is a triage tool within an urgent pathway. A commonly used 4 mm threshold must follow the applicable cancer protocol, image quality and recurrence history.
- NICE advises endometrial biopsy in the context of hysteroscopy for selected high-risk heavy-bleeding presentations and advises against blind biopsy in that pathway.
- Ultrasound describes morphology, not final histology. Polyps, hyperplasia and cancer can overlap, and an inadequate scan should trigger another diagnostic method rather than a normal label.
Key red flags
Postmenopausal bleeding requires urgent cancer-pathway assessment; a thin endometrium reduces probability but persistent or recurrent bleeding still needs review.
A complex adnexal mass, ascites, peritoneal nodularity or unexplained abdominal distension warrants urgent specialist ovarian assessment rather than interval reassurance.
Severe sudden unilateral pain with vomiting can represent ovarian torsion; Doppler flow does not reliably exclude torsion when clinical suspicion is high.
Positive pregnancy testing with pain, bleeding, an empty uterus or free fluid requires an early-pregnancy pathway because hCG and ultrasound findings must be integrated.
Focal endometrial abnormality, irregular thickening or inadequate visualisation should not be reduced to one thickness number; hysteroscopy or sampling may be required.
Any bleeding after established menopause is abnormal and enters urgent assessment; recurrent bleeding remains important after an initially reassuring thickness.
Solid vascular components, papillary projections, irregular multilocularity, bilateral complex lesions or ascites increases malignant probability and specialist urgency.
Abrupt unilateral pain, vomiting and an adnexal lesion suggest torsion; sonographic enlargement and oedema support it, but preserved flow cannot exclude it.
Investigation priorities
Obtain detailed views of endometrium, myometrium, ovaries, adnexa and early pregnancy.
Management branches
Heavy menstrual bleeding requires investigation because history or examination suggests structural or endometrial disease.
- Use outpatient hysteroscopy first when persistent intermenstrual bleeding or risk factors suggest a cavity or endometrial lesion, explaining biopsy and treatment possibilities.
- Use pelvic ultrasound first for a palpable uterus, suspected pelvic mass or difficult examination, and prefer transvaginal scanning when adenomyosis is suspected.
- If the preferred test is declined, offer an acceptable alternative and explain the particular lesions it may miss before agreeing follow-up.