• Triage and risk stratification for postmenopausal bleeding (PMB)
• Determining the necessity for invasive endometrial sampling (biopsy or hysteroscopy)
• Evaluating asymptomatic thickened endometrium found incidentally on imaging

• Measured via Transvaginal Ultrasound (TVUS) in the mid-sagittal plane
• Represents the maximum anteroposterior dimension of the endometrial echo (double-layer thickness)
• Caliper placement: from the echogenic interface at the myometrium-endometrium junction to the contralateral interface
• If intracavitary fluid is present, measure both single layers separately and sum them (do NOT include the fluid in the measurement)

• A 4 mm cutoff is extremely reliable for ruling out cancer, but it has low specificity (many false positives from polyps or hyperplasia).
• An unmeasurble endometrium, or one with heterogeneous echotexture regardless of thickness, requires biopsy in a patient with PMB.

• In premenopausal women, thickness varies radically based on the menstrual cycle phase (can be up to 16 mm in secretory phase); fixed cutoffs do NOT apply.
• Tamoxifen use classically causes subendometrial cystic changes that mimic thickening; TVUS often overestimates true endometrial thickness in these patients.
• Do not interpret a "normal" thickness as reassuring if the patient has persistent or recurrent bleeding; biopsy is still warranted.

• Evaluate TVUS results: Thickness ≤ 4 mm.
• If bleeding has stopped: Observation is appropriate. No biopsy required.
• If bleeding is recurrent or persistent: Proceed to hysteroscopy or sonohysterography despite a normal thickness.
• If thickness > 4 mm: Perform in-office pipelle endometrial biopsy.
• If biopsy yields insufficient tissue AND bleeding persists: Proceed to hysteroscopy with D&C.

The shift from universal D&C for all postmenopausal bleeding to a non-invasive initial triage approach accelerated in the late 1990s as high-resolution transvaginal probes became widely available, driven strongly by the landmark 1998 JAMA meta-analysis.