Ultrasound Assessment of Adenomyosis and Endometrial Thickness

Diagnostic Criteria for Adenomyosis

The American College of Radiology states that a markedly enlarged uterus (approximately 13 × 8 cm) with heterogeneous myometrial echotexture and no discrete fibroid is highly suggestive of diffuse adenomyosis【1】.
Transvaginal ultrasound provides a pooled sensitivity of ≈ 82 % and specificity of ≈ 85 % for diagnosing adenomyosis【1】.
When co‑existing fibroids are present, ultrasound sensitivity for adenomyosis falls dramatically from ≈ 98 % to ≈ 33 %; the absence of discrete fibroids therefore improves diagnostic confidence【1】.

An endometrial thickness of ≥ 5 mm in a postmenopausal patient mandates tissue sampling to exclude endometrial carcinoma or hyperplasia【4】.
An endometrial thickness of 11 mm exceeds the 4 mm threshold that yields a > 99 % negative predictive value for cancer, reinforcing the need for histologic evaluation【1】.
Ultrasound alone cannot determine the cause of endometrial thickening; definitive diagnosis requires histologic sampling (biopsy, D&C, or hysteroscopy)【4】.
In premenopausal patients, no validated upper limit for endometrial thickness exists because measurements vary with the menstrual cycle; pathology can be present even when thickness is < 5 mm【1】.
Clinical symptoms (abnormal uterine bleeding, pelvic pain) should guide the decision for tissue sampling in premenopausal patients rather than thickness alone【1】【6】.
Abnormal endometrial echogenicity or texture correlates with significant pathology independent of measured thickness, and any observed heterogeneity should raise suspicion for sampling【1】.

Step 1 – Menopausal status: Postmenopausal patients proceed directly to endometrial tissue sampling; premenopausal patients should have the decision correlated with symptoms and cycle timing【4】.
Step 2 – Advanced imaging: If ultrasound findings are equivocal, magnetic resonance imaging (MRI) of the pelvis with contrast and diffusion‑weighted sequences is the gold standard for confirming adenomyosis【4】. MRI demonstrates a sensitivity of ≈ 78 % and specificity of ≈ 93 % for adenomyosis【3】.
Step 3 – Endometrial characterization: Saline‑infusion sonohysterography can further delineate focal endometrial lesions (e.g., polyps, submucosal fibroids) but cannot reliably exclude malignancy【4】.

Leiomyosarcoma cannot be definitively excluded by ultrasound or MRI alone; clinical red flags include rapid uterine growth, presentation after menopause, or atypical symptom patterns【10】.

The absence of free pelvic fluid and adnexal masses on ultrasound is reassuring and argues against acute complications such as ovarian torsion, ruptured cyst, or ectopic pregnancy【4】.
Adenomyosis is a common cause of abnormal uterine bleeding and pelvic pain in premenopausal women, with symptom severity typically peaking during the perimenopausal years【10】.