What are the features of adenomyosis on a 3D (three-dimensional) ultrasound scan?

3D Ultrasound Features of Adenomyosis

3D transvaginal ultrasound demonstrates high diagnostic accuracy (90%) for adenomyosis when at least two characteristic features are present, with the most specific findings being junctional zone thickening ≥8 mm, myometrial asymmetry, and hypoechoic striations. 1

Direct Features of Adenomyosis on 3D Ultrasound

These features indicate the presence of ectopic endometrial tissue within the myometrium:

• Myometrial cysts: Small anechoic or hypoechoic round lesions within the myometrium, representing ectopic endometrial glands 2

• Hyperechogenic islands: Bright echogenic foci scattered throughout the myometrium, reflecting areas of ectopic endometrial tissue 2

• Echogenic subendometrial lines and buds: Linear or nodular hyperechoic structures extending from the endometrium into the myometrium 2

Indirect Features of Adenomyosis on 3D Ultrasound

These features reflect secondary myometrial changes:

• Junctional zone abnormalities: The most diagnostically useful finding, with maximum junctional zone thickness (JZ max) ≥8 mm showing 83% specificity 1. Poor definition of the junctional zone demonstrates 86% sensitivity on 3D ultrasound 3. 3D ultrasound optimizes visualization of the junctional zone compared to 2D imaging 2

• Myometrial asymmetry: Unequal thickness of anterior versus posterior myometrial walls, with 83% specificity 1

• Hypoechoic striations: Linear hypoechoic bands extending from the endometrium into the myometrium (also called "fan-shaped shadowing"), with 83% specificity 1

• Globular uterus: Diffuse enlargement with rounded contour of the uterus 2

• Irregular or interrupted junctional zone: Loss of the normal smooth interface between endometrium and myometrium 2

• Translesional vascularity: Abnormal blood flow patterns extending through adenomyotic lesions 2

Diagnostic Performance

• Overall accuracy: When at least 2 ultrasound features are present, 3D ultrasound achieves 90% accuracy (sensitivity 92%, specificity 83%, positive predictive value 99%, negative predictive value 71%) 1

• Heterogeneous myometrium: Shows the highest pooled sensitivity at 86% across studies 3

• 3D versus 2D comparison: 3D ultrasound shows pooled sensitivity of 88.9% and specificity of 56.0%, with no significant improvement in overall accuracy compared to 2D ultrasound 3. However, 3D provides superior visualization of junctional zone anatomy 2

Critical Diagnostic Considerations

Important caveat: Diagnostic accuracy drops significantly in specific clinical scenarios:

• Post-endometrial ablation: Accuracy decreases to 50% because ablation alters junctional zone appearance 1

• Patients on medical therapy: Accuracy decreases to 60% due to hormonal effects on myometrial architecture 1

• Coexisting leiomyomas: Sensitivity of transvaginal ultrasound for adenomyosis drops from 97.8% to 33.3% when fibroids are present, as they obscure adenomyotic features 4

Practical Imaging Algorithm

The American College of Radiology recommends the following approach:

1. Initial evaluation: Transvaginal ultrasound (2D with Doppler) as first-line imaging, with pooled sensitivity 82.5% and specificity 84.6% 4, 5

2. 3D ultrasound enhancement: Consider 3D reconstruction when 2D findings are equivocal or to better characterize junctional zone abnormalities and localize adenomyotic lesions within specific myometrial walls 1

3. MRI for problem-solving: When ultrasound is inconclusive or adenomyosis obscures endometrial visualization, MRI should be performed, as it can display the endometrium even when obscured by adenomyosis on ultrasound 4, 6

Common Diagnostic Pitfalls

• Asymptomatic patients: Approximately 16% of symptomatic patients may not demonstrate any direct ultrasound signs despite having clinical adenomyosis, creating false negatives with strict application of diagnostic criteria 6

• Inadequate junctional zone assessment: Standard pelvic ultrasound protocols do not routinely include the detailed assessment needed to identify adenomyosis features 6

• Relying on single features: Using isolated findings rather than the presence of multiple features significantly reduces diagnostic accuracy 1

Clinical integration is essential: Imaging findings must be interpreted in the context of clinical symptoms (pelvic pain, abnormal uterine bleeding) and risk factors, especially when direct ultrasound signs are absent but adenomyosis remains clinically probable 6, 7