Ultrasound Findings of Adenomyosis
The most accurate ultrasound signs of adenomyosis on 2D transvaginal ultrasound are heterogeneous myometrium, myometrial cysts, subendometrial microcysts, and hyperechoic myometrial spots, with the combination of these features significantly improving diagnostic specificity to 86.1%. 1
Primary Diagnostic Features
The American College of Radiology recommends transvaginal ultrasound (2D with Doppler) as first-line imaging, achieving pooled sensitivity of 82.5% and specificity of 84.6%. 2 The following features demonstrate the highest individual accuracy (55.7-62.1%) for adenomyosis detection:
Most Reliable Signs
- Heterogeneous myometrium: Irregular echotexture throughout the myometrial tissue, representing the most common finding 3, 1
- Myometrial cysts: Anechoic round spaces within the myometrium, representing ectopic endometrial glands 3, 1
- Subendometrial microcysts: Small cystic spaces immediately adjacent to the endometrium 1
- Hyperechoic myometrial spots: Bright echogenic foci scattered within the myometrium 1
Additional Supportive Features
- Myometrial linear striations: Hypoechoic linear bands extending from the endometrium into the myometrium 3, 4
- Asymmetrical myometrial thickening: Unequal thickness of anterior versus posterior myometrial walls, often with straight vessels extending into the hypertrophic myometrium on power Doppler 4
- Ill-defined endometrium: Loss of clear demarcation between endometrium and myometrium 3
Diagnostic Accuracy Considerations
When combining the three most accurate signs (subendometrial microcysts, myometrial cysts, and heterogeneous myometrium), specificity increases dramatically to 86.1% compared to 35.2-81.7% for individual markers. 1 This combination approach is critical for reducing false-positive diagnoses.
Signs with Lower Reliability
- Uterine enlargement: Shows poor specificity (41.7%) and sensitivity (60.8%) as an isolated finding 1
- Asymmetrical myometrial thickening: Demonstrates low specificity (49.3%) and sensitivity (52.3%) when used alone 1
These features should not be relied upon independently but may support diagnosis when combined with more specific signs.
Advanced Ultrasound Techniques
3D ultrasound provides superior visualization of junctional zone anatomy with pooled sensitivity of 88.9%, though specificity is lower at 56.0%. 2 Key 3D measurements include:
- JZmax ≥ 8 mm (maximum junctional zone thickness): Suggestive of adenomyosis 4
- JZdiff ≥ 4 mm (difference between maximum and minimum junctional zone thickness): Indicates irregular junctional zone thickening 4
Strain elastography used with routine transvaginal ultrasound shows increased diagnostic accuracy, with adenomyosis appearing as brighter irregular-shaped lesions due to endometrial glands and stroma within myometrium. 5
Critical Diagnostic Pitfalls
Coexisting Pathology
The presence of leiomyomas dramatically reduces ultrasound sensitivity for adenomyosis from 97.8% to 33.3%, as fibroids obscure adenomyotic features. 2 When fibroids are present, proceed directly to MRI for definitive diagnosis.
False-Negative Results
Approximately 16% of symptomatic patients demonstrate no direct ultrasound signs despite having clinical adenomyosis. 2 In symptomatic women with negative ultrasound findings, MRI should be performed rather than dismissing the diagnosis.
Distinguishing from Fibroids
On sonoelastography, fibroids appear as well-delineated dark areas (stiffer tissue), while adenomyosis shows brighter irregular lesions. 5 This distinction is valuable when conventional ultrasound features overlap.
When to Escalate to MRI
MRI should be performed when ultrasound is inconclusive or when adenomyosis obscures endometrial visualization, as MRI can display the endometrium even when obscured by adenomyosis on ultrasound. 2 MRI offers greater specificity and positive predictive value than ultrasound. 6
Specific indications for MRI include:
- Coexisting fibroids preventing adequate ultrasound assessment 2
- Equivocal ultrasound findings in symptomatic patients 2
- Need to exclude leiomyosarcoma when atypical features present 5
- Inability to visualize endometrium on ultrasound 2
Technical Examination Requirements
A combined transabdominal and transvaginal approach provides optimal assessment, with transvaginal offering higher spatial resolution and transabdominal providing overall anatomical context. 7 Doppler color and spectral evaluation is essential to assess vascularity patterns and differentiate adenomyosis from other pathologies. 7