Adenomyosis is ectopic endometrial glands and stroma within the myometrium, with surrounding smooth muscle hypertrophy. On transvaginal ultrasound you diagnose it by finding at least one direct MUSA feature: a myometrial cyst, a hyperechogenic island, or an echogenic subendometrial line or bud. On MRI the classic criteria are a maximum junctional zone thickness of 12 mm or more, a junctional zone thickness difference of 5 mm or more, or a junctional zone to myometrial thickness ratio above 40 percent, together with ill-defined T2 hypointensity and small T2 hyperintense foci [1][7][11].
That 12 mm number is the one everybody quotes, and it is also the one that has held up worst. This article gives you the current ultrasound lexicon, what the junctional zone measurement is and is not good for, the atypical forms that get missed, and how to separate adenomyosis from the leiomyoma sitting next to it.
- What adenomyosis is, and who has it
- Transvaginal ultrasound or MRI first?
- Ultrasound features of adenomyosis: the MUSA lexicon
- MRI features of adenomyosis
- Adenomyoma and the atypical forms
- Adenomyosis vs fibroid: how to tell them apart
- What adenomyosis looks like on CT
- Why the diagnosis matters: fertility and pregnancy
- Management in brief, and what the gynaecologist needs from you
- Frequently asked questions
- References and further reading
What adenomyosis is, and who has it
Adenomyosis was historically called endometriosis interna, a name best retired: it is a distinct disease from peritoneal endometriosis, even though the two coexist often. The dominant model is invagination of the endometrial basalis into the myometrium through a disrupted junctional zone, with a second population arising from outside in, from deep posterior endometriosis invading the outer myometrium, and a third arising de novo by metaplasia [12].
It is common and it is under-diagnosed. Histological prevalence in hysterectomy series varies enormously with how many sections the pathologist cuts and where the depth cut-off is set; in one prospective imaging series with hysterectomy correlation it was 33 percent [7]. In women with subfertility, a meta-analysis of 21 studies and 25 600 women found a pooled prevalence of isolated adenomyosis of 10 percent, rising when endometriosis or fibroids coexist [13].
Typical presentation is dysmenorrhoea, heavy menstrual bleeding and a bulky tender uterus in a multiparous woman in her thirties or forties, but it is also found in young nulligravid women and in women with no symptoms at all. Symptom severity tracks with the number of features and the depth of involvement rather than with the label alone, which is why the description in your report is worth more than the diagnosis on its own.
Transvaginal ultrasound or MRI first?
Transvaginal ultrasound first, MRI as the problem-solver. That is not a cost argument, it is an accuracy argument: the two modalities perform about the same. A head-to-head meta-analysis restricted to studies that did both tests in the same women with hysterectomy as the reference standard found no significant difference [4].
| Modality | Pooled sensitivity | Pooled specificity | Source |
|---|---|---|---|
| Transvaginal ultrasound | 75% | 81% | Head-to-head meta-analysis, 6 studies, 595 women [4] |
| MRI | 69% | 80% | Same meta-analysis, same women [4] |
| 2D transvaginal ultrasound | 74% | 76% | Imaging meta-analysis, 827 patients [5] |
| 3D transvaginal ultrasound | 84% | 84% | Imaging meta-analysis [5] |
| MRI | 78% | 88% | Imaging meta-analysis, 317 patients [5] |
Two practical caveats. Ultrasound sensitivity falls when large leiomyomas obscure the myometrium, which is exactly when MRI earns its place [7]. And three-dimensional ultrasound outperforms two-dimensional ultrasound because the coronal reconstruction is where the junctional zone is best seen; the MUSA group specifically recommends 3D for junctional zone assessment [1][5].
Reach for MRI when the ultrasound is inconclusive, when fibroids dominate the uterus, when you need a map of disease extent before uterus-sparing surgery, or when the differential includes a uterine sarcoma.
Ultrasound features of adenomyosis: the MUSA lexicon
The Morphological Uterus Sonographic Assessment (MUSA) group published the original sonographic lexicon in 2015 [2] and revised it by Delphi consensus in 2022 [1]. The single most useful change in the 2022 revision is the split into direct features, which show ectopic endometrial tissue in the myometrium, and indirect features, which show the myometrium reacting to it.
| Type | MUSA feature | Revised definition (2022) |
|---|---|---|
| Direct | Myometrial cysts | Rounded or oval cystic spaces of any size within the myometrium. |
| Direct | Hyperechogenic islands | Hyperechogenic areas within the myometrium with no connection to the endometrium. No minimum size, distance or number. May be regular, irregular or ill-defined. |
| Direct | Echogenic subendometrial lines and buds | Hyperechogenic lines or buds disrupting the junctional zone, in continuity with the endometrium. As a rule of thumb, any invasion of endometrial tissue into the myometrium counts, even if it is not line-shaped or bud-shaped. |
| Indirect | Globular uterus | The myometrial serosa diverges from the cervix in at least two directions instead of running parallel to the endometrium. False positive with fibroids or an intracavitary lesion. |
| Indirect | Asymmetrical myometrial thickening | Rule of thumb: the anterior and posterior myometrial wall thicknesses differ by more than 5 mm. |
| Indirect | Fan-shaped shadowing | Hypoechogenic stripes behind the myometrial lesion, sometimes alternating with linear hyperechogenic stripes. |
| Indirect | Translesional vascularity | Vessels running through the lesion rather than around it. |
| Indirect | Irregular junctional zone | Junctional zone made irregular by cystic areas, hyperechogenic dots, buds or lines. |
| Indirect | Interrupted junctional zone | Part of the junctional zone cannot be seen in any plane on 2D or 3D transvaginal ultrasound. |
The rule that matters: in the absence of a direct feature that is, no myometrial cyst, no hyperechogenic island and no subendometrial line or bud the indirect features are not conclusive for adenomyosis [1]. A bulky globular uterus with fan-shaped shadowing and nothing else is a description, not a diagnosis.
Two further points from the same consensus that often get lost. First, the MUSA experts explicitly rejected measuring maximum junctional zone thickness on ultrasound, because there is no evidence that the number is clinically relevant; assess the junctional zone for regularity and continuity instead, preferably on 3D any-plane slicing [1]. A regular, uninterrupted junctional zone argues against adenomyosis. Second, the relative weight of the individual features is still unknown, so do not treat any single feature as a rule-in test.
Which feature performs best individually? A systematic review of the sonographic criteria found echogenic subendometrial lines and buds to be the best single criterion [8], while the older prospective series comparing ultrasound with MRI found the myometrial cyst to be both the most sensitive and the most specific ultrasound sign [7]. Both are direct features, which is the point.
The older descriptive terms are still worth recognising in reports and in exams. The “venetian blind” or “rain shower” appearance is fan-shaped shadowing. A “heterogeneous myometrium” with a poorly defined endometrial-myometrial border and focal tenderness under the probe is the classic gestalt, but it is a prompt to go looking for direct features, not a diagnosis in itself.
MRI features of adenomyosis
MRI is best on sagittal and axial oblique T2-weighted images through the uterus, with a T1-weighted fat-saturated sequence to pick up haemorrhagic foci. Time the scan away from menstruation if you can, because a transient uterine contraction mimics focal junctional zone thickening.
- Bulky, globular uterus with preserved overall shape, in contrast to the lobulated contour of a fibroid uterus.
- Ill-defined T2 hypointense thickening of the junctional zone, reflecting smooth muscle hyperplasia, with a poorly defined border with the outer myometrium.
- Punctate T2 hyperintense foci within the hypointense area, representing ectopic endometrial glands and cystically dilated glands. This is the single most useful sign.
- T1 hyperintense foci on fat-saturated images, representing haemorrhage in the ectopic glands. Specific but insensitive [7].
- Linear striations radiating from the endometrium into the myometrium.
- Look actively for coexisting disease: leiomyomas, ovarian endometriomas with T2 shading, and deep infiltrating endometriosis.
The junctional zone criteria, and how far to trust them
| MRI criterion | Cut-off | Comment |
|---|---|---|
| Maximum junctional zone thickness (JZmax) | 12 mm or more | The classic criterion. High specificity in the original hysterectomy series [7], but see the caveat below. |
| Junctional zone differential (JZmax minus JZmin) | 5 mm or more | Captures focal thickening that a single maximum measurement misses. Most useful in the indeterminate 8 to 12 mm band; below 8 mm adenomyosis is unlikely [11]. |
| JZmax to total myometrial thickness ratio | Above 40% | Normalises for uterine size; performed comparably to the 12 mm cut-off in the original series [7]. |
| High signal intensity myometrial foci on T1 or T2 | Present | As specific as the 12 mm cut-off but less sensitive [7]. |
| Irregular junctional zone (irregular borders, focal thickening, high-signal foci, fingerlike indentations) | Present | Sensitivity 74%, specificity 83%; the best-performing junctional zone sign in a prospective hysterectomy-controlled study [6]. |
Do not use 12 mm as a threshold. In a prospective study of 93 premenopausal women who all underwent MRI and hysterectomy, JZmax did not distinguish women with adenomyosis from those without (10.3 mm versus 10.1 mm, AUC 0.57), and a JZmax of 12 mm or more was present in 53 percent of those with adenomyosis and 44 percent of those without. Morphology beat measurement: an irregular junctional zone gave 74 percent sensitivity and 83 percent specificity [6].
The practical reading is that the junctional zone measurement is a supporting observation, not the diagnosis. A junctional zone that is thickened and irregular, contains high-signal foci and blends into the outer myometrium is adenomyosis. A uniformly thickened but smooth and sharply defined junctional zone in a woman scanned in the secretory phase may simply be a contraction, and repeating the sagittal T2 sequence a few minutes later will settle it.
Adenomyoma and the atypical forms
Focal adenomyosis that forms a discrete lesion is an adenomyoma. It matters because, unlike diffuse adenomyosis, it can be excised. The imaging signature is an ill-defined T2 hypointense myometrial lesion with small internal T2 hyperintense cystic foci, with or without T1 hyperintense haemorrhagic foci, and with minimal mass effect for its size.
| Form | Key imaging features | Why it matters |
|---|---|---|
| Diffuse adenomyosis | Globular uterus, diffusely thickened irregular junctional zone, scattered myometrial cysts across more than one wall. | Uterus-sparing excision is usually not feasible. |
| Focal adenomyosis / adenomyoma | Ill-defined T2 hypointense lesion with internal T2 hyperintense foci, no capsule, minimal mass effect. | Can be excised. Describe the wall, depth and distance from the cavity and serosa. |
| Cystic adenomyoma | Dominant blood-filled cavity, T1 hyperintense and T2 variable, surrounded by a thick hypointense wall. | Mimics a degenerating fibroid or a non-communicating rudimentary horn; causes severe dysmenorrhoea in young women [9]. |
| Polypoid adenomyoma | Lesion projecting into the endometrial cavity, ill-defined T2 hypointense with cystic foci. | Associated with tamoxifen therapy; the atypical variant carries a risk of coexistent carcinoma [9]. |
| Adenomyosis in pregnancy | Thickened junctional zone with decidualised foci; may enlarge or appear to regress. | Associated with obstetric complications; do not mistake for a mass [9]. |
| Malignant transformation | New solid enhancing component, restricted diffusion, rapid growth in a known adenomyotic uterus. | Rare but reported; adenocarcinoma arising within adenomyosis [9]. |
There is still no accepted MRI classification or descriptor set for adenomyosis, unlike the situation on ultrasound where MUSA supplies one [9]. The most widely quoted MRI scheme remains the four-subtype system based on which uterine layer is involved: subtype I is confined to the inner myometrium, subtype II to the outer myometrium, subtype III is a solitary lesion unrelated to either layer, and subtype IV is advanced heterogeneous disease [12]. On ultrasound, the MUSA group has published a structured classification and reporting system that records type, location, extent and severity, which is the format worth adopting in a report [3].
Adenomyosis vs fibroid: how to tell them apart
This is the question that actually gets asked at the workstation, and it is answered by margins and mass effect rather than by signal.
| Feature | Adenomyosis / adenomyoma | Leiomyoma (fibroid) |
|---|---|---|
| Margin | Ill-defined, blends into surrounding myometrium; no capsule | Well circumscribed, often a pseudocapsule and a cleavage plane |
| Shape of the uterus | Globular, symmetric or asymmetric wall thickening | Lobulated, focal bulge |
| Junctional zone | Thickened and irregular, in continuity with the lesion | Displaced and compressed, otherwise normal |
| Mass effect on the endometrium | Minimal or none for the size of the lesion | Usually present, cavity distorted or displaced |
| T2 signal | Ill-defined low signal with punctate hyperintense cystic foci | Homogeneous low signal, no cystic foci unless degenerating |
| T1 fat-saturated | Punctate hyperintense haemorrhagic foci may be present | No haemorrhagic foci (except in red degeneration) |
| Doppler / vascularity | Translesional: vessels run through the lesion | Circumferential rim vascularity around the lesion |
| Long axis | Follows the plane of the myometrium (elongated, ovoid) | Round or spherical |
| Shadowing | Fan-shaped, from within the lesion | Edge shadowing from the margins |
The two coexist frequently, and a fibroid is the commonest reason for a false-negative ultrasound for adenomyosis, so a fibroid uterus is a reason to look harder, not to stop looking [7].
The other mimics
- Transient uterine contraction. A focal, smooth, low-signal myometrial bulge that changes or disappears on a repeat sequence. The commonest false positive on MRI.
- Deep endometriosis with myometrial infiltration. Outer myometrial involvement arising from a posterior deep endometriotic nodule, tethering the uterus and obliterating the pouch of Douglas. Assess the pelvis, not just the uterus [9].
- Accessory cavitated uterine mass (ACUM). An isolated blood-filled cavity lined by endometrium in the anterolateral myometrium at the level of the round ligament insertion, in a young woman with severe dysmenorrhoea and an otherwise normal uterus. Frequently misread as a cystic adenomyoma [9].
- Uterine sarcoma. Rapid growth, a discrete solid mass with irregular margins, restricted diffusion with low ADC, intermediate to high T2 signal, necrosis and haemorrhage. Ill-defined T2 hypointensity with tiny cystic foci is reassuring; a growing heterogeneous mass in a postmenopausal woman is not.
- Endometrial carcinoma with myometrial invasion. Begins at the endometrium and disrupts the junctional zone focally, with an enhancing soft tissue mass rather than scattered cystic foci.
What adenomyosis looks like on CT
CT is not a diagnostic test for adenomyosis and should never be the basis for the diagnosis, but adenomyosis is frequently the explanation for a uterus that looks odd on a CT abdomen done for something else. Findings are a bulky, globular, symmetrically enlarged uterus, ill-defined low-attenuation thickening of the myometrium, an indistinct endometrial-myometrial interface, and occasionally punctate low-attenuation myometrial foci. None of this is specific. If the CT raises the question, the next test is a transvaginal ultrasound, not a contrast-enhanced CT.
Why the diagnosis matters: fertility and pregnancy
Adenomyosis is not a benign incidental label on a report. In a meta-analysis of 17 observational studies, women with adenomyosis undergoing assisted reproduction had a lower clinical pregnancy rate (odds ratio 0.69, 95% CI 0.51 to 0.94) and a higher miscarriage rate (odds ratio 2.17, 95% CI 1.25 to 3.79). Independent of the mode of conception, adenomyosis was associated with pre-eclampsia, preterm delivery, Caesarean section, fetal malpresentation, small-for-gestational-age infants and postpartum haemorrhage [14].
Since one in ten subfertile women has isolated adenomyosis [13], the direct MUSA features are worth hunting for on every pelvic ultrasound done for subfertility, not only on scans requested for pelvic pain.
Management in brief, and what the gynaecologist needs from you
The older teaching that hormonal therapy works poorly in adenomyosis has not aged well. The 2023 SOGC guideline makes a strong recommendation, on moderate-quality evidence, that combined oral contraceptives, the levonorgestrel-releasing intrauterine system and dienogest are all first-line medical options for pain and heavy menstrual bleeding from adenomyosis [15].
| Approach | Options | Notes |
|---|---|---|
| Medical, first line | Combined oral contraceptives, levonorgestrel-releasing intrauterine system, dienogest | Strong recommendation, moderate evidence [15]. NSAIDs and tranexamic acid for symptom control alongside. |
| Medical, second line | Other progestins, GnRH analogues | GnRH analogues are generally a bridge to surgery or to assisted reproduction rather than long-term therapy. |
| Interventional | Uterine artery embolisation | Recommended for symptomatic adenomyosis in women who have completed childbearing and wish to keep the uterus. Pooled recurrence 29.5%, reintervention 12.8% [16]. |
| Image-guided ablation | High-intensity focused ultrasound, radiofrequency ablation | Pooled recurrence 10.0%, reintervention 8.2% [16]. |
| Uterus-sparing surgery | Adenomyomectomy / excision of focal disease | Pooled recurrence 12.6%, reintervention 2.6% [16]. Feasible for focal disease; counsel on uterine rupture risk in a later pregnancy. |
| Definitive | Hysterectomy | The only cure. Endometrial ablation is an option for bleeding when the disease is superficial. |
A reporting checklist
- Which direct MUSA features are present: myometrial cysts, hyperechogenic islands, subendometrial lines or buds. If none, say so and do not call adenomyosis.
- Which indirect features are present: globular uterus, asymmetrical thickening, fan-shaped shadowing, translesional vascularity, irregular or interrupted junctional zone.
- Diffuse or focal, and if focal, whether it forms an adenomyoma and whether it is cystic.
- Inner myometrium or outer myometrium, and which wall: anterior, posterior, fundal, lateral.
- Extent: how much of the myometrial wall thickness and how many walls, plus uterine volume.
- Distance of a focal lesion from the endometrial cavity and from the serosa, if uterus-sparing surgery is a possibility.
- Coexisting disease: leiomyomas and their FIGO location, ovarian endometriomas, deep infiltrating endometriosis, pouch of Douglas obliteration.
- On MRI, junctional zone measurements as supporting data, with a note on junctional zone regularity and continuity.
Related reading on this site: imaging of endometriosis, tamoxifen-associated endometrial changes, and normal radiology measurements.
Frequently asked questions
References and further reading
- Harmsen MJ, Van den Bosch T, de Leeuw RA, et al. Consensus on revised definitions of Morphological Uterus Sonographic Assessment (MUSA) features of adenomyosis: results of modified Delphi procedure. Ultrasound Obstet Gynecol. 2022;60(1):118-131. PMID: 34587658.
- Van den Bosch T, Dueholm M, Leone FP, et al. Terms, definitions and measurements to describe sonographic features of myometrium and uterine masses: a consensus opinion from the Morphological Uterus Sonographic Assessment (MUSA) group. Ultrasound Obstet Gynecol. 2015;46(3):284-298. PMID: 25652685.
- Van den Bosch T, de Bruijn AM, de Leeuw RA, Dueholm M, Exacoustos C, Valentin L, et al. Sonographic classification and reporting system for diagnosing adenomyosis. Ultrasound Obstet Gynecol. 2019;53(5):576-582. PMID: 29790217.
- Alcazar JL, Vara J, Usandizaga C, Ajossa S, Pascual MA, Guerriero S. Transvaginal ultrasound versus magnetic resonance imaging for diagnosing adenomyosis: a systematic review and head-to-head meta-analysis. Int J Gynaecol Obstet. 2023;161(2):397-405. PMID: 36461921.
- Tellum T, Nygaard S, Lieng M. Noninvasive diagnosis of adenomyosis: a structured review and meta-analysis of diagnostic accuracy in imaging. J Minim Invasive Gynecol. 2020;27(2):408-418. PMID: 31712162.
- Tellum T, Matic GV, Dormagen JB, et al. Diagnosing adenomyosis with MRI: a prospective study revisiting the junctional zone thickness cutoff of 12 mm as a diagnostic marker. Eur Radiol. 2019;29(12):6971-6981. PMID: 31264010.
- Bazot M, Cortez A, Darai E, et al. Ultrasonography compared with magnetic resonance imaging for the diagnosis of adenomyosis: correlation with histopathology. Hum Reprod. 2001;16(11):2427-2433. PMID: 11679533.
- Liu L, Li W, Leonardi M, et al. Diagnostic accuracy of transvaginal ultrasound and magnetic resonance imaging for adenomyosis: systematic review and meta-analysis and review of sonographic diagnostic criteria. J Ultrasound Med. 2021;40(11):2289-2306. PMID: 33502767.
- Brandao A, Oliveira BC, Ferreira IAG, et al. Imaging spectrum of typical and atypical adenomyosis. Radiographics. 2025;45(5):e240152. PMID: 40310751.
- Tamai K, Togashi K, Ito T, Morisawa N, Fujiwara T, Koyama T. MR imaging findings of adenomyosis: correlation with histopathologic features and diagnostic pitfalls. Radiographics. 2005;25(1):21-40. PMID: 15653584.
- Agostinho L, Cruz R, Osorio F, Alves J, Setubal A, Guerra A. MRI for adenomyosis: a pictorial review. Insights Imaging. 2017;8(6):549-556. PMID: 28980163.
- Kishi Y, Suginami H, Kuramori R, Yabuta M, Suginami R, Taniguchi F. Four subtypes of adenomyosis assessed by magnetic resonance imaging and their specification. Am J Obstet Gynecol. 2012;207(2):114.e1-7. PMID: 22840719.
- Mishra I, Melo P, Easter C, Sephton V, Dhillon-Smith R, Coomarasamy A. Prevalence of adenomyosis in women with subfertility: systematic review and meta-analysis. Ultrasound Obstet Gynecol. 2023;62(1):23-41. PMID: 36647238.
- Nirgianakis K, Kalaitzopoulos DR, Schwartz ASK, et al. Fertility, pregnancy and neonatal outcomes of patients with adenomyosis: a systematic review and meta-analysis. Reprod Biomed Online. 2021;42(1):185-206. PMID: 33191131.
- Dason ES, Maxim M, Sanders A, Papillon-Smith J, Ng D, Chan C, Sobel M. Guideline No. 437: diagnosis and management of adenomyosis. J Obstet Gynaecol Can. 2023;45(6):417-429. PMID: 37244746.
- Liu L, Tian H, Lin D, et al. Risk of recurrence and reintervention after uterine-sparing interventions for symptomatic adenomyosis: a systematic review and meta-analysis. Obstet Gynecol. 2023;141(4):711-723. PMID: 36897132.
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