Ultrasound of the Endometrium According to IETA/ISUOG 2026: Measurement and Description
Why a Unified IETA Language is Needed
The IETA/ISUOG 2026 Consensus standardizes how to perform gynecological ultrasound of the endometrium and how to formulate a report in cases of abnormal uterine bleeding and suspected endometrial cancer. The main goal is to ensure that measurement, morphological description, and Doppler assessment are reproducible among specialists and suitable for routing.
The report should separate three levels of information: technical feasibility of the study, measurable parameters, and terminological description. It is not permissible to substitute the description with a single word like 'hyperplasia,' 'polyp,' or 'cancer' without specifying thickness, structure, endometrium-myometrium boundary, intracavitary fluid, and vascular pattern.
Minimum Scanning Conditions
The basic approach is transvaginal ultrasound. Transabdominal access is used as an additional or alternative method if transvaginal examination is impossible or insufficiently informative. The examination begins with an overview assessment of the uterus: position, size, contours, myometrium, cavity, cervix, adnexa, and presence of free fluid.
For endometrial assessment, grayscale 2D imaging is used, followed by color or power Doppler. If necessary, 3D reconstruction is applied, especially when clarifying the shape of the cavity, localization of a lesion, or extent of endomyometrial boundary disruption. If the cavity is poorly differentiated, this is directly noted: 'endometrium not reliably visualized' or 'thickness not measurable.'
How to Measure Endometrial Thickness
Endometrial thickness is measured in the mid-sagittal plane of the uterine body, where the cavity is visible from the internal os to the fundus. The measurement is performed perpendicular to the longitudinal axis of the cavity at the point of maximum anteroposterior dimension. The result is indicated in millimeters.
The standard measurement is the maximum thickness of the 'double layer': anterior and posterior endometrial layers together. Myometrium, intracavitary fluid, clots, or clearly separate intracavitary lesions are not included in the measurement if the goal is to indicate the background endometrial thickness. If the boundaries are unclear, the protocol should include not only the number but also a comment on the low reliability of the measurement.
If Intracavitary Fluid is Present
Intracavitary fluid changes the measurement technique. According to IETA, the anterior and posterior single-layer components of the endometrium are measured separately, then their sum is indicated as the endometrial thickness without fluid. The thickness or size of the fluid component is described separately.
Fluid is characterized by echogenicity: anechoic, with low-level echoes, or mixed echogenicity. It is important to indicate whether the fluid freely occupies the cavity or surrounds a focal lesion. In the presence of bloody content, clots, or synechiae, the grayscale image may mimic solid pathology; therefore, Doppler and dynamic assessment with gentle probe pressure help avoid overdiagnosis.
Terms for Grayscale Description
The endometrium is described as homogeneous or heterogeneous. For homogeneous endometrium, echogenicity relative to the myometrium is indicated: hyperechoic, isoechoic, or hypoechoic. For heterogeneous endometrium, terms like 'heterogeneous,' 'with cystic inclusions,' 'mixed echogenicity' are used, and it is described whether the change is diffuse or focal.
The midline of the endometrium is described separately: linear, non-linear, irregular, or not defined. The endometrium-myometrium boundary is assessed as regular, irregular, interrupted, or not assessable. It is the disruption of this boundary, not just increased thickness, that is an important morphological sign that should be included in the protocol.
Focal Lesion in the Cavity
If a local intracavitary lesion is detected, it cannot be described only as 'polypoid.' Localization, relation to the walls, dimensions in 3 mutually perpendicular planes, contours, echogenicity, presence of cystic spaces, acoustic phenomena, and cavity deformation must be specified.
Localization is conveniently recorded anatomically: fundus, anterior wall, posterior wall, right or left lateral wall, tubal angle area, lower segment, cervical canal. If the lesion is broadly based on the wall or has a stalk, this is also described. In the case of multiple lesions, the number, dimensions of the dominant focus, and overall character of the lesion are indicated.
Doppler: Color Scale and Vascular Pattern
Color or power Doppler is included after grayscale assessment. Gain and frequency settings should allow visualization of slow blood flow without excessive color noise. According to IETA, the intensity of coloring is assessed semi-quantitatively on a 4-point scale, and the vascular architecture is described separately.
| IETA Parameter | How to Record in the Protocol |
|---|---|
| Endometrial Thickness | Maximum anteroposterior dimension of the double layer in the mid-sagittal plane, in mm |
| Fluid in the Cavity | Anterior single-layer endometrium + posterior single-layer endometrium; fluid is measured and described separately |
| Focal Lesion | 3 orthogonal dimensions, localization, contour, echogenicity, relation to the wall |
| Color score 1 | No color signal |
| Color score 2 | Minimal vascularization |
| Color score 3 | Moderate vascularization |
| Color score 4 | Marked vascularization |
The vascular pattern is described as absence of blood flow, single dominant vessel without branching, single dominant vessel with branching, multiple vessels with focal origin, multiple vessels with multifocal origin, scattered vascular pattern, or circular blood flow. This recording is more informative than the phrase 'blood flow present.'
What Must Be Indicated in the Clinical Context
Endometrial thickness is interpreted only with clinical data. The protocol should reflect age, premenopausal or postmenopausal status, day of the menstrual cycle in regular menstruations, duration of postmenopause, presence of abnormal bleeding, hormonal therapy, intrauterine devices, tamoxifen, and technical limitations of the study.
The consensus does not require turning the protocol into a histological report. The ultrasound specialist formulates signs: diffuse or focal thickening, regularity of the boundary, cavity character, presence of fluid, lesions, and vascular pattern. These signs are then compared with clinical risk to determine the need for biopsy, hysteroscopy, or dynamic observation.
IETA Description Template
A practical protocol can be constructed uniformly for all patients. First, indicate technical quality: access, cavity visualization, measurability of the endometrium. Then — endometrial thickness or reason for inability to measure. Next — structure: homogeneous or heterogeneous, echogenicity, midline, endomyometrial boundary, intracavitary fluid.
The next block — focal changes: localization, 3 dimensions, contours, echo structure, relation to the wall, and impact on the cavity. The final block — Doppler: color score 1–4 and vascular pattern. In conclusion, it is better to use the phrase 'Ultrasound signs...' with a list of IETA signs, avoiding categorical morphological diagnoses without verification.
Typical Errors in the Report
- Measurement not in the mid-sagittal plane but in an oblique section, which overestimates thickness.
- Inclusion of intracavitary fluid, clot, or polypoid lesion in the total endometrial thickness without explanation.
- Lack of comment on visualization: the number is indicated, but it is unclear how reliable the measurement is.
- Description 'endometrium heterogeneous' without midline, endometrium-myometrium boundary, and Doppler.
- Record 'vascularization increased' without color score and vascular pattern.
- Conclusion 'endometrial cancer' instead of describing signs requiring morphological verification.
Frequently asked questions
Should endometrial thickness be indicated if it is poorly visualized?
If it is not possible to reliably measure the endometrium, it is better to write 'endometrium not reliably measurable' and indicate the reason: uterine position, fibroid, adenomyosis, acoustic shadows, intracavitary content, or technical limitations. An unreliable number without comment reduces the protocol's value.
How to measure the endometrium when there is fluid in the uterine cavity?
Fluid is not included in the endometrial thickness. The anterior and posterior single-layer components are measured separately, summed, and the fluid is additionally described: size, echogenicity, and relation to focal lesions.
Is it sufficient to indicate only the endometrial thickness?
No. According to IETA/ISUOG 2026, morphology and Doppler are mandatory: uniformity, echogenicity, midline, endometrium-myometrium boundary, fluid, focal lesions, color score 1–4, and vascular pattern.