Study guide
21.2 Endometrium: Cyclic Changes, Hyperplasia & Cancer
ARRT Sonography Primary
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1 Introduction & Exam Overview
1.1 Current Exam Facts & Logistics 1.2 Scoring, Section Minimums & the August 2026 Cut-Score Change 1.3 Official Blueprint & Study Strategy
2 Patient Care: Ethics, Legal Practice & Communication
2.1 Ethical & Legal Aspects of Patient Care 2.2 Interpersonal Communication & Patient Education 2.3 Physical Assistance, Monitoring & Sonographer Ergonomics
3 Patient Care: Safety, Emergencies & Infection Control
3.1 Medical Emergencies & Critical Findings 3.2 Infection Control & Hazardous Materials 3.3 Ultrasound Safety & Interventional Procedure Care
4 Image Production: Transducers & the Ultrasound Beam
4.1 Piezoelectric Effect & Transducer Construction 4.2 Beam Configuration: Near Field, Far Field & Focus 4.3 Transducer Types, Selection, Care & Malfunctions
5 Image Production: Pulse Characteristics & Resolution
5.1 Pulse Characteristics: PRF, PRP, SPL & Duty Factor 5.2 Resolution: Axial, Lateral, Temporal, Elevational & Contrast 5.3 Frequency, Bandwidth, Q Factor, Power, Pressure, Intensity & Amplitude
6 Image Production: Imaging Modes & Doppler Principles
6.1 B-Mode & M-Mode Imaging 6.2 Spectral Doppler: Pulsed Wave vs Continuous Wave 6.3 Color Doppler & Power Doppler
7 Image Production: Optimization Controls
7.1 Power, Gain, TGC, Depth & Focal Zone 7.2 Frame Rate, Line Density, Dynamic Range, Harmonics & Compounding 7.3 Doppler Optimization Controls
8 Image Production: Sound–Tissue Interactions
8.1 Speed of Sound & the Range Equation 8.2 Acoustic Impedance, Reflection, Refraction & Scattering 8.3 Attenuation, Absorption & Intensity
9 Image Production: Signal Processing, Display & Bioeffects
9.1 Receiver, Signal Processing & Analog-Digital Conversion 9.2 Postprocessing, Magnification, Panoramic & 3D/4D Imaging 9.3 Bioeffects & Output Display Measures
10 Image Production: Image Evaluation & Artifacts
10.1 Criteria for Diagnostic Quality & Annotation 10.2 Grayscale Artifacts 10.3 Doppler Artifacts
11 Image Production: Real-Time Interpretation & Informatics
11.1 Real-Time Imaging, Echogenicity & Echotexture 11.2 Color & Spectral Analysis: Measurements and Waveforms 11.3 Imaging Informatics: HIS, RIS, EMR, PACS & DICOM
12 Procedures: Abdominal & Transplant Vasculature
12.1 Aorta, Its Branches & the IVC 12.2 Portal Venous System & Hepatic Vasculature 12.3 Liver & Renal Transplant Sonography
13 Procedures: Liver
13.1 Liver Anatomy, Variants & Examination Technique 13.2 Diffuse Liver Disease 13.3 Focal Liver Lesions
14 Procedures: Biliary System, Pancreas & Spleen
14.1 Gallbladder & Bile Ducts 14.2 Pancreas 14.3 Spleen
15 Procedures: Urinary Tract, GI Tract & Other Abdominal Structures
15.1 Kidneys & Ureters 15.2 Bladder & Prostate 15.3 GI Tract, Adrenals, Lymph Nodes, Hernias & Peritoneal Cavity
16 Procedures: First-Trimester Obstetrics
16.1 Early Gestation: Normal Development & Structures 16.2 First-Trimester Measurements, Dating & Maternal Anatomy 16.3 First-Trimester Abnormalities
17 Procedures: Second/Third-Trimester Biometry & Fetal Survey
17.1 Standard Biometry: BPD, HC, AC, FL & Growth Assessment 17.2 Fetal Anatomic Survey: Head, CNS, Face & Spine 17.3 Fetal Anatomic Survey: Heart, Chest, GI, GU, Skeleton & Fetal Position
18 Procedures: Chromosomal, Genetic & Structural Abnormalities
18.1 Chromosomal & Genetic Abnormalities 18.2 Major Structural Anomalies by System 18.3 Fetal Infection, Neoplasms & Hydrops
19 Procedures: Placenta, Amniotic Fluid, Cord & Cervix
19.1 Placenta: Normal, Previa, Abruption & Accreta 19.2 Amniotic Fluid Assessment & Growth Disorders 19.3 Umbilical Cord & Cervical Assessment
20 Procedures: Fetal Assessment, Doppler & Multiple Gestation
20.1 Biophysical Profile & Fetal Surveillance 20.2 Fetal & Uteroplacental Doppler 20.3 Multiple Gestations, Assisted Reproduction & Maternal Disease
21 Procedures: Gynecology — Uterus
21.1 Uterine Anatomy, Myometrium & Fibroids 21.2 Endometrium: Cyclic Changes, Hyperplasia & Cancer 21.3 Cervix & Congenital Uterine Anomalies
22 Procedures: Gynecology — Adnexa & Pelvis
22.1 Ovaries: Normal, Functional Cysts & Benign Masses 22.2 Ovarian Malignancy, Torsion & Fallopian Tubes 22.3 Cul-de-Sac, Vagina & Pelvic Floor
23 Procedures: Neck & Scrotum
23.1 Thyroid & Parathyroid 23.2 Salivary Glands & Neck Lymph Nodes 23.3 Scrotum & Testes
24 Procedures: Breast & Peripheral Vascular
24.1 Breast & Axilla 24.2 Venous Extremity Doppler 24.3 Carotid Doppler & Post-Catheterization Complications
25 Procedures: Pediatric, Interventional & Miscellaneous
25.1 Neonatal Head, Spine & Hip Sonography 25.2 Pediatric GI & Noncardiac Chest 25.3 Ultrasound-Guided Interventions, MSK & Superficial Masses
21.2 Endometrium: Cyclic Changes, Hyperplasia & Cancer
Key Takeaways Explain This Topic AI
Endometrial thickness is measured as a double-layer AP dimension in the midline sagittal plane near the fundus, excluding any intracavitary fluid
The late proliferative (periovulatory) endometrium is trilaminar (three-line); the secretory endometrium becomes uniformly echogenic and can measure up to about 14-16 mm
In a postmenopausal patient not on hormone therapy, an endometrium of 4-5 mm or less is reassuring, while a thicker stripe with bleeding warrants tissue sampling
Tamoxifen increases the risk of endometrial polyps, hyperplasia, and carcinoma and produces characteristic subendometrial cystic changes
An intrauterine device should appear as an echogenic, shadowing structure seated at the fundus; a device not seen on ultrasound with missing strings warrants a radiograph to exclude perforation or expulsion
Last updated: July 2026
Measuring and Interpreting the Endometrium
The endometrium is the mucosal lining of the uterine cavity and the structure that changes most dramatically over the menstrual cycle. Measure it in the midline sagittal plane at the thickest point near the fundus as a double-layer (anterior plus posterior) AP measurement , caliper to caliper on the echogenic basal layers. Exclude intracavitary fluid from the measurement — if fluid is present, measure each layer separately and add them.
Thickness and Appearance by Phase
- Phase Thickness Appearance
- Menstrual About 1-4 mm Thin, irregular, echogenic line; may contain fluid or debris
- Early proliferative About 4-8 mm Thin, isoechoic-to-hypoechoic single stripe
Late proliferative / periovulatory About 6-10 mm Trilaminar (three-line) : echogenic outer basal layers, hypoechoic functional layers, and a central echogenic line where the surfaces meet
Secretory About 7-14 mm (up to ~16 mm) Uniformly hyperechoic with loss of the trilaminar pattern; posterior enhancement may be seen
Postmenopausal (no HRT) 4-5 mm or less Thin, uniform echogenic line
The trilaminar pattern reflects a functionalis layer prepared for implantation under estrogen; after ovulation, progesterone makes the glands secretory and tortuous, and the endometrium becomes uniformly echogenic. The periovulatory trilaminar appearance is the pattern assessed in fertility workups.
Postmenopausal thresholds are high-yield exam material. In a woman not on hormone replacement therapy (HRT), an endometrial thickness of 4-5 mm or less has a very high negative predictive value for cancer. In a postmenopausal patient with bleeding , a thickness greater than about 4-5 mm warrants endometrial sampling. Patients on sequential HRT normally thicken and shed cyclically, so timing matters when interpreting their scans.
Endometrial Hyperplasia and Carcinoma
Endometrial hyperplasia is abnormal glandular proliferation driven by unopposed estrogen — chronic anovulation, polycystic ovary syndrome, obesity (peripheral conversion of androgens to estrogen), estrogen-only therapy, and estrogen-producing ovarian tumors. On ultrasound it appears as a diffusely thickened, usually homogeneous echogenic endometrium and cannot be reliably distinguished from early carcinoma by imaging alone; biopsy is required. Hyperplasia with atypia is the premalignant form.
Endometrial adenocarcinoma is the most common gynecologic malignancy and typically presents as postmenopausal bleeding — a symptom that must always be investigated. Sonographic features include:
- Thickened, heterogeneous endometrium with irregular margins
- An irregular or disrupted endomyometrial junction suggesting myometrial invasion
- Increased, disorganized internal vascularity on color Doppler
- Intracavitary fluid or hematometra if the tumor obstructs the cervix
Assessing the depth of myometrial invasion matters for staging (for example, invasion of less than versus more than half the myometrial thickness changes the stage and surgical plan). Transvaginal ultrasound can estimate invasion, but MRI is generally preferred for preoperative staging.
Tamoxifen , a selective estrogen receptor modulator used in breast cancer, has an estrogen- agonist effect on the endometrium. It increases the risk of polyps, hyperplasia, and carcinoma and characteristically produces subendometrial cystic changes — a thick endometrial complex with tiny cystic spaces at the endomyometrial junction. Any tamoxifen patient with bleeding deserves careful evaluation.
Endometrial Polyps
A polyp is a focal, benign overgrowth of endometrial glands and stroma. On ultrasound it appears as a focal echogenic mass within the cavity, sometimes containing tiny cystic spaces, and a single feeding vessel (pedicle artery sign) on color Doppler strongly supports the diagnosis. Polyps are a common cause of both premenopausal irregular bleeding and postmenopausal bleeding.
Saline infusion sonohysterography (SIS) — instilling sterile saline into the cavity during transvaginal scanning — distends the cavity and beautifully outlines focal lesions. It is the best ultrasound tool for distinguishing a focal process (polyp, submucosal fibroid) from diffuse endometrial thickening (hyperplasia) and for counting and localizing polyps before hysteroscopic removal.
Intrauterine Fluid, Synechiae, IUDs, and RPOC
A small amount of intracavitary fluid is normal during menses and around ovulation. In a postmenopausal patient, more than a trace of fluid suggests cervical stenosis and raises concern for an obstructing endometrial or cervical lesion; a large, echogenic, painful collection suggests hematometra or pyometra .
Asherman syndrome is intrauterine synechiae (adhesions) , usually caused by traumatic dilation and curettage (especially postpartum curettage) or infection. The echogenic bands crossing the cavity are often invisible on standard ultrasound unless the cavity is distended — they are best demonstrated with SIS. Clinically the patient may have hypomenorrhea, infertility, or recurrent pregnancy loss.
Intrauterine devices (IUDs) are easy to assess sonographically and this is a common exam topic:
A properly positioned IUD is a highly echogenic, shadowing linear structure (often with characteristic posterior shadowing or reverberation) seated in the endometrial cavity at the fundus
- A device sitting low in the body or cervical canal is malpositioned and less effective
- 3D coronal imaging is excellent for confirming the type and position of the device within the cavity
If no IUD is seen on ultrasound and the strings are missing, the device may have been expelled or may have perforated the uterus — obtain an abdominal radiograph to locate it
Retained products of conception (RPOC) after delivery, miscarriage, or termination appear as an echogenic intrauterine mass , sometimes with calcification. The key discriminator is Doppler: RPOC typically shows internal vascularity , whereas a simple intracavitary blood clot is avascular and may change shape or resolve on follow-up. RPOC is clinically important because it causes continued bleeding and infection risk and may require evacuation.