Uterine Pathology on Ultrasound: Fibroids, Adenomyosis, and Polyps

Uterine pathology is among the most common findings in gynecologic ultrasound. Fibroids, adenomyosis, and polyps are frequent incidental findings and are common causes of abnormal uterine bleeding, pelvic pain, and infertility. Here's how to recognize and describe each.

Fibroids (Leiomyomas)

Fibroids are the most common benign uterine tumors — present in up to 70% of women by age 50. They arise from smooth muscle and are estrogen-sensitive.

Sonographic Appearance

Classic features:

• Well-defined, rounded hypoechoic masses within or adjacent to the uterus
• Heterogeneous echogenicity (variable — can be hyper or isoechoic)
• Posterior acoustic shadowing from calcifications (especially in older fibroids)
• Peripheral vascularity on color Doppler (rim of blood vessels)
• Distortion of the uterine contour or endometrium

Degenerative changes in fibroids:

• Hyaline degeneration: Most common. Increased heterogeneity, cystic spaces.
• Calcification: Dense echogenic foci with shadowing — "whorled" calcification pattern.
• Red degeneration: In pregnancy; acute pain, fibroid appears heterogeneous.
• Cystic degeneration: Large anechoic areas within the fibroid.

FIGO Classification (Location)

Type	Location	Clinical Impact
0	Submucosal, pedunculated intracavitary	Bleeding, infertility — highest impact
1	Submucosal < 50% intramural	Significant bleeding
2	Submucosal ≥ 50% intramural	Significant bleeding
3	Contacts endometrium, 100% intramural	Moderate impact
4	Intramural	Variable
5	Subserosal ≥ 50% intramural	Least impact on cavity
6	Subserosal < 50% intramural	Minimal impact
7	Subserosal, pedunculated	Minimal impact

For reporting, the most important distinction is submucosal (FIGO 0–2 — contacts or distorts the endometrium) vs intramural vs subserosal.

Measurement

Measure each fibroid in three planes. For multiple fibroids, describe the dominant/largest and the overall uterine size. Note the location (anterior, posterior, fundal, lateral), depth relative to the endometrium, and relationship to the serosa.

Sonohysterography

For submucosal fibroids, sonohysterography (saline infusion — SIS) provides much better characterization. The saline fills the cavity, and submucosal fibroids bulge into the fluid. This is often requested for surgical planning.

Adenomyosis

Adenomyosis is the presence of endometrial glands and stroma within the myometrium. It causes heavy, painful periods and uterine enlargement. Diagnosis on ultrasound is challenging but characteristic features exist.

Sonographic Features

Global adenomyosis (diffuse):

• Enlarged uterus with globally thickened myometrium
• Heterogeneous myometrium — asymmetric thickening (often posterior wall)
• Myometrial cysts: Small (2–7 mm) anechoic or echogenic cysts in the myometrium — highly specific for adenomyosis
• Echogenic islands: Heterogeneous hyperechoic areas within the myometrium
• Subendometrial lines and buds: Irregular striation extending from the endometrium into the myometrium
• Junctional zone thickening: The inner myometrium normally measures ≤ 12 mm; thickening > 12 mm is suspicious
• Poor definition of the endometrial-myometrial border

Focal adenomyosis (adenomyoma):

• Poorly defined hypoechoic mass within the myometrium
• No well-defined capsule or peripheral vascularity (distinguishes it from a fibroid)
• Often elongated in shape rather than round

Adenomyosis vs Fibroid

Feature	Adenomyosis	Fibroid
Margins	Ill-defined	Well-defined
Vascularity	Diffuse internal	Peripheral rim
Shape	Irregular, elongated	Round or oval
Shadow	Rare	May shadow (calcified)
Capsule	None	Present
Uterine shape	Globular, symmetric	Focal contour distortion

MUSA Criteria

The Morphological Uterus Sonographic Assessment (MUSA) provides a standardized framework for describing adenomyosis on ultrasound. Key features: myometrial cysts, echogenic islands, irregular junctional zone, fan-shaped shadowing, translesional vascularity.

Endometrial Polyps

Endometrial polyps are focal overgrowths of endometrial glands and stroma. They cause irregular bleeding and are a common finding in perimenopausal women.

Sonographic Appearance

• Focal hyperechoic thickening of the endometrium
• Well-defined hyperechoic mass within the endometrial cavity
• May cause asymmetric endometrial thickening
• Feeding vessel sign on color Doppler: A single central pedicle vessel running into the polyp — highly specific
• Often small and easy to miss on routine survey — SIS dramatically improves detection

When to Suspect a Polyp

• Focal endometrial thickening asymmetric to the rest of the cavity
• Irregular endometrial contour
• Abnormal uterine bleeding with otherwise normal-appearing endometrium

Endometrial thickness reference:

• Premenopausal: variable by cycle phase (2–16 mm)
• Postmenopausal: ≤ 4–5 mm (if > 5 mm with bleeding — evaluate further)

Reporting Fibroids

What to include:

• Number: single or multiple (if > 5, "multiple" is acceptable)
• Dominant fibroid: location (anterior/posterior/fundal/right/left lateral), type (submucosal/intramural/subserosal), size (three dimensions)
• Relationship to endometrium (does it contact or distort it?)
• Overall uterine size
• Vascularity on color Doppler

Example language:

• "Multiple uterine fibroids. Dominant fibroid in the posterior fundal wall measuring 4.2 × 3.8 × 3.5 cm, intramural, with no contact with the endometrium. Additional intramural fibroids measuring up to 2.1 cm."
• "Single submucosal fibroid in the anterior lower uterine segment measuring 1.8 × 1.5 × 1.4 cm, contacting and mildly indenting the endometrial cavity. Sonohysterography may provide better characterization."

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SonoBuddy's Pathologies section includes uterine fibroid and adenomyosis US findings, differentials, and red flags.