Endometriosis Ultrasound Vs Normal and Fibroids: What to Know

Pelvic pain, heavy periods, and fertility concerns often prompt a pelvic ultrasound. But what should you expect to see on an ultrasound if you have endometriosis versus a normal scan or uterine fibroids? This guide explains how ultrasound works, what typical findings look like, and when additional tests may be helpful—so you can approach your appointment with clarity and confidence.

Quick takeaways

• Transvaginal ultrasound (TVUS) is a first-line, safe imaging test for pelvic pain and abnormal bleeding, useful for identifying endometriomas (ovarian cysts due to endometriosis) and fibroids. The FDA notes ultrasound is generally safe when used by trained professionals for medical indications.
• A normal ultrasound shows a smooth, uniform uterus and ovaries with follicles; no masses, fluid pockets, or distorted anatomy.
• Endometriosis may appear as ovarian endometriomas and, in expert hands, signs of deep infiltrating endometriosis (DIE); however, superficial endometriosis often does not show on ultrasound.
• Fibroids (uterine leiomyomas) are usually easy to see on ultrasound as well-circumscribed solid masses within or on the uterus.
• If ultrasound is inconclusive or detailed mapping is needed (e.g., suspected bowel endometriosis or numerous fibroids), MRI or surgical evaluation may be recommended.

How ultrasound helps—and its limits

Ultrasound uses sound waves to create real-time images of pelvic organs. Transvaginal ultrasound places a slim probe in the vagina to get high-resolution views of the uterus, endometrium (uterine lining), ovaries, fallopian tube regions, and nearby structures. It does not use radiation. The U.S. Food and Drug Administration (FDA) advises prudent use by trained providers and discourages non-medical uses like keepsake videos.

Limitations: ultrasound can miss very small lesions and superficial peritoneal endometriosis. Deep infiltrating endometriosis can be detected by specialized techniques (e.g., targeted tenderness-guided scans, assessing organ mobility), but accuracy depends on the operator’s experience.

What a normal pelvic ultrasound looks like

• Uterus and myometrium: Smooth, uniform muscle layer without focal masses. Size varies with age, parity, and hormones.
• Endometrium: A thin, central stripe that changes thickness during the cycle. It is typically thin just after a period and thicker before menstruation.
• Ovaries: Normal ovaries contain small follicles (fluid-filled sacs) that vary in number and size across the cycle. No complex cysts or solid nodules.
• Other: No free fluid beyond a small physiologic amount around ovulation; pelvic organs move freely relative to each other.

Endometriosis on ultrasound

Endometriosis occurs when tissue similar to the uterine lining grows outside the uterus, often causing pain, heavy periods, or fertility issues. While laparoscopy remains the definitive diagnostic method, ultrasound is highly useful—especially for endometriomas and for suggesting deep disease.

Common ultrasound findings:

• Ovarian endometriomas: Classically appear as round or oval cysts with homogeneous, low-level “ground-glass” internal echoes. They typically lack internal solid vascular nodules on Doppler. The wall may be thickened, and small echogenic foci can be present.
• Deep infiltrating endometriosis (DIE): Nodules or plaques can involve the uterosacral ligaments, rectovaginal septum, bowel, or bladder. Clues include fixed ovaries, loss of organ sliding (negative “sliding sign”), tender nodules when the probe presses specific areas, and hypoechoic lesions infiltrating nearby structures.
• Adhesions: Ovaries may appear stuck behind the uterus (“kissing ovaries”) or limited in mobility.

What ultrasound may miss: Small, superficial peritoneal implants and microscopic disease often do not appear on ultrasound. A normal ultrasound does not rule out endometriosis if symptoms are strong.

Fibroids on ultrasound

Uterine fibroids are common benign tumors of the uterine muscle. Ultrasound is the primary tool to detect, size, and locate them.

• Appearance: Usually well-defined, solid, round or oval masses. They are often hypoechoic (darker than surrounding tissue), may cast acoustic shadowing, and can calcify with age.
• Location: Intramural (within the wall), submucosal (bulging into the cavity), or subserosal (bulging outward). Submucosal fibroids are more closely linked to heavy bleeding and fertility issues.
• Vascularity: Doppler often shows peripheral blood flow around fibroids; internal flow varies with degeneration.
• Impact on anatomy: Fibroids can enlarge or distort the uterus and cavity, sometimes crowding or displacing the endometrium.

Endometriosis vs. fibroids: Overlap and key differences

• Symptoms overlap: Both conditions can cause pelvic pain and heavy or painful periods. Endometriosis pain often worsens around menstruation and may involve pain with sex or bowel movements; fibroids more commonly cause bulk symptoms (pressure, urinary frequency) and heavy bleeding.
• Ultrasound clues: A complex ovarian cyst with ground-glass echoes suggests an endometrioma; a solid, well-circumscribed uterine mass suggests a fibroid. Deep lesions from endometriosis may be seen in expert hands, while fibroids are typically straightforward to detect.
• Fertility: Both can affect fertility. Submucosal fibroids can disrupt implantation; endometriosis can impair egg quality, tubal function, and pelvic anatomy.

When ultrasound isn’t enough

Your clinician may recommend additional evaluation if symptoms persist despite a normal ultrasound, or if complex disease is suspected:

• MRI: Helpful for mapping deep infiltrating endometriosis (e.g., bowel, bladder involvement), differentiating adenomyosis from fibroids, and planning surgery for numerous or large fibroids.
• Diagnostic laparoscopy: A minimally invasive surgery that allows direct visualization and treatment of endometriosis. It remains the gold standard for diagnosis when imaging is inconclusive and symptoms are significant.

Who should consider ultrasound?

• Pelvic pain, painful periods, or pain with sex or bowel movements
• Heavy or irregular bleeding
• Difficulty conceiving
• Known fibroids with changing symptoms
• Ovarian cysts detected previously

Preparing for your scan

• Transvaginal ultrasound: Often requires an empty bladder. It offers the best resolution for pelvic organs and is typically well tolerated.
• Transabdominal ultrasound: May require a full bladder to act as a window; useful for large fibroids or when TVUS isn’t possible.
• Share your symptoms: Pointing to where it hurts can guide a tenderness-targeted exam that improves detection of deep disease.

Practical questions to ask your clinician

• Do my ultrasound findings fit better with endometriosis, fibroids, both, or neither?
• If nothing abnormal was seen, what are the next steps given my symptoms?
• Would MRI or referral to an endometriosis imaging specialist help?
• How might these findings influence my treatment options or fertility planning?

Bottom line

Ultrasound is a safe, powerful first step for evaluating pelvic pain and bleeding. A normal scan shows a smooth uterus and healthy ovarian follicles. Endometriosis may be suggested by endometriomas and signs of deep disease—though superficial lesions often remain invisible on imaging. Fibroids appear as solid uterine masses that are usually easy to characterize. If symptoms persist or complex disease is suspected, MRI or surgical evaluation can clarify the picture and guide care.

Trusted resources

• NICHD (NIH): Endometriosis – https://www.nichd.nih.gov/health/topics/endometri/conditioninfo
• MedlinePlus (NIH): Endometriosis – https://medlineplus.gov/endometriosis.html
• MedlinePlus (NIH): Uterine Fibroids – https://medlineplus.gov/uterinefibroids.html
• FDA: Ultrasound Imaging – https://www.fda.gov/radiation-emitting-products/medical-imaging/ultrasound-imaging
• ACOG: Endometriosis FAQ – https://www.acog.org/womens-health/faqs/endometriosis
• ACOG: Uterine Fibroids – https://www.acog.org/womens-health/faqs/uterine-fibroids

This article is for educational purposes and does not replace personalized medical advice. If you have concerning symptoms, consult a qualified healthcare professional.