Diagnosis of Uterine Fibroids: What to Know

Uterine fibroids (also called leiomyomas) are benign growths of the muscle tissue of the uterus. They are very common—by age 50, most women will have at least one fibroid—and many never cause problems. When symptoms do occur, a clear, evidence-based diagnostic approach helps distinguish fibroids from other conditions and guides the best next steps. This guide explains how fibroids are evaluated and diagnosed, what tests are used, and when to seek care—drawing on trusted sources such as the National Institutes of Health (NIH), the American College of Obstetricians and Gynecologists (ACOG), and the U.S. Food and Drug Administration (FDA).

Who is affected and when to consider evaluation

Fibroids can occur at any reproductive age but are most common in the 30s and 40s. Black women tend to develop fibroids earlier, with larger and more numerous tumors, and may experience more severe symptoms. Common symptoms that prompt evaluation include:

• Heavy menstrual bleeding (soaking pads/tampons in under 2 hours, passing clots)
• Prolonged periods or bleeding between periods
• Pelvic pressure, bloating, or a feeling of fullness
• Frequent urination or difficulty emptying the bladder
• Constipation or rectal pressure
• Pain with intercourse
• Infertility or pregnancy complications

Some fibroids are found incidentally during a routine pelvic exam or imaging for another reason. Asymptomatic fibroids often require only observation, not immediate treatment.

How clinicians diagnose fibroids

1) Medical history and pelvic exam

Your clinician will ask about bleeding patterns, pain, pressure symptoms, pregnancy plans, and medication use. On pelvic exam, an enlarged, firm, irregularly contoured uterus often suggests fibroids. While the exam raises suspicion, imaging confirms the diagnosis and maps the size and location.

2) First-line imaging: Ultrasound

Pelvic ultrasound—usually a combination of transvaginal and transabdominal—is the primary, most accessible test for fibroids. It uses sound waves (no radiation) to visualize the uterus and ovaries. Ultrasound can identify the number, size, and location of fibroids and distinguish types such as:

• Submucosal (projecting into the uterine cavity)
• Intramural (within the uterine wall)
• Subserosal (bulging outward from the uterus)

Color Doppler can help assess blood flow, but is not always necessary.

3) Saline-infusion sonohysterography (SIS)

If heavy bleeding or fertility concerns are present, SIS may be recommended. Sterile saline is instilled into the uterus during transvaginal ultrasound to better outline the uterine cavity. This test improves detection and measurement of submucosal fibroids and polyps, helping plan treatments like hysteroscopic removal.

4) Magnetic resonance imaging (MRI)

MRI offers the most detailed mapping of fibroids, especially in women with multiple or very large fibroids, or when surgery or uterine fibroid embolization (UFE) is being considered. MRI helps differentiate fibroids from adenomyosis and identifies degeneration or atypical features. For fibroid assessment, MRI is typically performed without gadolinium contrast. If contrast is considered, clinicians weigh benefits and risks; the FDA notes gadolinium can be retained in the body and recommends using the lowest dose necessary and only when needed.

5) Hysteroscopy

Diagnostic hysteroscopy involves inserting a thin camera through the cervix to directly view the uterine cavity. It is particularly useful when submucosal fibroids or polyps are suspected and allows for simultaneous treatment in many cases. It does not evaluate the outer uterine wall or ovaries.

6) Other tests (used selectively)

• Hysterosalpingography (HSG): Primarily part of infertility workups to assess fallopian tube patency; can outline cavity abnormalities but is not a first-line fibroid test.
• Computed tomography (CT): Not recommended for routine fibroid diagnosis due to lower soft-tissue detail and unnecessary radiation exposure compared with ultrasound and MRI.

Laboratory tests: Supporting—not diagnosing—fibroids

No blood test diagnoses fibroids. However, labs help evaluate symptoms and rule out other causes:

• Pregnancy test: Essential if there is abnormal bleeding or missed periods.
• Complete blood count and iron studies: Assess for iron-deficiency anemia due to heavy bleeding.
• Thyroid-stimulating hormone (TSH): Sometimes ordered, as thyroid disorders can contribute to abnormal uterine bleeding.
• Endometrial biopsy: May be recommended for abnormal bleeding, particularly if you are 45 or older or have risk factors (e.g., obesity, polycystic ovary syndrome, unopposed estrogen) to rule out endometrial hyperplasia or cancer. Note: biopsies do not diagnose fibroids but help exclude other conditions.

How fibroid characteristics guide care

Imaging helps classify fibroids by size, number, and location, which influences symptoms and management. For example:

• Submucosal fibroids often cause heavy bleeding and fertility issues; hysteroscopic removal can be both diagnostic and therapeutic.
• Intramural fibroids may contribute to bleeding and bulk symptoms, depending on size.
• Subserosal fibroids more commonly cause pressure symptoms (urinary frequency, constipation).

Some clinicians use the FIGO leiomyoma classification (types 0–8) to standardize location, especially when planning procedures. MRI or detailed ultrasound reports are key for tailoring treatment plans, including medications, myomectomy, UFE, or other options.

Distinguishing fibroids from other conditions

Several gynecologic issues can mimic fibroid symptoms or exam findings:

• Adenomyosis: Endometrial tissue within the uterine muscle causing heavy, painful periods; MRI can help differentiate from fibroids.
• Endometrial polyps: Benign growths in the uterine lining; SIS or hysteroscopy improves detection.
• Ovarian masses or cysts and pregnancy-related changes can enlarge the pelvis and require careful evaluation.

What about cancer? Uterine sarcomas (e.g., leiomyosarcoma) are rare. Rapid growth, especially after menopause, unusual imaging features, or new severe pain warrant prompt evaluation. Imaging can suggest but not definitively diagnose sarcoma; a conclusive diagnosis is typically made after surgical removal and pathology review.

Special considerations in pregnancy

During pregnancy, ultrasound is the imaging test of choice. Most fibroids remain stable; some can grow in the first trimester or cause pain due to degeneration. Management is generally conservative, focusing on symptom control and monitoring.

When to seek care urgently

• Heavy bleeding causing dizziness, fainting, or symptoms of anemia
• Severe, sudden pelvic pain
• Rapidly enlarging pelvic mass, especially after menopause

Preparing for your appointment

To make the most of your visit:

• Track menstrual cycles and bleeding (pad/tampon counts, clots, duration).
• Note pain patterns, pressure or urinary symptoms, and any fertility goals.
• List medications, supplements, and relevant medical history.
• Ask whether ultrasound, SIS, MRI, or hysteroscopy is most appropriate in your situation and why.

Key takeaways

• Ultrasound is the first-line test; SIS, MRI, and hysteroscopy are used selectively to answer specific questions or plan treatment.
• Blood tests support evaluation (e.g., anemia) but do not diagnose fibroids.
• Most fibroids are benign and many require only monitoring; testing is individualized based on symptoms and goals.
• Shared decision-making with a gynecologist—grounded in clear imaging and your preferences—leads to the most appropriate care plan.

Trusted resources

• NIH/NICHD: Uterine Fibroids
• MedlinePlus (NIH): Uterine Fibroids
• ACOG Patient FAQ: Uterine Fibroids
• U.S. Office on Women’s Health: Uterine Fibroids
• FDA on gadolinium-based contrast agents: Safety Communication

This article is for general education and does not replace personalized medical advice. If you have symptoms or concerns, consult a qualified healthcare professional.