A uterine fibroid ultrasound report describes the number, size, location, and appearance of benign growths in or on the uterus, giving your doctor the information needed to decide whether treatment is necessary and, if so, which kind. The report is not a diagnosis on its own so much as a detailed map, and most of the terminology in it is more straightforward than it looks. Understanding a few key elements of the report can help you have a more productive conversation with your gynecologist and feel less anxious about what was found.
What the Report Typically Includes
Most fibroid ultrasound reports follow a fairly standard structure. You will see the uterus described first: its overall size (measured in three dimensions, usually in centimeters), its position (anteverted or retroverted, meaning tilted forward or backward), and its general contour. If fibroids are present, each one is listed separately with its own measurements, its location within the uterus, and a description of how it looks on the screen. You may also see a note about the endometrial lining thickness, which is checked as part of any pelvic ultrasound. The ovaries are usually assessed as well, though they are separate from the fibroid findings.
Ultrasound is the first-line imaging tool for detecting and characterizing fibroids because it is widely available, relatively inexpensive, and involves no radiation. Transvaginal ultrasound, where the probe is placed internally, gives the clearest view of fibroids near the uterine cavity. Transabdominal ultrasound, performed through the abdomen, provides a broader view that helps when the uterus is very enlarged or fibroids are near the outer surface. Many exams use both approaches.
How Fibroids Appear on Ultrasound
Fibroids usually show up as well-defined, solid, round masses. Their echogenicity, or how bright they appear relative to surrounding tissue, can vary. Most are described as hypoechoic, meaning they look slightly darker than the normal uterine muscle around them.1PubMed Central. Ultrasonography of uterine leiomyomas Some match the myometrium closely, and occasionally one will appear brighter (hyperechoic) if it contains a lot of fibrous tissue. A phrase you will often see is “posterior acoustic shadowing,” which refers to a dark streak behind the fibroid on the image. This shadow is created because the dense tissue absorbs or deflects the ultrasound waves, and it is actually one of the hallmarks that helps identify a mass as a fibroid rather than something else.2Journal of Medical Ultrasound. Ultrasonography of Uterine Leiomyomas
If your report describes a fibroid as “heterogeneous” or mentions cystic areas, internal calcifications, or unusual echotexture, that usually reflects degenerative changes. Fibroids can outgrow their blood supply over time and undergo various types of degeneration: hyaline degeneration (the most common, where normal tissue is replaced by a glassy material), cystic degeneration (fluid-filled pockets form inside), or calcification (calcium deposits harden within the fibroid). These changes are benign. They can make the ultrasound appearance look more complex, but they do not mean the fibroid is cancerous.3International Journal of Medicine. Cystic Degeneration of Uterine Fibroid Mimicking a Malignant Uterine Neoplasm on MRI
What the Location Numbers Mean
One of the most clinically important parts of the report is where each fibroid sits. Many reports now use the FIGO classification system, which assigns a number (0 through 8) based on a fibroid’s position relative to the inner cavity, the muscular wall, and the outer surface of the uterus.4PubMed Central. Diagnosis and classification of uterine fibroids Even if your report does not use these exact numbers, it will use terminology that maps onto the same categories:
- Submucosal: These grow into or just beneath the uterine lining (endometrium). FIGO types 0, 1, and 2. They are the most likely to cause heavy menstrual bleeding and can affect fertility even when small.
- Intramural: These sit within the muscular wall of the uterus. FIGO types 3, 4, and 5. They are the most common type. Large intramural fibroids can distort the uterine cavity from outside and cause symptoms similar to submucosal ones.
- Subserosal: These grow outward from the outer surface of the uterus. FIGO types 6 and 7. They are least likely to affect menstrual flow or fertility but can cause pressure symptoms on the bladder or bowel if they get large enough.
- Pedunculated: These are attached to the uterus by a stalk rather than a broad base. FIGO type 0 (submucosal pedunculated) or type 7 (subserosal pedunculated). The stalk is clinically relevant because it affects surgical approach.
This classification system exists because fibroid location drives treatment decisions more than size alone. Accurate FIGO classification on ultrasound is essential for surgical planning, though MRI provides higher resolution when fibroids are numerous, large, or positioned in complex ways.5Egyptian Journal of Radiology and Nuclear Medicine. The role of ultrasound in the characterization of uterine fibroids compared with MRI using the FIGO classification system
Why Location Matters More Than Size for Many Decisions
A small submucosal fibroid can cause more problems than a large subserosal one. This is especially true for fertility. Submucosal fibroids have been linked to lower pregnancy and live birth rates, and removing them appears to improve those rates. Subserosal fibroids, by contrast, do not seem to affect fertility outcomes, and removing them does not help with conception. Intramural fibroids fall in a gray area: they may reduce fertility, but the evidence on whether removing them helps remains unclear.6PubMed Central. Uterine Fibroids and Infertility
For symptoms like heavy bleeding, the same principle applies. A fibroid pressing on or distorting the endometrial cavity is far more likely to cause prolonged or heavy periods than one sitting on the outer surface. So when you read your report, the location descriptor is often more important than the centimeter measurements.
Understanding Size Measurements and Growth Tracking
Fibroid size is typically reported as three dimensions (length, width, and depth) in centimeters. Some reports also calculate an estimated volume. If you have had a prior ultrasound, your doctor may compare measurements to look for growth. This is where things get tricky.
Ultrasound measurements of fibroids have inherent variability. A study examining repeat measurements by the same sonographer found that even when measuring the same fibroid twice, the maximum diameter could vary by about 6% on average, and the calculated volume could vary by roughly 13%.7PubMed Central. Intra-Observer Variation in Fibroid Size Measurements: Estimated Effects on Assessing Fibroid Growth Smaller fibroids showed higher measurement variability than larger ones. The practical implication is significant: an increase in diameter of up to 20% between two scans could be measurement error rather than true growth. Volume calculations are even more variable because they rely on three separate diameter measurements, each with its own margin of error, multiplied together.8European Journal of Obstetrics & Gynecology and Reproductive Biology. Measurement of uterine fibroid volume: a comparative accuracy and validation of methods study
This means that if your fibroid measured 3 cm last year and 3.4 cm this year, that “growth” might not be real. Your doctor should interpret small changes cautiously, especially for fibroids under 3 or 4 cm. Genuinely rapid growth, a dramatic increase between scans, or growth after menopause is a different story and warrants closer attention.
Doppler Findings and Blood Flow
Some ultrasound reports include Doppler assessment, which measures blood flow in and around fibroids. Your report may mention “peripheral vascularity” (blood vessels around the outside of the fibroid) or “central vascularity” (blood flow within the core). In one study of vascular fibroids, about half showed only peripheral blood flow, while around 44% had both peripheral and central flow.9PubMed Central. Doppler sonography of perifibroid and intrafibroid arteries of uterine leiomyomas
Doppler results matter for a few reasons. They help distinguish fibroids from adenomyosis, a condition where endometrial-like tissue grows into the uterine muscle. Fibroids tend to have lower resistance blood flow patterns compared to adenomyosis, and the difference in Doppler indices between the two conditions is statistically significant.10Journal of South Asian Federation of Obstetrics and Gynaecology. Adenomyosis or Fibroid? Making the Right Diagnosis Doppler information also helps with treatment planning: fibroids with extensive internal blood supply may respond differently to procedures like uterine artery embolization than those with minimal central flow.
When the Report Raises a Red Flag
The overwhelming majority of uterine fibroids are benign. Uterine sarcoma, a rare cancer that can mimic a fibroid, is uncommon but worth knowing about. On ultrasound, a sarcoma may appear as a large mass with uneven echogenicity, irregular cystic areas, and rich blood supply, without the typical shadowing or calcification seen in ordinary fibroids.11Glob Libr Women’s Med. Benign Myometrial Pathology (Fibroids): Ultrasound Features and Practical Tips If your report describes a mass with these features, your doctor may recommend further imaging with MRI or a tissue biopsy. This does not mean you have cancer; it means the ultrasound appearance is atypical enough to warrant a closer look.
Adenomyosis is a much more common source of confusion. It can coexist with fibroids, and the presence of fibroids can make it harder for ultrasound to diagnose or grade the severity of adenomyosis.12PubMed. Sonographic findings in patients with adenomyosis: can sonography assist in predicting extent of disease? If your symptoms seem out of proportion to what the fibroids alone would explain, your doctor may suspect coexisting adenomyosis and consider MRI for a clearer picture.
When MRI Adds Value Beyond Ultrasound
Ultrasound is a reliable first step, but it has limits. Its sensitivity for detecting individual fibroids is moderate; one comparison study found that while ultrasound had a very high positive predictive value (around 97%), its sensitivity for identifying all fibroids present was only about 40%, meaning it confirmed what it found but missed many smaller or harder-to-see fibroids.13PubMed Central. Magnetic resonance imaging and transvaginal ultrasound for determining fibroid burden: implications for clinical research A more recent study reported ultrasound sensitivity for fibroids at about 83%, with MRI reaching 95%.14Pakistan Journal of Medical and Health Sciences. Diagnostic Accuracy of Pelvic MRI and Transvaginal Ultrasound for Detecting Uterine Fibroids and Adenomyosis The gap between these figures likely reflects differences in how the studies were designed, but the general pattern is consistent: MRI picks up more fibroids and classifies them more precisely.
MRI is not needed for everyone. Research suggests it is most useful for women with pelvic pain, significantly impaired quality of life, multiple fibroids on ultrasound, or a plan for uterine-sparing surgery. In those scenarios, MRI is more likely to reveal findings that change the treatment approach.15PubMed. Evaluation of the routine use of pelvic MRI in women presenting with symptomatic uterine fibroids: When is pelvic MRI useful? For a straightforward case with a single small fibroid and mild symptoms, ultrasound alone usually provides everything your doctor needs.
Fibroid Reports During Pregnancy
Fibroids discovered on a pregnancy ultrasound are common and usually do not cause problems, but the report may include notes about fibroid behavior over the course of the pregnancy. Prospective studies tracking fibroid size with ultrasound during pregnancy found that the majority of fibroids, somewhere between 60% and 78%, do not significantly change in volume.16PubMed Central. Contemporary Management of Fibroids in Pregnancy Of those that do grow, the increase tends to happen in the first trimester, with little additional growth afterward. A systematic review found consistent evidence that fibroids tend to enlarge somewhat in early pregnancy, with the trajectory in the second and third trimesters being more variable, and overall size typically returning to baseline or decreasing after delivery.17PubMed. Uterine fibroid size modifications during pregnancy and puerperium: evidence from the first systematic review of literature
One thing to watch for on pregnancy ultrasound reports is a change in echotexture, specifically the development of a heterogeneous pattern or cystic spaces within a previously solid-looking fibroid. In one study, this change was associated with severe abdominal pain in seven out of ten patients who developed it, suggesting degeneration of the fibroid during pregnancy.18PubMed. Leiomyomas in pregnancy: sonographic study This kind of degeneration, often called “red degeneration,” is painful but self-limiting and does not usually threaten the pregnancy itself. If your pregnancy ultrasound mentions a fibroid that has changed appearance, your provider will be watching for this possibility.
Fibroids After Menopause
Fibroids are estrogen-responsive, so they tend to shrink after menopause as hormone levels drop. If you have a postmenopausal ultrasound that reports a fibroid, it may look different from what is typically described. Long-standing fibroids in postmenopausal women can become heavily calcified, appearing as very bright masses with dense shadowing underneath. In extreme cases, calcification is so extensive that ultrasound cannot see through the mass at all, resulting in what has been described as a “popcorn appearance” on imaging.19PubMed Central. Popcorn Appearance of Severely Calcified Uterine Leiomyoma: Image-Pathological Correlation These calcified fibroids are essentially harmless remnants, but the heavy shadowing can make the rest of the pelvic exam suboptimal, which is why the report may note limited visualization of surrounding structures.
A fibroid that appears to be growing after menopause is more concerning than one found during reproductive years. Without the hormonal stimulus of estrogen, fibroids should not be getting larger. Post-menopausal growth, especially with atypical ultrasound features, prompts most clinicians to investigate further with MRI or biopsy to rule out sarcoma.
How Imaging Reports Guide Treatment Choices
Your fibroid report is not a standalone verdict. It feeds into a broader decision-making process that also accounts for your symptoms, your age, whether you want to become pregnant, and how close you are to menopause. As more conservative treatment options have become available for fibroids, including hormonal medications and minimally invasive procedures, the detail in the ultrasound report has become more important rather than less. The size, number, and exact location of each fibroid influence which procedures are feasible, whether a hysteroscopic approach can reach a submucosal fibroid, or whether uterine artery embolization is likely to succeed.20PubMed Central. Reporting of uterine fibroids on ultrasound examinations: an illustrated report template focused on surgical planning
A well-structured report that follows FIGO classification and includes detailed measurements, fibroid location relative to the endometrial cavity, and notes about the overlying myometrium thickness helps your surgeon plan more effectively. If your report feels vague, asking for a follow-up scan at a center experienced in gynecologic ultrasound is reasonable, particularly if surgery or a procedure is being considered.
Artificial Intelligence in Fibroid Detection
An emerging development worth knowing about is the use of artificial intelligence to assist with fibroid detection on ultrasound. Research groups have developed deep learning models that can identify fibroids in ultrasound images with high accuracy. In one study, junior ultrasonographers using an AI assistance tool reached accuracy levels comparable to senior ultrasonographers, improving their diagnostic accuracy from about 87% to roughly 95%.21Scientific Reports. Artificial intelligence-aided method to detect uterine fibroids in ultrasound images: a retrospective study Another system achieved real-time detection at under a third of a second per image with an average precision above 98%.22Ultrasound in Medicine & Biology. Real-Time Automatic Assisted Detection of Uterine Fibroid in Ultrasound Images Using a Deep Learning Detector
These tools are not yet standard in clinical practice, and your current ultrasound report was almost certainly generated by a human sonographer and read by a radiologist or gynecologist. But the technology is maturing quickly, and its greatest potential benefit is reducing the gap between less experienced and highly experienced operators. Given that fibroid measurement variability is already a known challenge, AI-assisted detection could eventually lead to more consistent and complete reports, especially in settings where specialist sonographers are not always available.