Fibroids are most often discovered during a routine pelvic exam, when a doctor feels a firm, irregularly shaped uterus. From there, imaging confirms the diagnosis, determines the size and location of each fibroid, and guides treatment decisions. The process typically starts simple and only moves to more advanced tools when needed.
What a Pelvic Exam Can Reveal
During a standard bimanual pelvic exam, your doctor presses on your lower abdomen with one hand while examining internally with the other. Fibroids make the uterus feel enlarged, lumpy, or asymmetrical rather than smooth and pear-shaped. A single large fibroid can make the uterus feel like it’s the size of a grapefruit or larger, while multiple smaller ones create an irregular, bumpy contour.
This exam alone can’t confirm fibroids with certainty. An enlarged uterus could also point to adenomyosis (a condition where uterine lining tissue grows into the muscular wall), pregnancy, or rarely something more serious. So a pelvic exam raises suspicion, but imaging is what nails down the diagnosis.
Ultrasound: The Standard First Test
A transvaginal ultrasound is the go-to imaging tool for suspected fibroids. A small probe is inserted into the vagina to produce detailed images of the uterus, and the exam is quick, painless, and widely available. On the screen, fibroids typically appear as round, dark (hypoechoic) masses with well-defined borders.
Ultrasound is very good at confirming fibroids when they’re present, with a specificity around 95%, meaning it rarely mistakes something else for a fibroid. Its sensitivity is lower, though, particularly for small fibroids or those in tricky locations. This means ultrasound catches most clinically significant fibroids but can miss smaller ones, especially when the uterus is very large or contains many growths.
An abdominal ultrasound (the wand-on-the-belly type) is sometimes used alongside or instead of the transvaginal approach, particularly when the uterus has grown too large for the vaginal probe to capture the full picture.
Saline Infusion Sonography for Cavity Detail
When your doctor needs a closer look at fibroids that may be pushing into or growing within the uterine cavity, a saline infusion sonography (also called sonohysterography) offers a sharper view. During this test, sterile saline is gently infused through a thin catheter into the uterus, expanding the cavity so each wall can be seen individually on ultrasound.
This technique is particularly useful for submucosal fibroids, the type that bulges inward toward the uterine lining. These are the fibroids most likely to cause heavy bleeding and fertility problems, so knowing exactly how far they project into the cavity matters for treatment planning. On this imaging, fibroids appear as round, broad-based masses that lose the normal border between the lining and the muscle wall, and they form a wide angle where they meet the endometrium. This helps distinguish them from polyps, which tend to look brighter on imaging and sit on a narrower stalk.
The procedure takes about 15 to 30 minutes and can cause mild cramping similar to a period. It’s often done between days 4 and 10 of your menstrual cycle, when the uterine lining is thinnest and easiest to evaluate.
MRI: The Most Detailed View
MRI is the most accurate imaging technique for detecting and mapping uterine fibroids. It produces high-resolution images that show the exact number, size, and position of every fibroid, along with their relationship to the uterine wall and surrounding structures. It’s especially valuable for large uteruses that are difficult to fully evaluate with ultrasound.
Doctors typically order an MRI in specific situations: when surgery is being planned (particularly a myomectomy to remove fibroids while preserving the uterus), when the ultrasound results are unclear, or when there are so many fibroids that ultrasound can’t reliably map them all. The detailed 3D images MRI provides can significantly streamline surgical planning by giving surgeons a precise roadmap before they operate.
An MRI also helps distinguish fibroids from conditions that can look similar, like adenomyosis. The two conditions sometimes coexist, and telling them apart matters because they’re treated differently.
Telling Fibroids Apart From Adenomyosis
Fibroids and adenomyosis can cause nearly identical symptoms, including heavy periods, pelvic pressure, and an enlarged uterus. They can also look similar on basic ultrasound. But several imaging features help doctors tell them apart.
Fibroids have well-defined edges and a characteristic blood flow pattern: vessels wrap around the outside of the growth like a ring, called peripheral vascularity, visible in about 89% of cases on Doppler ultrasound. Adenomyosis, by contrast, has blurry, ill-defined margins and blood vessels running through the center of the affected area (central vascularity), seen in roughly 93% of cases. Other clues pointing toward adenomyosis include tiny cysts (1 to 3 mm) scattered within the uterine muscle and an uneven thickening of the uterine wall without a distinct mass.
When standard 2D ultrasound leaves the diagnosis uncertain, 3D ultrasound can examine the junction between the uterine lining and muscle wall. An irregular or disrupted junction zone is found in about 86% of adenomyosis cases and is one of the strongest distinguishing features.
Hysteroscopy: Direct Visualization
A hysteroscopy lets your doctor look directly inside the uterus using a thin, lighted scope inserted through the cervix. It’s the definitive way to evaluate fibroids that affect the uterine cavity, and it doubles as a treatment tool since fibroids can often be removed during the same procedure.
You’ll typically be given sedation or anesthesia, then positioned with your legs in stirrups. Your cervix is gently dilated to allow the scope to pass through. The camera transmits a live image of the cavity, letting the doctor see exactly where fibroids are, how large they are, and how much of each growth protrudes into the open space. If a fibroid is suitable for removal, the procedure can shift from diagnostic to surgical (called a hysteroscopic myomectomy) without needing a second appointment.
Hysteroscopy is most commonly recommended when abnormal bleeding hasn’t been fully explained by ultrasound, or when submucosal fibroids need to be evaluated before a planned procedure.
HSG in Fertility Evaluations
Hysterosalpingography, or HSG, is an X-ray-based test primarily used during infertility workups. A contrast dye is injected through the cervix, filling the uterine cavity and fallopian tubes so their shape shows up on X-ray. Fibroids that push into the cavity appear as filling defects, areas where the dye can’t flow normally.
HSG isn’t a primary tool for diagnosing fibroids, but it plays an important role for people trying to conceive. Uterine cavity abnormalities contribute to fertility difficulties in roughly 10% of women, and that number climbs to as high as 50% in women with recurrent implantation failure after IVF. HSG can reveal whether fibroids are distorting the cavity in a way that might interfere with implantation, helping fertility specialists decide whether fibroid removal could improve outcomes.
Blood Tests for Related Complications
Blood work doesn’t diagnose fibroids themselves, but it’s a routine part of the workup because fibroids often cause heavy menstrual bleeding that leads to iron-deficiency anemia. A complete blood count checks your hemoglobin and red blood cell levels to determine whether you’ve become anemic.
Most women with fibroid-related anemia have mild to moderate drops in hemoglobin, but the bleeding can occasionally become severe enough to cause dangerously low levels. In extreme cases documented in medical literature, women with untreated fibroid bleeding have presented with hemoglobin levels below 2.0 g/dL, a fraction of the normal range of 12 to 16 g/dL for women. These cases are rare but underscore why monitoring blood counts matters when fibroids cause persistent heavy periods.
Your doctor may also check thyroid function or hormone levels if your bleeding pattern doesn’t clearly match a fibroid diagnosis, since other conditions can cause similar symptoms.
How the Diagnostic Path Typically Unfolds
For most people, the journey starts with symptoms like heavy periods, pelvic pressure, or frequent urination, followed by a pelvic exam and a transvaginal ultrasound. That combination is enough to confirm the diagnosis in the majority of cases. Additional imaging with saline sonography or MRI is reserved for situations where the basic ultrasound doesn’t provide a complete picture, or when a procedure is being planned and the surgical team needs precise mapping.
Hysteroscopy is typically the next step only when there’s a strong suspicion of submucosal fibroids affecting the cavity, or when your doctor wants the option to diagnose and treat in one visit. Many fibroids that cause no symptoms are found incidentally during imaging for something else entirely, and these often require no further workup at all.