Fibroids are most often discovered during a routine pelvic exam, when a doctor feels that the uterus is enlarged or irregularly shaped. From there, ultrasound is the standard first imaging test, with additional options depending on your symptoms, the size and location of suspected fibroids, and whether fertility is a concern.
The Pelvic Exam
A pelvic exam is usually where fibroids first show up on a doctor’s radar. During the exam, the doctor inserts one or two gloved fingers into the vagina while pressing down on the lower abdomen with the other hand. This lets them feel the size, shape, and contour of the uterus. A uterus that feels larger than expected or has an irregular, bumpy surface suggests fibroids may be present. Many people learn about their fibroids this way, with no symptoms at all.
A pelvic exam alone can’t confirm fibroids or tell you how many there are, how big they are, or exactly where they’re growing. It’s a starting point. If something feels off, imaging comes next.
Ultrasound: The First-Line Imaging Test
Ultrasound is the preferred initial imaging test for fibroids in the United States. It uses sound waves to create a picture of the uterus, and it’s the same painless technology used during pregnancy scans. There are two types, and your doctor may use one or both.
Transvaginal ultrasound involves a slim, wand-shaped probe inserted into the vagina. Because the probe sits close to the uterus, the images are detailed enough to detect most fibroids. Sensitivity ranges from about 90% to 99%, meaning it catches the vast majority of fibroids. It can occasionally miss very small ones or fibroids growing on the outer surface of the uterus.
Transabdominal ultrasound uses a probe moved across the outside of your belly, with gel applied to the skin. It gives a broader view and is useful for very large uteruses that a transvaginal probe can’t fully capture. When compared against tissue samples taken during surgery (the gold standard), ultrasound overall has about 99% sensitivity and 91% specificity, meaning it’s both good at finding fibroids that are there and good at ruling them out when they aren’t.
On an ultrasound image, fibroids typically appear as well-defined, darker masses surrounded by normal uterine muscle. They sometimes contain bright spots from calcifications or cast shadows behind them. These features help distinguish fibroids from other conditions like adenomyosis, which tends to cause a more globular uterus with a blurry, uneven texture throughout the muscle wall rather than distinct, round masses.
Saline Infusion Sonography
If your doctor suspects a fibroid is growing into the inner cavity of the uterus (the space where a pregnancy would develop), they may recommend saline infusion sonography, sometimes called a sonohysterogram. This test is especially useful when fibroids seem to be causing abnormal bleeding, because fibroids that bulge into the cavity are the type most likely to disrupt periods.
The procedure starts like a regular transvaginal ultrasound, but with an added step. A thin catheter is threaded through the cervix, and sterile saline is slowly pushed into the uterine cavity to expand it. With the cavity filled with fluid, the ultrasound image becomes much clearer, and fibroids that protrude into that space stand out sharply against the surrounding liquid. The fluid portion of the exam takes about five to ten minutes. You’ll likely be asked to take an over-the-counter pain reliever like ibuprofen about an hour beforehand to minimize cramping, and a urine pregnancy test is done right before the procedure.
MRI for Detailed Mapping
An MRI provides the most detailed picture of fibroids. It can show the exact number, size, and precise location of every fibroid in the uterus, along with their blood supply. This level of detail isn’t always necessary for a straightforward diagnosis, which is why MRI isn’t the first test ordered. It becomes valuable when surgery or a targeted procedure is being planned and the surgical team needs a complete map of what they’re working with. It’s also helpful when the uterus is very large, when ultrasound results are unclear, or when distinguishing between fibroids and other growths matters for treatment decisions.
A pelvic MRI for fibroids may be done with or without contrast dye injected into a vein. The scan itself is painless but requires lying still inside the MRI machine for 30 to 60 minutes.
Hysteroscopy: Looking Inside Directly
A hysteroscopy lets the doctor see the inside of the uterus directly, using a thin, lighted scope inserted through the vagina and cervix. It’s the most reliable way to identify fibroids that grow into the uterine cavity, and it has a practical advantage: if a fibroid is found during the procedure, it can sometimes be removed at the same time.
Hysteroscopy can be done in an office setting with local anesthesia or in a hospital under sedation, depending on the situation. It’s not typically the first step in diagnosis. Doctors usually reserve it for cases where imaging has already suggested a cavity-distorting fibroid, or when symptoms like heavy bleeding need both visual confirmation and potential treatment in one visit.
Imaging for Fertility Concerns
If you’re being evaluated for infertility and fibroids are suspected, your doctor may order a hysterosalpingogram (HSG). This test focuses on whether the uterine cavity and fallopian tubes are open and normally shaped. A contrast dye is injected through the cervix, and X-ray images track the dye as it fills the uterus and flows through the tubes. Fibroids that distort the cavity or block the tubes show up as filling defects, areas where the dye can’t go.
The HSG captures images at several stages: early filling to catch defects inside the cavity, full filling to assess the overall uterine shape, dye moving through the tubes, and finally dye spilling into the abdominal cavity (which confirms the tubes are open). If the dye doesn’t reach the abdominal cavity from one or both tubes, that signals a blockage. An HSG won’t tell you much about fibroids growing on the outside of the uterus, but it’s very effective at identifying the ones most likely to interfere with conception and implantation.
Blood Tests That Accompany Fibroid Diagnosis
Blood tests don’t detect fibroids themselves, but they’re a standard part of the workup because fibroids often cause heavy menstrual bleeding that leads to anemia over time. A complete blood count (CBC) checks your red blood cell levels, and an iron panel measures your body’s iron stores. Together, these tests reveal whether fibroid-related bleeding has caused iron-deficiency anemia, which can explain symptoms like fatigue, weakness, and shortness of breath that you might not have connected to your periods. If anemia is confirmed, treating it becomes part of managing the fibroids, not a separate issue.
What Determines Which Tests You’ll Get
Not everyone goes through every test on this list. The diagnostic path depends on your specific situation. A pelvic exam plus a standard ultrasound is enough to confirm fibroids for most people, especially if symptoms are mild or you’re not planning a pregnancy. Saline infusion sonography gets added when there’s heavy bleeding and the doctor needs to know whether a fibroid is inside the cavity. MRI comes into play when a procedure is being planned or the picture is complicated. HSG is reserved for fertility evaluations. Blood work is routine whenever heavy periods are part of the picture.
The whole process often starts and ends in a single appointment. A doctor who feels an enlarged uterus during a pelvic exam can frequently confirm fibroids with an in-office ultrasound the same day, giving you answers without weeks of waiting between tests.