Uterine fibroids are noncancerous tumors that can grow on the outside of the uterus (subserosal fibroids), inside the muscle of the uterus (intramural fibroids) or into the uterine cavity (submucosal fibroids).

Women with fibroids are frequently unaware that they have the condition because they are symptom-free. But doctors often discover fibroids while conducting a pelvic examination.

Fibroids may cause the uterus to feel bigger than it normally does or to appear irregularly shaped. Sometimes fibroids are not detected, but a woman is experiencing common symptoms of the condition, such as chronic pain or discomfort, heavy menstrual bleeding, periods that exceed a week, painful sex, frequent urination, difficulty emptying the bladder, constipation and back or leg pain.

Doctors may also perform a complete blood count test if a woman has experienced heavy menstrual bleeding, which can cause anemia from chronic blood loss. This evaluation is useful because fibroids can cause this symptom.

In these cases, doctors can use various techniques to capture an image of the uterus.

Ultrasound, which employs sound waves to create an image of the uterus, is one common diagnostic test. During the procedure, a doctor or technician moves a device over a woman’s abdomen to take pictures of the uterus; the device may also sometimes be inserted into the vagina. But “ultrasound often underestimates the number, size and location of a woman’s fibroids,” says Kecia Gaither, MD, MPH, a double board-certified ob-gyn and maternal fetal medicine physician.

Gaither prefers to use magnetic resonance imaging (MRI) because the technique is widely regarded as the one that offers the most information. A pelvic MRI utilizes a special magnet to take pictures of a woman’s uterus while she lies on a bed that moves through a doughnut-shaped MRI machine. The scan provides key details about the fibroids, such as their number, size and precise location.

A physician may also perform a saline infusion sonogram, or hysterosonogaphy, to diagnose fibroids. During this procedure, a salt solution is injected into the uterus to help expand it and enable the doctor to see the uterine lining, any fibroids that may be present and any areas of soft tissue not clearly visible via X-rays.

A test called a hysterosalpingography uses a special dye that’s inserted into the vagina and followed by scanning the uterus and fallopian tubes with an X-ray machine. In addition to locating fibroids, the exam allows doctors to check whether a woman’s fallopian tubes are open. This is key for reproduction, because eggs must be able to travel from the ovaries to the uterus through these tubes.

Hysteroscopy is a procedure that uses a small telescope with an attached light (hysteroscope) to view the uterus walls and fallopian tubes after the uterus has been made to expand via a saline injection. At this point, physicians may opt to remove fibroids with special instruments.