Role of Ultrasound in Uterine Fibroids Characterization Compared With MRI Using FIGO Classification System

Uterine fibroids, also known as uterine leiomyomata or myomas, are the most common gynecologic tumors occurring in 20-30% of women of reproductive age and in up to 80% of all women.

Leiomyomas have a wide spectrum of clinical presentations, but are mostly asymptomatic. Submucosal leiomyomas are more commonly associated with symptoms such as AUB, dysmenorrhea, infertility, and recurrent pregnancy loss. Subserosal leiomyomas can cause gastrointestinal or genitourinary symptoms related to size such as constipation, urinary retention, urinary frequency and urgency, or bladder and bowel incontinence.

Fibroids are monoclonal smooth muscle tumors arising from the myometrium. While benign, their growth is dependent on estrogen and progesterone levels, and thus fibroids may enlarge with pregnancy and use of oral contraceptives and regress during menopause.

Ultrasonography (USG) is the first-line imaging modality for any suspected structural anomaly of the female pelvis as well as the most appropriate imaging modality for abnormal uterine bleeding. USG has high sensitivity and specificity in diagnosing leiomyomas, but can vary with the experience of the operator performing the USG, ranging from 65 to 99%.

Pelvic USG usually consists of a combined approach to include both transabdominal (TAS) and transvaginal (TVUS) imaging. TVUS is generally considered to be more sensitive and specific with greater contrast and spatial resolution when compared to TAS. TVUS is more useful in obese patients, patients with a large amount of bowel gas, and in patients with incomplete bladder filling, all of which lower the sensitivity of TAS. TAS, on the other hand, is helpful in females with a larger uterus that extends superiorly from the pelvis and cannot be completely visualized in the field of TVUS. TAS provides an anatomic overview to better estimate overall uterine size and visualize the fundus in such cases.