Ultrasound in Fibroids – Leiomyomas (fibroids or myomas) are benign smooth muscle tumours with varying amounts of fibrous tissue and are the most common uterine neoplasm, reported in 20% to 30% of women over 30 years of age.
These are usually multiple, causing enlargement of the uterus with a lobular serosal contour and may present with
Intracavitary- fibroid located inside the uterine cavity.
Submucosal- fibroid located just beneath the endometrium.
Intramural- fibroid located in the uterine wall.
Subserosal– fibroid located on the outer surface of the uterus.
Pedunculated- fibroid attached to the uterus with a pedicle.
Approximately 5-10% of infertile women have fibroids. Their size and location determines whether fibroids affect fertility like sub mucosal or very large fibroids within the uterine wall.These are the basics of ultrasound in fibroids.
Typical features on ultrasound:
Heterogeneously enlarged uterus with lobular contour
Typically focal, well defined, round, sharply marginated, hypoechoic lesion within the myometrium or attached to it, often showing shadows at the edge of the lesion and/or internal fan shaped shadowing.
Hypoechoic, isoechoic, or echogenic relative to the myometrium. Majority are hypoechoic.
Small leiomyomas are typically homogeneous whereas those larger than 3 cm in diameter are often heterogeneous.
Surrounding myometrium can become compressed and form a pseudocapsule. Occasionally compressed lymphatics and vessels create a thin hypoechoic rim around intramural leiomyomas.
Edge refraction at the interface of the leiomyoma with the normal surrounding myometrium may help to identify an isoechoic leiomyoma.
Venetian blind artifact (shadows) – a sonographic finding typically associated with adenomyosis can also occur in uterine fibroids. The posterior shadowing may be dense or striated (comb-like). This is believed to be caused by the transitional zone between apposed tissues of different acoustic properties such as fibrous tissue and smooth muscle, as well as refraction from the edges of whorls and bundles of smooth muscle. Very helpful in differentiating an exophytic leiomyoma from an adnexal or ovarian mass
Peripheral blood flow on colour or power doppler images. fibroids appear as “ring of fire” on power doppler Fibroids which are necrotic or have undergone torsion will show absence of flow
Increased blood velocity and decreased RI and PI in both uterine arteries occur in patients with uterine leiomyomas compared to healthy volunteers .This feature may have predictable value in growth rate evaluation of a benign uterine mass.
Degeneration may result in oedema with cystic spaces, echogenic haemorrhagic areas, dystrophic calcification