Uterine fibroids

Uterine fibroids (leiomyomas) are benign tumours that arise from the muscle layer of the uterus termed the myometrium.

Fibroids are the most common type of pelvic tumour in women, usually arising in those of child-bearing age. They may be asymptomatic or present with a variety of symptoms including bleeding (e.g. menorrhagia), pelvic pain and/or infertility.

They are the most common type of pelvic tumour and a leading cause of hysterectomy.

The exact epidemiology of uterine fibroids is difficult to assess as many women are asymptomatic. In general, the incidence of uterine fibroids increases with age until the menopause with peak incidence in women in their 40s. They are considerably more common in black women.

Fibroids are a hormone driven growths, which are maintained by high levels of oestrogen and progestogens.

The importance of this hormonal-mediated growth is best represented by the age of onset of fibroids. Uterine fibroids do not occur in pre-pubescent girls and the overall prevalence of fibroids progressively increases towards menopause.

Fibroids are very similar to the normal muscular myometrium and they may occur anywhere within it. Depending on the location of fibroids, they may be classified as subserosal, intramural or submucosal.

The risk of developing fibroids is decreased by pregnancy.

There are several risk factors that increase the chances of a female developing fibroids.

• Early age of puberty
• Increasing age
• Obesity
• Ethnicity (e.g. black females)

Pregnancy reduces the risk of fibroids, progestogen-only contraceptives also appear to reduce the risk.

Uterine fibroids have an unpredictable natural history.

Many women will be asymptomatic with fibroids discovered incidentally on pelvic imaging. In others they can produce significant and debilitating symptoms.

If present, women may suffer from the following symptoms:

• Menorrhagia
• Abdominal swelling
• Pelvic pain
• Dyspareunia
• Dysmenorrhoea
• Urinary/bowel symptoms

In some cases, fibroids may undergo ‘red degeneration’ during pregnancy. Red degeneration is the result of rapid enlargement causing the fibroid to outgrow its blood supply. This can lead to acute severe abdominal pain. Another classical cause of severe abdominal pain associated with uterine fibroids is torsion of a pedunculated fibroid.

A pelvic ultrasound is considered the first-line investigation for evaluation of uterine fibroids.

A transvaginal ultrasound is the initial diagnostic modality of choice, but a transabdominal ultrasound can also be used. In clinical practice, the main reason for requesting a pelvic ultrasound is identification of a pelvic mass or menorrhagia that is not responsive to conventional treatment.

Other investigations:

• Full blood count: assessment of anaemia
• Pelvic MRI +/- hysteroscopy: if concern about intramucosal fibroids or malignancy

Pelvic MRI is the best imaging modality to assess fibroids and useful at differentiating between leiomyomas, adenomyosis (endometrial tissue in the myometrium), and adenomyomas (benign tumour variant of adenomyosis). Its use tends to be reserved for complicated cases or operative planning.

The management of fibroids depends on the presenting symptoms of the patient.

Menorrhagia is the most common problem associated with fibroids and thus management focuses on the treatment of heavy periods.

Treatment options for menorrhagia include the intra-uterine contraceptive system (IUS), non-steroidal anti-inflammatory drugs (NSAIDs), tranexamic acid and/or the combined oral contraceptive pill.

In cases of menorrhagia not responsive to medical therapy or where fibroids are causing significant pain or mass effect, surgical intervention with myomectomy or hysterectomy can be considered.

The complications of uterine fibroids can be divided into pregnancy and non-pregnancy related.

Pregnancy-related complications

• Infertility (distortion of uterine cavity)
• Malpresentation
• Placental abruption
• Intrauterine growth restriction
• Preterm labour

Non-pregnancy-related complications

• Prolapsed fibroid
• Anaemia
• Endocrine effects (polycythaemia, hypercalcaemia, hyperprolactinaemia)

Last updated: April 2021