Fibroids

Overview

Fibroids are the commonest benign (non-cancerous) growth of the uterus: the NHS estimates that around 1 in 3 women develop them at some point, most often between the ages of 30 and 50, and they are more common in Black women. They occur in anyone with a uterus, including trans men and non-binary people. Fibroids depend on oestrogen and progesterone, so they grow during the reproductive years and in pregnancy and usually shrink after the menopause. They are described by position: intramural fibroids sit within the myometrium, subserosal fibroids bulge from the outer surface towards the abdomen, submucosal fibroids push into the cavity and distort the lining, and pedunculated fibroids hang on a stalk inside or outside the uterus. Many cause no symptoms and are found by chance on a scan. When they do cause trouble it is usually heavy periods, pressure on the bladder or bowel, pain or, with submucosal fibroids, difficulty conceiving.

Symptoms

What a clinician may find

• An enlarged, firm, irregular uterus felt on abdominal or pelvic examination
• A mass in the lower abdomen that can be large enough to resemble pregnancy
• Pallor and other signs of iron deficiency anaemia from heavy bleeding
• A normal examination when the fibroids are small

Complications

• Iron deficiency anaemia from heavy or prolonged periods
• Pressure effects: frequent urination or difficulty emptying the bladder, constipation, and rarely blockage of a ureter
• Subfertility and miscarriage, particularly with submucosal fibroids that distort the cavity
• Problems in pregnancy: pain from degeneration of a fibroid, an awkward position of the baby, obstructed labour, caesarean birth and heavier bleeding after delivery
• Torsion of a pedunculated fibroid, causing sudden severe pain
• Uterine sarcoma (leiomyosarcoma) is a rare cancer that can look like a fibroid on a scan; fibroids themselves are not thought to turn cancerous, but a fibroid that grows quickly, or any growth or bleeding after the menopause, needs prompt assessment

Diagnosis

Fibroids are often discovered on a scan done for another reason. When symptoms prompt investigation, the history covers the heaviness and pattern of bleeding, pressure symptoms and plans for pregnancy, and the examination feels for an enlarged or irregular uterus. Ultrasound, transvaginal or through the abdomen, is the first imaging and shows the number, size and position of the fibroids; NICE recommends it when the uterus can be felt through the abdomen or a pelvic mass is suspected. MRI maps fibroids more precisely before myomectomy or uterine artery embolisation and helps to distinguish them from adenomyosis. Hysteroscopy is used when submucosal fibroids are suspected and allows small ones to be removed at the same time. A full blood count is offered to anyone with heavy bleeding to check for anaemia; NICE does not recommend testing ferritin routinely, and iron treatment is guided by the blood count and symptoms. A pregnancy test is done in anyone of reproductive age with bleeding or a pelvic mass.

Treatment

Fibroids that cause no symptoms need no treatment, only review if they are large. For heavy bleeding the options are those for heavy menstrual bleeding generally. For fibroids smaller than about 3 cm, NICE advises the levonorgestrel intrauterine system as the first option where the cavity is not distorted, with tranexamic acid, a non-steroidal anti-inflammatory such as ibuprofen, the combined pill or cyclical progestogens if it is unsuitable, and iron to correct anaemia. Fibroids of 3 cm or more are referred for specialist assessment. GnRH analogues shrink fibroids and stop bleeding by inducing a temporary menopause; they are used for a few months before surgery, with add-back hormone therapy to protect bone. Procedures that keep the uterus are myomectomy (removal of the fibroids through the abdomen, laparoscopically or hysteroscopically), uterine artery embolisation, in which a radiologist blocks the blood supply so that the fibroids shrink, endometrial ablation for small fibroids with heavy bleeding, and MRI-guided focused ultrasound where it is available. The effect of uterine artery embolisation and myomectomy on future pregnancy is uncertain and is discussed before choosing between them; endometrial ablation is not suitable for anyone who may want a pregnancy. Hysterectomy is the definitive treatment for those who have completed their family and whose symptoms are severe.

Prevention

There is no proven way to prevent fibroids. Keeping to a healthy weight may lower the risk. Treating heavy periods early prevents iron deficiency anaemia, and regular review of known fibroids catches growth or new symptoms before they cause complications.