Uterine fibroids

Uterine fibroids develop within the wall of the uterus.

What are uterine fibroids?

Uterine fibroids are nodules of smooth muscle cells and fibrous connective tissue that develop within the wall of the uterus (womb). Medically, they are called uterine leiomyomata (singular: leiomyoma). Fibroids may grow as a single nodule or in clusters and may range in size from 1 mm to more than 20 cm in diameter. They may grow within the wall of the uterus or they may project into the interior cavity or toward the outer surface of the uterus. In rare cases, they may grow on stalks or peduncles projecting from the surface of the uterus.

The vast majority of fibroids occur in women of reproductive age, and according to some estimates, they are diagnosed in black women two to three times more frequently than in white women. They are seldom seen in young women who have not begun menstruating and they usually stabilise or regress in women who have passed menopause.

A fibroid uterus is the most frequently diagnosed tumour of the female pelvis. It is important to know that fibroids are benign tumours. They are usually not associated with malignancy, since they only rarely develop into cancer, which then is called a sarcoma. The risk that a sarcoma develops from a fibroid is estimated to be between 0.2 to 0.5 percent, and contrary to fibroids, sarcomas tend to develop in older women. Generally, fibroids do not increase a woman’s risk for uterine cancer.

Cause

The factors that initiate fibroid growth are not known, but are thought to be closely related to either the levels of circulating oestrogen, or an increased sensitivity to oestrogen.

What are the symptoms?

Depending on their location and size, fibroids often do not cause any symptoms and do not require treatment other than regular observation by a medical practitioner. Fibroids may be discovered during routine gynaecological examination or during antenatal care check-ups.

Some women who have uterine fibroids may experience symptoms such as excessive or painful bleeding during menstruation, bleeding between periods, a feeling of fullness in the lower abdomen, frequent urination resulting from a fibroid that compresses the bladder, pain during sexual intercourse, or low back pain.

Reproductive symptoms such as infertility, recurrent spontaneous abortion, and early onset of labour during pregnancy have also been attributed to fibroids. However, in South Africa the association of fibroids with infertility is frequently based on occlusion of the Fallopian tubes following pelvic inflammatory disease.

Removal of fibroids from the uterus (the operation is called myomectomy) will not restore fertility in all cases, particularly, if the Fallopian tubes are shown to be blocked before the operation. This may be done by doing a special X-ray investigation called a hysterosalpingogram, involving the injection of a liquid contrast medium through the cervix, or by doing a laparoscopy and checking whether the tubes are open by injecting a dye through the cervix. In rare cases, a fibroid can compress and block the Fallopian tube, preventing fertilisation and migration of the ovum (egg). After surgical removal of the fibroid, fertility may be restored.

During pregnancy, fibroids tend to grow due to the increased circulating oestrogens from the foetus and placenta. Labour complications include abnormal fetal position, ineffective labour contractions and obstruction of the birth canal. There is also a greater risk that, following the delivery of the baby, the uterus does not contract adequately causing a postpartum haemorrhage (bleeding).

Prevalence

It has been estimated that up to 20 to 30 percent of women of reproductive age have fibroids, though not all have been diagnosed. More careful studies, however, indicate that the prevalence may be much higher. A study of 100 uteri that had been removed in consecutive hysterectomies yielded the following results: 33 had been diagnosed as having fibroids prior to surgery; routine pathological examination disclosed that 52 had fibroids. However, a surprising 77 specimens were found with fibroids upon very close examination. The majority of the tumours were less than 1 cm in diameter and were missed during routine pathological examination. These results indicate that possibly more than three-quarters of women have uterine fibroids.

This is a small study, however, and its results should not be interpreted as applying to the entire female population, but as an indicator that perhaps the prevalence of fibroids is much higher than has been believed.

What are the risk factors?

No risk factors have been found for uterine fibroids other than being a female of reproductive age. However, some factors have been described that seem to be protective. In some studies, again of small numbers of women, investigators found that as a group, women who have had two live born children have one-half the risk of having uterine fibroids compared to women who have had no live born children. It could not be discerned whether having children actually protects a woman from developing fibroids or whether fibroids contributed to the infertility of women who had no children.

Obese women in some studies were at increased risk of having fibroids, but other studies failed to confirm this. A lower risk has been found in both smokers and users of oral contraceptives in some studies, but not in all. However, it is important to note that smoking poses far greater health hazards than do uterine fibroids. Athletic women also seem to have a lower prevalence compared with women who do not exercise regularly.

How is it treated?

Surgical removal of a fibroid uterus historically has been based on uterine size. Once the uterus reached the size that it would be in the 12th week of pregnancy, it was considered time to perform a hysterectomy. The decision was based mainly on the fact that fibroids of such volume could shield the presence of uterine cancer. However, improved imaging procedures such as ultrasound (or the rather costly magnetic resonance imaging) can now effectively determine whether or not a rapidly growing tumour is present, reducing the number of hysterectomies performed. Therapy for uterine fibroids should be based on symptoms and not the idea that uterine fibroids will continue to grow until it becomes necessary to perform a hysterectomy as most women will probably never experience symptoms before the menopause, when all fibroids start shrinking anyway.

If a fibroid is particularly troublesome in the younger age group of women, the gynaecologist often can remove only the tumour, leaving the rest of the uterus intact. This may leave the wall of the uterus weakened, in which case any pregnancy that occurs after myomectomy, most likely will be followed by a caesarean section to prevent rupture of the uterine scar during the delivery of the baby. Many women with fibroids have successful pregnancies with no undue incidence of a miscarriage or another unfavourable outcome.

More and more, medical practitioners are beginning to realise that uterine fibroids may not require any intervention or, at most, limited treatment. For a woman with uterine fibroids that are not symptomatic, the best therapy may be watchful waiting. Some women never exhibit any symptoms or have any problems associated with fibroids; in which case no treatment is necessary.

For women who experience occasional pelvic pain or discomfort, a mild, over-the counter anti-inflammatory or painkilling drug often will be effective. More bothersome cases may require stronger drugs available by prescription.

The fact that fibroids seemingly are oestrogen-dependent, has led to attempts to control them by reduction in available oestrogen. Hormone-like agents that counter the action of the gonadotropin-releasing hormone (GnRH) are being investigated as one such an agent. The use of a GnRH agonist lowers blood levels of oestrogen and reduces uterine volume by as much as 60 percent.

Of primary concern in the use of such agents, is the possibility of increasing blood cholesterol levels and reducing bone density, which may lead to osteoporosis. Although only modest increases in blood cholesterol have been noted in women undergoing this treatment, the therapy itself was of short duration. Unfortunately, the uterus returned to its pre-treatment size within three to six months after GnRH agonists were stopped.

It would seem from these observations that the use of GnRH agonists is of limited application. But, in fact, defined protocols have been worked out for administration of these agents for use in women who have symptoms, are poor candidates for surgery, and are nearing menopause. Also, for patients needing a hysterectomy, the use of GnRH agonists can reduce uterine size considerably, making removal of individual fibroids or abdominal hysterectomy easier or even allowing a vaginal hysterectomy rather than an abdominal one.

Three GnRH agonists are currently available. Two must be given by injection and the third is administered by an inhaler. Side-effects that have been found include hot flushes, depression, insomnia, decreased libido, and joint pain. Maximum uterine shrinkage is achieved after three months of therapy.

Studies have only just begun on the newest class of antihormonal agents, the antiprogestins, the best known of which is RU 486 which is not freely available in South Africa. Even though fibroids appear primarily stimulated by oestrogens, medications in this class which oppose the other major female hormone, progesterone, also seem to be effective for treatment of uterine fibroids. Studies using these medications are still in the early stages.

One of the most recently developed methods to treat symptomatic fibroids is selective embolisation of the blood vessels that supply the fibroid. This involves the placement of a small catheter in die main artery of the upper leg (similar to the way cardiac catheterisation is performed during the treatment of diseased blood vessels of the heart). This is then advanced under X-ray guidance to the uterus, followed by the injection of special microspheres into the blood vessels of the offending fibroid.

Although several thousand of these procedures are performed worldwide every year, only a small number of centres have radiologists with the necessary expertise. The procedure has a high success rate with the advantages of avoiding the risks of surgery and anaesthesia. It is particularly suitable for women with a single troublesome fibroid who wish to retain their uterus, but have completed their family, since it may adversely affect fertility.

The procedure is however not free from possible complications and these include infection, particularly if the fibroid was situated close to the inner lining of the uterus, pain after the procedure and some loss of ovarian function.

If a woman with fibroids in her uterus suffers from severe blood loss during menstruation, an alternative to the medical and surgical treatments already described may be offered in the form of an intra-uterine system that continuously releases small amounts of progestogen into the uterus. Provided the uterine cavity is not distorted by the fibroids, excellent results have been obtained. Studies have shown a reduction of blood loss after three months of up to 80% and more than 20% of women experienced minimal or no menstrual bleeding after one year of use. Similar in appearance to conventional intra-uterine devices, it additionally provides reliable contraception for five to seven years.

(Reviewed by Dr G.R. Verwoerd)