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Uterine fibroids are growths arising from the muscle wall of the uterus. It is a round and firm structure amid the soft muscle layer. When cut open, the pale and dense cut surface gives us the impression that it is a growth of densely packed fibrous tissue. The growth attracts the common name of fibroid because of these characteristics.
In medical term, fibroid is known as leiomyoma. It reflects the true nature that the growth is a benign (not cancerous) tumour developed from abnormal muscle cells of the uterus, not fibrous tissue.
Uterine fibroids are the most common noncancerous growths in women. They can develop in women of any age after the onset of menstruation. The incidence increases with age. By 40 years old, more than 50 percent of women would have one or more fibroids. It is not uncommon to see mother and daughters or sisters in the same family with uterine fibroids.
Uterine fibroids are typically silent in at least 60 percent of women. They are discovered on a routine examination of the pelvis or when an ultrasound scan of the pelvis is carried out for some other reasons. In the other 40 percent of women, uterine fibroids may cause one or more of the following symptoms:
On examination of the pelvis, a doctor may suspect a uterine fibroid if the uterus is found to be larger in size than normal or the contour of the uterus is irregular.
The diagnosis is typically based on the finding of a growth on ultrasound scan of the uterus. CT-scan or magnetic resonance imaging (MRI) scan of the abdomen and pelvis will also show the presence of uterine fibroids.
A common condition, uterine fibroids are found in many women who experience difficulty in becoming pregnant. There is, however, no evidence to show that uterine fibroids cause infertility. If they do, it happens only in a very small proportion of women, for example, in a situation when a fibroid of moderate size located near the fallopian tube causes a blockade in the tube.
It is a common belief that uterine fibroid can cause the pregnancy to miscarry. Research has not shown a conclusive evidence for this belief. Why miscarriage seems to happen commonly in women who have fibroids can be explained by the facts that both fibroids and miscarriage are commoner as a woman becomes older. In fact, the great majority of women with fibroids, including those with a large fibroid, continue the pregnancy with no abnormal outcomes.
A peculiar complication of uterine fibroids during pregnancy is an uncommon change in the fibroid known as ‘red degeneration’. This condition causes abdominal pain that may require treatment with pain killers. This condition, however, has no adverse outcome on the pregnancy in terms of miscarriage or premature birth of the baby.
Each uterine fibroid develops from a single muscle cell in which certain genes have been damaged or altered. The genetic changes lead to a more rapid cell division than usual in response to stimulation of hormones and growth factors. The cell division is also uncontrollable which results in a large number of abnormal muscle cells and the formation of a visible growth.
It is quite common for muscle cells from different parts of the uterus to develop these genetic changes over a period of time. This results in the forming of many fibroids on the same uterus.
The cause of genetic changes is currently unknown. It is clear that there is no fibroid gene that can be passed from mother to daughters in a direct genetic inheritance manner. There is also no association of fibroids with dietary habits or history of childbearing.
Although the muscle cells made up of fibroids are abnormal in their genes, they are responsive to oestrogen, the female sex hormone.
During the years that a woman is menstruating, oestrogen stimulation leads to the continual growth of fibroids. In general, a fibroid increases in size by 1 cm a year.
During pregnancy, fibroids are known to grow more rapidly than during the non-pregnant period.
At menopause as oestrogen secretion ceases, many fibroids shrink in size slowly in the post-menopausal years. However, fibroids will not disappear completely, even years after menopause.
Some other growth factors are known to influence the growth of fibroids. These growth factors are not changed by menopause. This explains why some fibroids fail to shrink or may even continue to grow despite menopause.
Uterine fibroids can be classified according to their size (Table 1) or by their location in the uterus (Table 2):
Table 1: Classification of fibroids by size
Table 2: Classification by location
It is very common for fibroids of different sizes and locations to be present on the same uterus.
The majority of women have small or moderate size fibroids. In general, these women do not experience any problem from the fibroids and do not require treatment. In other women, the decision on initiation and choice of treatment of fibroids depends on individual circumstances. The treatment available includes the following:
Treatment of heavy menstrual flow
Menstrual flow can be reduced with medication such as tranexamic acid, danazol, progesterone hormone or gonadotrophy releasing hormone analogues. This form of treatment is appropriate when the fibroid is small or moderate in size. It is also more appropriate among women who are close to menopause when treatment may be limited to a short period of time before menopause ensues. This treatment is not a cure of fibroids.
Hysteroscopic resection of fibroidSubmucus fibroid or fibroid polyp can be effectively removed by resection through a hysteroscope. It is a minimally invasive procedure through the vaginal and cervical approach. This technique is suitable for women of any age, including those considering pregnancy in the future.
Uterine artery embolisationSolitary fibroid of moderate or moderately large size can be treated by blocking the blood flow (embolisation) to the fibroid. This is an interventional radiology procedure involving inserting an arterial catheter to the uterine artery under fluoroscopic guidance. This technique is not a complete cure for fibroids.
Instead, after successful arterial embolisation, the size of the fibroid can shrink by almost 60 percent and the heavy menstrual flow can be reduced by almost 80 percent. The treatment is appropriate for women who want to avoid the risk of surgery. It is not appropriate for women whose fibroids need to be submitted for pathological tests.
Surgical removal of fibroids, also known as myomectomy
In this operation, fibroids are removed and the uterus is repaired for resumption of its normal menstrual and childbearing functions. Fibroids of moderate to moderately large sizes can be effectively removed through laparoscopic surgery. Laparoscopy is proven to be efficient and is associated with less pain and shorter recovery time compared to conventional surgery. Robotic surgery is an alternative minimally invasive procedure for treating these types of fibroids.
On the other hand, traditional open surgery remains the most versatile approach to remove all fibroids, regardless of the size and their location on the uterus. Good surgical repair on the incisions on the uterus confers additional safety on the integrity of the wounds in ensuing pregnancies.
Hysterectomy or removal of the uterus
For women who do not desire to conserve the fertility potential, removal of the uterus (hysterectomy) confers the most appropriate and complete treatment.
Once the fibroids are removed, the uterus resumes its normal structure. There remains a potential risk that some muscle cells may develop genetic changes leading to development of new fibroids. There is a 10-30 percent chance that new fibroids will develop after the myomectomy operation. There is obviously no recurrence of fibroids if a hysterectomy is performed.
Uterine fibroids are by nature non-cancerous tumours. The malignant form of fibroid is known as leiomyosarcoma. It is a very rare tumour developed from abnormal muscle cells unrelated to fibroids. It can occur in the uterus with existing fibroids or without fibroids. Development of malignancy within an existing fibroid is extremely rare and is not a consideration for decision for surgery on fibroids.