What are Uterine Fibroids?
Uterine fibroids are benign tumors that develop from the smooth muscle of the uterus. It is also known as leiomyomas, myomas, or fibromyomas. Uterine fibroids are extremely common in women of childbearing age and usually regress after menopause. Although there may be symptoms such as heavy menstrual bleeding, sometimes there may be no symptom at all and a woman may be unaware that she has a fibroid.
Uterine fibroids are usually round in shape and can grow to a massive size. It can occur as a single large growth or multiple smaller growths. Depending upon the size and location of the fibroid, it may lead to infertility or produce complications during pregnancy. Very rarely do uterine fibroids become cancerous.
How does a uterine fibroid develop?
Pathophysiology of Uterine Fibroids
The uterus is a pear-shaped organ composed of the body of the uterus on top and the cervix below, which connects at its lower end to the vagina. Extending from the upper part of the uterus on either side are the fallopian tubes. Near the end of each tube is an ovary.
The uterine wall is composed of smooth muscular tissue or myometrium, covered on the surface by a serous or peritoneal layer and on the inside by the mucosal layer known as endometrium. Hormones regulate the reproductive system in women and include :
- Gonadotropin-releasing hormone (GnRH) secreted by the hypothalamus.
- GnRH stimulates the pituitary gland to produce follicle stimulating hormone (FSH) and luteinizing hormone (LH).
- FSH and LH stimulate the ovaries to secrete estrogen and progesterone. The effects of these hormones are discussed further under female hormones.
The growth of uterine fibroids are hormone mediated. Estrogen, progesterone and growth factors play a role in tumor growth. Fibroids may grow rapidly during pregnancy due to the effect of hormones and are seen to regress after menopause. Drugs containing estrogen, such as oral contraceptives, may also cause fibroids to grow.
The term “fibroid” is often misleading since it does not contain any fibrous tissue but is made up entirely of smooth muscular tissue of the uterus. For this reason, the term “leiomyoma” is more accurate in describing the growth. Fibroids start in the muscle layer of the uterus where a single muscle cell may reproduce repeatedly to form a pale, firm, rubbery mass which is clearly demarcated from the surrounding muscle tissue. The cut surface of a fibroid shows a characteristic whorled, spiral pattern of fibers.
The fibroid may be confined within the muscular layer of the uterus (intramural), or may grow on the surface of the uterus beneath the peritoneum (subserosal), or it may grow into the uterine cavity beneath the endometrium (submucosal). When the muscular action of the uterus attempts to expel the submucosal tumor, it can give rise to a fibroid polyp or a pedunculated fibroid.
Types of Uterine Fibroids
There are different types of fibroids depending on its location in the uterus.
- Intramural or myometrial fibroids are situated within the muscular wall of the uterus.
- Subserosal fibroids are located on the outer surface of the uterus beneath the serosa or the peritoneum covering the outside of the uterus. Large subserosal fibroids may press upon the bladder in front or the rectum behind the uterus and give rise to urinary complications or constipation as a result.
- Submucosal fibroids are located within the uterine cavity underneath the endometrium. It likely to give rise to prolonged, heavy periods. Submucosal fibroids may occasionally be the cause of infertility and if very large, it may cause problems during pregnancy and childbirth.
- Pedunculated fibroids may be connected to the outside of the uterus by a pedicle or stalk. It may also be seen hanging within the uterine cavity by a stalk and are known as fibroid polyps or pedunculated fibroids. A pedunculated fibroid may form within the uterine cavity as a result of repeated attempts made by the uterus to remove a submucosal polyp.
Causes and Risk Factors of Uterine Fibroids
It is not known for sure what causes the development of uterine fibroids but certain factors may be involved.
- Female hormones estrogen and progesterone promote the growth of uterine fibroids. This is evident by the fact that fibroids occur in women of childbearing age, more frequently after the age of 30, and usually regress after menopause.
- Genetic factors may be involved in the development of fibroids.
- Family history – having a family member with fibroids may increase the risk of developing one.
- Obesity has been linked to increased risk of developing fibroids. Women with a high body mass index (BMI) are more likely to develop fibroids.
- Uterine infections, high blood pressure, and alterations in growth factor expression have all been suggested by researchers as risk factors.
- Potentially protective factors are pregnancy and childbirth. Nulliparous women (who have never given birth to a child) are more likely to develop fibroids.
- Early menarche is the onset of menstruation before the age of 10 years and may be an associated risk.
- Dietary factors have been suggested as possible risk factors with a focus on excessive consumption of red meat and alcohol. Eating plenty of green vegetables may have a protective action. More research is needed to prove such claims.
Signs and Symptoms
Menstrual problems and abnormal vaginal bleeding is the most common symptom of uterine fibroids. It is more likely to be caused by a submucosal fibroid. This includes :
- Prolonged periods
- Heavy periods
- Irregular periods – frequent or missed period
- Spotting or bleeding in between periods
- Dysmenorrhea – painful menstruation
Apart from menstrual pain, women with fibroids may also report intermittent or persistent pain and discomfort. This may include abdominal or pelvic pain and sometimes low back pain. There may also be pain during sexual intercourse.
There may also be a heaviness or pelvic discomfort with an enlarged uterus or abdomen that may be mistaken for pregnancy. Pressure on other pelvic organs like the rectum, bladder or even the spinal nerves may occur with a large fibroid on the outer surface of the uterus. Apart from pain and discomfort, there may also be associated symptoms like urinary frequency, retention, urgency and constipation.
Pregnancy with Uterine Fibroids
In most cases, fibroids do not cause any problems during pregnancy. However, certain complications may arise during pregnancy that can exacerbate the clinical presentation and jeopardize the pregnancy. Uterine fibroids often decrease in size after childbirth.
- Increased fibroid size may occur during pregnancy as the hormone levels rise and the blood flow to the uterus increases. This may cause additional discomfort and pain, especially between the first and second trimester.
- Red degeneration of the fibroid may cause severe pain during pregnancy.
- Recurrent miscarriage (spontaneous abortion) may occur in early pregnancy.
- Placental separation and bleeding may jeopardize the pregnancy.
- Premature labor and delivery, and abnormal presentations such as breech may occur in late pregnancy. This is more likely to occur with multiple fibroids or a large fibroid distorting the uterine cavity.
- Obstruction of the uterine opening by a large fibroid may complicate the delivery and require a Cesarean section.
- Postpartum hemorrhage or excessive bleeding after delivery of the baby may occur in the presence of a large fibroid.
Complications of Uterine Fibroids
Complications due to uterine fibroids are not common but may lead to one or more of the following :
- Torsion or twisting of a pedunculated fibroid on its stalk can cause severe abdominal or pelvic pain and may necessitate surgery.
- Acute pain may arise when large fibroids degenerate or break down if it outgrows its blood supply.
- Anemia due to excessive menstrual blood loss.
- Infertility is most often caused by a submucosal fibroid which may prevent implantation of the embryo in the uterine wall. In rare cases, infertility may arise due to distortion or blockage of the fallopian tube by the fibroid, or by it preventing sperm from reaching the fallopian tubes.
- Recurrent spontaneous abortion (miscarriage).
- Cancerous changes are extremely rare.
Diagnosing Fibroids in the Uterus
Most cases of uterine fibroids are asymptomatic – there is no signs or symptoms indicating a fibroid. Often uterine fibroids are detected incidentally in the course of a routine pelvic examination, when investigating the cause of infertility or during a prenatal ultrasound. In certain cases, such as in obese women, the diagnosis may become difficult at times. A fibroid may be confused with pregnancy, ovarian tumor or uterine adenomyosis and should be differentiated from uterine fibroid.
Taking a careful case history is the first step in diagnosis. A woman may visit a gynecologist with complaints of :
- menstrual irregularities
- heavy bleeding
- pelvic discomfort
- lower abdominal pain
- difficulty falling pregnant
These symptoms are not unique to uterine fibroids. Read more on Uterine Fibroids Symptoms.
The next step is doing a physical examination, including a pelvic examination. Sometimes, a fibroid may be large enough to be felt through the abdomen and may be mistaken for a pregnant uterus. In most cases, however, a pelvic examination is necessary and a fibroid may be detected as an enlarged, mobile, irregular uterus or a mass on the uterus. The pelvic examination is followed by one or more of the various imaging techniques below to accurately identify the shape, size, location, number and type of uterine fibroid. Read more on Types of Uterine Fibroids.
Ultrasound uses sound waves to create an image of the uterus and the surrounding structures can provide further information about the fibroid in addition to detecting its presence. The shape, size, position and number of fibroids can be detected with an ultrasound examination (ultrasonography).
A variation of ultrasound is the hysterosonography. This method uses sterile saline to expand the uterine cavity and thus give a better image of the uterine lining. The case history, along with a pelvic examination and ultrasonography are usually all that will be needed to confirm the diagnosis of fibroids. Further tests may be done as required in case to exclude other conditions and to rule out cancer.
The hysteroscope is a thin, flexible tube with a tiny camera and a light source at its end. This is inserted into the uterus through the vagina and cervix. The uterine cavity can be visualized by this device and any fibroid present can then be detected.
This is a special type of x-ray of the uterus and fallopian tubes done after delivering a radio-opaque dye into the uterus through the vagina. Fibroids within the uterine cavity and changes in the size and shape of the uterus and fallopian tubes can be detected by this method. HSG is usually advised when infertility is a concern.
CT Scan and MRI
Computed tomography (CT) scans and magnetic resonance imaging (MRI) are more accurate imaging tests but are rarely needed for diagnosis of fibroids unless ultrasonography reports are inconclusive. They may be helpful in recording growth of fibroids over time.
Biopsy of the uterine lining involves taking a tissue sample from the uterus by passing a small instrument through the vagina into the cervix and uterus. It may need to be done if cancer is suspected.
This is a minimally invasive surgical procedure where a small fiberoptic camera is inserted into the abdomen through a tiny incision on the abdomen, just below or through the umbilicus (belly button). Fibroids on the surface of the uterus can be seen by this method.
Treatment of Uterine Fibroids
Not all fibroids require treatment. Fibroids that are asymptomatic, are very small, or if diagnosed in a woman approaching menopause may require no treatment at all. Since most fibroids regress after menopause and rarely become cancerous, a “wait and watch” approach with periodic re-evaluation is usually favored in such cases.
Treatment may become necessary in case of
- Prolonged, heavy periods over a considerable time, leading to anemia.
- Heavy or painful periods affecting daily functioning
- Bleeding in between periods
- A fibroid that is growing rapidly in size
- Uncertainty in diagnosis, where there is doubt about whether the tumor is a fibroid or some other growth, such as a tumor
- Pelvic pain
- Infertility with a history of recurrent spontaneous abortion.
Treatment, where necessary, will be guided by factors such as age, severity of symptoms, possible causes of the uterine fibroid, the patient’s desire to fall pregnant, and her wish to retain her uterus.
Medication may provide symptomatic relief for pain, regulate heavy periods, or reduce growth of the fibroid. The commonly used drugs include :
- Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen may be used for pain relief.
- Oral contraceptive pills may decrease heavy menstrual bleeding and pelvic pain. However, the estrogen* in the pill may increase the size of the fibroid.
- Gonadotropin-releasing hormone (GnRH) analogues such as leuprolide act by decreasing estrogen production and thus help to limit the fibroid size. Its often used pre-operatively when surgery is contemplated as reducing the size of the fibroid makes surgery easier.
- Progestins * such as medroxyprogesterone and oral contraceptives have no action on reducing growth of fibroids but are helpful in controlling symptoms such as heavy periods.
- Antiprogestins such as mifepristone may help reduce fibroid growth.
- Selective estrogen receptor modulators (SERMs) such as raloxifene may also help reduce fibroid growth.
- Progestin-releasing intrauterine device (IUD) may help to reduce heavy menstrual bleeding.
- Danazol is a synthetic drug similar to testosterone and is effective in reducing size of the fibroids as well as reducing heavy periods. However, it has certain undesirable side effects such as facial hair growth, deepening of the voice, weight gain, oily skin, and fatigue which may limit its use.
In this procedure the fibroid is removed but the uterus is left intact. Women eager to have fall pregnant in the future may opt for this procedure. However, the chance of fibroid recurrence is a possibility. Depending on the location and size of the fibroid, myomectomy may be performed by any of the following methods – laparotomy, laparoscopy, or hysteroscopy.
With laparoscopy, tiny incisions are made in the abdomen and the fibroid is viewed by means of the laparoscope – a long, flexible, fiberoptic tube with a camera and light source at its end. This instrument is passed through one of the incisions. Other tiny surgical instruments are introduced through the other incisions and the fibroids are removed.
In laparotomy, a larger incision is made in the abdomen for removal of the fibroids.
In hysteroscopy, an instrument called the resectoscope is introduced through the hysteroscope into the uterine cavity through the vagina. The resectoscope uses electricity or laser to destroy fibroids protruding into the uterine cavity and to control bleeding caused by deep-seated fibroids within the uterine wall.
Hysterectomy is the surgical removal of the uterus and fibroids. This offers a permanent solution for uterine fibroids. The ovaries may or may not be removed. However, women who wish to fall pregnant in the future cannot consider a hysterectomy as pregnancy is not possible afterwards. Hysterectomy is usually recommended when the fibroids are very large, the symptoms of pain and abnormal menstrual bleeding are not relieved with other treatments, or when other forms of treatment are not possible.
Other Surgical Procedures
- Endometrial ablation involves using any form of energy such as heat, microwave energy or electric current to destroy the uterine lining. Women with heavy periods or with fibroids smaller than 3 centimeters can be treated by this method. There is risk of bleeding and infection. Women treated by this method may find it difficult to fall pregnant.
- Uterine artery embolization involves introducing tiny embolic agents into the arteries supplying the uterus by means of a catheter passed through a tiny incision in the groin. By interfering with the blood supply, the fibroids are made to shrink. The effect of this procedure on future pregnancy is not yet clear.
- Myolysis is a laparoscopic procedure where an electric current or laser is used to destroy the fibroid.
In cryomyolysis, liquid nitrogen is used to freeze the fibroid.
- Focused ultrasound surgery or MRI-guided ultrasound surgery is a non-invasive procedure where the patient is placed inside a specially-designed MRI machine. High energy sound waves are used to destroy the fibroids.