Uterine
Fibroids & Uterine Artery Embolization for Fibroids
Background
What Are Uterine Fibroids?
Fibroids are benign tumors arising from the smooth muscle that
makes up the uterus. They are also called leiomyomas or myomas.
Fibroids may arise in different parts of the uterus, as shown
in the figure.
How Are Fibroids Named?
Fibroids are named according to their position within the uterus;
submucosal, intramural, and subserosal. A submucosal fibroid
lies just under the inner lining of the uterus, which is called
the endometrium. Some of these fibroids grow on a stalk. These
are referred to as "pedunculated". An intramural fibroid
that lies completely within the muscular wall of the uterus ("intra" means
within and "mural" means wall). A serosal or subserosal
fibroid lies on the outer part of the uterus, just under the
covering of the outside of the uterus, which is called the serosa.
Subserosal fibroids may also grow on a stalk and be called pedunculated.
Abnormal bleeding is usually caused by submucosal or intramural
fibroids. Intramural and subserosal fibroids are the usual cause
of pelvic pain, back pain, and the generalized pressure that
many patients experience.
Who Gets Fibroids?
All women are at risk of getting fibroids. Uterine fibroids
are the most common tumors of the female genital tract. They
occur in 20 to 25 % of women of childbearing age. The presence
of fibroids is the most common reason for a woman to have a hysterectomy.
There are approximately 20,000 hysterectomies performed in Canada
each year. In addition, many patients suffer symptoms from fibroids
but never undergo a hysterectomy.
African-Canadians are as much as 3.2 times as likely to develop
fibroids as Caucasians. There is some variation among other racial
groups. The reason for this increased risk is not known, although
genetic variability is presumed to be a significant factor. While
fibroids may appear in patients in their twenties, most patients
do not have any symptoms until their late thirties or forties.
What causes fibroids?
The cause for fibroid development is not known. Leiomyomas
arise after menarche (beginning of menstruation in adolescence)
and regress after menopause, which suggests that the development
of fibroids is dependent on the presence of hormones (primarily
estrogen). But the triggering event for the development of the
fibroid is not known and the interaction of the various hormones
and growth factors likely to be involved is not well understood.
Once fibroids appear, their growth rate is also dependent on
estrogen, progesterone and possibly other hormones. Growth rates
vary greatly among women and the exact cause for this variability
is not known, making the prediction of the behavior of fibroids
very difficult.
What Symptoms are caused by Uterine Fibroids?
Most leiomyomas do not cause symptoms. While 25% of women develop
fibroids during their lives, only 10 to 20% of these women have
symptoms. Therefore, only a minority of women ever require treatment.
Heavy Menstrual Bleeding
The most common symptom associated with fibroids is abnormal
bleeding, which typically presents as heavy menstrual bleeding,
often with clot formation. Anemia (low blood count) is a common
side effect. The medical term for heavy menstrual bleeding is
menorrhagia (pronounced men-o-ray-ja). As the bleeding severity
increases, clot passage with the menstrual period commonly occurs.
The clots form because the blood stays in the uterus long enough
to clot prior to being expelled into the vagina. As these clots
pass, they may cause severe menstrual cramping.
How fibroids cause abnormal bleeding is not known. Fibroids
are believed to alter muscular contraction of the uterus, which
may prevent the uterus from controlling the degree of bleeding
during a patient's period. In addition, it has been shown that
fibroids compress veins in the wall of the uterus. This results
in dilation of the veins of the uterine lining. As the pressure
in these veins increases, the the lining of the uterus becomes
engorged. This may result in heavy bleeding during a menstrual
period. It may also contribute to abnormal bleeding.
Heavy menstrual bleeding is usually caused by fibroids deep
within the wall of the uterus (intramural) or those just under
the inner lining of the uterus (submucosal). Very small fibroids
in the wall of the uterus or fibroids in the outer part of the
uterus (subserosal) usually do not cause abnormal bleeding.
There are many other potential causes of heavy menstrual bleeding
and so a careful gynecologic history and physical examination
is an important part of the evaluation of a patient with heavy
bleeding. Just because a patient has fibroids, it does not mean
that the fibroids are the cause of abnormal bleeding. Other causes
include endometrial hyperplasia (an abnormal thickening of the
uterine lining), endometrial polyps, adenomyosis, and even uterine
cancer. The likelihood of these causes can often be determined
based on a gynecologic history and physical examination, but
on occasion additional tests may be needed.
Pelvic Pain and Pressure
Another symptom is pelvic pain. On rare occasions, a fibroid
may suddenly degenerate (spontaneously shrink and scar due to
decrease in blood supply). This is a painful process that may
last several days or weeks. This type of severe pain is unusual.
Severe or burning pain during a menstrual cycle is perhaps more
commonly caused by other conditions, such as endometriosis. However,
because of the broad range of presenting symptoms of fibroids,
gynecologic evaluation is needed to confirm the diagnosis.
If fibroids cause symptoms related to the pressure they exert
on other structures, they most commonly cause a sensation of
pressure or discomfort in the pelvis. This may feel like heaviness,
bloating, a dull ache, or mild tenderness of the fibroids themselves.
The discomfort may be greater with exercise, while bending over
or during sexual intercourse. As fibroids grow, they may compress
nerves that supply the pelvis and the legs, causing pain in the
back, flank, or legs. Patients also report increasingly severe
menstrual cramps with the growth of their fibroids.
Urinary Symptoms and Other Symptoms
Pressure on the urinary system also may be caused by fibroids.
Typically, this results in urinary frequency (increased frequency
of urination, including the need to get up at night to urinate).
Fibroids may also contribute to incontinence (urine leakage)
or rarely, they may partially block the outflow of the bladder,
making it difficult to empty the bladder. Occasionally, an enlarged
uterus may press on other urinary structures resulting in partial
blockage of the urine flow from the kidneys. On occasion, fibroids
may also cause rectal pain or pressure.
Many of these symptoms may be cyclic, worse in the days leading
up to the menstrual period and during the period. If the fibroids
get large enough, the pressure and discomfort they cause may
occur at any time.
What is the Effect of Fibroids on Fertility?
It has often been suggested that infertility and/or repeated
miscarriage can be caused by fibroids. However, the statistical
evidence for infertility is lacking and other factors are more
likely to cause infertility in fibroid patients. Some researchers
have suggested that the presence of fibroids may predispose a
patient to miscarriage, but again firm statistical evidence to
support this possibility is not yet available. There have been
studies in infertile women in whom the only identifiable cause
is the presence of fibroids. After myomectomy (surgical removal
of the fibroids, leaving the uterus in place), these studies
have shown that 40 to 60 % of these women have been able to become
pregnant. However, because large studies have not been completed
and infertility may have many causes, it is imprudent to assume
that fibroids are the cause without a careful evaluation for
other problems.
What is the Risk of Malignant Tumour with Fibroids?
A common question is whether a large mass in the uterus, presumed
to be a benign fibroid, could be a malignant tumor. The answer
is yes, although these tumors, called leiomyosarcomas, are very
rare. They occur in about 1 in 1000 cases. Based on recent genetic
studies, it does not appear that these malignant tumors result
from a preexisting benign tumor. It appears that they arise separately
from any existing fibroids.
The problem is that it can be impossible to tell a benign fibroid
from a malignant tumor without surgery. No imaging test, such
as ultrasound or MRI, can reliably distinguish these tumors.
There is no blood test that can detect them. By history, they
are often suspected when a presumed fibroid grows very rapidly.
However, the majority of rapidly growing"fibroids" are
just that, benign fibroids.
Biopsy also cannot reliably distinguish benign from malignant
tumors of the uterus, because the sample may be taken from a
relatively benign appearing portion of the mass.
Unfortunately, the reliable means of detecting malignant solid
tumors of the uterus is surgery. This would either be by removal
of the fibroids alone (myomectomy) or hysterectomy. Hysterectomy,
with surgical removal of lymph nodes near the uterus is the primary
treatment for leiomyosarcoma.
Uterine Artery Embolization for Fibroids Case Study
Sanjoy Kundu BSc., M.D., F.R.C.P.(C), D.A B.R., FASA, Division
of Interventional Radiology
Scarborough Hospital – General Division, Scarborough, Ontario,
Canada
Case History:
47 year old female presented with a one year history of very
heavy periods lasting for four days during each menstrual
cycle. Her past medical and surgical history was otherwise
unremarkable. A MRI demonstrated a dominant intramural
fibroid in the uterine fundus (Figure 1). After assessing the
different therapeutic options, the patient chose to go ahead
with a
Interventional Procedure (Case performed at Scarborough General
Hospital – General Campus):
Uterine Artery Embolization Procedure for her fibroids. The
patient’s right common femoral artery was accessed. Using
a C2 catheter, the patient’s left uterine artery was cannulated
(Figure 2). One and a half vials of Contour SE PVA measuring
500-700um was injected, until there was complete stasis in
the main left uterine artery (Figure 3). Cannulation of the
right uterine artery was also performed followed by injection
of one and half vials of Contour SE PVA.
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Figure 1 |
Figure 2 |
Outcome:
A nine month follow up MRI demonstrated greater than 50 percent
reduction in size of the index fibroid. The patient’s menstrual
cycles also normalized with no episodes of heavy bleeding
during her periods (Figure 4).
Comments:
Uterine artery embolization for fibroids is a attractive,
less invasive treatment for women with symptomatic fibroids.
Uterine artery embolization is a viable and effective alternative
to surgical myomectomy or hysterectomy, without the postoperative
risks of bleeding, ureteric injury or pulmonary thromboembolism.
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Figure 3 |
Figure 4 |
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