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.
|
|
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.
|
|
Figure 3 |
Figure 4 |
|