What are Uterine Fibroids?

June 22, 2011

Fibroids are non-cancerous (benign) growths of the muscle wall of the uterus. They are probably responsible for more unnecessary gynecologic surgery than any other condition. Every year a staggering 600,000 American women have a hysterectomy. And about 30 percent of those hysterectomies, 180,000 in all, are performed because of fibroids. For many years gynecologists have surgically removed these growths, often because of fear of the problems they might cause in the future. And those problems are often overstated.

What Are Fibroids?
Fibroids are non-cancerous (benign) growths of the muscle wall of the uterus. They are probably responsible for more unnecessary gynecologic surgery than any other condition. Every year a staggering 600,000 American women have a hysterectomy. And about 30 percent of those hysterectomies, 180,000 in all, are performed because of fibroids. For many years gynecologists have surgically removed these growths, often because of fear of the problems they might cause in the future. And those problems are often overstated.

Fibroids are extremely common. More than 75 percent of women can be found to have small fibroids using MRI, a very sensitive imaging technique. However, only about 30 percent of all women will have fibroids large enough to be noted during a pelvic exam, and the vast majority of even these women, more then 80 percent, will never have symptoms and will never require treatment. And for the rare patient who does have problems, there are a number of sound and effective options available. Hysterectomy should be the solution of last resort.  

What Causes Fibroids?
While there is much we don't know about fibroids, we do know that each individual fibroid starts from a single cell growing the wrong way. Recently, gene mutations have been discovered in fibroid cells that alter the cell's growth. It is very likely that the cause of fibroids relates to genes, but the entire mechanism has not yet been worked out. There may also be environmental causes that stimulate fibroid growth. It is important to realize that there is no evidence that fibroids turn into cancer. Fibroids are benign from the beginning and remain benign.

We do know that the female hormones estrogen and progesterone are necessary for fibroids to grow. Fibroids do not occur before puberty when estrogen and progesterone production begins, and fibroids shrink after menopause when hormone production declines. It appears that fibroids start from a single cell mutation, but growth of the fibroid requires the complex interaction of estrogen, progesterone, and cell growth factors. Studies are now under way to try to determine how fibroids arise and what influences their growth.

Fibroids usually do not develop until between ages twenty-five and thirty-five. You might expect that women with fibroids are making too much estrogen or progesterone. However, if we measure hormone levels in the blood, these women have absolutely normal amounts. It appears that the muscle cells in the uterus undergo a change that causes these cells to use up, or metabolize, more of the estrogen and progesterone in the blood than usual. As a result, the cells are stimulated to overgrow, causing a round swelling of the uterine muscular wall. Importantly, this change in metabolism does not appear to affect any other area of the body. Women with fibroids are not more prone to fibrocystic changes in the breast, a totally unrelated condition and they are not more prone to develop any other benign or cancerous conditions.

What Are the Different Types of Fibroids?
All fibroids begin as a growth somewhere within the uterine muscular wall. The symptoms caused by fibroids depend on where they grow in the wall (see fig. 4.1). Fibroids that grow and bulge toward the outside of the uterus, called subserosal fibroids, can press on (but not injure) the organs surrounding the uterus such as the bladder or rectum. Sometimes, they may grow large enough to push outward and cause a noticeable swelling in the abdomen.

Fibroids that grow and bulge toward the inside of the uterus are called submucosal fibroids. These grow directly below the lining cells of the uterus and may lead to heavy or irregular bleeding. Fibroids that stay mostly embedded within the middle of the wall of the uterus are called intramural fibroids. Some fibroids may form on stalks that connect them to the uterus. These are called pedunculated fibroids and can be either submucosal or subserosal in location.

What is the Best Way to Make the Diagnosis of Fibroids?
Fibroids are most commonly diagnosed during a pelvic examination. Fibroids are benign tumors of the uterine muscle wall and, as such, cause the uterus to feel larger than normal and irregular. If the size of the uterus is hard to determine or the diagnosis is uncertain, a pelvic ultrasound can be helpful. Ultrasonography is fairly accurate at determining the sizes and positions of fibroids within the uterine wall. However, sometimes the exact position of the fibroids are hard to accurately determine with ultrasound.

The best test to tell size and position of fibroids is an MRI. Fibroids contain more collagen than normal uterine muscle and, as a result, the fibroids appear distinct and darker on the MRI. Getting an MRI may be a good idea if the ultrasound is not clear or it is important to know exactly where the fibroids are. I use this test if a laparoscopic myomectomy is being considered. MRI gives me a good idea as to whether it will be possible to get all the fibroids out with the laparoscopic instruments. If ultrasound is not clear, MRI can also be used to see if submucous fibroids are present. This can be helpful if unexplained heavy bleeding is present or fertility is a concern.

MRI Image of fibroids

 

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