A “structural” cause of heavy menstrual bleeding means that excessive bleeding is due to actual problems within the cavity or walls of the uterus. Some examples of this would include: infections of the lining of the uterus, fibroids of the uterus, endometriosis of the muscular wall of the uterus (“adenomyosis”), polyps of the uterine lining, or even uterine cancer. Overall, among heavy bleeders between the ages of thirty and fifty, only 40% of women will have a completely normal uterus. The other 60% may have one of the following culprits responsible for excessive bleeding.
An infection in the lining of the uterus (“endometritis“) creates inflammation. The elements involved in an inflammatory response destabilize the uterine lining. This leads to both increased bleeding, and more breakthrough bleeding. Chronic infections of the uterine lining have been found in 22% of patients participating in an in vitro fertilization program, 14% of patients with unexplained infertility, and in some 23% of patients with first trimester miscarriages (Cravelo, 1997).
The most common causes of endometritis have been proposed to be chlamydia or ureaplasma (Cravello, 1997). Yet in a much larger study of 438 women with chronic endometritis the most frequently cultured pathogen was common bacteria (58%), with ureaplasma (10%) and chlamydia (2.7%) being less frequent (Cicinelli, 2008). Surprisingly most women do not get treatment. M. Smith and colleagues (2010) found that only 3% of 105 women with chronic endometritis received antibiotics or other treatments.
Certainly if a woman has a known pelvic infection (i.e., PID) she should get the recommended dose of antibiotics to prevent a chronic infection in the lining of her uterus. Given the difficulty of getting a culture from inside the uterus (as opposed to putting a Q-tip to opening of the cervical canal) a woman may be given antibiotics in an attempt to stop abnormal bleeding without having a positive lab result.
Fibroids of the uterus can be found in several locations: inside the cavity of the uterus (“submucosal”), inside the walls of the uterus (“intramural”), on the outside surface of the uterus (“subserosal”), or even hanging on a stalk from one of the walls of the uterus (“pedunculated”). They are created when a normal uterine muscle cell is transformed by growth factors into a fibroid cell (Blake, 2007). Thus it can be said that fibroids are a benign overgrowth of uterine muscle tissue.
There are two postulated mechanisms whereby fibroids can promote heavy bleeding. The initial link between fibroids and bleeding was thought to be the mechanical presence of these large, and often multiple, masses. The uterus would be unable to contract down firmly to help stop bleeding. This would be especially true for fibroids inside the cavity and in the wall of the uterus.
It was then noticed that bleeding problems could be present no matter where the fibroids were located. The second explanation came to include new findings about how fibroids seemed to change blood flow. Both the blood vessels on the surface of the fibroids and the blood vessels in the walls of the uterus had higher specific volumes compared to normal uterine tissue samples (Sapozhnikov, 1897). Also small blood vessels in the wall of the uterus show increased blood flow into the blood vessels surrounding fibroids (ESHRE, 2007).
Who is most likely to have fibroids? By age 45, more than 60% of white females will have fibroids present; the incidence is higher still for African American females. There is a strong genetic predisposition to having fibroids so having a family history of fibroids increases one’s risk. Some medical conditions seem to be predisposing factors. These diagnoses include: being obese, having polycystic ovarian syndrome, diabetes, high blood pressure, and never having had a pregnancy (Okolo, 2008).
A more recent study (Huang, 2010) suggests another predisposing condition — endometriosis. Of 131 women who were given hysterectomies or myomectomies (surgical removal of fibroids while leaving the uterus in place), 113 were found to have endometriosis as well. That means only 18 had just fibroids. This could imply that endometriosis of the wall of the uterus (“adenomyosis“) may be a contributing factor to abnormally heavy bleeding.
Adenomyosis represents a spectrum of changes whereby glandular and connective tissues from the lining of the uterus are found inside the muscular walls of the uterus. The nearby smooth muscles of the walls seem to thicken (Gordts, 2008). Adenomyosis is a common cause of diffuse enlargement of the uterus when fibroids are not seen. In some women there may be tenderness of the uterus as well.
It is less clear how adenomyosis increases the frequency of heavy bleeding. One possible explanation states that the muscular walls of the uterus have an impaired ability to contract to help stop heavy bleeding. Prostaglandins have also been blamed for the increased bleeding of adenomyosis. More recently increased numbers of blood vessels have been found that seem to be growing in the muscular wall of the uterus when adenomyosis is present (Hickey, 2000).
It has been proposed that undetected adenomyosis may be responsible for unsuccessful attempts at treating heavy bleeding such as failed endometrial ablations, or resections, (Basak, 2009). Unfortunately, the most definitive diagnosis is made after hysterectomy when the pathologist examines the tissues of the uterus. An MRI is the best diagnostic imaging method; ultrasound does not visualize adenomyosis with reliability. The incidence of adenomyosis has been found to range from 15% (Ben Hamouda, 2007) to 48% (Weiss, 2009).
Polyps are composed of glands (like uterine lining tissue) in a fibrous tissue matrix which also contains blood vessels (Brechin, 1999). Therefore, like adenomyosis and uterine lining tissue, polyps are hormonally stimulated by estrogen. This prolonged exposure to estrogen likely accounts for the increasing numbers of uterine lining polyps seen in women as they age into their 30′s and 40′s.
Polyps can be single or multiple, with a size range from a pencil lead to a human thumb. The size differential may govern whether a polyp regresses without treatment. In one small study of 64 women without bleeding problems, four out of the seven that had polyps showed polyps regressing at the time of a second saline infusion ultrasound two and a half years later. Polyps that did not resolve tended to be larger in size and went on to cause bleeding abnormalities (Dewaay, 2002)
Polyps can prompt bleeding between menstrual periods or spotting after sex. Like the lining of the uterus or the cervical canal, the glands that make up the lining can produce a fragile, easy to bleed surface. The increased number of blood vessels, coupled with the fragile uterine lining tissue stretched over the surface of the polyp, likely contributes to increased bleeding. Additionally, polyps have increased numbers of activated mast cells compared to surrounding uterine lining (Al-Jefout, 2009). Mast cells can secrete histamine (dilates tiny veins) and heparin (keeps blood from clotting).
The over riding concern is whether polyps may contain abnormal, cancerous or precancerous cells. This is similar to the concern we have about a too thick lining of the uterus containing abnormal cells. Lee and colleagues (2010) reviewed studies containing a total of 1552 women who had polyps removed and sent to a pathologist. They concluded that both complaints of vaginal bleeding and being postmenopausal increased the risks of a polyp being cancerous or precancerous. Yet absolute numbers were small. Vaginal bleeders accounted for 4.1% of worrisome polyps and non-bleeders for 2.1%. Of women with polyps, the prevalence of cancerous or precancerous polyps in postmenopausal women was 5.4% compared with 1.7% in premenopausal women.
Like adenomyosis, polyps are not reliably diagnosed with simple vaginal ultrasound scans. On an ultrasound polyps may appear to be an irregularly thickened lining inside the uterus. Two of the better ways to diagnose polyps are a saline infusion ultrasound and a hysteroscope. When sterile saline is put into the uterine cavity, polyps will appear to “float” in the water — rather like sea grass on the ocean shore. In a comparison study, regular ultrasound was able to correctly identify polyps about 65% of the time while the use of saline increased the rate to 91% (Yildizhan, 2008). A flexible, fiber optic light scope (hysteroscope) can be inserted inside the uterus to get a direct look for polyps. Any polyps or other tissues of concern can be removed with micro-cutting tools at the time of the procedure.
And again, there are treatments for each of the causes of heavy bleeding we have discussed. So if you or someone you know has episodes of heavy blood loss rather than a normal period, talk to your doctor — there are ways to stop going with the flow.