Incidence of Endometriosis

Introduction
Definition
Incidence
Cause
Symptoms
Intestinal Endometriosis
Infertility
Diagnosis
Treatment
Adenomyosis
Are you too young to have
a laparoscopy?
Endometriosis and cancer
Treatment summary
Endometriosis and heredity

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Because Endometriosis is such a variable disease and because it is often misdiagnosed and under diagnosed, the true incidence is not known. It is generally agreed that probably at least 10% of women have symptomatic Endometriosis, and as many as 20% of all women have it, whether or not it is causing a problem. I personally believe the incidence is higher, given the number of women I see with obvious but undiagnosed Endometriosis. A study from the Mayo Clinic many years ago found that, in women undergoing open pelvic surgery regardless of indication, Endometriosis was found in 50%. Recent data suggests that 50% of women over 35 have Endometriosis. Regardless of which number you believe, it is definitely a more common problem than is usually appreciated.

Depending on how patients are selected, the incidence will vary greatly. For instance, 50% of infertile women without pelvic pain have Endometriosis either as their main problem or as a significant complicating factor. On the other hand, if an infertile woman has pain, her chance of having Endometriosis increases to 80%. In women with chronic pelvic pain (defined as pain, either constant or intermittent, of at least 6 months duration), where fertility is not an issue, the incidence is about 70%.

The more Endometriosis is studied, the more it is found. Every new report claims a higher and higher incidence. It is now becoming apparent that most, if not all women probably develop the condition Endometriosis at some time in their life but that only a small percentage exhibit the clinical disease we call Endometriosis with its associated pain or infertility. Supporting this theory is a recent report in which very careful laparoscopic examination of women with no pelvic symptoms found that 50% had peritoneal implants consistent with Endometriosis. It has therefore been suggested that at least in some women, Endometriosis is not truly a disease but perhaps an exaggeration of a normal process in which the endometrial cells shed into the abdominal cavity implant but fail to proliferate or create any significant pain, scar tissue, or interfere with fertility.

Baboons are one of the few animals in nature that will develop Endometriosis spontaneously. Studies have been done in which the baboons underwent repeated laparoscopies at regular intervals. What was quickly noted was the fact that these animals would develop early superficial peritoneal Endometriosis that would frequently disappear by the time of the next laparoscopy. Furthermore, animals that were noted to be free of all visible disease were often noted to have developed Endometriosis at the time of a subsequent laparoscopy.

There is similar data in humans that is now becoming apparent - that for many women Endometriosis is not a disease in the strict sense of the word, but a transient physiologic phenomenon. There is evidence to suggest that most if not all women will develop "temporary" Endometriosis at some during their life and whether or not you make the diagnosis is more a matter of when you happen to laparoscope them rather than whether they actually have the "disease" or not. The diagnosis of early peritoneal Endometriosis may therefore sometimes be more a matter of fortuitous luck than anything else.

However, it must be always kept in mind that except for those rare instances where the woman is undergoing a laparoscopy as part of a research project, all women who are having a laparoscopy are doing so because they either are in pain, are infertile, or have some other organic pelvic problem. The only exception to this is women undergoing elective sterilization. In these women, the incidence of Endometriosis is very low (2-3%), but it increases as the interval from that woman's last pregnancy increases. Nonetheless, we are now beginning to accumulate enough data to try to distinguish between Endometriosis, the "condition", and Endometriosis, the "disease".

Even if the theory is true that Endometriosis is a transient phenomenon for many women, this does not explain the fact that these women are frequently in pain (that's the reason they are having a laparoscopy) and it does not adequately explain why suppressing their Endometriosis relieves their pelvic symptoms. I believe therefore that even "transient" Endometriosis is capable of creating considerable problems, certainly pain. Furthermore, even though there is most likely not a cause and effect relationship between early Endometriosis and infertility, we have certainly known for many years that women with early Endometriosis have impaired fertility. Whether it is an association or truly "a cause and effect" situation, the woman is still unable to have a baby.

This then raises the question of how bad does the Endometriosis have to be and what kind of symptoms or problems is it causing to cross the line between a temporary, serendipitous phenomenon and a true disease.

Of course, the next question is: "What is it that eliminates the Endometriosis in most women, but it allows it to become a progressive disease in others?"

How often Endometriosis is diagnosed also depends on who is doing the diagnostic laparoscopy. A Reproductive Endocrinologist will diagnose Endometriosis more often than a general gynecologist because of our increased awareness of all the varied and often subtle appearance of the disease.

At one time, Endometriosis was believed to be primarily a disease of women in their 30's and 40's. It is now recognized that Endometriosis is not rare in teenage girls. A study from Boston found that 70% of teenage girls with chronic pelvic pain that did not respond to birth control pills had Endometriosis proven by laparoscopy! Think of how many teens have suffered needlessly over the years because they were led to believe that painful menstrual periods were "normal" and had to be endured or that their periods were painful because they did not exercise enough or some other well-intentioned but erroneous explanation. They suffered because the belief was that teenage girls did not get Endometriosis.