What is Endometriosis?
Endometriosis is a condition in which the layer of tissue that normally covers the inside of the uterus grows outside of it. Most often this is on the ovaries, fallopian tubes, and tissue around the uterus and ovaries; however, in rare cases it may also occur in other parts of the body. Endometriosis affected 10.8 million women as of 2015.
What are the symptoms?
Pain and infertility are common symptoms, although 20-25% of women are asymptomatic.
A major symptom of endometriosis is recurring pelvic pain. The pain can range from mild to severe cramping or stabbing pain that occurs on both sides of the pelvis, in the lower back and rectal area, and even down the legs. The amount of pain a woman feels correlates weakly with the extent or stage (1 through 4) of endometriosis, with some women having little or no pain despite having extensive endometriosis or endometriosis with scarring, while other women may have severe pain even though they have only a few small areas of endometriosis. Symptoms of endometriosis-related pain may include:
- dysmenorrhea – painful, sometimes disabling cramps during the menstrual period; pain may get worse over time (progressive pain), also lower back pains linked to the pelvis
- chronic pelvic pain – typically accompanied by lower back pain or abdominal pain
- dyspareunia – painful sex
- dysuria – urinary urgency, frequency, and sometimes painful voiding
Compared with women with superficial endometriosis, those with deep disease appear to be more likely to report shooting rectal pain and a sense of their insides being pulled down. Individual pain areas and pain intensity appear to be unrelated to the surgical diagnosis, and the area of pain unrelated to area of endometriosis.
There are multiple causes of pain. Endometriosis lesions react to hormonal stimulation and may “bleed” at the time of menstruation. The blood accumulates locally if it is not cleared shortly by the immune, circulatory, and lymphatic system. This may further lead to swelling, which triggers inflammation with the activation of cytokines, which results in pain. Another source of pain is the organ dislocation that arises from adhesion binding internal organs to each other. The ovaries, the uterus, the oviducts, the peritoneum, and the bladder can be bound together. Pain triggered in this way can last throughout the menstrual cycle, not just during menstrual periods.
Also, endometriotic lesions can develop their own nerve supply, thereby creating a direct and two-way interaction between lesions and the central nervous system, potentially producing a variety of individual differences in pain that can, in some women, become independent of the disease itself. Nerve fibres and blood vessels are thought to grow into endometriosis lesions by a process known as neuroangiogenesis.
Rarely, endometriosis appears in other parts of the body, such as the lungs, brain, and skin .
Rectovaginal or bowel endometriosis affects approximately 5-12% of women with endometriosis, and can cause severe pain with bowel movements.
Endometriosis may spread to the cervix and vagina or to sites of a surgical abdominal incision, known as “scar endometriosis.”Risk factors for scar endometriosis include previous abdominal surgeries, such as a hysterotomy or cesarean section, or ectopic pregnancies, salpingostomy puerperal sterilization, laparoscopy, amniocentesis, appendectomy, episiotomy, vaginal hysterectomies, and hernia repair.
Endometriosis may also present with skin lesions in cutaneous endometriosis.
About a third of women with infertility have endometriosis. Among women with endometriosis about 40% are infertile. The pathogenesis of infertility is dependent on the stage of disease: in early stage disease, it is hypothesised that this is secondary to an inflammatory response that impairs various aspects of conception, whereas in later stage disease distorted pelvic anatomy and adhesions contribute to impaired fertilization.
Other symptoms include diarrhea or constipation, chronic fatigue, nausea and vomiting, headaches, low-grade fevers, heavy and/or irregular periods, and hypoglycemia.
In addition to pain during menstruation, the pain of endometriosis can occur at other times of the month. There can be a pain with ovulation, pain associated with adhesions, pain caused by inflammation in the pelvic cavity, pain during bowel movements and urination, during general bodily movement like exercise, pain from standing or walking, and pain with intercourse. The most severe pain is typically associated with menstruation. Pain can also start a week before a menstrual period, during and even a week after a menstrual period, or it can be constant. The pain can be debilitating and the emotional stress can take a toll.
There is an association between endometriosis and certain types of cancers, notably some types of ovarian cancer, non-Hodgkin’s lymphoma and brain cancer. Endometriosis is unrelated to endometrial cancer.
Are there risk factors?
The cause of endometriosis is not entirely clear.
Genetic predisposition plays a role. Daughters or sisters of women with endometriosis are at higher risk of developing endometriosis themselves; low progesterone levels may be genetic, and may contribute to a hormone imbalance. There is an about six-fold increased incidence in women with an affected first-degree relative.
It has been proposed that endometriosis results from a series of multiple hits within target genes, in a mechanism similar to the development of cancer. In this case, the initial mutation may be either somatic or heritable.
Some factors associated with endometriosis include:
- not having had yet given birth
- prolonged exposure to estrogen – for example, in late menopause or early menarche
- obstruction of menstrual outflow – for example, in Müllerian anomalies
Several studies have investigated the potential link between exposure to dioxins and endometriosis, but the evidence is equivocal and potential mechanisms are poorly understood. A 2004 review of studies of dioxin and endometriosis concluded that “the human data supporting the dioxin-endometriosis association are scanty and conflicting”, and a 2009 follow-up review also found that there was “insufficient evidence” in support of a link between dioxin exposure and women developing endometriosis. A 2008 review concluded that more work was needed, stating that “although preliminary work suggests a potential involvement of exposure to dioxins in the pathogenesis of endometriosis, much work remains to clearly define cause and effect and to understand the potential mechanism of toxicity”.
How is endometriosis diagnosed?
Diagnosis is usually based on symptoms in combination with medical imaging. Biopsy is the most sure method of diagnosis.
A health history and a physical examination can lead the health care practitioner to suspect endometriosis. Although doctors can often feel the endometrial growths during a pelvic exam, and these symptoms may be signs of endometriosis, diagnosis cannot be confirmed by exam only. Use of pelvic ultrasound may identify large endometriotic cysts (called endometriomas). However, smaller endometriosis implants cannot be visualized with ultrasound technique.
Laparoscopic image of endometriotic lesions in the Pouch of Douglas and on the right sacrouterine ligament.
Laparoscopy, a surgical procedure where a camera is used to look inside the abdominal cavity, is the only way to officially diagnose endometriosis as it permits lesion visualization unless the lesion is visible externally, e.g. an endometriotic nodule in the vagina. If the growths are not visible, a biopsy may be taken to determine the diagnosis. Surgery for diagnoses also allows for surgical treatment of endometriosis at the same time.
To the eye, lesions can appear dark blue, powder-burn black, red, white, yellow, brown or non-pigmented. Lesions vary in size. Some within the pelvis walls may not be visible, as normal-appearing peritoneum of infertile women reveals endometriosis on biopsy in 6–13% of cases. Early endometriosis typically occurs on the surfaces of organs in the pelvic and intra-abdominal areas. Health care providers may call areas of endometriosis by different names, such as implants, lesions, or nodules. Larger lesions may be seen within the ovaries as endometriomas or “chocolate cysts”, “chocolate” because they contain a thick brownish fluid, mostly old blood.
Frequently during diagnostic laparoscopy, no lesions are found in women with chronic pelvic pain, a symptom common to other disorders including adenomyosis, pelvic adhesions, pelvic inflammatory disease, congenital anomalies of the reproductive tract, and ovarian or tubal masses.
Surgically, endometriosis can be staged I–IV by the revised classification of the American Society of Reproductive Medicine from 1997. The process is a complex point system that assesses lesions and adhesions in the pelvic organs, but it is important to note staging assesses physical disease only, not the level of pain or infertility. A person with Stage I endometriosis may have a little disease and severe pain, while a person with Stage IV endometriosis may have severe disease and no pain or vice versa. In principle the various stages show these findings:
- Stage I (Minimal)
- Findings restricted to only superficial lesions and possibly a few filmy adhesions
- Stage II (Mild)
- In addition, some deep lesions are present in the cul-de-sac
- Stage III (Moderate)
- As above, plus the presence of endometriomas on the ovary and more adhesions.
- Stage IV (Severe)
- As above, plus large endometriomas, extensive adhesions.
Is there a cure?
Unfortunately there is no cure but a number of treatments may improve symptoms.
Limited evidence indicates that the use of combined oral contraceptives is associated with a reduced risk of endometriosis.
While there is no cure for endometriosis, there are two types of interventions; treatment of pain and treatment of endometriosis-associated infertility. In many women menopause (natural or surgical) will abate the process. In women in the reproductive years, endometriosis is merely managed: the goal is to provide pain relief, to restrict progression of the process, and to restore or preserve fertility where needed. In younger women, surgical treatment attempts to remove endometrial tissue and preserve the ovaries without damaging normal tissue.
In general, the diagnosis of endometriosis is confirmed during surgery, at which time ablative steps can be taken. Further steps depend on circumstances: a woman without infertility can be managed with hormonal medication that suppresses the natural cycle and pain medication, while an infertile woman may be treated expectantly after surgery, with fertility medication, or with IVF. As to the surgical procedure, ablation (or fulguration) of endometriosis (burning and vaporizing the lesions with an electric device) has shown a high rate of short-term recurrence after the procedure. The best surgical procedure with much lower rate of short-term recurrence is to excise (cut and remove) the lesions completely.
Conservative treatment consists of the excision of the endometrium, adhesions, resection of endometriomas, and restoration of normal pelvic anatomy as much as is possible. Endometrioma on the ovary of any significant size (Approx. 2 cm +) -sometimes misdiagnosed as ovarian cysts- must be removed surgically because hormonal treatment alone will not remove the full endometrioma cyst, which can progress to acute pain from the rupturing of the cyst and internal bleeding. Laparoscopy, besides being used for diagnosis, can also be used to perform surgery. It’s considered a “minimally invasive” surgery because the surgeon makes very small openings (incisions) at (or around) the belly button and lower portion of the belly. A thin telescope-like instrument (the laparoscope) is placed through one incision, which allows the doctor to look for endometriosis using a small camera attached to the laparoscope. Small instruments are inserted through the incisions to remove the endometriosis tissue and adhesions. Because the incisions are very small, there will only be small scars on the skin after the procedure, and all endometriosis can be removed, and women recover from surgery quicker and have a lower risk of adhesions.
55% to 100% of women develop adhesions following pelvic surgery, which can result in infertility, chronic abdominal and pelvic pain, and difficult reoperative surgery. Trehan’s temporary ovarian suspension, a technique in which the ovaries are suspended for a week after surgery may be used to reduce the incidence of adhesions after endometriosis surgery.
Conservative treatment involves excision of endometriosis while preserving the ovaries and uterus, very important for women wishing to conceive, but may increase the risk of recurrence.
Endometriosis recurrence following conservative surgery is estimated as 21.5% at 2 years and 40-50% at 5 years.
A hysterectomy (removal of the uterus) can be used to treat endometriosis in women who do not wish to conceive. However, this should only be done when combined with removal of the endometriosis by excision, as if endometriosis is not also removed at the time of hysterectomy, pain may persist
For women with extreme pain, a presacral neurectomy may be very rarely performed where the nerves to the uterus are cut. However, this technique is almost never used due to the high incidence of associated complications including presacral hematoma and irreversible problems with urination and constipation.
- Progesterone or progestins: Progesterone counteracts estrogen and inhibits the growth of the endometrium. Such therapy can reduce or eliminate menstruation in a controlled and reversible fashion. Progestins are chemical variants of natural progesterone. An example of a progestin is dienogest (Visanne). Whilst progesterone is often given as part of a combined hormonal therapy with the addition of oestrogen, progesterone-only therapy may be an acceptable alternative.
- Avoiding products with xenoestrogens, which have a similar effect to naturally produced estrogen and can increase growth of the endometrium.
- Hormone contraception therapy: Oral contraceptives reduce the menstrual pain associated with endometriosis. They may function by reducing or eliminating menstrual flow and providing estrogen support. Combined estrogen and progestin contraceptives are the first line treatment for most women with endometriosis due to their ability to be used over long periods of time, relative inexpensiveness and ease of use, and additional benefit of reducing ovarian/endometrial cancer risk.
- Danazol (danocrine) and gestrinone are suppressive steroids with some androgenic activity. Both agents inhibit the growth of endometriosis but their use remains limited as they may cause hirsutism and voice changes.
- Gonadotropin-releasing hormone (GnRH) agonists: These drugs are thought to work by decreasing hormone levels. A 2010 Cochrane review found that GnRH agonists were more effective for pain relief in endometriosis than no treatment or placebo, but were no more effective than danazol or intrauterine progestagen, and had more side effects than danazol.
- Aromatase inhibitors are medications that block the formation of estrogen and have become of interest for researchers who are treating endometriosis. Examples of aromatase inhibitors include anastrozole and letrozole. Evidence for aromatase inhibitors is limited due to the limited number and quality of studies available, though show promising benefit in terms of pain control.
- NSAIDs: Anti-inflammatory. They are commonly used in conjunction with other therapy. For more severe cases narcotic prescription drugs may be used. NSAID injections can be helpful for severe pain or if stomach pain prevents oral NSAID use. Examples of NSAIDs include ibuprofen and naproxen.
- Opioids: Morphine sulphate tablets and other opioid painkillers work by mimicking the action of naturally occurring pain-reducing chemicals called “endorphins“. There are different long acting and short acting medications that can be used alone or in combination to provide appropriate pain control.
- Following laparoscopic surgery women who were given Chinese herbs were reported to have comparable benefits to women with conventional drug treatments, though the journal article that reviewed this study also noted that “the two trials included in this review are of poor methodological quality so these findings must be interpreted cautiously. Better quality randomised controlled trials are needed to investigate a possible role for CHM [Chinese Herbal Medicine] in the treatment of endometriosis.”
- Pentoxifylline, an immunomodulating agent, has been theorized to improve pain as well as improve pregnancy rates in women with endometriosis. A 2012 Cochrane review, however, found that there was not enough evidence to support the effectiveness or safety of either of these uses. Current American Congress of Obstetricians and Gynecologists (ACOG) guidelines do not include immune-modulators, such as pentoxifylline, in standard treatment protocols.
- Angiogenesis inhibitors lack clinical evidence of efficacy in endometriosis therapy. Under experimental in vitro and in vivo conditions, compounds that have been shown to exert inhibitory effects on endometriotic lesions include growth factor inhibitors, endogenous angiogenesis inhibitors, fumagillin analogues, statins, cyclo-oxygenase-2 inhibitors, phytochemical compounds, immunomodulators, dopamine agonists, peroxisome proliferator-activated receptor agonists, progestins, danazol and gonadotropin-releasing hormone agonists. However, many of these agents are associated with undesirable side effects and more research is necessary. An ideal therapy would diminish inflammation and underlying symptoms without being contraceptive.
Proper counseling of women with endometriosis requires attention to several aspects of the disorder. Of primary importance is the initial operative staging of the disease to obtain adequate information on which to base future decisions about therapy. The woman’s symptoms and desire for childbearing dictate appropriate therapy. Not all therapy works for all women. Some women have recurrences after surgery or pseudo-menopause. In most cases, treatment will give women significant relief from pelvic pain and assist them in achieving pregnancy.
The underlying process that causes endometriosis may not cease after a surgical or medical intervention. Studies have shown that endometriosis recurs at a rate of 20 to 40 percent within five years following conservative surgery unless hysterectomy is performed or menopause reached. Monitoring of women consists of periodic clinical examinations and sonography.
While the exact cause of endometriosis remains unknown, many theories have been presented to better understand and explain its development. These concepts do not necessarily exclude each other. The pathophysiology of endometriosis is likely to be multifactorial and to involve an interplay between several factors.
The main theories for the formation of the ectopic endometrium are retrograde menstruation, müllerianosis, coelomic metaplasia and transplantation, each further described below.
Retrograde menstruation theory
The theory of retrograde menstruation (also called the implantation theory or transplantation theory) is the most widely accepted theory for the formation of ectopic endometrium in endometriosis. It suggests that during a woman’s menstrual flow, some of the endometrial debris flow backwards through the fallopian tubes and into the peritoneal cavity, attaching itself to the peritoneal surface (the lining of the abdominal cavity) where it can proceed to invade the tissue as endometriosis.
Retrograde menstruation alone is not able to explain all instances of endometriosis, and additional factors such as genetic or immune differences need to be invoked to account for the fact that many women with retrograde menstruation do not have endometriosis. Researchers are investigating the possibility that the immune system may not be able to cope with the cyclic onslaught of retrograde menstrual fluid. In this context there is interest in studying the relationship of endometriosis to autoimmune disease, allergic reactions, and the impact of toxic materials. It is still unclear what, if any, causal relationship exists between toxic materials, autoimmune disease, and endometriosis. There are immune system changes in women with endometriosis, such as an increase macrophage-derived secretion products, but it is unknown if these are contributing to the disorder or are reactions from it.
In addition, at least one study found that endometriotic lesions differ in their biochemistry from artificially transplanted ectopic tissue. This is likely because the cells that give rise to endometriosis are a side population of cells. Similarly, there are changes in for example the mesothelium of the peritoneum in women with endometriosis, such as loss of tight junctions, but it is unknown if these are causes or effects of the disorder.
In rare cases where imperforate hymen does not resolve itself prior to the first menstrual cycle and goes undetected, blood and endometrium are trapped within the uterus of the woman until such time as the problem is resolved by surgical incision. Many health care practitioners never encounter this defect, and due to the flu-like symptoms it is often misdiagnosed or overlooked until multiple menstrual cycles have passed. By the time a correct diagnosis has been made, endometrium and other fluids have filled the uterus and fallopian tubes with results similar to retrograde menstruation resulting in endometriosis. The initial stage of endometriosis may vary based on the time elapsed between onset and surgical procedure.
The theory of retrograde menstruation as a cause of endometriosis was first proposed by John A. Sampson.
- Stem cells: Endometriosis may arise from stem cells from bone marrow and potentially other sources. In particular this theory explains endometriosis found in areas remote from the pelvis such as the brain or lungs.
- Environment; Environmental toxins (e.g.; dioxin, nickel) may cause endometriosis.
- Autoimmune: Graves disease is an autoimmune disease characterized by hyperthyroidism, goiter, ophthalmopathy, and dermopathy. Women with endometriosis had higher rates of Graves disease. One of these potential links between Graves disease and endometriosis is autoimmunity.
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