Endometriosis is usually confined to the peritoneal or serosal surfaces of pelvic organs, commonly the ovaries, broad ligaments, posterior cul-de-sac, and uterosacral ligaments.
Less common sites include the fallopian tubes, serosal surfaces of the small and large intestines, ureters, bladder, vagina, cervix, surgical scars, and, more rarely, the lung, pleura, and pericardium.
Bleeding from peritoneal implants is thought to initiate sterile inflammation, followed by fibrin deposition, adhesion formation, and, eventually, scarring, which distorts peritoneal surfaces of organs, leading to pain and distorted pelvic anatomy.
Reported prevalence varies but is probably about
6 to 10% in all women
25 to 50% in infertile women
Average age at diagnosis is 27 years, but endometriosis also occurs among adolescents.
Etiology and Pathophysiology of Endometriosis
The most widely accepted hypothesis for the pathophysiology of endometriosis is that endometrial cells are transported from the uterine cavity during menstruation and subsequently become implanted at ectopic sites. Retrograde flow of menstrual tissue through the fallopian tubes is common and could transport endometrial cells intra-abdominally; the lymphatic or circulatory system could transport endometrial cells to distant sites (eg, the pleural cavity).
Another hypothesis is coelomic metaplasia: Coelomic epithelium is transformed into endometrium-like glands.
Microscopically, endometriotic implants consist of glands and stroma identical to intrauterine endometrium. These tissues contain estrogen and progesterone receptors and thus usually grow, differentiate, and bleed in response to changes in hormone levels during the menstrual cycle; also, these tissues can produce estrogen and prostaglandins. Implants may become self-sustaining or regress, as may occur during pregnancy (probably because progesterone levels are high). Ultimately, the implants cause inflammation and increase the number of activated macrophages and the production of proinflammatory cytokines.
The increased incidence in 1st-degree relatives of women with endometriosis and in large twin studies (1 Etiology and pathophysiology reference In endometriosis, functioning endometrial tissue is implanted in the pelvis outside the uterine cavity. Symptoms depend on location of the implants and may include dysmenorrhea, dyspareunia... read more ) suggests that heredity is a factor.
In patients with severe endometriosis and distorted pelvic anatomy, the infertility rate is high, possibly because the distorted anatomy and inflammation interfere with mechanisms of ovum pickup, oocyte fertilization, and tubal transport.
Some patients with minimal endometriosis and normal pelvic anatomy are also infertile; reasons for impaired fertility are unclear but may include the following:
Increased incidence of luteinized unruptured ovarian follicle syndrome (trapped oocyte)
Increased peritoneal prostaglandin production or peritoneal macrophage activity that may affect fertilization, sperm, and oocyte function
Nonreceptive endometrium (because of luteal phase dysfunction or other abnormalities)
Potential risk factors for endometriosis are
Family history of 1st-degree relatives with endometriosis
Delayed childbearing or nulliparity
Shortened menstrual cycles (< 27 days) with menses that are heavy and prolonged (> 8 days)
Müllerian duct defects
Exposure to diethylstilbestrol in utero
Potential protective factors seem to be
Long-term use of low-dose oral contraceptives (continuous or cyclic)
Regular exercise (especially if begun before age 15, if done for > 4 hours/week, or both)
Etiology and pathophysiology reference
Symptoms and Signs of Endometriosis
Cyclic midline pelvic pain, specifically pain preceding or during menses (dysmenorrhea Dysmenorrhea Dysmenorrhea is uterine pain around the time of menses. Pain may occur with menses or precede menses by 1 to 3 days. Pain tends to peak 24 hours after onset of menses and subside after 2 to... read more ) and during sexual intercourse (dyspareunia Genitopelvic Pain/Penetration Disorder Genitopelvic pain/penetration disorder involves involuntary contraction of the pelvic floor muscles when vaginal entry is attempted or completed (levator ani syndrome, or vaginismus), pain that... read more ), is typical and can be progressive and chronic (lasting > 6 months). Adnexal masses and infertility are also typical. Interstitial cystitis Interstitial Cystitis Interstitial cystitis is noninfectious bladder inflammation that causes pain (suprapubic, pelvic, and abdominal), urinary frequency, and urgency with incontinence. Diagnosis is by history and... read more with suprapubic or pelvic pain, urinary frequency, and urge incontinence is common. Intermenstrual bleeding is possible.
Some women with extensive endometriosis are asymptomatic; some with minimal disease have incapacitating pain. Dysmenorrhea is an important diagnostic clue, particularly if it begins after several years of relatively pain-free menses. Symptoms often lessen or resolve during pregnancy.
Symptoms can vary depending on location of implants.
Large intestine: Pain during defecation, abdominal bloating, diarrhea or constipation, or rectal bleeding during menses
Bladder: Dysuria, hematuria, suprapubic or pelvic pain (particularly during urination), urinary frequency, urge incontinence, or a combination
Ovaries: Formation of an endometrioma (a 2- to 10-cm cystic mass localized to an ovary), which occasionally ruptures or leaks, causing acute abdominal pain and peritoneal signs
Adnexal structures: Formation of adnexal adhesions, resulting in a pelvic mass or pain
Extrapelvic structures: Vague abdominal pain (sometimes)
Pelvic examination may be normal, or findings may include a retroverted and fixed uterus, enlarged or tender ovaries, fixed ovarian masses, thickened rectovaginal septum, induration of the cul-de-sac, nodules on the uterosacral ligament, and/or adnexal masses. Rarely, lesions can be seen on the vulva or cervix or in the vagina, umbilicus, or surgical scars.
Diagnosis of Endometriosis
Direct visualization, usually during pelvic laparoscopy
Diagnosis of endometriosis is suspected based on typical symptoms. Misdiagnosis as pelvic inflammatory disease, urinary tract infection, or irritable bowel syndrome is common. Negative cervical and/or urine cultures should suggest the possibility of endometriosis.
The diagnosis of endometriosis must be confirmed by direct visualization, usually via pelvic laparoscopy but sometimes via laparotomy, vaginal examination, sigmoidoscopy, or cystoscopy. Biopsy is not required, but results may help with the diagnosis.
Macroscopic appearance (eg, clear, red, brown, black) and size of implants vary during the menstrual cycle. However, typically, areas of endometriosis on the pelvic peritoneum are punctate red, blue, or purplish brown spots that are > 5 mm, often called powder burn lesions. Microscopically, endometrial glands and stroma are usually present. Stromal elements in the absence of glandular elements indicate a rare variant of endometriosis called stromal endometriosis.
Imaging tests, including ultrasonography (1 Diagnosis references In endometriosis, functioning endometrial tissue is implanted in the pelvis outside the uterine cavity. Symptoms depend on location of the implants and may include dysmenorrhea, dyspareunia... read more ), are not specific or adequate for diagnosis. However, they sometimes show the extent of endometriosis and thus can be used to monitor the disorder once it is diagnosed. Because endometrial tissue has a unique MR signal, MRI is becoming increasingly useful for evaluating patients who may have endometriosis (2 Diagnosis references In endometriosis, functioning endometrial tissue is implanted in the pelvis outside the uterine cavity. Symptoms depend on location of the implants and may include dysmenorrhea, dyspareunia... read more ). However, MRI is limited by the skill of the radiologist and the extent of disease; small endometriotic implants cannot be seen on MRI scans.
The serum cancer antigen 125 level may be elevated, but obtaining this level is usually neither helpful nor specific in diagnosis or management.
Pearls & Pitfalls
Testing for other infertility disorders Overview of Infertility Infertility is usually defined as inability of a couple to conceive after 1 year of unprotected intercourse. Infertility is defined as a disease by the World Health Organization (WHO). Frequent... read more may be indicated.
Staging endometriosis helps physicians formulate a treatment plan and evaluate response to therapy. According to the American Society for Reproductive Medicine, endometriosis may be classified as stage I (minimal), II (mild), III (moderate), or IV (severe), based on
Number, location, and depth of implants
Presence of endometriomas and filmy or dense adhesions (see table Stages of Endometriosis Stages of Endometriosis In endometriosis, functioning endometrial tissue is implanted in the pelvis outside the uterine cavity. Symptoms depend on location of the implants and may include dysmenorrhea, dyspareunia... read more )
The endometriosis fertility index (EFI) has been developed to stage endometriosis-associated infertility; this system can help predict pregnancy rates after various treatments. Factors used to score the EFI include
The woman's age
The number of years she has been infertile
History or absence of prior pregnancies
The least-function score for both fallopian tubes, fimbria, and ovaries
The American Society for Reproductive Medicine endometriosis (lesion and total) scores
1. Nisenblat V, Prentice L, Bossuyt PM, et al: Combination of the non-invasive tests for the diagnosis of endometriosis. Cochrane Database Syst Rev 7, 2016. doi: 10.1002/14651858.CD012281.
2. Guerriero S, Saba L, Pascual MA, et al: Transvaginal ultrasound vs magnetic resonance imaging for diagnosing deep infiltrating endometriosis: systematic review and meta‐analysis. Ultrasound Obstet Gynecol 51 (5):586–595, 2018. doi: 10.1002/uog.18961.
Treatment of Endometriosis
Nonsteroidal anti-inflammatory drugs (NSAIDs) for discomfort
Drugs to suppress ovarian function
Conservative surgical resection or ablation of endometriotic tissue, with or without drugs
Total abdominal hysterectomy with or without bilateral salpingo-oophorectomy if disease is severe and the patient has completed childbearing
Symptomatic medical treatment begins with analgesics (usually NSAIDs), hormonal contraceptives, and progestins. More definitive treatment must be individualized based on the patient's age, symptoms, and desire to preserve fertility and on the extent of the disorder.
Conservative surgical treatment of endometriosis is excision or ablation of endometriotic implants and removal of pelvic adhesions during laparoscopy.
Drugs and conservative surgery are used mainly to control symptoms. In most patients, endometriosis recurs within 6 months to 1 year after drugs are stopped unless ovarian function is permanently and completely ablated. Endometriosis may also recur after conservative surgery.
Total abdominal hysterectomy with or without bilateral salpingo-oophorectomy is considered definitive treatment of endometriosis. It helps prevent complications and modify the course of disease as well as relieving symptoms; however, endometriosis can recur.
Drugs that suppress ovarian function inhibit the growth and activity of endometriotic implants. The following are commonly used:
The following drugs are usually used only when women cannot take combination oral contraceptives or when treatment with combination oral contraceptives is ineffective:
Gonadotropin-releasing hormone (GnRH) agonists and antagonists
GnRH agonists temporarily suppress estrogen production by the ovaries; however, treatment is limited to ≤ 6 months because long-term use may result in bone loss. If treatment lasts > 4 to 6 months, a progestin or a bisphosphonate may be used concurrently (as add-back therapy) to minimize bone loss. If endometriosis recurs, women may need to be treated again.
The GnRH antagonist elagolix also suppresses estrogen production by the ovaries. It is available in 2 different doses; the higher dose is available to treat dyspareunia as well as other symptoms of endometriosis. Long-term use may result in bone loss. If treatment lasts > 6 months, a progestin may be used concurrently (as add-back therapy) to minimize bone loss.
Danazol, a synthetic androgen and an antigonadotropin, inhibits ovulation. However, its androgenic adverse effects limit its use.
Cyclic or continuous combination oral contraceptives given after danazol or GnRH agonists may slow disease progression and are warranted for women who wish to delay childbearing.
Drug treatment does not change fertility rates in women with minimal or mild endometriosis.
Most women with moderate to severe endometriosis are treated most effectively by ablating or excising as many implants as possible while restoring pelvic anatomy and preserving fertility as much as possible. Superficial endometriotic implants can be ablated. Deep, extensive implants should be excised.
Specific indications for laparoscopic surgery include
Moderate to severe pelvic pain that does not respond to drugs
Presence of endometriomas
Significant pelvic adhesions
Fallopian tube obstruction
A desire to maintain fertility
Pain during intercourse
Lesions are usually removed via a laparoscope; peritoneal or ovarian lesions can sometimes be electrocauterized, excised, or, uncommonly, vaporized with a laser. Endometriomas should be removed because removal prevents recurrence more effectively than drainage. After this treatment, fertility rates are inversely proportional to the severity of endometriosis. If resection is incomplete, GnRH agonists are sometimes given during the perioperative period, but whether these drugs increase fertility rates is unclear. Laparoscopic resection of the uterosacral ligaments with electrocautery or a laser may reduce midline pelvic pain.
Rectovaginal endometriosis,the most severe form of the disease, can be treated with the usual treatments for endometriosis; however, colonoscopic resection or surgery may be required to prevent obstruction of the colon.
Hysterectomy with or without ovarian conservation should usually be reserved for patients who have moderate to severe pelvic pain, who have completed childbearing, and who prefer a definitive procedure. Hysterectomy is done to remove adhesions or implants that adhere to the uterus or cul-de-sac. If women < 50 require hysterectomy with bilateral salpingo-oophorectomy, supplemental estrogen should be considered (eg, to prevent menopausal symptoms). Also, concomitant continuous progestin therapy (eg, medroxyprogesterone acetate 2.5 mg orally once a day) is often recommended because if estrogen is given alone, residual tissue may grow, resulting in recurrence. If symptoms persist after salpingo-oophorectomy in women > 50, continuous progestin therapy alone (norethindrone acetate 2.5 to 5 mg, medroxyprogesterone acetate 5 mg orally once a day, micronized progesterone 100 to 200 mg orally at bedtime) can be tried.
Endometriosis is a common cause of cyclic and chronic pelvic pain, dysmenorrhea, dyspareunia, and infertility.
The stage of endometriosis does not correlate with severity of symptoms.
Confirm the diagnosis usually by laparoscopy; a biopsy is not mandatory but may aid in the diagnosis.
Treat pain (eg, with NSAIDs) and, depending on patient fertility goals, usually use drugs that suppress ovarian function to inhibit the growth and activity of endometriotic implants.
For moderate to severe endometriosis, consider ablating or excising as many implants as possible while restoring normal pelvic anatomy.
Reserve hysterectomy for women who have completed childbearing or who prefer a definitive procedure.