Endometriosis: From Identification to Management

IN THIS ARTICLE

• Staging endometriosis
• Medications for treating endometriosis
• Complications

Endometriosis is a gynecologic disorder characterized by the presence and growth of endometrial tissue outside the uterine cavity (ie, endometrial implants), most commonly found on the ovaries. Although its pathophysiology is not completely understood, the disease is associated with dysmenorrhea, dyspareunia, and infertility.^1,2 Endometriosis is an estrogen-dependent disorder, predominantly affecting women of childbearing age. It occurs in 10% to 15% of the general female population, but prevalence is even higher (35% to 50%) among women who experience pelvic pain and/or infertility.^1-4 Although endometriosis mainly affects women in their mid-to-late 20s, it can also manifest in adolescence.^3,5 Nearly half of all adolescents with intractable dysmenorrhea are diagnosed with endometriosis.⁵

ETIOLOGY

The etiology of endometriosis, while not completely understood, is likely multifactorial. Factors that may influence its development include gene expression, tissue response to hormones, neuronal tissue involvement, lack of protective factors, inflammation, and cellular oxidative stress.^6,7

Several theories regarding the etiology of endometriosis have been proposed; the most widely accepted is the transplantation theory, which suggests that endometriosis results from retrograde flow of menstrual tissue through the fallopian tubes. During menstruation, fragments of the endometrium are driven through the fallopian tubes and into the pelvic cavity, where they can implant onto the pelvic structures, leading to further growth and invasion.^2,6,8 Women who have polymenorrhea, prolonged menses, and early menarche therefore have an increased risk for endometriosis.⁸ This theory does not account for the fact that although nearly 90% of women have some elements of retrograde menstrual flow, only a fraction of them develop endometriosis.⁶

Two other plausible explanations are the coelomic metaplasia and embryonic rest theories. In the coelomic metaplasia theory, the mesothelium (coelomic epithelium)—which encases the ovaries—invaginates into the ovaries and undergoes a metaplastic change to endometrial tissue. This could explain the development of endometriosis in patients with the congenital malformation Müllerian agenesis. In the embryonic rest theory, Müllerian remnants in the rectovaginal area, left behind by the Müllerian duct system, have the potential to differentiate into endometrial tissue.^2,5,6,8

Another theory involving lymphatic or hematologic spread has been proposed, which would explain the presence of endometrial implants at sites distant from the uterus (eg, the pleural cavity and brain). However, this theory is not widely understood.⁶

The two most recent hypotheses on endometriosis are associated with an abnormal immune system and a possible genetic predisposition. The peritoneal fluid of women with endometriosis has different levels of prostanoids, cytokines, growth factors, and interleukins than that of women who do not have the condition. It is uncertain whether the relationship between peritoneal fluid changes and endometriosis is causal.⁶ A genetic correlation has been suggested, based on an increased prevalence of endometriosis in women with an affected first-degree relative; in a case-control study on family incidence of endometriosis, 5.9% to 9.6% of first-degree relatives and 1.3% of second-degree relatives were affected.⁹ The Oxford Endometriosis Gene (OXEGENE) study is currently investigating susceptible loci for endometriosis genes, which could provide a better understanding of the disease process.⁶

CLINICAL PRESENTATION

The most common symptoms of endometriosis are dysmenorrhea, deep dyspareunia, chronic pelvic pain, and infertility, but 20% to 25% of affected women are asymptomatic.^4,10,11 Pelvic pain in women most often heralds onset of menses and worsens during menstruation.¹ Other symptoms include back pain, dyschezia, dysuria, nausea, lethargy, and chronic fatigue.^4,8,10

Endometriosis is concomitant with infertility; endometrial adhesions that attach to pelvic organs cause distortion of pelvic structures and impaired ovum release and pick-up, and are believed to reduce fecundity. Additionally, women with endometriosis have low ovarian reserve and low-quality oocytes.^6,8 Altered chemical elements (ie, prostanoids, cytokines, growth factors, and interleukins) may also contribute to endometrial-related infertility; intrapelvic growth factors could affect the fallopian tubes or pelvic environment, and thus the oocytes in a similar fashion.⁶

In adolescents, endometriosis can present as cyclic or acyclic pain; severe dysmenorrhea; dysmenorrhea that responds poorly to medications (eg, oral contraceptive pills [OCPs] or NSAIDs); and prolonged menstruation with premenstrual spotting.¹

The physical exam may reveal tender nodules in the posterior vaginal fornix; cervical motion tenderness; a fixed uterus, cervix, or adnexa; uterine motion tenderness; thickening, pain, tenderness, or nodularity of the uterosacral ligament; or tender adnexal masses due to endometriomas.^8,10

PATHOLOGIC CHARACTERISTICS AND STAGING

Gross pathology of endometriosis varies based on duration of disease and depth of implants or lesions. Implants range from punctate foci to small stellate patches that vary in color but typically measure less than 2 cm. They manifest most commonly in the ovaries, followed by the anterior and posterior cul-de-sac, posterior broad ligament, and uterosacral ligament. Implants can also be located on the uterus, fallopian tubes, sigmoid colon, ureter, small intestine, lungs, and brain (see Figure).³