© The Author(s) 2015
Sajal Gupta, Avi Harlev and Ashok AgarwalEndometriosisSpringerBriefs in Reproductive Biology10.1007/978-3-319-18308-4_11. Introduction to Endometriosis
(1)
Assistant Professor, Lerner College of Medicine and Case Western Reserve University, American Center for Reproductive Medicine, Cleveland Clinic, Cleveland, OH, USA
(2)
Professor, Lerner College of Medicine and Case Western Reserve University, American Center for Reproductive Medicine, Cleveland Clinic, Cleveland, OH, USA
(3)
American Center for Reproductive Medicine, Cleveland, OH, USA
(4)
Lecturer, Soroka University Medical Center, Fertility and IVF Unit, Ben-Gurion University of the Negev, Beer-Sheva, Israel
1.1 Definition
1.5.1 Historical Perspectives
1.1 Definition
According to Webster’s New World/Stedman’s Concise Medical Dictionary, Endometriosis (En’do-me-tri-o’sis) is “ectopic occurrence of endometrial tissue, frequently forming cysts containing blood.”
The word Endometriosis is derived from the Greek words endon, meaning “within,” metra, meaning “uterus,” and osis, meaning “abnormal or diseased condition.” Endometriosis is a complex yet common debilitating gynecological disease where the functional endometrial glands and stroma, which are normally part of the innermost lining of the uterine cavity (the endometrium), are present outside the uterine cavity. These locations include, but are not limited to, the ovaries, fallopian tubes, pelvic peritoneum, gastrointestinal tract, bladder, rectovaginal septum, and less commonly, the pericardium and pleura [1].
1.2 Classification of Endometriosis
In 1921, Sampson first classified ovarian hemorrhagic cysts—he described them as endometrial, stromal, corpus luteal, and follicular. Based on the histologic appearance, he also staged the endometrial hematomas [4]. Since then, numerous classification systems have been created based on the histologic appearance, anatomic location, size, and extent of endometrial tissue growth.
1.2.1 ASRM Classification (Stage 1 to Stage 4)
According to the American Society for Reproductive Medicine (ASRM) endometriosis can be classified as minimal (stage I), mild (stage II), moderate (stage III), or severe (stage IV) depending on the extent of tissue growth [5]. Revised for the third time in 1996, it is the most commonly used system to classify endometriosis. Each occurrence of endometriosis is assigned to one of these stages based on a point value system that ranks certain attributes of the disorder. These components include: whether the endometriosis is superficial or deep, whether the posterior cul-de-sac is partially or completely obliterated and, lastly, whether the adhesions that form around the ovaries and fallopian tubes are flimsy or dense. Also, the morphology of the endometriotic lesions is recorded as red, red-pink, clear, white, yellow-brown, black, or blue.
Limitations of ASRM Classification: However, despite providing a simple means of documenting the extent of endometrial lesions, the ASRM staging system only weakly parallels pain symptoms [5, 6] and the risk of infertility. In addition, staging reproducibility is limited due to observer bias [7]. Visual discrepancies are common and can depend on the timing of laparoscopy. Further, documentation and staging during laparoscopy may differ from those made during laparotomy [8].
Although this system accurately assesses the placement and degree of endometriosis, it fails to convey the probability of achieving pregnancy following treatment [9]. While the ASRM’s current classification system is helpful to surgeons who require standard terms to discuss this disease, it still has significant limitations. Namely, the depth of the endometrial tissue does not always correspond to pain levels, but this is not expressed in the diagnostic scale [10]. While it is evident that infertility may be a direct consequence of endometriosis, a specific causal link has yet to be established [11].
Newer classification systems include the EFI (endometriosis fertility index)—a clinical tool that is used to assess fertility outcomes for women with endometriosis-associated infertility who have undergone surgical staging for their disease. EFI rates the predicted prognosis in order to tailor the most suitable treatment plan [7]. The EFI combines the score of the patient’s medical history and her surgical factors into a combined EFI score [12]. This index was validated by several studies [13].
1.3 Disease Burden: Prevalence of Endometriosis Worldwide and in North America
The exact prevalence of endometriosis may never be known because a laparoscopic procedure needs to be performed in order to establish a definitive diagnosis [14]. Moreover, some women remain asymptomatic and often go undiagnosed [5, 15, 16].
However, it is estimated that it affects 6–10 % of reproductive aged women [17]. The ASRM reports that 24–50 % of infertile women may have endometriosis along with 20 % of women with chronic pelvic pain. This prevalence increases to 50 % in infertile women with a normal menstrual cycle and whose partner has healthy sperm [18]. Current estimates report that seven million women in the United States and more than 70 million women around the world have the disease.[19] Although hysterectomy was a relatively common treatment for endometriosis, in the United States as of 2010, hysterectomy rates due to endometriosis declined by 65 % as compared to 1998 [20]. Approximately 10–25 % of women who choose ART (assisted reproductive technology) have endometriosis. Additionally, ovarian endometriomas are present concomitantly in 17–44 % of these females [21, 22].
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