**1. Introduction**

Endometriosis is classically defined as the growth of endometrial glands and stroma at extra-uterine sites, most commonly implanted over visceral and peritoneal surfaces within the female pelvis (1). Though endometriosis has been described for the first time in 1690 by the German physician, Daniel Shroen, researchers remain still unsure as to the definitive cause of this disease (2). The most widely accepted theory for the pathogenesis of endometriosis (retrograde menstruation/transplantation), proposed in the 1927 by Sampson (3). Although a great deal has been learned about endometriosis since Sampson's land mark studies, there is still a lot about it that is unclear and controversial. It remains an enigmatic disorder in that the cause, the natural history, and the precise mechanisms of its presentation are not known (4).

Endometriosis is most commonly found on the pelvic peritoneum but may also be found on the ovaries, rectovaginal septum, ureter, and rarely in the bladder, pericardium, and pleura. More rarely, colon, small intestine, appendix, umbilical scar and even sites not closely contiguous to the pelvis (e.g., lung and brain tissue) may also be involved (5). It is a leading cause of disability in women of reproductive age, responsible for dysmenorrhea, pelvic pain and subfertility. The most common symptoms for women who have endometriosis are pelvic pain and infertility; both adversely affecting the quality of life. The pregnancy rate in women with endometriosis is about half of women with tubal factor infertility and is negatively correlated with the severity of disease. The cause of reproductive failure may be due to poor oocyte development, implantation or embryogenesis. In addition to infertility, a strong cause–effect relationship between endometriosis and pelvic pain is commonly observed (6, 7). Dysmenorrhoea is associated with cyclic recurrent microbleeding within various entities of ectopic endometriotic implants and consequent inflammation. Endometriosis-related adhesions and compression or infiltration of nerves in the subperitoneal pelvic space by ectopic lesions also cause painful symptoms (8, 9).

In the last few years, there is a growing interest in endometriosis, because of the large number of women it affects (about 3–10% of the female population in the reproductive age, and up to 40–80% of women complaining of pelvic pain) and the significant morbidity

Endometriosis 5

including their inability to predict clinical outcomes, especially pregnancy rates (PRs) in infertile patients. In 1979, the American Fertility Society (AFS) (now the American Society for Reproductive Medicine, or ASRM) first proposed a classification system. This was extensively evaluated, modified in 1985, and is still used today. Despite these revisions the currently used revised AFS system has serious limitations, including not effectively

The endometriosis fertility index (EFI) is a simple, robust, and validated clinical tool that predicts PRs for patients after surgical staging of endometriosis (see figure below). The EFI score ranges from 0–10, with 0 representing the poorest prognosis and 10 the best prognosis. Half of the points come from the historical factors and half from the surgical factors. Uterine abnormality was not included in the score. The EFI is very useful in developing treatment plans in infertile patients with endometriosis. The EFI is useful only for infertility patients who have had surgical staging of their disease. It is not intended to predict any aspect of endometriosis-associated pain. It is required that the male and female gametes are sufficiently functional to enable attempts at non-IVF conception. One factor found to predict pregnancy that is not included in the EFI is uterine abnormality. Sensitivity analysis showed that even with substantial variation in the assignment of functional scores the EFI varies

predicting the outcome of treatment.

very little (65).

associated with this disease, mainly with regard to the possible consequences on reproductive function and on the risk of developing gynecologic tumors, such as ovarian cancer (10-12). The prevalence in women without symptoms is 2-50%, depending on the diagnostic criteria used and the populations studied (9). The incidence of endometriosis is difficult to quantify, as women with the disease are often asymptomatic, and imaging modalities have low sensitivities for diagnosis. The primary method of diagnosis is laparoscopy, with or without biopsy for histologic diagnosis (13, 14). Using this standard, investigators have reported the annual incidence of surgically diagnosed endometriosis to be 1.6 cases per 1,000 women aged between 15 and 49 years. The incidence is 40-60% in women with dysmenorrhoea and 20-30% in women with subfertility. The severity of symptoms and the probability of diagnosis increase with age. The most common age of diagnosis is reported as around 40, although this figure came from a study in a cohort of women attending a family planning clinic (15).

The clinical picture of endometriosis is widely heterogeneous. A correct diagnostic work-up of these patients can sometimes be very difficult, since there are a number of gynecological, intestinal and systemic diseases mimicking endometriosis, as well as other conditions that could be associated with or area consequence of this disorder. Therefore, multidisciplinary care should been courage to ensure correct evaluation and improve the management of these patients (16).
