Endometriosis is a common gynecologic condition in which endometrial tissue is present outside the uterine cavity. Endometrial tissue located within the myometrium is termed adenomyosis and is discussed in Chapter 9 (p. 213). With its molecular basis further elucidated, endometriosis now is seen more as a systemic disease, with the implants of endometriosis leading to an inflammatory response. Although some women with endometriosis may be asymptomatic, many others present with subfertility or various forms of chronic pelvic pain (CPP). Endometriosis often strikes women during their early career or schooling, and the long-term harm to professional or social development can be profound (Lamvu, 2019). As endometriosis is an estrogen-dependent disease, hormone-based treatment is a mainstay of therapy. However, if disease is unresponsive to medical management, surgery may be required.
Approximately 10 percent of all reproductive-aged women are affected by endometriosis (Rogers, 2009). Given that many women with endometriosis are asymptomatic, the true prevalence is difficult to quantify. Imaging modalities of any pelvic compartment generally have low specificities (Wall, 2015). Thus, the “gold standard” diagnostic method is laparoscopy, with or without biopsy for histologic diagnosis (Dunselman, 2014). With this, the annual incidence of surgically diagnosed endometriosis is 1.6 cases per 1000 reproductive-aged women (Houston, 1987). In asymptomatic women, the prevalence of endometriosis ranges from 6 to 11 percent, depending on the population studied and diagnostic mode (Buck Louis, 2011; Mahmood, 1991). Among patients with infertility, endometriosis is more common, and prevalence rates lie between 20 to 50 percent. In those with CPP, it ranges from 40 to 50 percent (Balasch, 1996; Eskenazi, 2001; Meuleman, 2009). Nearly two thirds of adolescents undergoing diagnostic laparoscopy for pelvic pain have evidence of endometriosis (Janssen, 2013).
Of potential risk factors, lower body mass appears to positively correlate with endometriosis risk (Peterson, 2013; Shah, 2013). Early menarche, especially before age 14, carries increased risk for endometriosis. Similarly, nulliparas have a higher risk that likely is secondary to a greater number of ovulatory cycles (Missmer, 2004; Treloar, 2010; Vercellini, 2010). Evidence for racial differences in prevalence is conflicting (Jacoby, 2010).
The definitive cause of endometriosis remains unknown, but several theories are proposed. The most favored one describes retrograde menstruation through the fallopian tubes (Sampson 1927; Tal, 2019). The refluxed endometrial fragments invade the peritoneal mesothelium and develop a blood supply for implant survival and growth. In correlation, women with outflow tract obstruction also have a high incidence of endometriosis, which often resolves following obstruction relief (Sanfilippo, 1986; Williams, 2014). Interestingly, >90 percent of women experience retrograde menstruation, yet only a small fraction develop endometriosis (Halme, 1984). ...