Endometriosis: A Narrative Review

Abstract

Although much progress has been made since endometriosis was first scientifically described centuries ago, numerous unanswered questions still surround this chronic, inflammatory condition. For instance, one theory on the pathogenesis of endometriosis suggests that the condition begins from retrograde menstrual flow implanting on surfaces in the abdomen and pelvis (Samson’s theory), which is a logical mechanism given the high rates of endometriosis in patients with obstructive anomalies of the lower genital tract and significant retrograde flow. This explanation has many shortcomings however, as retrograde menstruation occurs more commonly than the reported 10% prevalence of endometriosis. Additionally, endometriosis lesions can be found in areas quite remote from the pelvis, such as the thoracic cavity. As such, research has been increasingly focused on identifying immune, genetic, and local environmental factors that likely play critical roles in the development of endometriosis. This growth of benign endometrial-like tissue outside of the uterus can sometimes be asymptomatic, but it can also cause debilitating pain, infertility, ovarian cysts (endometriomas), and can invade surrounding organs such as the bowel or bladder. There are three main phenotypes of endometriosis: superficial lesions, deeply infiltrating endometriosis (including nodules), and ovarian endometriomas.

While the exact etiology may be obscure, the societal and economic impacts of this condition are undeniable. Patients diagnosed with endometriosis are at a significantly higher risk of absenteeism from work or school, lower quality of life, chronic pelvic pain, and are more likely to receive a mental health diagnosis such as depression or anxiety. Apart from direct and indirect incurred costs to patients (estimated at approximately $5000 per patient annually), at a national level the economic burden of endometriosis exceeds $2 billion annually in Canada, and approaches $80 billion in the USA.