A Primer on Clinical Classification and Pathophysiology of Endometriosis

Endometriosis is defined as the presence of endometrial tissue outside the uterus at an ectopic site. It affects around 18% of reproductive-age females worldwide. Currently, endometriosis is diagnosed laparoscopically and is classified into four different types, viz (1) Revised American Society for Reproductive Medicine (rASRM), (2) ENZIAN classification, (3) Endometriosis Fertility Index (EFI) and (4) American Association of Gynaecological Laparoscopists (AAGL). This grouping is proposed to categorise endometriosis on grounds of severity and progression. However, there is no optimal classification scheme and each of the systems has its own merits and shortcomings. Also, the therapeutic value of such a classification system is not yet clear. In terms of pathophysiology, Sampson’s retrograde menstruation theory is the most frequently recognised explanation for the origin of endometriosis, but factors like (1) genetic predisposition, (2) Oestrogen dependence, (3) progesterone resistance and (4) inflammation are thought to be involved in disease development and progression. However, our understanding of endometriosis is far from clear, and there is still much to learn and do. There is a need for an ideal categorisation strategy that appropriately reflects the severity of symptoms, disease progression and response to treatment. Till then, women with endometriosis will continue to suffer, and clinicians will remain in dilemma while managing this complex condition.