Endometriosis is a condition where tissue similar to that which lines the inside of the uterus (endometrium) grows outside of the uterus and in various parts of the body, causing pain and other symptoms. The American Fertility Society created a system where the severity of endometriosis can be classified into four stages, depending on the location, extent, and depth of the endometrial tissue growth. The stages of endometriosis are as follows:

Stage 1 (minimal): In stage 1 endometriosis, there are small implants or scattered areas of endometrial tissue on the pelvic lining. There may also be some mild scar tissue or adhesions in the pelvis.

Stage 2 (mild): In stage 2 endometriosis, there are more implants and a deeper invasion of endometrial tissue into the pelvic lining. There may also be some ovarian cysts (endometriomas) present.

Stage 3 (moderate): In stage 3 endometriosis, there are many deep implants and endometrial tissue growths. There may also be scar tissue and adhesions that cause organs to stick together. This can result in infertility, painful intercourse, and bowel or bladder dysfunction.

Stage 4 (severe): In stage 4 endometriosis, there are extensive endometrial tissue growths that may involve the bladder, bowel, and other organs in the pelvic region. There may also be large ovarian cysts and significant scar tissue and adhesions. The pain and other symptoms of stage 4 endometriosis can be severe and debilitating.

The staging of endometriosis is important in determining the most appropriate treatment approach for each individual. Medical treatment options for endometriosis include pain relief medication, hormone therapy, and surgery. The type of surgery that is most appropriate depends on the stage and extent of the endometrial tissue growth, as well as the individual’s age, overall health, and desire for future fertility.

It is important to note that this classification of Endometriosis stages has it’s limitations, as endometriosis can be found in extra-pelvic regions. Calls are being made in the medical society to update this classification to more accurately reflect this.

References:

1. The American Society for Reproductive Medicine. (2012). Revised American Society for Reproductive Medicine classification of endometriosis: 1996. Fertility and Sterility, 98(3), 569-570. doi: 10.1016/j.fertnstert.2012.06.032.
2. American College of Obstetricians and Gynecologists. (2019). ACOG Committee Opinion No. 754: The diagnosis and management of endometriosis. Obstetrics and Gynecology, 133(1), e27-e43. doi: 10.1097/AOG.0000000000003011.
3. Giudice, L. C. (2010). Clinical practice. Endometriosis. The New England Journal of Medicine, 362(25), 2389-2398. doi: 10.1056/NEJMcp1000274.
4. Johnson, N. P., Hummelshoj, L., & World Endometriosis Society Montpellier Consortium. (2013). Consensus on current management of endometriosis. Human Reproduction, 28(6), 1552-1568. doi: 10.1093/humrep/det050.
5. Lee SY, Koo YJ, Lee DH. Classification of endometriosis. Yeungnam Univ J Med. 2021 Jan;38(1):10-18. doi: 10.12701/yujm.2020.00444. Epub 2020 Aug 7. PMID: 32764213; PMCID: PMC7787892.