Endometriosis is the benign disease, where endometrial-like tissue is found in places other than the uterus¹. Possible locations include the ovaries, fallopian tubes, peritoneum( the thin membrane that covers the pelvic organs), bowel, urinary tract (urinary bladder and ureters), as well as less common locations (such as nerves, diaphragm, abdominal wall, lungs).

This hormone-sensitive disease (sensitive to oestrogens) affects around 10% of women of the reproductive age². In women with infertility or chronic pelvic pain, the frequency of the disease ranges from 35% to 50%³. This makes endometriosis the second most common disease in the United Kingdom⁴. As the disease is hormone-sensitive, it typically gets better after the menopause.

Endometriosis is a heterogeneous disease that may be associated with a variety of different symptoms. Typically, it is associated with infertility⁵ and pelvic pain⁶. The pain can vary from mild to intense and may occur before, during or after the menstrual period. In some cases, the pain may not be related to menstruation. Depending on the location of the disease, it may be associated with symptoms from the bowel ( pain on opening the bowels, bleeding from the back passage, bloating, constipation, loose stools), the urinary tract( burning on passing water, bleeding, passing water frequently, inability to fully empty the bladder), pain during sexual intercourse, pain in the right shoulder (endometriosis of the diaphragm), pain in the back or lower limbs (endometriosis of the sacral plexus or sciatic nerve). It may also be associated with fatigue and tiredness. In certain cases, it may cause no symptoms at all(asymptomatic). There is no direct correlation between the type/severity of symptoms and the type/extent of endometriosis⁷.

References:

1. Sampson, J. A. Peritoneal endometriosis due tο premenstrual dissemination of endometrial tissue into the peritoneal cavity. Am. J. Obstet. Gynecol. 14, 422–469 (1927).
2. Zondervan, KT, Becker, CM, Koga, K, et al. Endometriosis. Nat Rev Dis Primers 2018; 4(1): 9.
3. Bulun, SE. Endometriosis. N Engl J Med 2009; 360: 268–279.
4. University College London Hospitals. General information about Endometriosis. Accessed February 2014
5. Hurd, W. W. Criteria that indicate endometriosis is the cause of chronic pelvic pain. Obstet. Gynecol. 92, 1029–1032 (1998).
6. Berkley, K. J., Rapkin, A. J. & Papka, R. E. The pains of endometriosis. Science 308, 1587–1589 (2005).
7. Working group of ESGE, ESHRE, and WES, Keckstein J, Becker CM, Canis M, Feki A, Grimbizis GF, Hummelshoj L, Nisolle M, Roman H, Saridogan E, Tanos V, Tomassetti C, Ulrich UA, Vermeulen N, De Wilde RL. Recommendations for the surgical treatment of endometriosis. Part 2: deep endometriosis. Hum Reprod Open. 2020 Feb 12;2020(1):hoaa002.