Endometriosis is a condition in which foci of endometrial tissue are found at sites distant from the uterus. The disease affects around 5% of women and presents during the reproductive years.


Various sites can be affected by endometriosis. Common locations are the ovaries, fallopian tubes, rectovaginal pouch and broad ligament. The peritoneum, mesentery and intestines are also not unusual sites. The undersurface of the diaphgram is sometimes involved. Much more rarely endometriosis can be present in the pleural cavity and has even been reported in the brain. The umbilical region can be involved, particularly if the patient has had a previous laparoscopy

Foci of endometriosis within the peritoneum form small, blue nodules. Microscopically the foci are composed of benign endometrial glands and stroma. Haemorrhage or haemosiderin deposition are often seen. For a diagnosis of endometriosis to be made at least any two of endometrial glands, stroma and evidence of haemorrhage must be present.

Endometriosis of the ovary can form a larger, cystic structure. The cyst is lined by the endometriotic tissue and contains altered blood. These cysts are sometimes called 'chocolate cysts' due to the appearance imparted to them by the altered blood.

Regions of endometriosis often feature fibrosis due to the attempts by the body to deal with the haemorrhage. This fibrosis can account for some of the clinical features of endometriosis.

Retrograde menstruation, in which sloughed menstrual endometrium enters the peritoneal cavity via the fallopian tubes, is postulated as the mechanism by which endometriosis arises. This proces may need to be coupled with a predisposition to be unable to clear the endometrial tissue under such circumstances; the function of T cells has also been proposed as being contributory. Retrograde menstruation can explain peritoneal endometriosis. Even pleural endometriosis is plausible if the patient has tiny fenestrations in her diaphgram. However, the rare cases of cerebral endometriosis do not seem to be explicable by retrograde menstruation and there may be other components to the pathogenesis of endometriosis.

Clinical Features

Endometriosis can be asymptomatic but may also be associated with pelvic pain, dysmenorrhoea, deep dyspareunia and infertility. Endometriosis is found in a significant proportion of women who are infertile and can impair fertility by distorting the anatomy and position of the fallopian tubes and uterus.

Endometriosis is often cited as a cause of menorrhagia and intermenstrual bleeding. However, given that the endometriosis is distant from the uterine cavity there is no direct route by which the endometriosis can contribute to the menstrual blood loss. Nevertheless it may be possible that the factors which gave rise to the endometriosis somehow also impact upon the behaviour of menstrual blood loss.

Less commonly the endometriosis can cause diarrrhoea or constipation; severe fibrosis can result in bowel obstruction. Endometriosis of the bladder may produce urinary frequency or dysuria.

Rarely there can be a haemorrhagic pleural effusion or even seizures.


Ultrasound scans may disclose foci of possible endometriosis, particularly ovarian cysts. However, definitive diagnosis usually requires laparoscopy and biopsy.


The aim of pharmacological treatment is to suppress menstruation and the menstrual cycle in order to deprive the endometriosis of the cyclical supply of oestrogen and progesterone that it requires. The options include exogenous progesterones, the oral contraceptive pill, danazol and GNrH analogues.

Surgery may concentrate only on removing the foci of endometriosis themselves but in other situations a total abdominal hysterectomy and bilateral salpingo-oophorectomy may be performed to control the symptoms (especially chronic pelvic pain).