Rehan Salim MD MRCOG

Consultant Gynaecologist & Subspecialist in Reproductive Medicine

Wolfson Fertility Centre - Hammersmith Hospital

Endometriosis is a benign gynecological disease, characterised by the presence of endometrial tissue (tissue normally lines the inside of the uterine cavity) outside the uterine cavity. Clinically associated with pelvic pain and it is an important cause of female infertility. The endometrial tissue in the endometriosis is commonly implanted and attached to the organs within the female pelvis, such as the ovaries and fallopian tubes. On rare occasions, endometrial tissue may even spread beyond the pelvic region. This tissue responds to the hormones of the menstrual cycle with growth and shedding (period) as would occur in the uterus. This bleeding is essentially the cause of the problems with the blood becoming an irritant to surrounding organs and causing pain and scar tissue. The scar tissue can then cause cysts in the ovaries (endometriomas) and block Fallopian tubes which ultimately causes fertility problems.


The exact mechanism of endometriosis is still unknown. However, there are several possible explanations:

  • Retrograde Menstruation: In almost all women, part of the menstrual blood, which contains endometrial cells flows back through the fallopian tube into the pelvis instead of out of the uterus. In some women, the displaced endometrial cells can attach to the organs of the pelvis. Once attached, this tissue can implant, grows, continues to thicken and bleed during every menstrual cycle.

  • Coelomic metaplasia theory: Endometriosis develops from an abnormal change in the nature of the cells that line the plelvis due to infections and hormonal or other inductive stimuli.

  • Induction theory: Is an extension of previous theory (coelomic metaplasia theory) and proposes that internal biochemical or immunological factors can induce undifferentiated cells into endometrial tissue.

  • Embryonic rest theory: Cell rests of Mullerian ducts (embryologic origin) could be activated to differentiate into endometrium in the presence of a specific stimulus.

  • Lymphatic and vascular spread theory: Endometriotic cells can develop and grow at the distance spread through the lymphatic system or blood vessels.

  • Surgical Scar Implant After surgery, endometrial cells may attach to a surgical incision (Eg. C-section, hysterectomy).


Endometriosis is a complex condition that is difficult to diagnose by evaluating the symptoms alone. It is possible that you have endometriosis if you are having fertility problems, severe menstrual cramps, pain during intercourse, or chronic pelvic pain. If you have a persistent ovarian cyst, then there is a possibility of you having endometriosis. It is often found that endometriosis is a condition that is in related family members i.e. mother or sister. But, there are instances where women with endometriosis show no symptoms at all.

For women with fertility problems, a detailed ultrasound scan with an experienced consultant will often show moderate to severe forms of endometriosis. However, more subtle forms may require a laparoscopy for diagnosis.


Treatment of endometriosis will depend on the desire to conceive, the age, the severity of the symptoms and whether the fertility should be maintained. In this case, one has to be as conservative as possible and avoid major surgery since this will reduce significantly the ovarian reserve (= number of eggs in the ovaries) and the chance of possible conception.

For women with fertility problems, treatment of mild to moderate endometriosis via laparoscopy has been shown to significantly improve the chances of achieving a pregnancy naturally. However, surgical removal of more severe forms of endometriosis, whilst being able to be treated surgically, have not been shown to improve chances of natural pregnancy.

Many patients ask if treatment of endometriosis would improve chances of conception with IVF. This is no clear single answer for this question and it very much depends on the severity of the endometriosis, the presence of ovarian cysts, the ovarian reserve, if the Fallopian tubes are damaged. A detailed discussion should enable a tailor made plan.