A pelvic examination by the doctor is important as this can reveal localised tenderness. A combination of the site of the symptoms, the bladder, bowel or vagina, and the site of tenderness can indicate exactly where the disease is.
A protein CA-125 is sometimes helpful following the course of the disease when it is severe. It is less reliable as an indicator in the early stages.
The doctor diagnosing endometriosis requires special training and experience to make a reliable diagnosis. Some changes in the pelvis that look like endometriosis are not, so that tissue always needs to be removed and checked by a pathology service to confirm the diagnosis.
Ultrasound will not detect most types of endometriosis. However, it is useful in picking up endometriosis that has formed a lump inside the ovary which cannot be seen from the outside, for detecting whether the ovary or uterus is fixed or mobile due to adhesions from endometriosis, and detecting endometriosis in the uterus which is called adenomyosis.
Laparoscopy is the most reliable way of diagnosing endometriosis. This may be necessary to establish the diagnosis, to check for cure, recurrence, or the possible effect of the endometriosis on fertility.