Endometriosis Diagnosis

Endometriosis can only be definitively diagnosed via a diagnostic laparoscopy. Additionally, other tests may be useful in certain instances in evaluating the extent of endometriosis.

Endometriosis is first suspected on the basis of symptoms discussed on the Endometriosis Causes & Symptoms page.


The gold standard for diagnosing endometriosis is via diagnostic laparoscopy. During this procedure, a laparoscope (camera) is inserted through a tiny cut in the abdomen and the surgeon surveys the pelvic cavity for lesions of endometriosis.

Endometriosis can have a variety of appearances. The images below were taken by Mr. Trehan during diagnostic laparoscopies and demonstrate the appearance of endometriosis on the peritoneum and organs.


The image below demonstrates the normal appearance of the peritoneum:

In early endometriosis, significant neovascularation occurs resulting in the appearance of an increased number of blood vessels; forming red lesions:

The endometrial cells bleed during menstruation as shown in the images below:

This bleeding and shedding of the endometrial cells induces the formation of an early scar which appears as black lesions:

As this process continues, the formation of the scar results in a paradoxical reduction in the blood supply (devascularisation). The absence of blood vessels within this scar in turn results in the scar appearing white:

Endometriosis may also be observed as clear vesicles:

Endometriosis may also form ‘psuedopouches’:


Endometriosis may be present on the surface of the ovaries:

The endometriosis may subsequently invade the ovaries resulting in the formation of ovarian cysts, known as chocolate cysts due to their dark appearance due to the accumulation of blood within them:

In advanced stages of endometriosis the ovaries may come together and join, a phenomenon known as ‘kissing ovaries’:

Intestines (bowel)

Endometriosis may be present on the intestines (bowels). When this occurs, it is most commonly on the rectum of the large intestine (bowel):

However, it may also be present on the small intestine (bowel) or appendix:


Endometriosis may be present on the peritoneum covering the bladder:

However, in more advanced stages, endometriosis may penetrate the wall of the bladder to form a bladder nodule:


In advanced stages of endometriosis, the diaphragm, the muscular sheet which separates the lungs from the abdominal cavity may also be inflicted with endometriosis:

Such patients may experience right shoulder and chest pain particularly at the time of menstruation since the same nerve innervates the diaphragm and the skin of the right shoulder and chest.


The endometrial implants also induce the formation of pelvic adhesions (abnormal bands of scar tissue which join two or more internal surfaces together) in advanced stages of the disease:

In milder stages of the disease, the changes described above may be subtle and hence only an endometriosis specialist may pick such changes up.


During a diagnostic laparoscopy, a biopsy (sample) may also be taken from suspected endometriosis lesions. This biopsy will then be sent to a laboratory and analysed under the microscope by a pathologist in order to discern whether it contains endometriosis or not.


Based on the amount and severity of endometrial lesions and pelvic adhesions (scar tissue), endometriosis is divided into four stages: stage I (minimal), stage II (mild), stage III (moderate) and stage IV (severe). It is however worth nothing that surprisingly, symptom severity does not correlate with the stage of the disease.

Other investigations

Ultrasound and magnetic resonance imaging (MRI) may also be used. However, both ultrasound and MRI tests lack sensitivity (ie. they don’t always detect endometriosis even when it is present) and specificity (ie. they may indicate the presence of endometriosis even when it is not present). Therefore confirming the presence or absence of endometriosis via these methods should not be undertaken; the only definitive means of diagnosis of endometriosis is via laparoscopy. Indeed, Mr. Trehan has seen many patients who have been misdiagnosed with or without endometriosis on the basis of ultrasound and MRI. However, MRI may be useful in some instances, for instance in investigating the extent of rectovaginal endometriosis (in terms of lesion size and penetration) and whether or not the ureters are involved. In addition, an MRI may be useful in the diagnosis of adenomyosis (endometrial cells present within the walls of the uterus).

In cases in which bowel endometriosis is suspected (in particular if rectal bleeding is occurring), a colonoscopy may be performed in which a camera in inserted into the anus and the colon is inspected. Similarly, in cases in which an endometriotic bladder nodule or interstitial cystitis are suspected, a cystoscopy may be performed in which a small camera in inserted into the urethra and the bladder is inspected.